Quad is sputtering badly, troubleshooters please help!

[leager440]

I ride my quad almost everyday, I have my own track. Sunday afternoon I was riding, had been for a couple of hours, quad running perfect. Suddenly it started to miss occasionally. I put it up because I was done riding and thought nothing of it. Cleaned the air filter, went riding on Monday. My fourwheeler cranks easily, idles perfect, but once you take off it won't even hardly run. Just spits and sputters and misses. If you just rev it up, it is fine until you reach about half throttle, then it is like you are hitting the rev limiter, it sounds exactly like that. I drained the gas, cleaned the carb, put it back together, nothing, still runs the same. My motor is mostly stock, has HRC cam, LRD exhaust. I've had this setup for a year now and never had the first problem. Any insight would be very helpful!!!

[300exOH]

Almost sounds like a main jet issue. It could have worked it's way out.:confused: Or even the float in the carb needs adjusted? Just throwing a couple ideas out there.

[wckedclownz69]

hmm mine did tht it was running perfect then, the next day it ran like crap... wht i found out was my jet fell out in the carb... it was laying in the bowl... put it back in and runs great now

I would also change the plug.

[leager440]

took the carb apart yesterday, cleaned it, everything was tight, I don't think it's a carb issue anymore.

[tar]

This happened to me on my 300ex I know its not the same fourwheeler but all I did is change the spark plug so try that It ran normally after that

[trick250r]

Originally posted by TRX450R_Racer
I would also change the plug.







my thoughts exactly

[Jstbnme]

I'd almost bet the farm on a bad ignition coil. Those symptoms were the same as what I encountered during a race earlier this season. I scratched by head until I wore a bald spot in it, not to mention getting so desperate I took it to my local black hole, I mean dealership, in hopes of finding an answer. After a month and a half at the dealership, it was discovered that the ignition coil was the culprit.

I also have a buddy who just experienced the same exact problem with his YFZ. He purchased a CDI and coil before I found out what was going on. Just for grins, I told him to start with the coil, as it was the cheaper of the two should he desire to return the CDI. Turns out I was right ... although you know those YFZ owners, they don't trust us Honda guys for nothing ... he went ahead and replaced the CDI too.

bad gas? i had thyat problem a couple days ago

[leager440]

Ok, so far this is where I'm at. Changed plug, Cleaned carb, check everything in carb, all is well. Flushed fuel out and replaced with new. I had an extra cdi box laying around, tried it, didn't help. I did a compression test today and it only came up to 75psi. I know the book calls for 108psi, but I'm not sure how low is too low and if what I'm describing could come from low compression. I tore it down to check the valve clearances, but the motor hasn't cooled yet to check them. Here's another thing to note: I was toying around today and pulled my air filter off, I learned a trick a few years ago where if there is something clogged in the carb, sometimes you can put your hand over the intake and pull it off real quick and sometimes get lucky! Well, when I pulled the filter off, it ran better. I could rev it and it didn't seem like it was cutting out. As soon as I would put the filter back on, it ran terrible again. The plug I pulled out was really, really rich looking too. So, any ideas???

[leadfoot_52]

A quad will spit and sputer when it is running rich. did you put the carb back together correctly? what size is the main jet in your carb and are you running with the airbox lid on or off?

[watts16]

What MJ are you running. Sounds rich. I had the same problem with mine.

[USAF Dirtboy]

Ok I have seen this b4 on my friends KFX, so I am not sure if this will apply the same with your 450r. Chack to see if you are on reserve on the gas tank. I know this may sound retarded but it wont hurt to check:)

[leager440]

I jetted the carb and tuned my setup a year and a half ago when I built the quad. I know my setup is right. It didn't start blacking the plug like this until the other day when it started running bad. So something has changed. I haven't tested the coil yet. That will be my next task.

[dirtmomma]

We just had some bogging/sputtering issues w/ our 04' 450R the last time we rode it on the MX track, well we just got it back yesterday from the dealer & they suggested we take off the aftermarket shorty gas vent hose & put a long stock one back on it, well we did & the hubby took it around the track a couple times & it didn't do it anymore?? The shop also cleaned the fuel system out too!!
We NEVER take our stuff to a shop but we just bougth it 5 wks ago & we didn't feel we should have to fix it ALREADY!! They said if it does it anymore to bring it on back

so the moral is haha what kind of gas vent hose do you have on your gas cap?? I know I know it sounds crazy :rolleyes:

[leager440]

well, I did think of that actually, I do have a short hose on it, but I tried running it both ways the other day and it didn't make a difference. Thanks for the info though!

[MR.BIG]

Sounds like its time to rebuild it. Maybe you stuck a ring or something but its gonna be time to upgrade to a high comp. piston.