Ever since I got my 04 Bruin 350 4x2, it's had this issue. I was hoping it was bad gas from sitting for a little bit before I got it, but now even after getting that gas out and giving it a fresh tank and a little seafoam, it's still happening.

Doesn't matter if you're in neutral and sitting still, or in gear trying to gain speed, but if you give it more than about 1/3 throttle it spits and sputters. When in neutral, it WILL actually try to gain RPM's, spitting and sputtering the whole way there, but it will gain some RPMs, to a point it seems anyway. But if you're in gear and moving forward, it just refuses to get going much faster than maybe 20-25mph, as it starts loosing power as soon as it starts sputtering, and holding it wide open makes it just fall on it's face...

Last weekend I pulled the accelerator pump off the side of the carb just because it was easy to get to... Didn't see anything abnormal, no tares in the diaphragm and the actuation of it seemed smooth and normal, so I think I can rule that out. Nothing seemed to change after pulling it off and reinstalling it. I tried to spray some starter fluid around the intake both where the carb mounts to it and where it mounts to the head as it was running, to see if there was any RPM or running change that would indicate an air leak after the carb, but that lead nowhere as there seemed to be no change. I also played with the choke attachment, making sure that it was going fully open when it was suppose to, and that seems to be working like it should as well.

What's the next logical step, pull the carb and give it a good thorough cleaning? The carb looks fairly clean from the outside, almost like new, and the guy I bought it from told me that he actually replaced it not long ago (with no mention of this running issue of course...), but who knows... it looks like it's a PITA to get off the quad...


Thanks!

 

Give it a new plug and check the voltage at the battery with engine running, make sure it doesn't go over 14.5v. If it is still spluttering clean the carb out. I rarely take them off. Get it out of intake and airbox boot, and turn sideways so you can undo the float bowl. Remove the jets inside and blow them, and the holes they came from out with compressed air. Check you can see through them, and replace. Clean float bowl, checking for water and dirt in the bottom, if there is, you may well get more problems as some dirt/water will still be in the tank.

 

Will do.

What's the deal with the possibility of the voltage being over 14.5v? I've read that somewhere else, just curious.

Thank you!

 

New spark plug, nothing changed.

Voltage stays 14.3 - 14.4 when running, either at idle or with RPM.

Completely pulled the carb off and blew it apart. There was a little junk inside, so I had high hopes for just cleaning it out and putting it back on, but afterwards it's still doing the same thing.

I ordered a cheap $20 CDI replacement, should be here by this weekend hopefully, and I'll toss that on and see if anything changes. If that changes nothing, I may try the coil next after that.

What's the chance it's jumped a timing tooth? I've seen references to that on other threads about other bikes, but how common is that really? And would it start right up, idle fine, and still run great up to that 1/3 throttle input if it jumped timing?

 

If it helps, here's a video I shot of it "doing it's thing"

Note, this is before I pulled the carb apart, but it still does the exact same thing after the carb cleaning.


https://youtu.be/vPT5wRjY6OY

 

Well, you have the choke on all the time, so it isn't going to run right.

 

Okay I'm going to feel really stupid... But choke isn't full right on the lever? Full left isn't choke off?

 

Wow, yep I feel retarded...

This is what happens when it's your first quad and you don't have a manual with it lmao

Guess I'll try running it WITHOUT the choke and see what happens... I'll report back, hopefully with good news lol

 

Well it wasn't that simple unfortunately... Now that I know I have the choke completely off and open... It's still doing the exact same thing, no change what so ever. I'm still hoping for it being just the CDI box...

 

I'm having a similar issue on my Suzuki. Starts and idles great, runs great to about 1/4 throttle, then falls on its face at anything higher. When I describe it and showed a video to three of my buddies independently, all three said it sounds like the float is set too low. It's a pita to get my carb off so I have not checked it yet, but following in case you get yours solved first...