45mm bbk compression

[iceman77]

i finally got my rings on my piston and everything back together. i did a compression test and it was 139. i was wanting some input from the scooter gurus. is this compression ok?


Thanks:
TJ

[bonesv]

Iceman, are you using the stock head, with what gasket? It's the kit from Patrick?

[iceman77]

Iceman, are you using the stock head, with what gasket? It's the kit from Patrick?

sorry i got in a rush posting.

yes stock head and i'm using the gasket that came w/ the kit from patrick.




TJ

[Mystic]

you may want to order an aftermarket 45mm head to match or take your stock head to a machine shop to have them match it to your cylinder. You can probably run it like that but I wouldnt

[iceman77]

you may want to order an aftermarket 45mm head to match or take your stock head to a machine shop to have them match it to your cylinder. You can probably run it like that but I wouldnt

just curious what issues it would have if i ran it w/ the stock head?


thanks:
TJ

[Mystic]

the area around the spark plug is your combustion chamber and the area around the edge is the squish band. The squish band reduces the chance of detotation by concentrating most of your fuel mixture within the combustion chamber, the rest of the mixture helps with cooling the cylinder basically. There is more to it I am sure but that is my understanding of it. With higher compression and a larger mismatched squish area you increase the risk of detonation and overheating

[iceman77]

the area around the spark plug is your combustion chamber and the area around the edge is the squish band. The squish band reduces the chance of detotation by concentrating most of your fuel mixture within the combustion chamber, the rest of the mixture helps with cooling the cylinder basically. There is more to it I am sure but that is my understanding of it. With higher compression and a larger mismatched squish area you increase the risk of detonation and overheating

got ya. thanks for the input. i diff don't want over heating.



thanks:
TJ

[Mystic]

THere are other that should be able to explain it better like Bear or bakaracer

[bakaracer]

Find a malossi or polini head. The squish band angle is already set and the diameter cutout will be really close to what you need it to be.

[iceman77]

got ya.

but for now i have the stock head on and the compression is 139. will i be ok to run it?



thanks:
TJ

[bakaracer]

I wouldn't run it like that. The stock head is to small and the flat area that sticks out into the cylinder area will cause flow turbulance which will cause lower power then should and over heating issues from engine knock. The squish band prevents that from happening.

[iceman77]

I wouldn't run it like that. The stock head is to small and the flat area that sticks out into the cylinder area will cause flow turbulance which will cause lower power then should and over heating issues from engine knock. The squish band prevents that from happening.

ok... i have a head from a 51mm ruima bore. would that be ok to use?



TJ

[bonesv]

Probably not going to have enough compression with that. I have the same cylinder kit, the stock head was not allowing good enough power without the excess heat. It just wouldn't cool enough AND run well. I had it apart at least 5 different times and did not see any abuse or noticable wear.
I now use a malossi 47mm aluminum head with an o-ring gasket AND an aluminum head gasket which keeps the compression at 125 psi.
I am also running a PG Short exhaust pipe. A small but usable 19mm oko carb, jetting at 120 main/42 pilot, clip in the middle. No posted speeds yet.
The set up I run currently max. rpm at 8600 which is far above what this is rated for but I've done some port work and polishing.
Check with Keith and order a new head, you won't regret it: http://www.hondaspree.net/phpBB3/viewto ... =2&t=19538 He is FAST shipper!
You won't ruin your motor running it like it is but at least put a cht gauge on it so you know when to adjust it. Happy Trails!

[kingkamehameha]

Dont fool around with the stock head or mismatched heads. Get the one thats designed for the bore or go pay a machine shop to cut the head to the right size. Either way your gonna have to shell out 30 bucks to get the right size