What is too much compression?

[gary55]

Would an engine with a head like this have too much compression and hurt the engine in the long run?
http://www.ebay.com/itm/RSE-High-Co...788805?hash=item3d10f97485:g:tPMAAOSwPc9W2FK-

This head will not increase your compression over that of a stock slant plug head. It will in fact lower it, and needs material removed by decking the cylinder to function properly. They should read high performance father than high compression.

 

[Deleted member 12676]

that head is a bad design because the surface area is less than a stock head.
more surface area = more cooling

 

[Steve Best]

that head is a bad design because the surface area is less than a stock head.
more surface area = more cooling

I have not had any problems with cooling, but this is not a very warm climate here (especially today,Dec28th!).

 

[butre]

my 6cc fred head has enough surface area to keep my motor cool in my pretty harsh environment. it got to 80 degrees today in the dead of winter.

 

[gary55]

I think the looks of this head is deceiving and if you took the ringed fins, cut them off, and stacked them vertically atop it would have very close to if not more surface area than a stock head. Not to mention the 3/4" + solid alum. base heat sink.

 

[gary55]

I am using one of those heads, somewhere i had a post of the exact volume but I cannot remember now.

The head works well. No tendency to over heat and gives great torque.
It is not a high speed head, an extra 5mph can be had with less squish and compression.
As Crassius mentions, the compression does take its toll on many things such as wristpin bearings and plating.
More power = less life.

Your compression can be adjusted to a degree by adjusting base gaskets and head gasket thickness.
The gap between piston and head can be anywhere from 0.020" to 0.060" which will make a significant difference in compression.

Steve

I got 7.9cc

 

[Frankenstein]

I have not had any problems with cooling, but this is not a very warm climate here (especially today,Dec28th!).

More power to the cool folks.

 

[Nate888]

agree with the above - these motors are made with chinese materials that are just not up to usual standards - they are a good utility motor, but trying to get more power is risking a blown motor

that said, the GF's bike is at 165psi cold, and runs in the mid 40s with 44T sprocket - stock head, but ported to the max with shaved barrel - she doesn't really care if it blows up

man, where can I find a girl like that?

 

[Street Ryderz]

I had just finished a customer rebuild today and I checked the compression just out of curiosity and box stock just cleaned up the transfer ramps and flash and it read 160 psi so I don't see how 130 psi is to much! And it's operating temp after 20 min run time was 285 f between the head and jug above exhaust port witch is where the hottest readings are usually found!

 

[Frankenstein]

I had just finished a customer rebuild today and I checked the compression just out of curiosity and box stock just cleaned up the transfer ramps and flash and it read 160 psi so I don't see how 130 psi is to much! And it's operating temp after 20 min run time was 285 f between the head and jug above exhaust port witch is where the hottest readings are usually found!

Well report back the next time he needs a rebuild, that will tell us if it's too much.