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 Belt slap and what I've found so far

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Oldschool
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PostSubject: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Feb 10, 2021 3:49 pm

Hello all.
I just never could get along with the vibration of my 2011 SW-T 600. This is a common problem, from what I read on the internet. My Sw-t does this in the middle of the rev counter, or under some acceleration. When the belt slaps, you can fell it all over the back of the bike. Its like riding with motocross tires on the street. I've done some investigation over the past few weeks about this.
Things to consider: The belt is brand new from honda. As a matter of fact, i now have two new belts from honda, because i thought that the first one had a manufacture issue. The clutch is also new from honda. I found that the reason why the bike vibrates at around 4k rpm is due to excessive belt slap. It has nothing to do with the fact that the belt also hits the lower end of the case. I've ridden the bike without the case, and the vibration was there. I installed a big washer behind the contra spring and the problem got minimized, but only because the belt slap is now in the upper rpm range, let's say about 5k. But it's there. Variator is clean and the rollers are in good shape. I can see that the belt slap question is common to other cvt bikes, but none seems to get the vibrations into the chassi of the bike, like the silverwing does. I know that what causes belt slap is the belt being too loose, or not enough tension on it.
But we get out of options, because you just can't tension the belt or buy a smaller size.
Has anyone here ever had this experience?
Did you fix it successfully?
If so, please share. I made a video which shows my Sw-t running with new belt, and excessive belt play.
YouTube search for swt belt slap.
Cheers.
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Cosmic_Jumper
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Feb 10, 2021 5:16 pm

Oldschool wrote:
(Snip) I installed a big washer behind the contra spring and the problem got minimized, but only because the belt slap is now in the upper rpm range, let's say about 5k. But it's there.(Snip)

Hello Pedro. Welcome to the forum. What size “big washer” did you install? Where did you get it? How thick is the washer? Did you install the washer at the Driven Pulley moveable face end of the spring or at the outside end?

Thanks



We all benefit from shared information.
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Oldschool
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Feb 10, 2021 5:32 pm

Hello.
I found a hard plastic washer about 3mm thickness and the exact diameter of the contra spring. I installed it on the outside end. The difference is the bike shifts higher. Let's say you travel full stock at 50 mph at 4k rpm. With the washer creating more tension on the spring, you travel at the same 50 mph but at 4.200 rpm (approximately values).
This minimizes the belt harmonic vibration, but doesn't solve the problem.
Thanks.
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Mech 1 twa
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeThu Feb 11, 2021 8:43 pm

Might just be an engine vibration that you are feeling.? By changing RPM at a certain speed it moved it to a different speed. All engines vibrate at a certain RPM. Some are more sensitive to vibration felt in bars or through bike. Engine has balance shafts but it's not perfect.
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Dave Weller
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeFri Feb 12, 2021 8:16 am

Have you stuck your finger inside the sealed outer bearing of the CVT driven pulley set up, I've just had my 2010 sealed for life (not) replaced. My needle bearing was fine but hidden away is this sealed ball bearing. Some time ago the bearing had seized and blued the stub axle.
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john grinsel
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeFri Feb 12, 2021 9:51 am

With over 400,000 miles with rubber band drive scooters since 1990----belt slap may exist, best fix totally stock drive train, new OEM belt----then what you think is belt slap...stop, run engine up against brakes for 10 seconds or so----things smooth out....at least for a while. My first new SilverWing, 2009, had times of ruff/jerky power take up. Used this method to smooth out. Rode up to 50,000 miles, traded for another new SilverWing, left over 2013. The 2009 never let me down, belts changed at Honda recommended intervals with OEM belts. I never walked!!
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Loosemarbles
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeFri Feb 12, 2021 3:32 pm

Well Oldschool, I've shared your pain since I got my 2001 SW which had not been looked after very well. I've learned to tell the difference between belt slap and mechanical vibration, just from experience and getting to know my bike. I've also noticed different behaviour from the drive system depending on the ambient temperature.

