Its been doing this for a while now (Not always though). I've had the carb off and took all the jets out, cleaned with carb cleaner and used compressed air to ensure that all the jet and carb orfices are clean. Still does the same thing. To describe the way it runs better, it breaks up almost like its running out of fuel and back fires quite a bit. Also back fires a little but (1-2 times) if you rev it up and let off the throttle. The engine will not idle. The backfiring to me almost seems like a timing problem to me. However if you put the choke on, it does run a little bit better. That indicates a lean condition in the carb according to the experience I've had. Anyone experienced this same problem before? Wheres a good place to buy individual Mikuni jets that fit this carb (Besides the dealer, hehe). Thanks

 

You may want to check your diaphram, mine had a hole in it and it was similar to what yours sounds like. Hope this helps.

Later
Chiknhawk

 

It does sound like it is running lean. Have you changed anything on your setup, or did it start doing this on its own?

 

Is the jet needle in the 4th groove from the top down?

 

chiknhawk, on the carb you mean? I haven't checked that but I'll definetly take a look at it.

DSNUT, Nothings been changed. Its bone stock except for a gearing change that was done within the first 2 weeks of ownership. No exhaust changes or anything else. Still running an OEM airfilter (Has been replaced) also.

Oldmanracing, I have not been into the needle/slide area but I'll look at that also when I check the diaphram.

 

Is it backfiring at the exhaust or back through the carb?

 

At low rpms, in the 1500range its back through the carb. When it happens at higher RPM like when I mentioned letting off the throttle, its through the exhaust.

 

Just to make sure I understand you, you bought this quad, did a gearing change shortly after purchase, it ran fine throughout the rpm range when you bought it, then one day it started acting up? Has it been acting up on the same tank of fuel?

 

I didn't buy it, my mom bought it for my dad and he has been the primary rider of it since it was new. The gearing change was done for him, because it was way to tall for where he rides at. Its been rode pretty much everyday since the purchase and has only started giving problems within the last 3-4 months. Its gotten progressivly worse to where it is now at the point it simply will not run at all below 2,000rpm. Its done it on several different tanks of fuel, even fuel bought from different stations. I've ran the same gas mixed in my 250R and Tri-Z without any problems.

 

Does it start really hard? Ya know, by the time I quit asking questions, some expert is going to pinpoint your problem so hang in there.