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250cc not accelerating when warm

dave2

By dave2
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dave2 Apprentice

dave2

Posted
Posted

Hi folks,

I have a 2005 Chinese quad that is a knockoff of the Yamaha Bruin or Bear Tracker. I bought it used with a couple of headaches that seem to be tied together. Here's the problem and what I've done:

1) wouldn't start with the electric start but would start with the 1st pull of the rope.

(replaced plug, drained and put in fresh gas) Started better with rope and would run fine and randomly shut off when you stop and be hard to start.

Bought a new chinese 250 cc ATV carb from ebay for about 50 bucks, installed it and it starts 1st pull and every now and then w/ the electric start.

2)

Ran fine a while, now, after it warms up, it runs fine as long as you stay on the throttle, but when stopped is real hard to take off again for a few seconds. Backfires threw the carb and chokes out when you try to accelerate but takes off and runs fine until you stop and try to take off again.

Any suggestions on how I can get this thing dependable again would be appreciated.

Thanks, Dave

outlander560 Mentor

outlander560

Posted
Posted

welcome to quadcrazy Dave... at first it sounded like ur jets were clogged but since u changed the carb it kinda sounds like ur carb is putting in to much gas.. could possibly be that ur jets r to big.. wen at an idle does it sound like it is idleing very fast? idk it sounds like wen ur driving it it is burning off the gas that it needs to keep at the speed but wen ur stopped the carb is still forcing the same amount of gas into the engine kinda drowning the engine causing it to stall.. now im not to good with carbs but if im not mistaken ur float might have something to do with this also

dave2 Apprentice

dave2

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Posted (edited)

Makes sense because it does fine until the choke closes (is no longer needed) and the rich fuel is still flowing in. I'll check it out and clean things up. Thanks for the nudge.

Dave

BTW: It does rev hi for no reason.

Edited by dave2
dave2 Apprentice

dave2

Posted
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Thanks!

The carb from a parts dealer for that vehicle (Jianshe) was about 300 bucks, so I went on ebay and found a carb for a 250 cc chinese ATV with the same measurements on the 2 necks and an electric choke. Installed it and things were peachy for a little while. Now it starts and warms up a little before I can ride it and does just fine for 50 yds or 2 miles (until I stop/get off the throttle) then you have to coax it into taking off again while it sputters and burps through the carb a little while before zooming along to the next stop.

The revving is random at idle and not always. Usually I start it and let it idle a couple minutes before I get on, sometimes the idle speed will climb to what sounds like about half throttle and not slow down until I shut it off and start again and everything is then normal (except for the acceleration problem). I'm thinking that finding a new carb for 50 bucks is like playing lottery and wondering if I should just get another one.

Dave

Ajmboy Grand Master

Ajmboy

Posted
Posted
Thanks!

The carb from a parts dealer for that vehicle (Jianshe) was about 300 bucks, so I went on ebay and found a carb for a 250 cc chinese ATV with the same measurements on the 2 necks and an electric choke. Installed it and things were peachy for a little while. Now it starts and warms up a little before I can ride it and does just fine for 50 yds or 2 miles (until I stop/get off the throttle) then you have to coax it into taking off again while it sputters and burps through the carb a little while before zooming along to the next stop.

The revving is random at idle and not always. Usually I start it and let it idle a couple minutes before I get on, sometimes the idle speed will climb to what sounds like about half throttle and not slow down until I shut it off and start again and everything is then normal (except for the acceleration problem). I'm thinking that finding a new carb for 50 bucks is like playing lottery and wondering if I should just get another one.

Dave

Is the choke working or getting stuck on that thing?

dave2 Apprentice

dave2

Posted
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I guess...... Is there a way to test it besides pulling it out and watching it move (which it does)? I found one like the one I bought and it says it's vacuum operated to eliminate an accelerator pump. My problem isinitial acceleration, could it be that I don't have a vacuum line hooked up or one hooked up wrong? Anyone that has the same setup and can tell me what to look for?

Thanks, Dave

DirtDemon Veteran

DirtDemon

Posted
Posted

Is the choke a butterfly flap that opens and closes? If so, does it rest in the open position? Try disconnecting the electric choke after it warms up, and make sure it stays open. See if that helps.

dave2 Apprentice

dave2

Posted
  • Author
Posted

The choke on this thing is no flap. It's a valve (jet?) that lets in more fuel when it's cold. As soon as it has electric on it, it gradually heats/expands to close the jet. If I take it out or unhook it, the jet won't close and it will be like leaving the choke on.

Dave

Ajmboy Grand Master

Ajmboy

Posted
Posted
The choke on this thing is no flap. It's a valve (jet?) that lets in more fuel when it's cold. As soon as it has electric on it, it gradually heats/expands to close the jet. If I take it out or unhook it, the jet won't close and it will be like leaving the choke on.

Dave

What controls the elctric to it? Is there a temp sensor somewhere?

  • 2 weeks later...
  • 2 weeks later...
dave2 Apprentice

dave2

Posted
  • Author
Posted

Life is good........... Even starts with a bump of the electric starter. Now, I can get to a little cosmetics. Is there something better than fiberglass to work on the fenders (couple cracks and one missing chunk)?

Thanks, Dave

DirtDemon Veteran

DirtDemon

Posted
Posted

The best thing for fenders is new ones. I don't think fiberglass will work very well on plastic fenders. You can drill holes on either side of the cracks and use zip-ties to hold it together for a cheap fix.

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