Over time, I've changed the clutch drum, new clutch shoes, new springs, new rollers, new belts, cleaning, measuring and double checking all is working correctly. Yet, I have that vibration at 4000rpm. I occasionally get some vibration on a gunning take off.

It took me while to learn to not 'overgrease' the driven shaft and bearings: this led to grease escaping from the stub axle into the clutch drum although this usually producing a howling or squealing noise but still accompanied by heavy vibration. I try to keep the drive pulley, shaft and collar spotlessly clean.

I reckon, if you're happy that all is well with the drive train, (it sounds as though you've covered most of it), then just enjoy the ride.

The only thing I had not considered is the ball bearing race mentioned by John Weller above so give it a check. Whatever you want to investigate, I'm sure that it's been covered on this forum so do some searching if you want to get to the bottom of this issue. We're all glad to help if we can. thumbs up
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Terry Smith
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeFri Feb 12, 2021 9:43 pm

I have replaced the outboard bearing in the drive casing, I could hear mine rattling when the engine was idling, which was annoying because with the casing opened, the drive was smooth and quiet. I don't think that you would ever describe the rattle as belt slap however as it was steady and obvious without any acceleration.
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Oldschool
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeSun Feb 21, 2021 10:06 am

https://youtu.be/4AAxlLs4Nt8
That's the problem. Its not a mechanical vibration. It's the belt for sure.
Its a bit shame that the engine runs so smooth and quiet, but a with a poor belt design, that sucks.
The bearings are all in good order. No strange noises.
Thanks for all the help.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeSun Mar 14, 2021 1:15 pm

There's not a lot that can be done with that. It is due the power delivery characteristics of a two-cylinder engine. From all outward appearances the output shaft of the engine always turns at the same speed, but it really doesn't. Due to torsional vibration in the crankshaft, every time a cylinder fires the output end of the crank is constantly speeding up and slowing down. This is why larger engines have torsional vibration dampers (commonly called a "harmonic balancer") to damp torsional twisting of the crankshaft every time a cylinder fires. Torsional dampers have been used on automotive engines for better than 100 years.
https://en.wikipedia.org/wiki/Torsional_vibration

This is what causes your belt slap at certain harmonics where the torsional vibration frequency of the crankshaft excites the natural frequency of the belt on the slack side of the belt. So it slaps the bottom of the case. Usually when it does it, adding more throttle or backing off a little to change the amplitude of the crank's torsional vibration will stop it. That doesn't make it less annoying, but it is a design flaw in the torsional damping of the Silverwing's crankshaft (which basically doesn't exist because it doesn't have a torsional damper).

All the balance shaft does is counter secondary vibration since it is a single pin counter-weighted crank where both pistons go to TDC at the same time, but one is on compression stroke, the other on exhaust stroke. There is no rocking couple like there would be with a non-even fire crank. Primary balance is achieve with crank counterweights to counter the mass of the pistons and rods.

Secondary balance is due to the pistons traveling further during the top half of the crankshaft’s rotation than during the bottom half, which results in non-sinusoidal vibration. The difference in distance traveled is due to the movement of the connecting rod. At 90 degrees after top dead center the crankshaft end of the connecting rod is exactly at the halfway point of its stroke. However, the angle of the connecting rod (i.e. the left–right movement, when looking down the crankshaft) means that the piston end of the connecting rod must be lower than the halfway point, in order for the connecting rod to maintain a fixed length. The same also applies at 270 degrees after TDC, therefore the piston end travels a greater distance from 270 degrees to 90 after TDC than it does in the 'bottom half' of the crankshaft rotation cycle (90 degrees to 270 degrees after TDC). In order to travel this greater distance in the same amount of time, the piston end of the connecting rod must experience higher rates of acceleration during the top half of its movement than in the bottom half. This is the vibration that the balance shaft counters.

