Cylinder head designs for the 80cc / 66cc 2-stroke Chinese bicycle engine

A lot of talk about how the cylinder heads look like, nothing about what is really important! the combustion chamber looks - squishband- Worthless clips
 
nothing about what is really important! the combustion chamber looks - squishband- Worthless clips

Dear Mr max350, may i suggest that you invest in a set of prescription glasses, because the video clearly shows the cylinder head combustion chamber designs, furthermore, both of the manufacturers billet cylinder head designs in the video have squish bands that match the 47mm piston crown.

May i suggest that you review your comments because they could be seen to be worthless.
 
It sucks that my internet is so bad, I'd have been interested to see the video you posted.

Do you think there is room to modify the Happy Time OEM slant head to include a compression release valve meant for chainsaws etc?

EDIT: Never mind, I found jefuchs' thread. :)
 
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I am waiting for someone to make a head without a squish band since that is what these engines need for these two reasons:
1) a squish band is only truly effective in increasing engine power when the cranking pressure is above 150psi and the upper RPM is above 9000. These cylinders shouldn't have any more than 140psi because above that weakens the chrome lining which is temperature sensitive. US Chrome says that chrome liners can't withstand more than 400 degrees Celsius. Also a squish band decreases engine power if the piston to squish band clearance is more than .8mm.
2) a squish band on a small engine leaves too little room for the central combustion dome and as a result all these heads create too much cranking pressure. One of them creates 185psi!!! High pressure creates high head temperatures which can damage the head.

If you have a head with squish band then you need to buy a compression tester and make sure your pressure isn't over 140psi. Dremel away at the dome sides to lessen the pressure.
 
You need to find someone with high speed internet access, and that will solve all of your problems.

I got through it eventually. :) I wouldn't say that solves all my problems though! But it does let me see a little better what will be coming in my HT kit and gives me an idea what to read and ask about. :)

The after-market billet cylinder heads are expensive (and so is the shipping for me!) so what cheap/free "kitchen table" modifications can be done to improve the HappyTime heads?


1. In the video Fabian focused a lot on the relative cooling efficiency of the different designs of cylinder heads.
I read on MBc about attaching extra home-made cooling fins to the cylinder head; but I've never seen photos or diagram of how this is done. I'm assuming/expecting I would need to grind the edges of the cooling fins flat to allow a good contact area with the bolt-on fins, then drill the home-made fins and the original fins to accept bolts and somehow simply bolt to the original fins. Does anyone have experience of making this type of modification, and is it as simple as I'm thinking, and is it actually effective?

2. In the video, Fabian told us that the most common HT straight head has very low compression; but MBc is full of threads about increasing compression so I'm not going to ask about that.
I will have a slant head in the kit that is available here, and in the video Fabian tells us that this is a very high compression head. Bearing in mind what jaguar says in his post #6: Is there enough material (thickness) in the cylinder head to make significant changes to the slant head's combustion chamber? It appears to be mostly squish band and very little dome, with a tiny or nonexistent blending radius between squish band and dome. Could the dome be enlarged, reshaped, or the blending radius increased, or the squish angle increased to lower compression? If it is possible, would this be as advantageous as it appears to a layman like me?
 
The slant head's combustion chamber does not have a squish band. If you watch the video again, you will see that it only has a 4mm vertical wall coming off the combustion chamber dome.
 
I have heard from a freind of mine, the motorcycle bum who rides year round even in the blizzards of ny. He has a freind who was experimenting with channels in an x or star shape running from the spark plug port to distribute the ignition faster throughout the cylinder. has anyone heard of or tried this?
 
the cooling fin heat sink extention sounds like a good idea. Maybe someone should come out with a cylinder head with oversized cooling fins!
 
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