Drive belt tension?

I popped a new drive belt on last week with help from the picwalkthru here. An easy enough job and I cleaned all the gubbins inside at the same time and removed 8 years of dust and fluff

When I reinstalled the belt, I noticed that the new belt flapped around a bit when revving the engine up and down, not a clean, flat slide up and down the pulleys as I expect from this sort of drive, but one edge/side of the belt was always slightly higher than the other until a constant speed was held when the belt then ran flat and true. Is this normal?

Like a fool, I had not noticed what was happening with the old belt!

Hi Steve, When you got the bike back on the road, how did it feel to you? Better, I hope.

bigbird wrote:

steveR wrote:

When I reinstalled the belt, I noticed that the new belt flapped around a bit when revving the engine up and down, not a clean, flat slide up and down the pulleys as I expect from this sort of drive, but one edge/side of the belt was always slightly higher than the other until a constant speed was held when the belt then ran flat and true. Is this normal?

Perfectly normal. The belt adjusts its tension automatically, based on its position on the front and rear sheaves.

Cheers. I was surprised that the belt did not stay flat as the 2 pulleys opened and closed in synch. This is what happens with other belt and pulley systems I have seen and used, hence my concern!

You might have noticed wear marks on the aluminum casing at the center of the top and bottom. This is from the belt rubbing from this movement. It is also the source of the rumble many riders hear/feel upon take-off.

A J Costa variator seems to stop this. Lighter variator weights would probably also help quiet the noise at take-off.

As it stands, I would not worry about it, even if you leave it stock. These machines go 100,000 miles without wearing out the casing, and 16,000 miles on the belt.

Assuming that you did install the new belt with the arrows facing forward, and you did insure that the belt was not jammed in the variator sheave when you torqued the bolt to the correct reading, I'd say that the flapping noise is normal.

Cosmic_Jumper wrote:

Assuming that you did install the new belt with the arrows facing forward, and you did insure that the belt was not jammed in the variator sheave when you torqued the bolt to the correct reading, I'd say that the flapping noise is normal.

Hopefully all were correct!! I actually double checked the belt direction, just in case....

DennisB wrote:

Hi Steve, When you got the bike back on the road, how did it feel to you? Better, I hope.

Seemed fine Dennis, maybe a little more rumble than normal at first, but after a 30mile run tonight with a good mix of roads and speeds, I came back and am happy with the behaviour of the drive.