Took head off after breakdown

  • Well , finally opened the engine , this piston did 400 miles , find out that 300ml trans oil left , bit in coolant and lot in crank case. Sparkplug was badly fouled , similar to the piston on the pic . I was probably burning it as well but didnt smell or didnt seen any bad smoke... Trying to figure out what actually happened.







    Aaand this 😓

  • Any idea what I did wrong?

  • Administrator

    Did you replace the crankshaft seal?

    If so did you have it on the right way round?

  • Which seal is it?

  • The piston looks like you went to lean.
    Google "lean piston" and you see many like them.

  • @Calum googled it , no I didnt. Used the old ones.

  • Administrator

    @Zrako It looks incredibly oily.

    I thought you said you rebuilt the engine sorry?

    It's hard to say what the problem is, although if it's lost gearbox oil, and oil was in the crank case and the piston is filthy, then it could have been the crank seal.

  • @Calum yes I did rebuilt it like 3 months ago I think. Gonna get the seals and replace them soon . I have a spare mitaka piston , but both looks slightly different than the one before. Will post a pics tomorrow...

  • Administrator

    @Zrako So what did you rebuild exactly? If you used old components then that might be the problem. I think they're only a couple of quid and for the sake of them I'd just replace them.

  • @Calum My bottom end bearing gone before so I got the new conrod and piston , got the crank rebuilt , used new gaskets and fasteners, new clutch plates and springs,installed kickstart ,new oil and waterless coolant... same big one pipe as I had before but in good condition... Thats it basically.

  • Administrator

    @Zrako what! And you didn't replace the crank seals? For the few quid and two seconds it takes?

    If the big end bearong went then it's likely that it took the seals with it. I would replace both of, which means splitting the cases unfortunately.

  • @Calum well ,Im failed again then... never did it before but will remeber that for future. Ordered them now. Thanks for help

  • Administrator

    @Zrako Let's hope this was the failure point.

  • @Calum thinking about build it up again and give it to someone to check and tune it properly as Im lost confidence haha .

  • Administrator

    @Zrako Not really mate. It's so simple and we are here to help.

    Literally it's the crank seals. Yoy gotta imagine that when the bearings went they would have gone for the softest part of the engine, whih is the seals.

  • @Calum yeah , didnt thought about it as I think I checked them , silly mistake. Do you think I will need a new head gasket ? Im did the light skim as you made the tutorial for it , dont know how to identify if the head gasket is bad or reuseable...

  • Administrator

    @Zrako Head Gaskets are not reusable.

    My advice, don't take the head off, but I'm guessing it's too late for that now.

    Athena head gasket is only a tenner.

  • Well , here we go again . 2nd rebuild . Now with new crank bearings and seals 🙄 , new piston and rings , new - used clutch , removed kickstart and got new used stay for the sprag clutch and installed starter motor, fresh gear oil.

    Here is what it sounds like . First start was surprisingly smooth ,was idling bit higher so turned it down and bled autolube . Feel strange as it was maybe too good to be true lol .
    Let me know what you think about the sound. Havent jump on it yet btw.

  • @Zrako Sounds like a 4 stroke with the airbox lid off. LOL

    Great job tho!!! 👍

  • 0_1500242402424_20170716_225845.jpg


    Well , brand new iridium br9eix after like 30 minutes idling. First 5 minutes was bleeding oil pump. Doesnt smoke too much . 🤕


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