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Too much air?

376 Views 17 Replies 5 Participants Last post by  MagnoliaHunter
2006 Rhino 660
I replaced the entire top end of the engine as well as the carb.
I also put in a high-flo fuel pump and a new filter
It starts and runs but is choppy. It smooths out if I put my hand over the air intake.
I checked and rechecked the valve adjustments.
Any thoughts or ideas on what might be going on?
When putting it back together, I was careful with the timing but could it be slightly off?
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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.

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
No. Same hot or cold. I checked the carb. I then switch it out for a new one and same thing
Okay how is the exhaust system? Is there any damage at all that would cause a flow issue?
You say you put a new carb on did you check the fuel/float level? Somthing like the image I posted?

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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.
Thank you!
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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?
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