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1982 xr250

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http://www.thumpertalk.com/forum/showthread.php?t=500969

go to this post. and answer here if you have an answer.. Thanks

If you dont feel like going theres heres the short story.

got a 1982 honda XR250R..had it rebored .040 over with a higher compression wiseco piston. it has an opened up exhaust, and an opened up airbox. so i got it all together..timed it and everything..wouldnt start..i still had the stock 125 main in the carb. so i got a 130 as suggested by someone on here and it started.. ran for a lil while then made a loud pop and shut off. ..would not start back up. and backfires if i try to start it. could it be that i still have it too lean? or what could cause it? Thanks

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Sounds like you cam chain is one tooth off. Check the valve clearance as well. Unless you put the carb together wrong I doubt the carb is your current issue.

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alright...update..i took the right side cover off..and there was something hanging there..it had unscrewed itself. i don know the name of the part but i put it back on right and tightened it. re-did the timing chain. as in realigned it with the timing mark. cleaned the carb. and still wont start..its getting spark and fule..when i pulled the spark plug it was black..which led me to believe that the bike was in fact NOT running lean or else it would be white..so idk whats wrong with it

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today i am tearing the whole motor apart..cleaning everything setting the clearance and all that jazz..if it doesnt start when i put it back together..im screwed pretty much.

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alright..heres an update...i found out that it might need a new countershaft bearing in the right hand crankcase..i think this only beacuse in the manual it says if you experience kickback..which i am. it needs a new countershaft bearing. the thing is i cant find the instructions to get it out and install a new one..is it hard, do i need special tools? also. could this cause a bike not to star???

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You're probably getting kickback because your auto decompression isn't working properly, or may need to be adjusted.

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thats the thing with older xr's..they fire everytime the piston goes up. you can either install the cam lobes up or down stating the manual..it fires like a 2-stroke but is a 4-stroke. so theres really no wrong way to put the cam in..i have all the timing marks lined up. and i know its getting spark. pretty sure its getting gas..the kickback friggin hurts sometimes..like real bad. i might try a lil bigger main jet. the carb was stock. should i have touched the air screw??i have a better filter..bigger pipe..higher compression piston..should i be running a certain kind of gas with a higher compression piston? and its bored .040 over

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the auto decompression doesnt work at all..the little thing that moves with the kick started doesnt work.. i could do a manual but i dont have the right cables or mounts..does anyone make an aftermarket manual decompression for it?

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You seem to be under the misconception that your bored .040 over engine is some kind of gigantic big bore now, and that isn't the case, by any means. A Wiseco P4 piston is only an increase to the bore of 1mm, and the final numbers below are stock and .040 over...

Stock - 7.4 x 7.4 x 5.78 x .7854 = 248.589cc

.040 over - 7.5 x 7.5 x 5.78 x .7854 = 255.353cc

Personally, until you fix the auto compression, you are going to have the kickback, due to the lack of compression release in the cylinder. Also, having a spark with the plug outside the plug hoe is one thing, but it may be too weak to fire off in the cylinder, also due to the compression.

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You seem to be under the misconception that your bored .040 over engine is some kind of gigantic big bore now

no i dont think its some gigantic bore now. its just a little bit higher compression than stock too. ill see about the auto decompression because for some reason the little tab by the kick started doesnt move when you kick start it. it started perfect about 2 weeks ago without the decompression..but since the timing advance thing decided to come odd while riding it hasnt ran..everything is put back together right.

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One other thing to take into consideration is whether or not you readjusted the valves after reinstalling the head.

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yes. i used the feeler gauge i got and adjusted them. i will re adjust them sunday because tomorrow i will be out of town. but ill double check that and the timing marks to make sure they are lined up .

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i have same bike and same problem. just got and trying to figure it out but just like you i'm still alittle lost. i'll keep working and keep you informed if/when i get it

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are you making sure that the piston is at top dead center (up) when you do the cam timing? I always install the cam lobes down make sure the marks on the cam sprocket are flush with the head and the piston at TDC.

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no i dont think its some gigantic bore now. its just a little bit higher compression than stock too. ill see about the auto decompression because for some reason the little tab by the kick started doesnt move when you kick start it. it started perfect about 2 weeks ago without the decompression..but since the timing advance thing decided to come odd while riding it hasnt ran..everything is put back together right.

You say that it started fine until the pulse rotor came off!

I would double check that and make sure you didn't damage the pulse coil.

I have two of these bikes with a lot more mods then yours and I don't have a problem starting them even with the stock jets they started just fine and I don't get any kickback.

Are you sure pulse rotor is timed right

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Backfiring and Kickback on attempted starting indicate to me that you have the Timing wrong..Double/Triple check the Valve timing. Tight tappets are no good.Come to think of it rip the Tappet cover off and make sure everything is lined up correctly with the bottom marks..then of course recheck the tappets.

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