I know it sounds absurd, most unlikely, but:

Contaminated fuel, e.g., moisture in the float bowl, can cause your problem.

Moisture can enter a fuel tank, just from condensation from daily temperature changes (you don't have to cross the Mississippi River or leave your quad outside during a downpour). Sounds like your quad's been laid up for modifications for a spell; a good opportunity for gas to "go bad."

Moisture settles in the bottom of the float bowl of your carburetor; the pilot jet permits normal operation at low throttle openings by providing dry fuel from a higher layer in the float bowl, but: when you open up the throttle, fuel flows from the main jet, the lowest jet in the carburetor, contaminated fuel (moisture) flows from the bottom of the float bowl, and the engine sputters and misfires, producing very little power.

Drain your fuel tank (from the RESERVE position of the petcock), drain your carburetor (from the dump screw or by removing the float bowl). (Notice how freely the fuel flows from the tank petcock; make sure it isn't clogged; make sure you fuel lines are open; check and see if you get a steady flow from the dump tube of the float bowl. If any of these answers are "no," you need to clean out whatever is clogged in the fuel supply system).

Replace with absolutely righteous and dry gasoline; add some fuel conditioner and stabilizer as a precaution if you like.

Then try it! So far, you've made the easiest check and eliminated the most likely cause of power loss at high throttle openings.

If no help, check the float level; if that's not the problem, clean the carburetor! If merely spraying joy-juice doesn't do the trick; disassemble the carb, checking all adjustments and cleaning and inspecting all components, with special attention to the main jet/air tube/needle jet/ needle (the components involved in the high-speed fuel circuit).

These suggestions, inexpensive and relatively easy, eliminate several possible causes of your problem. Good luck!

Tree Farmer

 

Ijust went through my top end on my LT 250R new Boyesen reeds, a new wiseco piston,ported and polished, and an FMF pipe and silencer. It cranked right up but has no power. It idles and runs great until I kick it in geat, then it runs like my soms LT 80.
I ran it wide open in 4th then killed it and took out the plug it looks clean and dark brown. what could be wrong?

Clark

 

I thought of that too but my carb is just about 3 weks old and worked great last week. I drained the tank and cleaned the fuel filter when i did the overhaul. I may have to take the top end back off and see if I am losing compession.

Finally i found my problem I was losing compession one of my head bolts was loose the heli coil threads had not held. a drill and hew threads and I am running now
Thanks brent

[This message has been edited by Clark (edited 08-17-1999).]