Leaking Head/Gasket

Discussion in '2-Stroke Engines' started by Tom5ive, May 17, 2010.

  1. Tom5ive

    Tom5ive New Member

    Hey guys, I'm new here (as a member) but have been reading for months now. My name is Thomas (Tom) i live in nsw Australia and im 17. I did weeks of looking here before i even got an engine. Thanks to these forums, this build went perfect, no trouble but one thing.

    I have a 66cc Skyhawk gt5 on a mountain bike, bit tricky to fit the odd frame but its all in and running now.

    My problem is this everything is A1 working great, no loss in performance at all. I noticed after about the first 50k's of riding, that there was some oily residue on the frame near my exhaust. Ok no worries clean her up start her and look for the leak. Ahhh **** it, it was coming from between the head gasket and cylinder, not exhaust, fuel line or carb. Over the next 2 days i check the head torque (perfect) change the gasket and re torque the head and go for a ride, still the same thing. Its not leaking real bad, but if u look close u can see it bubbling kinda thing in a few spots round where the head meats the cylinder/gasket.

    So i have had my bike sitting for a week now waiting for a mate to make me a copper gasket, this same mate thinks this will fix my problem.

    My question's are, will this help? Is lapping the head a good idea?

    And also there is a copper gasket adhesive i know of (for head gaskets) is this safe to use on these engines? This engine is still under warranty, should i send it back? warped head/barrel maybe?

    Thanks so much guys.

    Oh a picture, this is not finished it is about 3 quarters done, had to make a custom carb intake and bend exhaust to fit nice.
    So it kinda looks allot better than these pic ill get more soon.

    Attached Files:

  2. Tom5ive

    Tom5ive New Member


    Anyone able to help at all, PLEASE?
  3. Fabian

    Fabian Well-Known Member

    Hi Tom5ive,

    Get used to the oil leaks.
    My motor pukes filthy black greasy oil (like a BP Oil Slick) from every corner of my engine.

    The day your engine doesn't leak oil, is the day you'll be walking home.

    There's a good saying service mechanics of World War 2 radial aircraft engines used to swear by, and it relates directly to our 2-stroke bicycle engines.

    If it ain't leaking any oil, it doesn't have any!

    Last edited: May 18, 2010
    Nahom likes this.
  4. Al.Fisherman

    Al.Fisherman Active Member

    Hi and welcome. Working with these engines can be fun and at times frustrating. There are some hard and fast rules "I" have when building a bike and mount a Chinese engine to it. I won't go into all of them as you can go to my profile an search through my posts. Now for your problem. Although you say your torque is ok..what did you torque the head to? I change out all the OEM hardware, as it is junk, soft and will stretch. If the head bolts are 8mm the MAX torque (because of the cast aluminum and not the stud) is 204 inch pounds...I use between 150 and 175. I also use a inch pound torque wrench for accuracy. Stock gaskets are fine, but I use a thin cut one (more compression). If using a "thin" aftermarket gasket make sure of the fit. I've had some cut too small in diameter and destroy a cylinder, piston and head. I NEVER put a head on without milling the head. This is very easy and can be found in a search. Also I use lock tite on all "studs" and copper coat on the head gasket. I had the same problem on my first build, being a nubee, but none what so ever in the last 4 builds.
  5. Tom5ive

    Tom5ive New Member

    Thank you so much

    Hey, thanks guys. I has thought that this might be the case, so im fine to ride then? YAYYYYYY. I have been so down about "not being able to ride".

    As for the copper gasket and sealant, will this work? i mean will it minimize the oil? i mean its not tooo bad, i don't mind cleaning a bit up after a few rides. But i would love to not have it kinda build up in a tiny hot drop then be whipped of by the wind and spat on my leg :( *laughs*. If not some other method would be appreciated.

    Also i have realized i stripped an exhaust stud from the engine, just today.
    I have been told that lock tight liquid metal is the go, mix fill and re-tap yeah?


    Oh 150 inch pounds, ill put a bit more on and see if it improves, i didn't want to go more than instructions said :S
    Last edited: May 19, 2010
  6. Tom5ive

    Tom5ive New Member


    I forgot pics These are complete pics.
    Have added a few tweaks and mods, better chain runner, neater wires, shorter clutch cable (stock is awfully long) all little tings

    Attached Files:

  7. AussieSteve

    AussieSteve Active Member

    Welcome, Tom, I'm in Nowra. Where in NSW are you?
    Liquid Metal won't really do the job. Try it, but you might need to buy another barrel, unless you want to mess with heli-coils. (A barrel is not expensive, and it's the best fix.)

    Where did you buy your kit? ZBox?

    Regarding the head leak, as Ron says, mill the head and fit a new gasket.
    To mill the head, a sheet of wet and dry paper on a sheet of glass should work OK.
    A copper gasket would seal well, but be careful of piston-head clearance if you have a slant head.

    Next you need to do away with that horrible RHS sprocket and tensioner and fit a shift-kit.
  8. Tom5ive

    Tom5ive New Member

    Hey, im from the central coast, i got my kit from the ebay store mpb imports, yeah i have a slant head, and what is a heli-coil?
  9. Al.Fisherman

    Al.Fisherman Active Member

    Last edited: May 19, 2010
  10. Tom5ive

    Tom5ive New Member


    ahh, i understand, seems like it might be the go, depending on cost, as i am not working at present
  11. Al.Fisherman

    Al.Fisherman Active Member

    Hold it there... you "didn't want to go more then instructions said" tells me Ummmm I said inch pounds...NOT foot pounds

    Stock hardware calls for what 12-17 foot pounds? 17 foot pounds X 12 = 204 (max for 8mm in cast aluminum) inch pounds
  12. Alson

    Alson Member


    12 Ft/lb is all you need
  13. gator joe

    gator joe Member

    Ok. First thing I have to tell you is good job on ur first build..now to get to ur problem that really hasent caused u any problems. Other than u think there is or should be one.....well yes and no is the correct answer my friend. ..I have the same motor only in silver and I to thought exactly as u did...let me share with you a fact about these motors. .u r right wile at the same time it does this for a very good reason. Especially wile in break in period. ..in fact if u don't c this as well as a few drops of oil after u let ur bike sit say over night. I personally didn't ride more than 15 or 20 minutes. .for my first 2 or 4 tanks. .a lot of people say they don't leak they mark there territory lol.dont worry it's fine now as long as u check ur head bolts and adjust them to 5en pounds in a x pattern after heating her up to temp then letting her cool.ur good. The chance is that ur cap may b worped. .a lot have been known to b...after about 500 miles u can pull cap off and sand it perfectly flush and replace head gasket even I've heard some people putting to head gaskets
  14. bigj

    bigj Guest

    Hey people just would like to say that a lot of these problems that happen are due to quality control and the lack thereof, i mean you get many parts for dirt cheap, honda, ktm, etc.. would be a fortune for the same thing. i have had a lemon, im on my fourth motor and have found that each one has its own personality and has a frequency that it runs best at, if you listen carefully to the motor you will hear a hamonic balance that repeats itself over and over in a set. this is the motors most efficient rpm to run at, they all seem to be close.
    obviously the rider plays a huge factor some people run at full rpm for long periods , overheating,, or also not ptoper mix of fuel ...the list goes on...
    It sure is fun though and keeps you happily out in the garage, half the fun