compression


compression

Postby MIKE DAVIS » Sat Jan 13, 2018 7:53 pm

what should the compression be for a newly bored CBX in psi. Not broken in.
MIKE DAVIS
Forum Regular
Forum Regular
 
Posts: 49
Joined: Thu Feb 25, 2016 1:35 pm
Location: SPARKS NV

Re: compression

Postby daves79x » Sun Jan 14, 2018 8:40 am

Depends on what compression the pistons are. Is it a Cruzinimage kit, or a higher compression Weisco, or something else. 170 at a minimum for any, higher for the high-compression kits.

Dave
daves79x
ICOA Technical Director
ICOA Technical Director
 
Posts: 3304
Images: 0
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA

Re: compression

Postby MIKE DAVIS » Tue Jan 16, 2018 5:50 pm

It is a Cruzin Image set. set up at .001. valves were lapped. 85 psi accross the board
MIKE DAVIS
Forum Regular
Forum Regular
 
Posts: 49
Joined: Thu Feb 25, 2016 1:35 pm
Location: SPARKS NV

Re: compression

Postby daves79x » Tue Jan 16, 2018 6:59 pm

185 you mean?

Dave
daves79x
ICOA Technical Director
ICOA Technical Director
 
Posts: 3304
Images: 0
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA

Re: compression

Postby MIKE DAVIS » Tue Jan 16, 2018 7:41 pm

No, 85 psi.
MIKE DAVIS
Forum Regular
Forum Regular
 
Posts: 49
Joined: Thu Feb 25, 2016 1:35 pm
Location: SPARKS NV

Re: compression

Postby jnnngs » Wed Jan 17, 2018 5:07 am

Mike,

Did you do the reading with the throttle wide open (if the carbs are fitted)? It does make a difference.

85 is very low, may also want to check your gauge is reading correctly / accurate.

Paul.
jnnngs
ICOA Member
ICOA Member
 
Posts: 313
Joined: Tue Feb 10, 2015 3:05 pm
Location: Hants/UK

Re: compression

Postby daves79x » Wed Jan 17, 2018 8:15 am

Even having not run the bike, I would have expected much higher. Do you plan on running it soon? Did you suspect something was wrong that led you to do the compression test on a new engine? If you are this far, and are absolutely sure the engine is assembled correctly (cam installed correctly especially), I'd run it some break-in miles and see what you have. But I still would expect much higher readings now. Do you trust your compression gauge?

Dave
daves79x
ICOA Technical Director
ICOA Technical Director
 
Posts: 3304
Images: 0
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA

Re: compression

Postby MIKE DAVIS » Wed Jan 17, 2018 7:29 pm

I tried two different gauges, still the same. Even tried it withe the carb slides out. Also pulling only 2 1/2 inches of vacuum. I'm beginning to expect valve problems even tho I lapped them. 4,500 ft of elev. could be part of the vacuum issue but only a little. I think there's no choice but to pull the head, again.
MIKE DAVIS
Forum Regular
Forum Regular
 
Posts: 49
Joined: Thu Feb 25, 2016 1:35 pm
Location: SPARKS NV

Re: compression

Postby tevan » Wed Jan 17, 2018 8:57 pm

MIKE DAVIS wrote:I tried two different gauges, still the same. Even tried it withe the carb slides out. Also pulling only 2 1/2 inches of vacuum. I'm beginning to expect valve problems even tho I lapped them. 4,500 ft of elev. could be part of the vacuum issue but only a little. I think there's no choice but to pull the head, again.

Did you do a wet test on your head after laping them?
User avatar
tevan
ICOA Member
ICOA Member
 
Posts: 489
Joined: Sun Apr 25, 2010 8:47 am
Location: Charleston, Illinois, USA


Return to ENGINES: Maintenance, Performance, Parts Sources

Who is online

Users browsing this forum: No registered users and 1 guest