However, none of this compensates for the torsional vibration. Probably more than you wanted to know, but that's the reason for it.
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steve_h80
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeSun Mar 14, 2021 1:53 pm

Well explained Chris 👍
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Mech 1 twa
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeSun Mar 14, 2021 5:15 pm

Longer the crankshaft and number of cylinders the worse it is. Short crankshaft like SW not so bad.
Ever ride next to someone with a loose chain and watch how it slacks from drive to decel? Belt is doing the same thing.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeSun Mar 14, 2021 7:38 pm

If the Silver Wing had a heavy flywheel on it instead of a relatively lightweight aluminum variator it would help to mitigate the torsional vibration in the crank somewhat. But people wouldn't like the lack of snappiness of the engine with a heavy flywheel.

The more power pulses the crankshaft receives per revolution, the less pronounced torsional vibration is. An inline-four is worse than a V-8, a parallel twin is worse than an inline-four. A single cylinder engine is the worst.

Parallel twins can be:
- 360 deg crankshaft (Silver Wing): This configuration creates the highest level of secondary imbalance, however, the primary-plane imbalances are minimized and the even firing order provides smoother power delivery but no overlapping power strokes.
- 180 deg crankshaft: This configuration produces primary-plane imbalance and an uneven firing order, however, the secondary imbalances are half as strong (and at twice the frequency) compared with a 360 deg crank.

There is very few engine configurations that achieve perfect primary and secondary balance. One that gets close is the inline-three
- Firing interval is perfectly even, although the power strokes are not overlapping.
- Primary and secondary reciprocating-plane balance is perfect.
- Primary and secondary rotating-plane imbalances are present.

The inline-six with firing order 1-5-3-6-2-4 is one configuration that achieves perfect primary and secondary balance without use of weights or external balance shafts. Does not need a torsional vibration damper, an inline-six can have a bent-wire crank without counterweights. The inline six has:
- Perfectly even firing interval with overlapping power strokes spaced at 120 deg.
- Primary and secondary reciprocating-plane balance is perfect.
- Primary and secondary rotating-plane balance is perfect.

The Silver Wing's parallel twin with 360 deg crank is nothing more than an enhanced single-cylinder engine. With the extra cylinder it provides one power stroke for every revolution instead of one power stroke for every two revolutions. So its secondary rotating-plane vibration frequency is double that of a single cylinder engine. But the torsional vibration amplitude is 1/2 that of the single-cylinder engine.


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Loosemarbles
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 2:51 pm

I used to worry about the vibration from my SW until I discussed it with my friend who has an HD Sportster. He said that his mirror is a complete 'blur' while cruising at moderate speeds.

I know the HD is a different beast but if my mirrors were a blur while riding, then I'd be worried!

The in-depth information above is fascinating and quite reassuring. In fact, I always thought the pistons on the SW were so close together that they might as well be one piston. I'm glad they're not though.

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steve_h80
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 2:59 pm

That reminds me of a mates old Buell. It was smooth when riding it but everything we stopped the tickover vibrations made the whole thing a blur 😆
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Loosemarbles
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 3:23 pm

My warped mind can actually picture that Laughing
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 3:41 pm

Loosemarbles wrote:
I used to worry about the vibration from my SW until I discussed it with my friend who has an HD Sportster. He said that his mirror is a complete 'blur' while cruising at moderate speeds.

The Sportster engine is a crude version of the Harley Big Twin. V-configurations are whole different animal. The Harley Big Twin with 45 deg Vee cylinder configuration fires once per revolution, but it is odd-fire because the crank has a single crankpin. The H-D Big Twin has two heavy flywheels that double as crank counterweights that the Sportster engine does not have.

But this does not mean it is a "bad" engine. The Harley 45 deg V-twin with single crankpin is the most successful motorcycle engine of all recorded time and has been around over 100 years. It has gone thru several iterations from the Knucklehead to Panhead to Shovelhead, Blockhead (Evo), Twin Cam and Milwaukee Eight. But it has successfully powered more heavyweight motorcycles over the last 100 years than all other engine configurations combined.

