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Thread: I blow up top ends like its my job

  1. #1
    200xkwit is offline Registered User Arm chair racerAt the back of the pack
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    I blow up top ends like its my job

    well here I am sicker then ((Don't Bypass the Word Filter!)) hanging around and I thought id take a look at my blow head gasket on my 200x motor I pull earlier in the month. I break it down and find the blow head gasket I knew was there and then I see rust all on the piston and the piston was slightly seized in there. I mean theres not even 10 hours on this thing. I blew the gasket in the middle of a race because my clutch went (it was horrible to begin with) and I was in 3rd gear pinned and the motor got reved sky high. I dont understand it though besides the clutch the bike was running mint. I think its got to be the carb with a lean setting. my main jett is a 105 I think, everyone tells me that its too small for the motor. I have uni intake/exhaust/max bore high compression piston and I run race gas. One thing I did notice tho was theres small amounts if no carbon deposits on the piston top. I dont know what to make of all these lost top ends. this is got to be my 5th
    Last edited by OldSchoolin86; 10-24-2005 at 08:28 PM.

  2. #2
    Join Date
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    What did your plug look like? You should have done some plug chops to see how it was running.

  3. #3
    Join Date
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    Not even 10 hours ?

    and this is your 5th ???

    I think you need to have a proffesional help you out.. or find another shop if you are having the work done. like.. whoa..

    Are you breaking in the new motor properly ? how many hours do you need to run a new piston in ? Were the valves ticking ? etc...
    Currently :

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  4. #4
    Join Date
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    how high of a compression piston is it? Maybe its too much if your blowing you head gasket out
    Nate

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  5. #5
    Join Date
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    wisconsin
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    you only have a 105 jet, dont they come stock with a 108 well thats what my 84 200x had on it, but now i put a pipe and **** on it and have a 115

  6. #6
    200xkwit is offline Registered User Arm chair racerAt the back of the pack
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    the carbs got to be set really lean or somthin. the thing is tho when i do plug chops and check the plug and everything its always good nice tan color no white spots or nothin

  7. #7
    Join Date
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    Salisbury, NC
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    I had a CR125 that went through top-ends like that, it turned out to be an slightly "egg-shaped" cylinder (It was new from the factory that way).

    It would run perfect then POOF......went through half a dozen top-ends before finding the problem.

  8. #8
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    Massachusetts
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    Do you break it in correctly? Or do you go like a bat out of hell the first day you ride it?

  9. #9
    Join Date
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    Quote Originally Posted by Rm250RF900R
    Do you break it in correctly? Or do you go like a bat out of hell the first day you ride it?
    Even so he should get more then 10hrs
    '02 Honda 416ex - A seasoned blend of 11 herbs and spices
    '04 Honda Recon - The yard machine and snow plow
    '88 Honda CR250R - Another chapter in my torrid all terrain affair

  10. #10
    YAMAHA_Jim's Avatar
    YAMAHA_Jim is offline 4 Motos, 3 Wheels, 2 Classes, 1st Place Arm chair racerJust too addicted
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    Sry to hear about your bad luck. I guess some people have better luck than others.I havent blown a top end since I was 14 yrs old(29 now). That was on a 1984 rm 80. It blew up while I was in the air.WHen it locked up the bike flipped frontwards instantly and I had a spectacular crash.lol Since then I've raced a KDX200,KX250,owned a few sleds,Tri-Z's and Blasters and have ridden them for yrs without any motor problems.Just recently I replaced the base gasket on my trailriding blaster.I blew the base gasket over the summer and rode it as is for a few months in mud and fairly deep water and she kept right on running.I only fixed it b/c of the slight power loss from the gasket leaking.When I had the top end off I didnt notice any damage either. Been about a month since I installed the new base and head gasket and the blaster still runs like new.

  11. #11
    Solid Snake is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Quote Originally Posted by Motoboy
    I had a CR125 that went through top-ends like that, it turned out to be an slightly "egg-shaped" cylinder (It was new from the factory that way).

    It would run perfect then POOF......went through half a dozen top-ends before finding the problem.


    You may want to see if your problem is similar to this. The gasket surface may have become slightly warped over time and that would definately cause blown gaskets. Next time you have the top end off take it to a shop and have them check for any warpage on the gasket surface of the jug and the head (the two surfaces that squeeze the gasket) and if there is any they can hone it into spec for you.
    Trikes
    1984 Honda 200x, 1984 Honda 200m
    Bikes
    1995 Honda CR125R, 1985 Honda XL100 (gone), 1982 Kawisaki KZ550 LTD,
    2001 Yamaha TT-R 125L, 1983 Honda XL185S (current project), 2001 Suzuki SV650S

  12. #12
    Join Date
    Jul 2005
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    Richland WA
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    Super high revs make the cylinder pressure go very high, might have been too much for the stock design, but ill bet theres some warpage too, especially since its gone out before. Detonation can do it too.

    Not hard to fix with sandpaper and plate glass if its not too severe.

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