PC high compression head

I recommend against it. I have a MM Gen II head that I ran on my last motor. IMO it's not worth the wear and tear, for the tiny bit of extra power.

I'm not against extra power. I just don't think high compression is the way to get it with these china girl motors. Expansion chamber, yes. Bigger carb, yes. More compression, no, not for street riding.

getting a different head is recommended just for the fact that they cool better than the stock the extra compression is a added benefit. to decrees compression double up on head gaskets.

desolation said:

getting a different head is recommended just for the fact that they cool better than the stock the extra compression is a added benefit. to decrees compression double up on head gaskets.

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Hey Desolation, you touch on a very important point.

According to my engine experience, the poor cooling of the stock cylinder head is a paramount reason to get a different head which has better cooling. From my experiences when I upgraded my engine even slightly, the engine temp. rose to the point where the lubricant could not maintain it's film strength, and I was noticing fast wear in the cylinder wall. Once I started running a high compression head with better cooling fins, I not only got an increase in power and fuel efficiency, my cylinder walls are looking gorgeous. With that said, I must say that I have not done any tests with a Pirate cycles head or the manic mechanic head, so I can't speak for those designs. I used to have a lot of engine trouble. Now I have enough power to propel my bike to 45 MPH, and am not experiencing any engine trouble. I have been conducting a lot of testing with these engines, taking careful notes of any wear problems, and this conclusion is a result from that.

So, for whatever it's worth, that is what I have experienced/observed.

-Fred

ive decided on going with the puch heads over too mm and pc heads

Have u checked out the billet head that Crmachineman offers in the swap & shop section. If its suitable for ur motor (depends on piston crown height), that would b the way 2 go. If its not suitable u could try asking him 2 profile the squish band & chamber 2 suit ur piston, he may b accomodating. I mean, there's only 2 heights that i know of, 0.160" & 0.100". It would b best if he did both. Cheers

Hello Hoze 513.

I can offer some information about why the two types of chambers exist. There are some advantages to both types of designs. Both types have valid reasons for their use.

So, the center plug location can have an advantage in combustion efficiency due to the fact that it is located directly in the center of combustion activity. This is important because it is beneficial to complete the burning of the mixture quickly in order to reduce the chances of detonation to occur.

With that said, I'm not saying that it is impossible to design a slant head design which minimizes the problems of having a spark plug which is offset from the center of the combustion chamber. I believe it's just a little tricky, and a more complex combustion chamber shape is in order. In fact, I found the combustion chamber shape of the GT-5 head, when modified to incorporate a squish band had really good characteristics, but bad cooling, as you could expect as with all of the stock heads.

The slant head design has a distinct advantage over the center located spark plug hole in that it simply takes up less space. Some bike builders don't have much room above the engine for a center located spark plug design, and must use some kind of slant design.

So, how did I do? This comment is just based on my most up to date understanding about combustion efficiency, and why the two types of designs exist. I'm sure there are other things that I'm leaving out, but that's why we have this cool forum. It's kind of like a new kind of "open engineering" where anybody can actually impact how things are to be made.



-Fred

I have the RSE head which appears 2 have similar chamber design. I bought because the Gen11 MM wasnt available & neither was this 1. I definitely would have gone with this 1 for the extra cooling. The center plug is the best design if u research it. I intend 2 liquid cool the RSE head in the near future. Cheers

Hey Ivan!
Wow, liquid cool eh? Damn! you're a madman! But I like the level you are trying to achieve. Very cool! Do you know if you will use a water pump, or would you just try thermo siphon?

-Fred

Arrow Cycles has rechambered high comp heads for $35. I may get one soon. http://www.arrowmotorizedcycles.com/shop-now---stock-rechambered-cylinder-heads.html

ivan H said:

Have u checked out the billet head that Crmachineman offers in the swap & shop section. If its suitable for ur motor (depends on piston crown height), that would b the way 2 go. If its not suitable u could try asking him 2 profile the squish band & chamber 2 suit ur piston, he may b accomodating. I mean, there's only 2 heights that i know of, 0.160" & 0.100". It would b best if he did both. Cheers

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just ordered 1 and plan to throw the piston in the ol lathe and adjust my squish to my preferences i will also deck cylinder to my preferences ive built alot of these motors trying to find happy medium between power and reliability ive got 2 designs ive done im really happy with. lots of power and staying together so far just need to cool them down a bit and should be solid motors (keep wrenchin) we all have our ways PEACE AND CHAIN GREASE !!!!!

Ur onto it brother. I've done a few of these 4 others, still on my 1st myself. It came with crankcase leak so split the cases & put in NTN main & countershaft bearings & end floated crank to 4thou, just added RSEreeds/ported piston/boost ported jug . Have RSE head/squish 30thou, SBP chamber & shift kit, 16mm mikuni,/32.5 pilot/92.5 main. Will go 1 main richer yet. Cant b happier now. Will soon transfer learned spec 2 70cc overbored RSE cylinder & ceramic coated piston. Keep on riding. Cheers

crmachineman said:

Hey Ivan!
Wow, liquid cool eh? Damn! you're a madman! But I like the level you are trying to achieve. Very cool! Do you know if you will use a water pump, or would you just try thermo siphon?

-Fred

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Hi Fred, I plan 2 use an impeller pump, remove the primary reduction gear's screw & replace with a drive coupler. I'm scrounging 4 bits at the moment. Cheers

Of course, I'll have 2 cut a hole in the reduction gear cover & mount the pump externally, & put a protective cage over it so there's no chance of wiping it off. I'll also put a small thermostat on the fluid exit of the head. Cheers

I can see that in my mind. A watercooled add on to a RSE head . A bolt on DONUT. brilliant .

anyone ever use this head ?????????? Any advice/info would be fckn excellent

http://www.gasbike.net/Racing-CNC-Cylinder-Head.html