The 45 deg V-twin is almost the "perfect" motorcycle engine. It has a narrow profile, excellent fuel efficiency with a small bore and long stroke, doesn't need to spin at high rpm's and produces almost 100% torque at only 2,000 rpm, uses a cam-in-block design with hydraulic lifters (Evo's and newer) with pushrod and rocker operated overhead valves that has stood the test of time without failure.

The H-D V-twin can be made to run absolutely vibration-free as witnessed by some of the Evo and Twin-Cam touring models with balance shafts. But most owners don't want them that way. They like the "feel" (and sound) of the engine in its raw form. This is the part that the metric manufacturers did not "get" when it became apparent they could not compete with H-D in the heavyweight V-twin cruiser market. They tried to "improve" on something (using offset crankpins, etc.) that the market did not want "improving" on.

In the end, H-D's design philosophy won. Not every market wants (or needs) fancy high-technology sewing-machine push-button luxury. The "fun factor" and aftermarket availability of customization is what sells bikes. If you go with the high-technology luxury path somebody can always one-up it by bolting on more fancy gizmos and gadgets, which is where Honda eventually lost the race with Suzuki and their Burgman. Eventually Honda reached a fork in the road - are we gonna dump more money into this thing to try to update it in the technology race? Or just drop it and move on, seeing as how the market for this stuff is not really all that great to begin with?

H-D never found it necessary to get into that ratrace. They listened to their customers, and they build what sells.
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john grinsel
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 4:33 pm

With 175,000 miles of experience and 4 new ones, Helix could have belt slap , too. Engine was smooth.


Comment on Harleys: they ain't selling right now---45 degree v shakes. I have had 4 big twins, 2 bought new----run hard besides shaking, they have problems getting rid of heat!!. Had 3 new Sportsters---883 is quite reliable, but a real paint shaker. Also had WLA 45---they didn't shake so bad due to low out put. Years ago HD offered FL and FLH big twins---FL lower compression and maybe soft cam, they ran smooth. Before that EL 61 twin was known to be smoother than big twin 74. Had friend in Japan who had 60 or 61 FL, his mother bought him new, Asian models had compression as low as 4.5 to one (pistons) and they ran as nice as Brigg & Stratton lawn mover engine.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 6:54 pm

We've had a number of Harley's, our 1986 Evo ElectraGlide (FLHT) is smooth as silk on the highway. It has almost 300,000 miles on it. We rode that bike two-up to Inuvik, Northwest Territories from Wisconsin in 2018. Our Twin Cam Ultra (FLHTCUI) is also silk smooth on the highway. We've traded that one on a new 2021 TriGlide Ultra with a 114 cube Milwaukee Eight with 10.5:1 compression.

Our new TriGlide is supposed to be here in May. All of our Harley's (even in the '86) has belt final drive. None of them have belt slap. But then, Harley has a very innovative torsional damper built into the clutch too that the Silver Wing does not have.

Edit:
H-D even offers upgrades for their torsional damper (they call it the "compensator")
https://www.harley-davidson.com/us/en/shop/Screamin-Eagle-Big-Twin-Compensator/p/40100061

Why Honda could not think of this for a twin-cylinder engine to smooth out the power pulses from the crank is beyond my understanding. It's not like it's anything new and engineers have known about it for years in engines that do not have overlapping power strokes.
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Mech 1 twa
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeMon Mar 15, 2021 9:39 pm

Apples to Oranges on SW drive belt to a Harley drive belt. Harley is a cog belt has teeth and when properly tensioned is tight more like a chain and that's after going through the transmission. SW has a much different system as you know. Saw one Harley parked with belt laying behind it about 50 feet away so nothing is perfect.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 8:41 am

Mech 1 twa wrote:
Apples to Oranges on SW drive belt to a Harley drive belt. Harley is a cog belt has teeth and when properly tensioned is tight more like a chain and that's after going through the transmission.   SW has a much different system as you know.   Saw one Harley parked with belt laying behind it about 50 feet away so nothing is perfect.

