what cyl pressure should be?/?

mega cycle list 2 different cam profiles with .410 lift...one is 250 duration one ise 270 duration and a .384 lift ex cam.
both are said to be dialed in at 108/108 lobe centers.
the plot thickens

The motor on my 78 was running at 110 on all 4 but it was fouling plugs with the hairy black soot after about an hour of riding.

kzz1p wrote:

I do not know the opening and closing points, of the intake cam or it's timing? With those numbers, I would take a better guess.

I recently spread my cam lobe centers. As noted, intake timing has a dramatic effect on cranking compression. I tried retarding the intake cam by 4 degrees and saw a 30psi drop in cranking compression - from 160 to 130. I advanced it back to where it was and the compression came back to 160. I accomplished the lobe separation on the exhaust side. Exhaust cam timing has much less of an affect on cranking compression.

well I think the mystery is close to being solved....now I just have to confirm the degree numbers and we should be off to the races.

Pretty cool motor ...it basically has the stg IV set up. have the reciepts for everything including carbs, Pipe,...the only thing that I dont have one for is the transmission...but who knows

BIG thanks to Bob for the old catalog and the info....I ow ya one

Ben thats good stuff!

Does the bike have a Yosh head on it? (the one with the small valve stems) or the lightened cam buckets?

I may be talking out of my butt here, but I'll take another compression guess:

10.5:1 piston with a intake valve timing of 26*/56*. I will say the compression should be in the range of 256 psi.

You could retard the intake cam to lower the pressure, but your performance will suck! and your power band will be raised, and bottom end power will suffer. Yes your L/C would be higher and your LSA would be higher.

Pretty much a set of cams made for racing. That's how they got the big dyno numbers.

When you check the numbers and find the running duration, I am guessing it will be appx 300*

As for the 56* of overlap, that's alot in a 1015 motor.

Ben the stage IV says oil sump. Do you have any pictures of that?

no...put i can take one in a min or two...I'm pretty sure it has 10.25 to 1 wiesco's in it now....and the pressure when dyno'd was 195 across the board....seems on par with where you are with 10.5 to 1