Did my 66cc motor come with a 50cc head? Is yours like this?

Toadmund

Toadmund

New Member
CYLINDER diameter 4.7cm

after the taper at the top of cylinder the gasket mating surface is 4.9cm diameter.

HEAD gasket squishband surface 5.25 OD, 4.1 ID

Here I will concern us all with the OD of the head which is 5.25cm and subtract that from the cylinder mating surface of 4.9cm

5.25cm - 4.9cm =0.35cm

result:
I have a gasket mating surface of 1.75mm (note mm not cm) around the circumference.
What the ****, is that right, a mating surface of less than 2mm?!

I feel compelled to mill the head band right off and make a thicker gasket(s) that will seal all around tight around the bolt holes and the whole surface.
I just realised this morning that I have a bunch of aluminum flashing left over from a door replacement I did, that could make gaskets.
 
The head gaskets are made of dead soft aluminum and are ment to be crushed with the proper torque. That band width is pretty narrow, though. Mime was around 4 mm on a 66 mm. The compression on a china motor leaves a lot to be desired so milling the head and removing the ring couldn't hurt. The head gasket would have a great deal of surface to spread the torque load. I'd advise a spray-on gasket sealer. I use Permatex Copper Spray-A-Gasket. Apply as advised, I've never had a leak.

And, really, taking off the band won't raise the compression much. You have to get pretty radical on a mill job on one of these for that to happen. To do that the best way is go to treatland and get the Puch Hi-Compression 70cc head. It's a dandy. $30. I don't know what they make it from but the cylinder head was clean, and I mean clean, and the piston crown had a thick layer of carbon burned on after running it for 3 months. The mounting holes are a bit off and need to be drilled out for an 8mm stud. The nuts need to be 13mm, you can not get a 14mm socket to go inbetween the fins. The sick bikes parts 8mm head stud kit has the 13mm nuts.
 
Thank you Jebus!

Anyway, the edge of the gasket gets crushed against the taper somewhat I believe, so that would increase my surface area closer to amount of mm you state.

So, I am just torquing it up and I am going to 'Go with throttle up'.

If it don't work, I'll fix it.

Thanks for the advice, I will look into after market heads.
 
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