66cc leaking from head?!

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joelnotroll

joelnotroll

Member
Jun 11, 2009
59
0
6
san diego
I have a 66cc engine and its been leaking from the head gasket area since I got it. It seems significantly slower than my friends 66cc that is the exact same type of engine(we ordered them from the same guy at the same time).

When the engine is running, I can feel air (exhaust?) shooting out around where the head meets the jug on both the left and right side.
I tried double gasketing it, and still feel the leak. So I tried a different head, a head from a puch moped engine, and I still feel the leak. I have it torqued down to about 12-15ft-lbs.

Would you guys happen to have any tips or solutions for this?

thanks
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
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first, clean it well so you can spot whether oil is coming from head or from exhaust

if it is the head, break off the caps of the acorn nuts or replace them with regular nuts & retorque them

if it is exhaust, check that the gasket is good (replace if needed) and then check that your muffler hanger is supporting the weight of th muffler properly from the muffler to the frame
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
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Littleton, Colorado
Are you certain the leak is from the cylinder head or the spark plug?
Some kit instructions tell you to "finger tighten the spark plug". That is wrong. You need to torque it to about 80 inch pounds.

If you determine the head gasket is actually leaking you might want to check the gasket mating surface of the cylinder. It isn't common but you might need to 'lap' the cylinder to get a good gasket seal.

The cylinder fasteners need to be torqued to 120 to 140 inch pounds and as crassius suggested, get rid of the acorn nuts and replace with hex nuts. It is a common problem that the kit acorn nuts will bottom out and not allow the cylinder head to be torqued down properly.

Tom
 
mew905

mew905

New Member
Sep 24, 2012
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Moose Jaw
a note on 2-doors post: lapping is generally recommended to all new motors, regardless of issues. Not only can it save you from blowing gaskets by having a nice even seal and no 'weak spot' to break through, but when it eventually does go, if you have a smooth enough mating surface, you can get away with using no gasket at all (thats what I'm doing).

However as 2-door said, lapping the cylinder sounds like it could be your remedy. According to some members here, you can get one more use out of a squashed gasket after working the head by flipping it upside down.
 
Ghost0

Ghost0

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Mar 7, 2008
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I would also recommend lapping the head as well as the cylinder. The heads have a higher chance of not being flat than the cylinder.
 
K

k.mah

New Member
Nov 22, 2012
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oceanside,ca
shoot the area with carb cleaner while its running. if theres a leak itll bog down or stop running. at times if the leak is minimal, it wont make a huge difference, but most of the time it works wonders!
then like everyone above mentioned, lap both the head and cylinder for a perfect mating surface between the two
 
rustycase

rustycase

Gutter Rider
May 26, 2011
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Left coast
If you can FEEL the leak, it must be quite large!
Perhaps some white printer paper, taped in place around the top of the cylinder will help you locate the problem with a very short run period, in place.
That being said, it is most likely the situation can be improved by lapping the top of the cylinder to the head.
The machine work at the sparkplug may also be shabby, preventing a seal.
Unfortunately, there is always a problem of metallurgy and quality control with a chinagirl. There may be a pinhole in the casting allowing gasses to escape from the combustion chamber, to the exterior.
Good luck with your problem.
Please advise us when you are able to get it repaired.
rc

IMO, a doubled gasket will NOT be a solution.
There is a possibility 'ringing' the gasket might help.
 
joelnotroll

joelnotroll

Member
Jun 11, 2009
59
0
6
san diego
Im going to ask my friend if we can test out my 66cc head on his engine to see if that leaks. That should help determine if its the head or the cylinder.
 
O

Ouch that Hurt

New Member
Jul 27, 2013
38
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0
Port Alberni, BC, Canada
dunno if this helps but; with my motor I found that the head would make contact with the areas at the outer most corners. Where the studs are; before sealing the the circular part of the bore.

you could see the studs and some light shining through where the metal and the studs met.

I just filed down the corners where the studs go through and bam; problem solved.

Hope this helps...dunno if its bad casting or overheating from break-in that causes this.
 
joelnotroll

joelnotroll

Member
Jun 11, 2009
59
0
6
san diego
I think its bad casting. My studs were also exposed. The lapping will probably help.

Are there any links to tips for lapping it properly?
 
O

Ouch that Hurt

New Member
Jul 27, 2013
38
0
0
Port Alberni, BC, Canada
before ya go lapping/decking your head; just try to file off the outside corners of the head until it seats properly.

if its a new motor, ya dont wanna go stressing it with extra compression just yet. might go blowin other parts out.

after the breakin then go nuts for sure!!!

or whatever you feel comfortable with...lol...weee

if ya wanna deck your head....use a piece of sand paper taped to a piece of glass and do figure 8s til ya get it flat....different grit til ya get to where ya wanna be.
 
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O

Ouch that Hurt

New Member
Jul 27, 2013
38
0
0
Port Alberni, BC, Canada
well with my motor i could see light coming through the studs because the head was warped, I just filed off..(dunno what tools ya have at ur disposal) the corners of the head where the head met the jug until I got a good seat on the combustion chamber. there is only a few millimetres to play with there. (the ring around your head)

a piece of glass with sandpaper taped on top of it makes sure it is perfectly flat....rather than just using a hand file or similar attempt. (do not do)

try filing off the corners before ya try to deck your head cause that is likely where the problem exists.

DO NOT FILE THE RING AROUND THE TOP OT THE HEAD!!!
 
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2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
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Littleton, Colorado
joelnotroll said:
Ive had the engine since july. Ive been riding it as is. It may be past the break in.

What do you mean a piece of glass?
Click to expand...
A sheet of glass large enough to be able to tape a standard sheet of sandpaper to. Ball park, 12" X 12". Lay the glass, with the sandpaper on a solid, flat surface and holding the cylinder head in your hand, press it down on the glass and start sanding. There are several methods, all will work, but what you're trying to accomplish is to get a flat surface for the gasket to seat properly.

I like to 'paint' the gasket surface with a Magic Marker before starting the lapping process. Just a few gently swipes across the sandpaper will quickly show you where the high or low places are that need to be addressed. Keep sanding until all the Magic Marker ink is gone and you have a uniform surface.

You can use the figure eight method as suggested above or the old 'wax on, wax off' motion rubbing in a circular pattern. Just make sure to rotate the head in your hand every few moments so you don't sand an angle into the gasket mating surface.

Use the search feature, keyword, 'lapping' and you'll have plenty to read on the subject.

Tom
 
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