Iknow this is the Polaris section but as I understand these 90cc kids atvs are all the same .It all started with a plugged spark arrestor. The bike would idle but wouldn't go had little to no power. After removing the spark arrestor it ran great for about 2min the it would die under load. After going through the carb 2 times I still had the same issue. i checked dry compression and had 60psi. So now ive installed new top end complete and still have the same problem. It almost feels as if its leaning out. I have not replaced the spark arrestor which Im going to try tonight. Seems to flow fuel from the tank to carb . I read somewhere that removing the spark arrestor can cause a lean condition. Its definitely starving for fuel. Any thoughts or insight would be greatly appreciated.

 

1 way to find out, put the spark arrestor back in. I don't know if Dynajet makes a Stage 1 kit, but if they do, you could play with rejetting. Once you know what the stock jets are, you can try a couple richer pilot and main jets. Check that the neoprene diaphragm is seated and has no tears or leaks. Lastly, if you play with jets, it's safer to go rich than too lean. hope tis helps...

 

Engine might be similar to Polaris but doesn't sound like the muffler is. Couldn't remove the baffles on these little machines,but I and a lot of customers used long punches to drive into them. Not orthodox but it opened up the exhaust flow and didn't increase noise level.Either that or buy a new exhaust system if soaking them in kerosene didn't open them up.

 

I have removed the arrestor but now it seems to die under load. fires right back up . Pulled the plug seems dry and have plenty of spark.

 

Start at the easy stuff first. Make sure the tank is vented and that you have good fuel flow to the carb.If you do then go through the carb and make sure the jets are clean and open,the needle and seat are ok.Like hydrex mentioned,reinstall the spark arrestor as that could be the part of the reason or the main reason for it dying.

 

2 threads on same subject...he needs to verify compression on his top-end rebuild...

 

I saw that one too...That's why you go from section to section when you double post on the same thing.