Timing Chain Tension on Chinese 250cc Quads
 

I have a CoolSports 250, and from what I have seen on numerous other chinese bikes, the engines pretty much seem to be the same. I have noticed a slight "pinging" sound as the engine runs once it is warmed up. I thought maybe it was valve slappage, but I have performed, and reperformed valve adjustments to make sure everything is set correctly.

The only other thing I can think of, is that maybe the timing chain has some slack in it?

I have also noticed that the engine seems just a tad weaker well into the ride. After about an hour after the ride begins, I start to noticed that it doesnt have the strength it did just after warm up. For example, during this "weak period", if I go into a slide with the rpms too low in 2nd gear, it dies when I straighten it up. Just after warm up, it would lag a lil once I straighten it up, but it still pulls out of it ok.

Overall I think the engine is a bit weak, but then again, I ride a Raptor 660, so I think it is just the big diff between the two.

Timing Chain Tension on Chinese 250cc Quads
 

Might be running a little to lean. Lean will cause pinging and cause the engine to run at a higher temp, which will give you performance issues. I would suspect that before the chain, unless of course you hear it rattling in there... ghcoe.

Timing Chain Tension on Chinese 250cc Quads
 

Thanks for the quick reply ghcoe. That actually makes quite a bit of sense. I have noticed the occasional popping sound when letting off the throttle as well. Now which direction is it on the air mixture to go rich? I cant remember if you back it out to richen, or screw it in. And then, what increments would you recommend I adjust, half turn, quarter turn at a time?

Timing Chain Tension on Chinese 250cc Quads
 

Maybe these will help. I am not sure what type of carb you have so I cannot be of much help. These are good write ups on carbs, how they work, and how to adjust. Maybe you can find what you need there.

http://www.usaatvs.com/pdf/Car...asic%20Principles.pdf


http://www.usaatvs.com/pdf/Adv...d%20Carb%20Tuning.pdf


Also, there is a lot of info here, but lots of reading. http://forums.atvconnection.co...0/threadid/477290.cfm


Good luck, ghcoe.