Leaking Head/Gasket

Tom5ive

New Member
Joined
May 17, 2010
Messages
7
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.
 

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Fabian

Well-Known Member
Joined
Sep 8, 2009
Messages
4,522
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!

Fabian
 
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Al.Fisherman

Active Member
Joined
Aug 13, 2009
Messages
1,965
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.
 

Tom5ive

New Member
Joined
May 17, 2010
Messages
7
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?

Cheers

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
 
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AussieSteve

Active Member
Joined
Oct 28, 2009
Messages
1,746
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.
 

Tom5ive

New Member
Joined
May 17, 2010
Messages
7
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?
 

Tom5ive

New Member
Joined
May 17, 2010
Messages
7
:)

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