200 lifan grass kart
 

Hi we are having a trouble getting my motor running right. It runs sweet with the air filter off but as soon as it goes on it drops 1000 rpm off full revs, it's a new k and n filter and we have tried replacing carb,coil, spark plug, cdi and filter. Hopefully someone can help us out, thanks

You're jetted too rich, also K&N filters are crap, get an oiled foam filter.

^What he Said^ :tup:

Spark plug is telling us its running lean, I've asked elsewhere and there was a bad bunch come into our country with timing issues so we are going to adjust the timing

Removing the air filter makes the engine run leaner... It could be that the timing is retarded causing it to run hot, making it look like it's lean, when in fact it's not. I still think you have too much fuel, but the only way to really know is get an AFR gauge. I'd make sure the exhaust isn't plugged up, too.

if the carb is a CVK carb and you are putting a pod filter style filter on that could be the issue as well... CVK style carbs dont like pods in *certain* circumstances...

It's a pz30b carb, we skipped a tooth on the timing wheel and its running way better increase of 500 rpm, so can't wait to test it on the track,

If you have a look at my profile I have a picture of my kart there

Well all that was a failure so got a new cam and timing chain put back to normal and its revving better than ever now have found the other problem is the fuel return has no restriction so its pumping the fuel down there instead of carb so we are going to put a tap in there to restrict it and hopefully it will stort it, what a headache its been