Too much air?

Air/fuel screw adjustment? I ended up at 2 3/4 turns out and I might need the next size pilot.

Always do the adjustment when it’s good and hot or normal running temperature and run it with lid on.

is it possible it sat long enough to clog the carburetor?

Also check to make sure things aren’t loosening up such as motor mount bolts (I found one missing),make sure the final drive mounts are tight, the drive shaft and anything that will vibrate under a load is tight.

When the muffler mount are screwed up or missing it will vibrate in a bad way.

Thanks for the reply. I appreciate it.
Like I said , it smooths out when I prevent as much air coming in by placing my hand over the air intake (filter snorkel)

Could the timing be off? WOuld that cause the issue?

Does it improve when the engine is good and hot with the lid/console on?

Maybe it’s needs to be jetted. The needle (low to midrange adjustment or the main jet could be clogged. Could be water or dirt in the bottom of the carb too.

Edited
I don’t think ignition timing but who knows right.

Eliminate things one at a time.I would check the entire fuel delivery system. All the way to intake manifold. Make there’s no leaks

No. Same hot or cold. I checked the carb. I then switch it out for a new one and same thing

The exhaust is old but in good condition. Plenty of fuel. I have clear lines so I can see it is getting gas. If I take the exhaust off would it make any difference?

Leave the exhaust on if it looks good. Sounds like you may need to jet the carb. There’s some threads on here about it already if you search. They did a really good job of describing every facet of the rejet process.

Maybe check this too?

04 660 rhino back fire and miss and sputter at mid range

Thank you!

rmdawber said:

Thank you!

Click to expand...

Good luck.👍🏻

tried everything suggested. No luck. It still acts like it is getting too much air

OEM or aftermarket carb?

Stock air intake? Stock exhaust?

I tried both -the OEM carb and the aftermarket (which is new) carb.
Stock air and exhaust.
I am completely baffled!

Spark plug good/bad/correct/gap? CDI box or connections to/from it acting up? Could be electrical. About a year ago on a ride, my 2006 660 started sputtering out of nowhere and I could only limp it back to the parking lot with the choke fully pulled and at about half to three quarter throttle. Turned out my CDI box connections had gotten some funk. Cleaned it all to a spit shine and she was running like new again. Just something else to try/weed out.

Have you checked the intake boot for cracks/air leak?

when you rebuilt the engine, did you go back stock CCs or oversize?