I have a 1999 that sat for a while. I rebuilt the carb (which was very nasty) and cranked pretty quick. But now will only run with choke on, backfires and sounds like something may be rattling in the engine. Any ideas?

 

While waiting I've taken off the gas tank and cleaned it. I'm going to re-clean the carb just in case some trash got through. I'm also going to by a new spark plug tomorrow.

 

while not familiar with your specific machine, have you sprayed the boot area with carb cleaner and checked for vacuum leaks? does it bog down when hitting the throttle? if so, i'd think you're on the right track with the main jet still being dirty. maybe even adjust the rich/lean screw and make sure the idle screw is set also.

 

It does want to quit when giving it gas. I did notice that the needled was 3 1/4 turns out and everything I've seen was around 2 1/2. How much difference will that make?

 

If it won't idle without the choke, your pilot jet is plugged, or the passage to the carb throat from the pilot jet is plugged. You will need to remove the pilot jet (small jet in front of the main jet), and push a wire through all the holes (some have one hole, some have side holes as well) I use a single strand from a large metal brush, just the right size and strength to go into the jet. While the jet is out, put the carb spray straw into the jet hole and spray it out, you should see some liquid come out in the carb body port. Once that is all cleaned out, it should idle. dying when you give it gas is typical of not having an idle circuit open, sucks in too much air when you open the throttle, and dies. as far as the noise, could be loose valves, probably needs the clearance set on a quad that old.

 

I re-cleaned the carb and put in a new plug. Seems to be running good now. As far as the valves, is that something I should take to the shop? I'm relatively mechanically inclined, never done it on a four wheeler.

 

A 20 dollar Clymer manual will save you lots of trips to the dealer, setting the valves is not hard, as long as you know how to get it on TDC (top dead center) by removing the inspection plug and the side plug and using a socket to manually turn the motor over to line up the "T" mark on the flywheel. Do this without the sparkplug in, turns much easier that way, you will know when you are at TDC, both rocker arms will be relaxed and ready for adjustment. For Yammys, usually around .004 for intake and .006 for exhaust.