50cc head on 70cc kit squishband issues

OK. So I've run 50cc heads on 70/64cc kits before. (Mainly puch polini)

I understand that a 50cc high comp head may "run" better b/c there is less squish band and you'll have higher compression.

But won't this lead to high temps around the piston? I was thinking maybe this is why all those puch polini piston chipped right on the edge. Ideas?

All things similar does anyone agree that a 70cc wouldn't be more reliable?

Does bells or jennings or bell talk about this?

THANKs!!

Re: 50cc head on 70cc kit squishband issues

I can't speak for the others But I end up modifying 50cc heads in order to get either and or piston clearance, remove sharp edges, the compresssion ratio I want, make a squish band. In the end it is a 70cc head. I bought a 70 cc HC head once and it made for a 18:1 comp ratio. Too high for me

Re: 50cc head on 70cc kit squishband issues

ok. BUT

1. What are the consequences of running a 50cc head on a 70cc kit?

2. Does the outermost diameter of the piston need to breath? or is blocking it off with a 50cc head OK?

Re: 50cc head on 70cc kit squishband issues

When you use a round file or other method to remove the outer circumference edge on the 50cc head to make that outer circumference the size of your new piston you are making it more ramped as a squish band is. You are probably going to have to mod it in this way for piston clearance. You want to remove the sharp edge to reduce hot spots anyway. What kit? The Polinis piston sits low in the bore. The K-Star comes to the top and you must alter the head or put too many head gaskets on. Just using Puchs as an example. Lots of people run 50cc heads successfully

Re: 50cc head on 70cc kit squishband issues

I have been running a 50cc hi comp head on my 70cc k-star for over 1000 miles now. Haven't had a problem yet.

Re: 50cc head on 70cc kit squishband issues

what about the stock head? my kstar has a 70 cc head and im just breaking in but it seems to get real hot, i also have the dmp/kstar crank. should i run the stock head for better reliablity less compression? what you guys think?

Re: 50cc head on 70cc kit squishband issues

Charles Cole (OFMC) /

I think this may help. 50cc to 65cc. Can be done to any head that has enough room to make bigger diameter. I did a series of pics showing the entire process. called HOBBIT HEAD

Re: 50cc head on 70cc kit squishband issues

I like to kick theory. Big picture stuff.

Reshaping the cylinder head for smoothness seems like the best option, when using a 50cc head.

Hey Cappy those pics don't work. I would love to see some before and after pictures. Stock 50cc head to modified for 70cc.

Re: 50cc head on 70cc kit squishband issues

Charles Cole (OFMC) /

Re: 50cc head on 70cc kit squishband issues

Charles Cole (OFMC) /

Close up pic

Re: 50cc head on 70cc kit squishband issues

Wow, What do those look like after 200 miles. Its gotta be good

Re: 50cc head on 70cc kit squishband issues

† CH∆D † /

You didnt adjust the 50 head at all? I have a 70 Kstar in the mail, but couldnt get high 70 head. I cant just top it with my stock 50cc?

Thanks

Re: 50cc head on 70cc kit squishband issues

Charles Cole (OFMC) /

What do you mean by 'adjust'? Do some reading on squish band & study the pics. Also, carbon has a hard time sticking to the polished surface.

Re: 50cc head on 70cc kit squishband issues

yha you can run it with stock head i did that before i got my hc head, i was just wondering what people thought of the compression ratio the kstar got with a stock head.

Re: 50cc head on 70cc kit squishband issues

Curbcast I modified in in now way. running no head gasket and one base gasket.

Re: 50cc head on 70cc kit squishband issues

i was wondering something. i ordered a 50cc tomos h/c head, got it and it looked kinda small. was told its the same for puch as tomos. made by kstar

was also told i can run it on my alukit no problem. true?

and lastly, which dirrection do i install it? it has 3 sets of fins the same length, 1 longer set. i had it long side down, ran ok. i turned it the other wat tonight on a friends advice, seems to run a little shittier on startup

Re: 50cc head on 70cc kit squishband issues

yall threadjackers is some simple moped folk.

peep this:

Yes of course you CAN run 50cc head on a 70cc cyl. And yes of course your k star will run fine with the stock head.

But your squishband isn't as dope as it could be. AND you have part of your head covering up the outer circumference of the piston, a place where mixture should have access.

I am discussing what is IDEAL and OPTIMAL and why.

Re: 50cc head on 70cc kit squishband issues

Charles Cole (OFMC) /

A: not a threadjack

B: NOT a Kstar! A Hobbit. Can be done to almost any head.

C: Sized to the cylinder (polini kit)

D: you can't read or see

E: sorry I tried to help!

Re: 50cc head on 70cc kit squishband issues

I'm not talking about you cappy. You are on point Your HOBBIT HEAD thread is awesome.

Look at all the other posters. besides SteveW and you, all irrelevant.

Re: 50cc head on 70cc kit squishband issues

A lot of the past posters to this forum who know what they are doing have abandoned it. I think there isn't much for them to learn from it anymore so they are out. At the same time there seems to be a lot of new people looking to acquire the knowledge or at least get a fast bike going. The noobs can get the "knowledge" all tangled around at times. So if you, anyone, can contribute it could save some of these people a lot of bewilderment and frustration

Re: 50cc head on 70cc kit squishband issues

Yeah, In two weeks when I'm done with grad school. I'm gonna read jennings and bell all the way through instead of posting here for a while

Re: 50cc head on 70cc kit squishband issues

The Jennings book has some good information about squish bands.

I don't think either head is ideal, because the 70cc head may have a bigger than ideal gap between the piston crown and the squish band, and the 50cc head would have higher compression everything else being equal.

I think the Jennings book says that a good squish band should help to prevent detonation, and the heat should be more concentrated in the center of the combustion chamber, but too much heat = melted piston crown.

The 50cc HC head has more material to take off to shape the combustion chamber the way you want. I think that may be the ticket, and anyways treats was out of the 70cc HC head :D

I NEED HELP ON MY A55 STREETMATE

I just bought my 2005 streetmate and have alot of questions like I also have a airsal kit for it. It has the bi-turbo exhaust on it now how do I get the most out of it?

Re: I NEED HELP ON MY A55 STREETMATE

Its me patgarret I forgot to say my streetmate has the a55 engine

Re: 50cc head on 70cc kit squishband issues

*facepalm*

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