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HELP, 05 kx250f wont kick start, just bump start

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Ok I have my buddys 05 kx250f and this mother is sooooo hard/damn near impossible to start by kick starting it. If you push start it it fires up SUPER easy, you barely even have to push it and pop the clutch and fires instantly. But even when I get it running it wont idle at all, have to keep bliping the throttle. Once its started it runs very very strong though, no flat spots or bogs anywhere.

Heres what the work I did and what I know....

Bike only has about 50 hours on it.

Brand new forged piston/rings. Cylinder is still in great shape and in round

Carb has been taken apart and cleaned twice, no clogged jets.

I just shimmed the valves and they are perfectly in spec

I know the timing is 100% correct

Plug is not brand new but not super old either.

brand new timing chain

brand new hot start cable and im sure its seating all the way

anyone have ANY ideas why this mother would be so hard to start with the kick starter? Yet start so easy when I bump start it?

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You need to take off the cam cover and check if a cam gear has spun on the camshaft. It happens.

The hole in the sprocket should line up perfectly with the hole in the outer lobe. When in TDC the lobes should point up/away from each other equally much.

And recheck timing, 12 dots between the inner marks.

kxfcamtiming.jpg

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I will check it again, this will make it bump start but not kick start? because it seems to run great when it bump starts. and i can get it to kick over when its warm. ill check it either way.

also, what exactly to you mean "The hole in the sprocket should line up perfectly with the hole in the outer lobe" do you mean the big hole in the cam gear itself, right above the timing marks?

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There are 3 slots and 1 hole in the cam sprocket. You can see them in the picture. The hole (which is roughly 6mm in diameter) is used for aligning when pressing the sprocket on to the shaft.

There could also be a problem with the automatic decompression. Check it for function.

decompressor.jpg

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took the cam out n looked at it. seems that the exhaust cam sprocket is spun about 1/2 a tooth or so. Would that cause this problem? Im guessing its time to go shopping for a new cam, any recommendations?

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Usually it slips a bit further than half a tooth, but it might just be a beginning problem.

You don´t need a new cam, the fix is free.

Press the sprocket off, realign, press back on, 2 small spots of weld to keep it from happening again. No biggie.

All bikes have pressfit cam sprockets. The cause of the problem might be assembly tolerances or overheating or cam seizure or something else or a combination. Hard to tell, lol....

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ok well, I adjusted the cam sprocket and it was barely a half tooth off if even. I put it back in and it didnt change anything at all. Same thing still, wont kick when cold, will bump start easy but when the bike is warm it will kick start if i give it a little throttle.

any more ideas?

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my bet would be the fuel screw. and idle. if the slide isnt open it wont pull air in, so thats kinda important. I say its not the engine or exhaust at this point, its wither electric or before the intake of the head...

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There are some things not fully straightened out yet.

Will it idle good after it will start? Or does it get better the warmer the engine gets? If so, the oil could be too thick.

Also the idle could just simply be set too low.

Could also be a fuel screw problem, make sure it has all the parts on in the correct order, it goes on spring - washer - oring. Make sure the tip is not broken off.

And has it always been this way? Or did it come after a rebuild or long time storage or something else?

Or is it just your starting technique?

When you fiddled with the cam, did the decomp seem to be in working order? Did the pin come out to the proper height to be able to push the valve lifter open?

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There are some things not fully straightened out yet.

Will it idle good after it will start? Or does it get better the warmer the engine gets? If so, the oil could be too thick.

Also the idle could just simply be set too low.

Could also be a fuel screw problem, make sure it has all the parts on in the correct order, it goes on spring - washer - oring. Make sure the tip is not broken off.

And has it always been this way? Or did it come after a rebuild or long time storage or something else?

Or is it just your starting technique?

When you fiddled with the cam, did the decomp seem to be in working order? Did the pin come out to the proper height to be able to push the valve lifter open?

It will not idle AT ALL, ive played with the idle adjuster and it doesnt change anything.

The bike is my buddys spare bike and it has only been ridden like twice in the last 18 months. If I recall the last time I did work on it it would not kick start either. As far as my technique I give it a few slow kicks, get it at TDC and kick the crap out of it and repeat until my foot hurts.

The decomp seems to be in good order and moves freely but I did not measure pin height or nothing.

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In your first post you said the carb had been cleaned twice, but maybe the problem is still there.

As for the idle adjuster, remove the wire cover on the right side of the carb and make sure the adjuster pushes the stop for the throttle wheel. It can not idle if the throttle is not held slightly open by the adjuster.

And btw, kicking it too fast will make the decomp stop working. Try to find the proper speed.

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Yah I'm thinking its a carb issue still. I'm going to take it off the bike tomorrow and look it over really good and soak it overnight.

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has it been mentioned possibly low compression? That will make it hard to start via kick starting..

just read that it was a new rebuild..

Ok, has anyone mentioned checking to make sure the fuel screw is in the carb along with if it is.. was the o-ring washer installed right..

it goes o-ring, washer, spring, fuel screw.. if it's not that will cause hard start along with poor idle..

check the neutral switch and wiring.. it will make starting hard.. that and a possible carb issue will add to the no idle..

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Ima tear it apart this week and will double check fuel screw tip n all that jazz. Will do a leakdown test also and report back my findings.

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ok im at my whits end. I completely tore the carb apart and cleaned every part of it, it is 100% clean and good to go and it still wont kick start. Any other ideas guys? Maybe something electrical?

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