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Discussion Starter #1
Hello, I recently bought a 01 trx250 and it runs great, there is one problem though and for being a "bullet proof" Machine I expect it to jump. When I jump the atv sometimes it will bog down and just stall when given gas. It doesn't fix itself by letting it sit off, and it usually doesn't fix when its just idling for a while. There are a few things that will fix it but they work less and less as they are used, adjusting the spark plug, adjusting the idle screw and, putting it in neutral and revving it until it revs up. I have looked all over online and have found people with similar problems, but theirs would usually bog down after some rough terrain also, mine doesn't it only does it on medium sized jumps. I originally thought it was the spark plug, but after replacing it I figured out that it is not. There is some crap in the gas tank but since the bogging down happens immediately I figured that it couldn't be that.

I just bought this recently from a owner who said they have rebuilt the engine, and the radiator isn't hooked up to the engine and there isnt a spot for it to hook up, you may think that it would be cooling then. Its not cooling as it happens after I let the atv sit off for hours then hit a jump right away.

Thats all thanks for your time, If you figure it out that would help me so much.
 

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First off - it (and no other ATV is) made for 'jumping' and doing so will ultimately damage the suspension (bend wheels, axles, break the u-joint and possibly rear axle bearings), but I understand your enthusiasm for a thrill. Just be aware that it will break and be prepared for the cost.

Bogging is always a fuel/air problem - when you open the throttle you are giving it air (not gas unless you consider air as gas) and bogging is usually an indication of air without sufficient fuel to support combustion, but since it happens only on jumping, you need to be more specific - does it bog on leaving the ground, in flight or upon landing and if upon landing is it upon touchdown or a distance after landing?

Now the radiator is only an oil cooler, but it's full flow and an integral part of the system - how was it not connected and no connections on the engine?

So your bogging problem is probably not heat related. In most cases there is no fuel being mixed with the air let in through the throttle due to an insufficient level of fuel in the carburetor float bowl which is usually caused by a blockage to air entering the fuel tank or a blockage of air escaping the float bowl as it fill with fuel, but in some cases the bog occurs upon landing which causes an excess of fuel to slosh out of the float bowl flooding the engine. Usually if it fuel slosh, the engine stumbles, bogs and eventually clears out and runs normally again until the next jump. If it bogs badly enough to die, it will restart using flooded engine starting technique. If it is a lack of fuel, try starting using choke or starting fluid - if it restarts either way (whether it stays running or not), you need to check the venting and fuel delivery from the fuel tank to carb. A kinked or pinched fuel line, clogged filter or obstructed float needle valve in the carb could be possible causes.

If you would be kind enough, please give me the VIN from the frame and the engine serial number.
 

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Discussion Starter #3
Upon landing and its right away not after a distance, its only when the back end hits the ground. And yes I do understand the costs Im not worried as the back axel was bent when I bought it so I am going to replace it anyways
 

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First off - it (and no other ATV is) made for 'jumping' and doing so will ultimately damage the suspension (bend wheels, axles, break the u-joint and possibly rear axle bearings), but I understand your enthusiasm for a thrill. Just be aware that it will break and be prepared for the cost.

Bogging is always a fuel/air problem - when you open the throttle you are giving it air (not gas unless you consider air as gas) and bogging is usually an indication of air without sufficient fuel to support combustion, but since it happens only on jumping, you need to be more specific - does it bog on leaving the ground, in flight or upon landing and if upon landing is it upon touchdown or a distance after landing?

Now the radiator is only an oil cooler, but it's full flow and an integral part of the system - how was it not connected and no connections on the engine?

So your bogging problem is probably not heat related. In most cases there is no fuel being mixed with the air let in through the throttle due to an insufficient level of fuel in the carburetor float bowl which is usually caused by a blockage to air entering the fuel tank or a blockage of air escaping the float bowl as it fill with fuel, but in some cases the bog occurs upon landing which causes an excess of fuel to slosh out of the float bowl flooding the engine. Usually if it fuel slosh, the engine stumbles, bogs and eventually clears out and runs normally again until the next jump. If it bogs badly enough to die, it will restart using flooded engine starting technique. If it is a lack of fuel, try starting using choke or starting fluid - if it restarts either way (whether it stays running or not), you need to check the venting and fuel delivery from the fuel tank to carb. A kinked or pinched fuel line, clogged filter or obstructed float needle valve in the carb could be possible causes.

If you would be kind enough, please give me the VIN from the frame and the engine serial number.
Also I don't feel comfortable posting the VIN on a public forum but what I assume to be the engine serial(All I could find ) was HM8-1
 

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I under your comfort level, so I sent you a private message - as a moderator, I can edit your post (add to or remove) something if you cannot and I can delete or hide your post if necessary.

Based on the HM8, I'm guessing the EX you have has a Recon engine instead of the EX engine - EX was HN6 casting - it may make a difference when trying to buy parts.

Here's the location of the numbers
4320
 

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The frame is a 2001 TRX250EX - the engine is a 2001 TRX250 Recon - not much difference, but the Recon did not have an oil cooler.

Engine crankcase is the same - only difference is the front crankcase cover - change the cover and you can connect the oil cooler, but that will not affect the bogging. You will need to determine if it is losing spark or if it is a fuel issue.
 

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Discussion Starter #7
Its not spark it idles great and starts right up, and the spark plug is new, so it must be fuel
 

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Im going up north this weekend so I can check it out. Anything else I should do besides cleaning the carb?
 
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