No, it is the same difference. The Silver Wing's belt runs at about the same tension as the Harley's, just that being part of a variable drive system it is tensioned by the spring on the rear pulley. It doesn't matter if the belt is v-style or gilmer-style. Any belt (or drivelline) will vibrate from torsional loading. Ever watch the 4" wide gilmer belt driving the blower on a competition V-8 engine? That big belt vibrates so severely they sometimes break.

The final drive belt on the Harley's normally runs 100,000 miles between replacements. The belt is the best drive system out there, compared to either chain or shaft drive. The belt is quiet, requires no lubrication, and only requires a tension check at oil changes. Shaft drives are not all great either and they are expensive to fix. Our Goldwings left us stranded twice with a blown shaft drive, once when the splines stripped out of the rear hub in Missoula, Montana with our '94. The second time on Highway 16 south of Rapid City, SD when the rear end locked the rear wheel on our '97 due to a broken pinion gear. Both times cost us over $2,000 to get back on the road again.

So none of them are perfect, but overall we tend to prefer the belt for least maintenance and reliability. The amount of heat produced by the drive is a good indication of power efficiency. The belt final on our Harley's runs only warm to the touch after extended freeway speeds at 100 deg in the shade. The tire is hotter than the belt. The rear end on every Goldwing we ever rode gets so hot you can't touch it with a bare hand.

Did you know that the Goldwing has "cush drives" (torsional dampers) on the clutch drum, the alternator drive and the shaft to the rear end inside the transmission? Those dampers are there to prevent gear rattle.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 9:44 am

Another interesting fact on torsional vibration damping in engines and drivelines; do you know why the overhead camshaft on an inline-four motorcycle engine is driven from the center of the crank instead of from the end?

It is because the torsional vibration at the center of the crank is cancelled by equal and opposite reaction on opposite ends of the crank with a 1-3-4-2 firing order. If driven from the end of the crank without a torsional damper the chain would vibrate so bad it would destroy it.

When Honda designed their GP250 inline-six two-stroke racing engine back in the day they broke numerous crankshafts driving the transmission from the end of the crank.

Iron or steel have little internal damping, exciting a crankshaft torsionally at its natural frequency causes its twist oscillation to increase in amplitude, subjecting it to very high stresses that break it. This is called resonance (what you see in the vibration of the belt on your Silver Wing). The natural frequency of the engine's torsional vibration matches that of the belt and it amplifies. Shoichiro Irimajiri figured out that driving the transmission from the center of the crank places the torsional loading at zero sum with the two-stroke inline-six and prevents broken crankshafts because it changes the natural torsional frequency of the crank.

In engineering vibration analysis the center of the crank in the above example is a called a "node" - a point of zero torsional motion, while leaving both crank ends free to vibrate torsionally. This lowers the natural frequency of the steel in the crank so it didn't resonate at the design 18,000 rpm that the engine had to run at with six power pulses per revolution (300Hz torsional vibration frequency).

Again, probably more than anybody wanted to know. I spent 37 years as a mechanical engineer doing engine design for Cummins before I retired, so I find some of the design flaws in production products to be interesting.
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minimac
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 10:11 am

Did it occur to anyone that a good part of that is the difference between a $9K (new) scooter and a $30K+ motorcycle?
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gustav
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 10:42 am

Chris, very interesting comments, was wondering what you're vocation was. Thanks, Paul
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 12:07 pm

minimac wrote:
Did it occur to anyone that a good part of that is the difference between a $9K (new) scooter and a $30K+ motorcycle?

That's some of it. Design and build a product to a price point. Cut corners where you can. But on the other hand, even a cheap Chinese-made single-cylinder GX160 clone drive in Chinese scooters has better torsional damping than a Silver Wing because they have a flywheel with a fan for air cooling that damps the power pulses from the crank. The flywheel's mass is relatively high compared to the crank mass. So those Chinese scooters actually have less vibration than a Silver Wing.

