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.

 

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.

 

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?

 

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.