I'm stumped....need help

[Jonesy]

OK my dad has a 1993 300ex, we put a high compression piston in it about a year and a half ago, soon after we decided to tear it down to the frame and paint everything to get rid of the horrible paint job the previous owner had done. I stripped everything off, motor was complete, wiring was complete. We finally got it back together in our spare time and tried to start it up. It would only rev up to about 1/4 throttle before it would spit and sputter really bad. I thought it was some dirt or build up in the carb so i took it off and put it in the ultrasonic cleaner, and nothing changed, so we changed carb, and nothing. We changed the entire wiring harness and nothing changed. Changed the stator and nothing. Tried playing with the clip and a few main jets we had laying around (145 was in it, put a 135 in it) nothing changed a bit. Tried with and without airbox lid, and nothing.

So i'm running out of ideas as to what to do. No matter what we do it doesn't change the way it runs in the slightest. The timing is spot on and the valves are adjusted correctly. We are stumped b/c it ran great before we took everything off the bike. The only mods the bike has is a 1 over high comp piston, and an uni air filter.

any and all help would be greatly appreciated

Thanks
Jonesy

[wantinga400ex]

Make sure your grounding to the frame. Probably since you painted the frame your not getting a good connection.

[JDiablo]

when i did my winter rebuild and then put it back toghter i couldnt start it,i thought i f'kd suttin up...but my uncle came to help me push start it....and thats what is was...started fluid didn't even work...and i just let it ran for a good 10 mins and it starts right up everytime...just prolly a lil crusty from not running in awhile....push start it in second and pop the clutch and you will get it going

[Jonesy]

The quad starts up and runs, but only up to about 1/4 throttle before it starts spitting and sputtering really bad.

I may try and throw a huge jet in there to see if it makes any difference at all.

Any other help would be appreaciated

Jonesy

[wilkin250r]

If it's spitting and sputtering, it sounds like the jetting is really rich.

[cals400ex]

you should probably take off the carb first and clean the heck out of it with carb cleaner. also, i assume you accidently don't have the choke on half way?

[TheFontMaster]

Make shure the pipe is on tight and the gas hose to the carb isnt blocked.

[HondaMan222]

long long long time ago i had a warrior and i snaped the parking brike bolt off on the rear brake, and it would run fine till about 1/4 throttle, so that could be a problem

[diesel-mech]

Don't they have a low rpm rev limiter for reverse? Is it built into the cdi? Just a shot in the dark but you don't have some wires plugged into the wrong spot do you? I agree with the ground problem also. Then again if its a fuel problem it may be that the main jet is plugged so that curcuit of the carb won't function correctly.
Really I have no clue what I'm talking about!!
I hate to ask but you didn't put a rag in the intake to keep dirt out then forget it was there did you?:D

[Cody_300ex]

Does it sound like you are in reverse? Find the two wires from the crankcase right above the brake pedal one is green and the other is a off white. You will have to take a little black cover off to see them. Now that you have found them follow them up to a little cluster of wires and make sure they are pluged in.

[Quad Dude]

i am having pretty much the exact same problem with my 300 that i put a wiseco high compression piston in and i tried every possible valve adujustment and i only gets worse or stays the same, and i have put a 152 main jet in and its all the same. and when i asked some one on the forums they told me to go one clip down on the needle but i dont know how to do it exactly

hope u have better luck than me.

[quadrider400]

Just wondering if it could be the CDI either not plugged in or just gone bad..... best idea I could come up with on short notice...:confused:

[cals400ex]

Originally posted by Quad Dude
i am having pretty much the exact same problem with my 300 that i put a wiseco high compression piston in and i tried every possible valve adujustment and i only gets worse or stays the same, and i have put a 152 main jet in and its all the same. and when i asked some one on the forums they told me to go one clip down on the needle but i dont know how to do it exactly

hope u have better luck than me.


a 152 seems way too big unless you have way more work than a high compression piston and cam.

[Jonesy]

Update:

This weekend i took the carb off and cleaned it really good, messed with different main jet sizes, and messed with the clip position. Nothing seemed to help. I took the carb off of my stock 300ex and put on and nothing changed. Changed the cdi and checked all the grounds that i could find. The reverse wires are cut off because we rigged the reverse mechanism so that we don't have to pushe the button on the clutch lever. and the wires coming out of the case are cut and taped up good.

I bought a few smaller jets for it to see if it helps any. Any other suggestions would be helpful

Thanks

[s-10s_rule]

I would make sure all the grounds are really good first. Second the big main connector in front of the motor seems to be bad about getting a bad connection so I would check that too. Finally make sure that the petcock on the gastank is flowing good, they can and will get junk in them cutting off fuel flow, just try taking the fuel line off of the carb and turning your gas on. Make sure that the fuel is flowing out freely if it isnt, check the petcock and your gas cap to see if either of them are not flowing properly. Thats my advise. Also if you flipped the motor around a little when you had it off you could have made the decompressor on the cam stick on, that happens with 400exs but I dont know about your 300. Just trying to think of anything, good luck!

[s-10s_rule]

Oh yeah, see if a friend will let you swap out cdi boxes just in case that is the problem.;)

[quadrider400]

Just a thought ... had a friend with a Raptor.... the valve in the line at the fuel cap went bad and would not allow air in ....so no fuel would flow... if you find a decreased flow out of the carb try it with either the cap off or the hose off......

good luck... let us know ya got me wondering...