A little engine help here
- Thread starter yamadogyz
- Start date
What bike is this?
Those sliders are normally pretty robust. I've not seen the chain guide come close to melting on any of the XR's or XL's that I've owned. Unless that bike is super high mile, there has got to be something that caused the issue. Could be something as simple as a stuck timing chain link. If it were heat only I would expect other engine damage.
I'm not normally a replace the timing chain whenever you open the engine type of guy, but bobkyle2 might be on to something. The part that failed is the guide that the chain tensioner acts on. The chain may be a bit longer on one part than another. When the long part goes by the guide the tensioner tightens down on the chain. When the short side goes by there is a tremendous force of the guide as most tensioners only move in the tighter direction. No idea if that is the issue, but something caused extra force on the chain to chain guide.
Anyhow be sure to check the chain, the sprockets, and for sure that the tensioner is working and is set correctly.
I've had big heat related problems with cam chain tensioners on my XR600. It's a completely different design though.
good luck and get a manual before doing anything else.
Those sliders are normally pretty robust. I've not seen the chain guide come close to melting on any of the XR's or XL's that I've owned. Unless that bike is super high mile, there has got to be something that caused the issue. Could be something as simple as a stuck timing chain link. If it were heat only I would expect other engine damage.
I'm not normally a replace the timing chain whenever you open the engine type of guy, but bobkyle2 might be on to something. The part that failed is the guide that the chain tensioner acts on. The chain may be a bit longer on one part than another. When the long part goes by the guide the tensioner tightens down on the chain. When the short side goes by there is a tremendous force of the guide as most tensioners only move in the tighter direction. No idea if that is the issue, but something caused extra force on the chain to chain guide.
Anyhow be sure to check the chain, the sprockets, and for sure that the tensioner is working and is set correctly.
I've had big heat related problems with cam chain tensioners on my XR600. It's a completely different design though.
good luck and get a manual before doing anything else.
That's another type of plastic.
That melts at around 500 degrees
https://en.wikipedia.org/wiki/Polycarbonate
An air cooled bike on a hot day that's been ridden hard can go into the low to mid 400's... hot enough to make it soft. If anything that tensioner is made from a more heat resistant plastic.
A motocross racer's past bike, clear enough? And thanks
I would guess that it is a phenolic thermosetting plastic. Thermosetting means that it does not melt at all. It stays hard right up to the point that it burns. Some phenolic can have service temps of 450F there are others like polyimide that are good to 550F and some recent products can take 650F.
Polycarbonate is known as a thermoplastic and starts to melt at 300F. Not good in an air cooled engine that's for sure.
Sorry SRAD, that plastic for the guides is some pretty hard stuff as far as plastic goes.
Polycarbonate is known as a thermoplastic and starts to melt at 300F. Not good in an air cooled engine that's for sure.
Sorry SRAD, that plastic for the guides is some pretty hard stuff as far as plastic goes.
