Low compression

[ccmnova]

Having trouble starting my 74 Penton 6-days so I ordered up a compression gauge and checked it - reading 75 psi - I believe that's too low for combustion and that it should be twice that.

[firstturn]

Way too low.

Ron Carbaugh

[Larry Perkins]

Should be no less than about 120psi.  Like Ron said way too low to start or run.  Do remember though when you check compression to do your kicking with the throttle wide open.  If not you will not get an accurate reading.

Larry P

[Steve Minor]

I have a low compression 1976 125 KTM...Any way to raise compression other than a re-bore, new piston and rings? Any tricks?

Steve Minor

[ccmnova]

quote:Originally posted by Larry Perkins

Should be no less than about 120psi.  Like Ron said way too low to start or run.  Do remember though when you check compression to do your kicking with the throttle wide open.  If not you will not get an accurate reading.

Larry P

Yes I rechecked it with the throttle open - unfortunately no difference !!

[454MRW]

Is the bikes at and someone might have put a rag in the intake to keep mice from getting into the carb, that might be worth checking, also on the exhaust side.

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Penton
1976 MC5 400
1978 KTM 78 GS6 250
L78-79 MX6 175-250 KTM's
1976-78 125-400 RM's
2007 CR125R Honda
1977 MC250 Maico
2017 KTM Freeride 250R

[Larry Perkins]

Steve there are ways to raise compression but pretty much rebore is the fix for low compression due to wear.  Not that hard really.

Larry P

[Steve Minor]

Yeah, I've been putting off a top end. I'll measure the bore to see if it's even possible. Thanks for the reply

Steve Minor