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-   -   Cam belts (/showthread.php?t=28228)

pcn1 15-Mar-2006 18:28

Cam belts
 
I changed my ST2 cam belts almost 2 years ago but have only done about 1000 miles since then. Although I have read every 12000 miles or 2 years I was going to leave it another year, unless you know any horror stories ........:o

Glyn 15-Mar-2006 19:04

better safe than sorry

must say id be tempted to leave them myself
could always whip of the covers and have a look

rockhopper 15-Mar-2006 21:47

Change them, for what they cost its a seriously false economy not to.

I'm as tight as a a sharks arse at 50 fathoms but i still change my belts on time!

Rushjob 15-Mar-2006 22:12

If you want to see the result of low mileage belts that have not been changed when their time is up, drop Nelly a line.
He has one which failed due to age... not a pretty sight and a hell of a lot more expensive to put right than a new pair of belts.

rockhopper 15-Mar-2006 22:36

Took this one off our monster last week. The clock says its done a few thousand miles but i guess its been on the bike a while.

pcn1 16-Mar-2006 11:58

Well the 2 years will be up June so I will give them a visual and check the tension before then. If there is no sign of fraying or surface cracks I'll let then run another year. For me that means 1000 miles tops ! As a maintenance engineer I have experience of these types of belts on automated machines and know they run for thousands of hours. Allowing for different running condtions and pulley sizing etc if they look OK then I'll be confident. Sometimes it can be a little paranoid to think a 23 month old belt is OK but a 25 month old belt has had it !

rockhopper 16-Mar-2006 12:04

Thing with not using the bike much is that the belts tend to remember the shape they have been in for a long time and as the engine usually stops in the same place it means the belts eventually loose their natural shape. The end result is that when you start the engine you get a tight spot on the belt and it breaks as the belt gets pulled tight.

For £30 or so its just not worth the risk in my opinion but hey, its your bike.

Jools 16-Mar-2006 12:38

Rockhopper is right. Because of the space restrictions on a motorcycle engine the cambelt pulleys are much smaller than most other applications and the belts are consequently wrapped around a much smaller radius when the bike is stationary. That means that the belts tend to adopt the shape of the pulleys that they are wrapped around on a bike that hasn't been used much and develop a little bumpy bit or tight spot.

As I understood it, reading it from the Sigma site or somewhere like that, the belt doesn't often break of it's own accord (although that's not to say it couldn't do that). What happens is that as this less flexible bit goes around and around (especially at 10,000 rpm) it can jump a tooth or two on the cam pulley, that puts the valve timing out of the window, piston then meets valve and the belt snaps when it can't jam the valve into the piston any harder.

£30 belts or thousands for an engine rebuild (which would write an ST2 off effectively)? As rockhoper says - your call.

pcn1 16-Mar-2006 15:27

Doh !!!! Your making me paraniod now :puzzled:

Now if Ducati made a bike with a non interference engine and no rubber bands .................. :lol:

rockhopper 16-Mar-2006 16:13

Just becasue you're not paranoid doesn't mean they are not out to get you.


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