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  1. #1
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    Help! Did I blow up my engine?

    As i was cruising along a gravel road at half throttle on 4th gear my bike sputtered and stalled. It still kicks over but there are two head bolts that missing. Actually one was broken off. There is black gunk/grease around the spark plug on top of the head and some antifreeze on the head. Does this sound like a big project? I am an amatuer with the wrenches. Would I be better off taking it in to a pro?
    any help advice would be appreciated.







  2. #2
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    sound like the top end is blown, i would see if it start and have compression.
    if it are broken the best way to know what state it is have to open it and check.

    For the repair, its a 2 stroke top end so its not hard to work with.
    if you arent enough confident in your skill get a service manual, it will give you better understanding of the bike/engine/repair and will make you good with a wrench



    m y   s i g n a t u r e:


    Mathieu
    98/01 yz125

  3. #3
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    Despite what mathd (maybe that is the grade he got in math?) advised DO NOT start the bike. You have 2 headbolts missing and if you try and are succesful you will only do more damage. Chances are you didn't have the headbolts torqued properly or the studs were stretched from use.
    You need to do a topend teardown and remove the head, cylinder, and piston to check out what happened. Be carefull to not drop anything down into the bottom through the cylinder. A manual will be your best friend as you do it so get a good manufacturers one instead of a generic clymers type.

    Once you have the head and cylinder (jug) off take some good clear pictures and post them. That is the best way to get real usable advice on how to proceed. At least it is a 2 stroke which makes working on it much easier



    m y   s i g n a t u r e:


    Participating in sports doesn't build character...IT REVEALS IT!!! Let the kids have fun riding and racing
    http://www.teamvrm.com/rider_profile...et sponsorred]

  4. #4
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    Thanks for the help. Once it stalled, I initially tried to kick it over, and it had less compression than normal, but after a few kicks I stopped and haven't kicked it over since.
    I got a manual with the bike. NOt sure if it is a good one or not. I will try get the pictures up ASAP.
    Thanks Again,
    Matt YZ 125




  5. #5
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    Quote Originally Posted by oldguy
    Despite what mathd (maybe that is the grade he got in math?) advised DO NOT start the bike. You have 2 headbolts missing and if you try and are succesful you will only do more damage.
    My bad, yeah am sorry i should been more clear.
    i trough the guy would consider fixing the bold before starting/testing it as its evident the engine cant run or have compression in this state the user also said it stalled and dosent run. after the gasket/bolt fixed he could kick once or twice as he already did kick it over a few time to see if it have enough compression to start ... So if it dont have compression or do not start its blown wich answer hes first question.
    I also said in my first post that the best way to know what state it really is, he have to open and check.
    The engine can not be blown but because of unknown internal engine damage it can blown in the near futur.
    At this point i would consider order a top end kit and make sure the cylinder/crankshaft and bearings/seals are fine and also check for debrits in the crankcase, like coolant etc. but he didnt ask for that only asked if it was blown, and I DID advice at the first post to tear it down and check for damage because it is broken!

    btw, i was really good in math, not good with french.
    mathd is my name, Mathieu D, so thanks for the comment.
    Last edited by mathd; 05-20-2009 at 09:44 AM.




  6. #6
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    Quote Originally Posted by oldguy
    Despite what mathd (maybe that is the grade he got in math?) advised DO NOT start the bike. You have 2 headbolts missing and if you try and are succesful you will only do more damage. Chances are you didn't have the headbolts torqued properly or the studs were stretched from use.
    You need to do a topend teardown and remove the head, cylinder, and piston to check out what happened. Be carefull to not drop anything down into the bottom through the cylinder. A manual will be your best friend as you do it so get a good manufacturers one instead of a generic clymers type.

    Once you have the head and cylinder (jug) off take some good clear pictures and post them. That is the best way to get real usable advice on how to proceed. At least it is a 2 stroke which makes working on it much easier

    i just completely rebuilt my entire 250 2 stroke engine with my my clymer manual and it is not by any means generic. i also have one for my 97 kx125 and my brother has one for his motorcycle and they are all great as i stated above. so, i dont know why you would say they are generic?

    -mike.

    -mike.




  7. #7
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    Quote Originally Posted by m4i2k2e2
    i just completely rebuilt my entire 250 2 stroke engine with my my clymer manual and it is not by any means generic. i also have one for my 97 kx125 and my brother has one for his motorcycle and they are all great as i stated above. so, i dont know why you would say they are generic?

    -mike.

    -mike.
    Often Clymers will lump together several years and or models where as the manufacturers manual is specific to that bike. A 2 stroke isn't so bad because the basics stay the same so I guess a clymers would work just fine. I stand corrected if they don't come that way anymore it has been many years since I bought a clymers




  8. #8
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    Quote Originally Posted by mathd
    My bad, yeah am sorry i should been more clear.
    i trough the guy would consider fixing the bold before starting/testing it as its evident the engine cant run or have compression in this state the user also said it stalled and dosent run. after the gasket/bolt fixed he could kick once or twice as he already did kick it over a few time to see if it have enough compression to start ... So if it dont have compression or do not start its blown wich answer hes first question.
    I also said in my first post that the best way to know what state it really is, he have to open and check.
    The engine can not be blown but because of unknown internal engine damage it can blown in the near futur.
    At this point i would consider order a top end kit and make sure the cylinder/crankshaft and bearings/seals are fine and also check for debrits in the crankcase, like coolant etc. but he didnt ask for that only asked if it was blown, and I DID advice at the first post to tear it down and check for damage because it is broken!

    btw, i was really good in math, not good with french.
    mathd is my name, Mathieu D, so thanks for the comment.
    Mathieu D proper sentance and paragraph structure (as well as some spell check) would have made your point clearer. As you typed it the first thing you told him to do was try to start it then some undecipherable gibberish
    if it are broken the best way to know what state it is have to open it and check.
    as the second thing to do hence my recomendation not to try starting it before tearing it down.




  9. #9
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    I opened up the head, and there was a little antifreeze on the crank. The piston was a little black on top, but didn't seem to have any major damage to the cylinder. On the other hand I can't imagine antifreeze on the crank would be very good. As an amatuer wrencher, is there maybe a crack in my engine somewhere? I just bought this bike for 850 and don't really want to put too much back into it at this point. After a couple more paycheck probably, but not now. Any guesses to what may be the problem and what it usually costs if I was to do it myself or get it done professionally?

    Matt yz 125




  10. #10
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    It would be normal when the head studs let loose for coolant to get into the cylinder and make its way to the lower end. You need to figure out why the studs let loose but I would guess as in my original answer they were not torqued correctly or they had just stretched over time.




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