I searched the forums to no avail...

I just bought this quad about a week ago. I am pretty mechanical and technically inclined, however I know nothing about this thing yet. I do have the service manual though.

Now to the main problem: The best I can explain it is that it sputters at full throttle. You can actually let off of the throttle to about half-way and it goes faster. Also, when I first got the quad, it only had this problem every now and then. Now it does it at every full throttle press.

Let me tell you what I know about it, which ain't much... It has been pretty well modified. I can't compare it to stock since I haven't been on a scrambler in years. When it takes the gas, it screams. It has a different higher performance head and piston (top end just rebuilt), a clutch kit, pipe, reed, and several other mods that he told me about.

I know nothing about this thing or where to start. I'm guessing it has something to do with fuel intake. I changed the fuel filter but it didn't seem to make a difference. I ran in totally out of fuel and put a fresh tank in. I am running 87 octane, surely that can't be it.

Any ideas where to start? Thanks for your input.

 

http://forums.atvconnection.co...tid/11/threadid/544885
No definitive answers about sputtering quads yet. Welcome to the forum Willie.

 

First check the air filter and the air intake tube to be sure the tube isnt colapsing(should have a wire or spring in it to hold it open.Next take the secondary clutch apart and check the ramps.Be sure to preload it the right direction.
Next unplug(it should be the black wire )on the rev limiter.

 

When you are on WOT, try applying the choke ever so slightly. This will check for a lean condition on top. If it clears up you know it is lean.

 

Thanks jumbofrank. I saw that thread but it didn't seem to have a solution, plus I was guessing the 450 may have been a 4-stroke.

I will try drlang's first since it's the easiest, lol. If that doesn't work I'll move to ftwlh's or other suggestions. Thanks a million guys. I've got some experienced Polaris mechanics lined up but until then I'll play around with it.

 

You're right Willie, that is a 4-stroke. Maybe something else causes sputtering on each type of engine.

 

Tried pulling the choke with WOT. No go, just started to die.

Could be already be to rich?

I've got an Polaris expereinced friend looking at it Weds so I'll let you guys know what the prob is.

 

same thing happened on my explorer...some things to try:

check the drain bolt on the bottom of the carb...leaking or a hole in the bottom from vibration

choke sticking- follow line till you find the boot , slide back and try adjusting

clogged exhaust or air filter...try short runs with no air filter..muffler should have clean out holes
hope this helps....................

 

I never even thought about the muffler before. Take out the clean-out plug. It can be REALLY stubborn on old machines. If you have to, use penetrating oil and a pipe wrench. If you wreck it don't worry. It's just a bolt that you can get from the hardware store. Crank up the quad and rev the engine up several times to blow out all the soot that the spark arrestor has been catching, maybe for the last 11 years. Shut it off and put the plug back in.

 

Hey i just got a 2000 scrambler400 2x4, the top light cover is missing i was wondering if you knew what is was supposed to be? the oil netural and reverse lights are there. the actual light works bit there is no symbol on it to tell me what it is. any ideas?