No fuel on top end

[sjc115]

The last time I ran my quad it started acting up at the end of the day. I cleaned the carb and changed the plug and it is still doing the same thing.

Here was/is the problem: The quad starts and runs (although the idle surges) and transitions pretty good through 1/2 throttle. When pinned to full throttle it acts like it is not getting any gas. If you back off the throttle a little bit the revs come back and it runs okay.

It's not jetting, because the carb has had the same jetting for 1-1/2 years before this problem arose. It used ran great. Nice low reliable idle, good tranistion and top end. It did not backfire, skip or pop anywhere in the throttle range.

I am out of ideas on what could be wrong. When I cleaned the carb I found no dirt and all of the vents/passages were clear (the best I could tell by spraying carb cleaner in them).

Please help! Any ideas are welcome.

[stevo3176]

DId you clean the jets and make sure they didn't have any thing in them? Also the stator maybe on its way out?

[sjc115]

Yes, I cleaned the jets and all the passages in side the carb. I found nothing.

How do I check the stator?

[cals400ex]

check to make sure none of the jets fell out along with the needle assembly

[sjc115]

All the jets are the, as is the needle.

try cleaning your filter and make sure there arent ne places for air to leak in ( are all the carb boots tight) what did your plug look like when you took it out

[sjc115]

The filter is clean. As for the seals on the carb, they are pretty old. Maybe my next step should be to replace all the seals and see what happens.

The plug was pretty black, but I'm thinking the blackness might be a resut of whatever the real problem is. I don't know.

[sjc115]

Could it be a carb float issue? If so, how could i determine if the float is bad? The float did move freely and was in adjustment according to the manual I have (haynes, chilton, clymer, i can't remember who's manual it is).

[bwamos]

Textbook symptom of a Lean Mainjet.

Put your airbox lid back on and see if it still does it. Or if lid is already on.. turn on your choke to the 1/4 notch.

I'm betting you need to go a couple sizes up on your main jet.

Worse case you may have an air leak at the intake boot between the carb and engine, or your o-ring on the Carb lid is out of place or torn.

Either of those 2 would make you idle very high also.

Most likley you just need a richer main jet.

[sjc115]

I don't think it is the jet, because it ran fine all day then just started doing that out of the blue.

I will check for air leaks, as the seals on the carb are very old. But it does have the same symtoms of a main jet problem. My first thought was a clogged main jet, but that was not the case. I will definitely be changing the carb gaskets.

Thanks for all the ideas guys, if you have any more suggestions keep them coming.

Thanks!