80 cc slant head?!?!?

[emdude]

Hi All:

Well, I just got what was supposed to be a high compression slant head cylinder head for my 80 CC HT in the mail. What I got was CLEARLY not for an 80 CC engine with a 47 mm bore. The head I got seems to be a stock head for something with a bore closer to 43 mm.

I know several on this forum have obtained 80 cc slant heads for their engines and reported substantial power increases. And looking at the head I got I could see where this would be the case due to clearly significantly higher compression...if the head fits.

Now, if any of you reading this did get a slant head that fits on the 47 mm bore 80 cc HT please let me know where you got it!!!!. I really want one and the one I did get is wrong. The head is made for a 8 mm studs where as my 80 cc HT has 6 mm studs. This would not really present a problem but the fact that the head was designed to go onto a cylinder with a bore of 43 mm IS a problem. The piston hits the head at TDC of course.

I've searched for ever and found only one vendor that said they had it. But it seems they're not too clear on what they have.

Any help appreciated.

 

[Pablo]

So it actually contacted ~ piston to head?

 

[emdude]

Yes it did, big time. But so does the "stock" 80 cc head that came with my HT if you don't use the head gasket...I have tried.

The problem with the slant head is that is clearly for a smaller bore engine.

There are complete slant head 80 cc engines available, or so they claim. So I assume a head could be had that would work on my 80 cc HT. But where do I get one?

 

[Pablo]

I got mine on. No contact. I will admit, it looks smaller - well it is. But the bore seems correct, it's just the squish zone makes the dome look small.

I got mine from Zoom. I'm now going for a ride.

 

[Pablo]

Wow. Whoa. Brain rush.

But I think I've reached my clutch limit......it slips, or when I tighten it, it grabs "too soon" - ie when pushing the bike with clutch pulled fully in.

The engine has more low end and goes to top RPM much faster. I just whip through the gears and was pulling my biggest hill in 5th, before maybe 3rd gear.

NICE $22 investment!!

 

[emdude]

Let me ask you this:

If you recall, does the piston of your engine protrude at all from the bore when the piston is at TDC. On my engine it does. I have not measured it but it's quite visible. This is also the reason that stock cylinder head on my engine cannot be used without a head gasket.

I have heard that there are/were engines where this is NOT the case. This could simplify things.

I got mine from ZOOM as well. Either they shipped me the wrong head OR this head does fit on some 80 cc engines even though it is for a smaller one. I'll see what ZOOM comes back with.

 

[Pablo]

What you say rings somewhat true in engines lacking a bottom gasket or just bad tolerance stack up.

The very crown of my piston is just above plane of the top of the cylinder to answer your question. IF the sides of the piston were that high I would have a real mess.