The power pulses from the Silver Wing's crank are quite pronounced at lower rpm's too, during early clutch engage and acceleration. It makes the windshield and fairing on the bike rattle.

So there's no doubt Honda could've stuck a little more engineering resources into the Silver Wing for what was supposed to be a "luxury scooter".
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Mech 1 twa
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 6:45 pm

Another interesting fact on torsional vibration damping in engines and drivelines; do you know why the overhead camshaft on an inline-four motorcycle engine is driven from the center of the crank instead of from the end? Quote

My 2005 FJR 1300 cams are driven from the right side of engine not center as are most inline 4's of newer design. No damper 3 gears, guides, chain and tensioner. SW cams are driven from end not center also. Millions of auto engines out the with chain on end they are still running just fine.

When Honda designed their GP250 inline-six two-stroke racing engine back in the day they broke numerous crankshafts driving the transmission from the end of the crank. Quote

Old Honda 250 was a 4 stroke that spun at 18,000 RPM yeah would take a little time to work out the issues.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 7:04 pm

Mech 1 twa wrote:

My 2005 FJR 1300 cams are driven from the right side of engine not center as are most inline 4's of newer design. No damper 3 gears, guides, chain and tensioner.

Yep, and the FJR's went thru how many different versions of the cam chain tensioner to keep it from failing? They are famous for jumping time on the cam drive because of loose rattly chain.

Oh, and on automotive engines, they are damped on both ends of the crank. Flywheel at one end, torsional damper on the other. They all have it or you'd never even be able to keep belts on the front accessory drive on the engine.

Most dampers are a rubber-mounted ring weight. Some (like the damper on the output shaft of the FJR) are cam-type dampers. And yet others, like used on Cummins NT-series engines are viscous (hydraulic) damper.

Any rotating shaft with uneven loading will have torsional issues. You can't ignore it or claim it doesn't exist because manufacturer A did (whatever). With early 80's versions of Cummins NTC's we had torsional vibration issues with the camshaft. It was so bad it affected the timing of the rear cylinders (cam operated injectors). We went thru several engineering changes in that engine series up to the Big Cam IV (which later became the N14). Even though the crank had a viscous damper which killed harmonics in the crank and prevented gear rattle in the front gearcase on the engine, the camshaft doesn't rotate smoothly because of pressure on the followers on the cam lobes. In the Big Cam series we increased the diameter of the camshaft to 2.5" to give it better torsional rigidity, plus changed the injector drives to the so-called "Top Stop" injectors. This reduced the pressure on the injector cam lobes and got rid of the torsional vibration issue.

So sometimes it's not as simple as just bolting on a damper. Sometimes it requires an engineering change in the part to alter the fundamental (or sometimes the secondary) harmonic that causes it to vibrate torsionally.

On the Honda GP250 (or RC166) you must not know that the first prototype of that engine was a two-stroke. Everybody was running two-strokes at the time, but Honda had developed their inline-4 four-stroke, which was successful. Shoichiro Irimajiri needed more rpm's and the two-stroke inline six was the first iteration of it where they solved most of the engineering problems. Then they married the existing engineering in the 250 inline-four with the six cylinder version as a four-stroke. And it was successful.

The engineering used in that original engine was later applied to the CBX. But the CBX, while kinda cool, was a flop in the market. Nobody wanted big wide six-cylinder engines. So Honda started building V's. Some of which were successful, some where not and had a lot of problems (like wiping out overhead cams).

But even so, Honda did not give up on two-strokes. They went on to build the NSR500, which was a V-4 and still probably one of the best-sounding engines they ever built. Also highly successful up until the early 2000's when MotoGP went to four-strokes.
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Mech 1 twa
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeTue Mar 16, 2021 8:33 pm

Famous? Very rare but it happens to any mass produced part not a common thing on FJR.  Google anything and the most negative results show up first.  RIDE ON. Spring is almost here have a good summer I'm going riding soon enough. Smile
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 1:14 pm

Mech 1 twa wrote:
Famous? Very rare but it happens to any mass produced part not a common thing on FJR.

