04 Grizzly 660 Carb Problems!

[lmbrjack25]

I come here all of the time for advice on my Grizzly. I have never had to post anything because the answer is always somewhere here in this forum. This time I can’t find exactly what I am looking for. So, here is what I got. I have an 04 660 Grizzly. When I bought it, it had an aftermarket pipe on it that was very loud. Since I bought it for hunting, the loud exhaust was not very practical for me. When I bought it, the stock exhaust came with it so I put it back on. The carburetor had been jetted for the aftermarket pipe but I just left it that way. It still ran good but just a little rich. Over the summer I didn’t ride my grizz much and when hunting season came around the carburetor was gummed up. I thought that since I was going to pull it off to clean it, that this would be a great time to put the factory jets back in. I ordered a stock jet kit and put it in after cleaning the carb. Here is where my trouble started. When I put everything back together and turned the gas on fuel started coming out of the overflow tube after only a few seconds. I tapped on the bowl but it still kept coming. I pulled the carb off and adjusted the floats to the factory setting and put it back on. Problem solved, no more overflow. I put the choke on and started it up. After about 10-15 seconds I turned the choke off and it sat there and idled great. I put it in gear and as I started to take off it spit and sputtered and quit. I started it back up and let it idle a minute and it was fine. I tried to take off and it sputtered and backfired and quit again. The next time I tried this, as I was trying to take off I pulled the choke about a third of the way on and kind of “feathered” the throttle and it started to go. As long as I stayed “in the throttle” in ran great. As soon as I would let out of the throttle and just try to maintain my speed it would start backfiring and sputtering terribly. If I got back into the throttle easy and then continued accelerating it ran great again. When I would let off I got the same thing again. Also, when I would come to a stop, if I didn’t turn the choke back off, it would quit. So here is what I have. It only idles with the choke off. It will only accelerate with the choke about a third of the way on. If you are trying to maintain a speed and not accelerate it backfires and spits and sputters terribly. If you try to accelerate without the choke it backfires and sputters. Any ideas?

[Delbert]

I read your problems twice and I might know the answer(s). You didn't readjust the air/fuel mixture screw after replacing everything back to factory stock. At least I didn't see this in your comments.
Recheck to be sure there's NO vacuum lines disconnected, all hose clamps tight on intake, as these will have an immediate lean-condition on carburator, even though it idles fine. Also cracked vacuum lines could cause same problems. Any rubber intake manifold carburator attachments could also have a crack in them. Take some WD-40 and some clean rags to cover up what you don't want to get sprayed, and when ATV is idling, spray around carburator and it's intake assembly to see if there's any difference in idling quality or RPM's raise, and note where you're spraying, as this will be where it's leaking and causing lean condition.
Did you readjust the jet metering rod back to it's proper setting? There's so much that could be the cause, that you may need to go back through all the steps of carburator rebuilding again to make sure you don't have any crud in one of the jet or air passage holes. Of course, always try the easiest things first. Good Luck, I hope you get it sorted out quickly.
Del

[CodyT]

Did you ever figure out the problem. My buddy's 04 grizzly is doing the same thing he only uses it at hunting time the carb was all gummed up we rebuilt it no leak out the bowl no adjustment of the air/fuel screw and we don't know

[Trikemaster]

Whether your bike is air or water cooled, you should start it and get it up to race temperature before tuning the pilot circuit. A hotter engine will run leaner than an old one, so failure to properly warm the bike will result in a too-rich setting. With the bike up to temp, adjust the airscrew so that the bike runs and responds best to slight throttle movements. Now, kill the motor and see how many turns out you have on the airscrew. Less than one, and your pilot is too lean. More than two, and it's too rich. Install the next-size pilot and repeat the test.

Your engine is basically an air pump, and your carb meters how much air and fuel are sucked into that pump. Even though they may differ wildly in size, shape and design, all four-stroke carburetors have the same basic parts or circuits. Your slide cutaway (or throttle valve) needle and needle jet will all affect your bike's acceleration from one-quarter to three-quarters throttle, and this is the most important area for off-road riders, since we spend the most time at these throttle settings. Due to the hassle of making changes to these circuits, these are the most neglected areas of tuning. Too rich jetting (too much cutaway, needle positions too high, too large a needle jet) can make your bike lunge and hard to control. If it's too lean in this area, the bike will feel really flat and down on power, but will respond quickly to changes in throttle position. It may detonate (ping) under a load too. Pinging can also be caused by too little octane or winterized fuel (oxygenated, blended with additives), so keep in mind any fuel changes if your bike suddenly starts detonating in otherwise "normal" conditions.

Your main jet is probably the most talked-about circuit,and it's as critical to get it right on a four-stroke as with a two-stroke. The main kicks in at half throttle and takes over metering duties as you hit full throttle. If your main is too rich, the bike will sputter and surge as it tries to burn all of that fuel. Too lean, and the bike will run flat or have a flat spot in the powerband. A severely lean main will cause your bike to seize just like a two-stroke. It's better to be slightly rich on the main than slightly lean, because it will run cooler.