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Discussion Starter · #1 ·
ok so every since i bought my 91 kx 250 iv had a harder then hell of a time to get it to run everytime ... it got a new topend maybe 2 hours on it now after the whole summer but befor i bought it it was bored out ... it got stock pipe and stock silencer off a 03. im assuming that the guy that owned it tryed to jet it him self and F*&$^@&^@* it hard!!! ... i got a 155 main jet and a 58 piolt. im thinking it should be a 165 and 48 .... whould this cause no start or very very hard start??? the air/fuel is 2 turns out and my needle clip is on the 3rd slot.. got lots of spark and the engine do get gas but it wont run. it ran last night no problems after a while ... it feels good power wise on the bottom end but gets boggy around the top.
 

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They generally like to be rich for a cold start, but if the plugs always wet and oily, its rich sounding all the time.

What gas/oil mix are you running?
 

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Discussion Starter · #7 ·
And its for sure got good compression, and it passed a leak down test, so the crank seals etc are good.
lots of compression .. i checked it out befor i rode it last and it got 220psi .. got a hi compression piston and bored .010 .... all new gaskets so i dout theirs any leaks anywhere .. the rubber boots look new on the carb ... noo 100% on the crank seals i have new ones here but im not shure if they were replaced when the guy i bought it off had the motor done
 

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lots of compression .. i checked it out befor i rode it last and it got 220psi .. got a hi compression piston and bored .010 .... all new gaskets so i dout theirs any leaks anywhere .. the rubber boots look new on the carb ... noo 100% on the crank seals i have new ones here but im not shure if they were replaced when the guy i bought it off had the motor done
Was the bottom end done, or just the top end.
 

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Discussion Starter · #9 ·
Was the bottom end done, or just the top end.
he orgional owner never told me he just said he brought to brians (one of the bust moto engine builders around here) and had the engine "done" so i dont know to what extent .... is thier a step by step online anywhere to changing the crank seal? i dont mind replacing it even if it is good justto have a frese one to narrow stuff down
 

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he orgional owner never told me he just said he brought to brians (one of the bust moto engine builders around here) and had the engine "done" so i dont know to what extent .... is thier a step by step online anywhere to changing the crank seal? i dont mind replacing it even if it is good justto have a frese one to narrow stuff down
Why not call the shop that did it and ask if they did the crank seals.
Shops keep a record of work done to a bike, or at least should.

Its not just a 5 minute job to change them.
 

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Discussion Starter · #11 ·
Why not call the shop that did it and ask if they did the crank seals.
Shops keep a record of work done to a bike, or at least should.

Its not just a 5 minute job to change them.
yeah ill give them a ring ... have to be tomorrow tho .. they closed about 30 mins ago. im not worried about how long or "hard" it could be just havent changed a crank seal on one of these bikes .. didnt know how complicated it is for it
 

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lots of compression .. i checked it out befor i rode it last and it got 220psi .. got a hi compression piston and bored .010 .... all new gaskets so i dout theirs any leaks anywhere .. the rubber boots look new on the carb ... noo 100% on the crank seals i have new ones here but im not shure if they were replaced when the guy i bought it off had the motor done
220 psi is a LOT of compression ! If you are running pump fuel, that right there might be your problem (detonation). You should try 100% race fuel like VP C12, or CAM II,

My KX500 with the optional .02 mm thinner head gasket puts out 170 psi.

If your ambient ait temps are in the 40's and 50's F , I would put the jetting back to stock (160 main) for the colder months.
 

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Discussion Starter · #13 ·
i was out in the garage tonight .... and befor trying to start it i warmed the engine up for a short while with a heater (used to have to do that on my thunder cat 900) nad it made a offer to go .. it would idel for a second or 2 and shut off again .. it did it about 6 times only 2 or 3 kicks each time ... double checked my compression and it was 210psi not 220psi .. and as far as race gas im going to have to ask around to find out where to get that stuff at ... i think the closes place is 100kms away
 
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