It is common enough. A good number of the LD riders were riding those, a couple of our friends had them. They were the go-to bikes after the ST1100 was discontinued and Honda pigged it out with the ST1300. Without looking it up it seems to me Yamaha went thru three revisions of that cam chain tensioner because they kept failing due to the severe duty location they chose to drive the cam from. Using the end drive did make the block shorter and more continuous for the cooling system though. Just because it didn't have the gap between the center two cylinders for the cam drive. So it reduced the overall weight of the engine. But the cam drive on the FJR is not maintenance-free like it is on the Honda fours.

We've already had our Silver Wings out this year. It went from 30 below in February to in the 40's here in March. Our new Tri Glide was supposed to be here in March. But H-D has had covid delays in production, they didn't even introduce the 2021 models until Feb. So now it's May delivery. We ordered the Tri Glide last October. Seven months to get a new machine. At the time they had three left-over 2020's, one of which we test rode and liked it. Could've gotten a good deal on those, but wife didn't like the colors.

Both of our "new" Silver Wings, which we bought new (mine with a few miles on it) have over 100,000 on them now. They don't build anything like it anymore so we're going back to two-up, this time with a trike. Which actually makes more sense for us. The huge trunk in the Glide is a plus for carrying "stuff". And my wife can ride it by herself, where she can't handle a 1,000 lb two-wheel Ultra.
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steve_h80
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 3:21 pm

Chris you need your own section on this forum; CycleWorld has Kevin Cameron, Silverwing600 has Chris Olson.
Excellent articles, keep them up!
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oldwingguy
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 5:56 pm

Agree with the above post and want to further it by asking is the belt slap reduced by easier but steady acceleration and deacceleration? I ask because I usually get off the line quickly but ease on down to a stop. This years inspection shows both a small shinny area on the belt case top and bottom. The belt itself has 9500+ miles on it. Then internals since I inspected them last year needed no cleaning this time.
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Chris Olson
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 6:19 pm

oldwingguy wrote:
Agree with the above post and want to further it by asking is the belt slap reduced by easier but steady acceleration and deacceleration?  I ask because I usually get off the line quickly but ease on down to a stop. This years inspection shows both a small shinny area on the belt case top and bottom. The belt itself has 9500+ miles on it. Then internals since I inspected them last year needed no cleaning this time.

That's normal to see those polish spots in the case. I doubt it can be reduced much because it happens at certain speeds where there is a harmonic. It doesn't really hurt anything because that belt is strong and if you replace it at the recommended intervals you'll likely never have a broken belt on the road. It's more of an annoyance than anything. On my bike at around 4,000 rpm at a steady speed, sometimes just a slight change in load will set it off and I can audibly hear the belt slapping on the case. Romp on the throttle a little to stop it and it goes away. But between my wife and I and three Silver Wings we've had, put a combined 200,000+ miles on them, we've yet to ever have a broken belt on the road.
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gustav
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 8:00 pm

[quote="steve_h80"]Chris you need your own section on this forum; CycleWorld has Kevin Cameron, Silverwing600 has Chris Olson.
Amen to that! Have really been enjoying this thread. Paul
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oldwingguy
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeWed Mar 17, 2021 9:49 pm

Thank you Chris.
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minimac
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PostSubject: Re: Belt slap and what I've found so far    Belt slap and what I've found so far  I_icon_minitimeThu Mar 18, 2021 9:53 am

Chris Olson wrote:

Both of our "new" Silver Wings, which we bought new (mine with a few miles on it) have over 100,000 on them now. They don't build anything like it anymore so we're going back to two-up....
I recently rode the new Kymco AK550. It certainly does everything my Silverwing does, but much better. When I tire of the Honda, that will be my next scoot. In all fairness though, that will probably be a couple years from now.
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