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OT: ATV starving (???) when hot.

A

Anonymous-0

Well-known Member
Hey folks,
My quad is a little under the weather. Wasn't doing worth a dam last fall and I bought a new carb off ebay that did the trick. FF to the last couple of days and it starts and runs fine until It gets good and warm and I stop. Then, when I try to take off again, it acts like it's running out of gas for about long enough for me to look like an idiot and folks to rubberneck, then takes off again and repeats step 1. The air intake was close to the exhaust so I rerouted it, fuel filter is new and the gas cap is vented. Choke works like it should. It's a chinese quad but it has a yamaha 250 4 stroke air cooled motor the whole thing is just a renamed Yamaha Bruin or Bear Tracker. Any idea how I can get passed this glitch? Could it be spark related and not fuel?

Thanks for any help,


Dave
 
Make sure it has good fuel flow to the carb. Also when it only does it warm it could be tight valves and need to be set.
 
(quoted from post at 02:35:25 03/20/09) Make sure it has good fuel flow to the carb. Also when it only does it warm it could be tight valves and need to be set.
Click to expand...

Thanks! The fuel flow is good TO the carb. It only does the starving routine a few seconds then is fine again until you stop and try to take off again (a few seconds then fine again, etc). Could it be vapor locking a little, or would that act different?

Dave
 
Check the timing, I can do that if it's not advancing, very common with any engine upon take off.

It could also be the ignition module or coil.
 
(quoted from post at 03:37:20 03/20/09) Check the timing, I can do that if it's not advancing, very common with any engine upon take off.

It could also be the ignition module or coil.
Click to expand...

Timing cannot be adjusted, but I checked it before replacing the carb last fall and it was OK. Would the module or coill make it act like that also? I had a MC a long time ago that ran like a striped a$$ed ape and would drop to half or less power, crawl for awhile then go back to normal.... Never new what it was, it just quit doing it after a while.

Thanks, Dave
 
Mine would do the same thing in the summer. Finally traced it to ethanol fuel. Started using straight unleaded fuel and it stopped the problem.
 
Vapor Lock? Ethanol added fuel? Try 91 Octane Fuel. It's all I ever use.No problems.My Stable-'01 500 Polaris Sportsman-01 Polaris 250 - 07 Arctic Cat 500.Based in Arizona.JC
 
It probably is the ethanol content or carb problem but once I had a set of [hypalon]plug wires that failed when hot on a motorcycle.There is a spark tester that you can put in line with your wires place at plug first then if it shows weakness go directly out of coil and if spark stays strong junk the wires.[Only problem is jap bikes have wire molded to coil]
 
my experience with two strokes is when you havve a problem change the plug first!could be the fuel,ive always heard to never run ethanol in two strokes but that could be bs.
 
I would also suggest changing the plug. Might not be the plug, but you never know...
What I would seriously suspect is H2O. The jetting in those carbs is so small it doesn't take much to plug one. We had a 300 Honda that gave us fits like that until I got the last of the water out of the tank. The only thing to do with that carb was break it down completly and blow it out with compressed air.

If you have the bike I'm thinking of, I've seen them around here with teh Baja name on them. Chink all the way, but they very closely resemble the old Yamaha YFM225 (Moto 4). We had a pair of them. They remain the toughest and most reliable bikes we ever owned. We've had a couple Honda's since and now have a CanAm Outlander and none were near the bike that the old Yamaha was...
We worked those things hard on farm work, then we beat the snot out of them bombing around. It took the better part of 15 years to kill them.
I miss the old Yamabomber...

Rod
 

I use super unleaded in it. It set for a couple of months with a half tank of fuel and some drastic temp changes so water is very likely. Kinda makes more sense than anything else sense someone mentioned it. I'll check the spark also because I suspected a weak spark in the past.
What if I was to hook up a VW coil that I have laying in the shop? Would it work, or cause damage? A spark is a spark isn't it?

Thanks, Dave
 
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