Degreeing Cam and Valve Lash Correction?


XS650 Member
Reaction score
Nashville, TN
I have been re-assembling my bored, rephased XS650SJ. I have hit snag while degreeing the cam, and want to ask your advice.

Background: Valve job, head re-surfacing, and boring (to 700) by Hoos. 447 crank and cam 277 rephased by Hugh's. New pistons, rings, cam chain, cam guides (both). Head torqued down to spec +2lbs.

Procedure: TDC'd each side with a piston stop, inspection valve lash set to .012" (and verified/adjusted by dial indicator to make sure it was dead on.) For each valve: to account for any error (procedural or observational), I measured everything (degrees at initial valve opening/closing, .05 open/close, full open (where the gauge appears to stop, and then starts to move back down)) three times. Then I moved the dial indicator to different part of the valve retainer and re-measured three more times. I threw out the two measurements that were the most off the curve, averaged the four that were left, ran some calculations, and compared that average to the Clymer manual's spec numbers. I was pretty meticulous. So I'm not sure how some of the numbers are way off spec, and others are almost dead on, short of 1 odd cam lobe. (Attaching a pic of my results.)

1. Which of these numbers do I need to worry about?
2. How can I correct without throwing everything else off? It looks like I may need to the advance the cam 2 degrees...or should I bother for 2 degrees? I REALLY don't want to pull the rocker cover, if I don't have to.
3. I'm thinking that if I tighten the lash on Cylinder #2's IV 2-3 hundredths, and Cylinder #1's IV by a hundredth, it would pull the Valve Lift, Initial Open, and Fully closed numbers closer to spec without affecting Lobe CL. Does that sound right?
4. I can't find a spec on the valve lift for IV and EV. Does anyone know that those should be?
5. Do you see anything else here I should worry about?


Thanks all!!
CeeAnton, excellent job of measuring and recording your valve events.

For those values to be meaningful, you'd need new parts, like:
New or precision ground camshaft.
New rockers or precision reground rocker pads.
New valve adjusters or precision reground adjuster tips.
New valves or precision reground valve tips.
Valveguide clearances close to new specs.

Shall we assume that the cam was used? Same for the rockers? Anything done to the valve adjusters and valve tips? Valve guides?

A slight bit of cam wear, and/or flattening of the rocker pads can show wild variations in event timing at smaller lift events, due to minuscule travels in the lash take-up and entry/exit ramps. Worn adjuster and valve tips don't help either.

Looking at your averaged 0.05 values shows more meaningful, and less erratic, event timings. In fact, looks to me that your cam is about 1 degree advanced, which is what I'd prefer, anticipating some camchain stretch to get it spot on.

Some cam lobe dimensions in post #2 of this thread:
Thanks 2m!

That’s better than I hoped then! Yeah, I was pleased with the .05 numbers (they seemed pretty dead on, and consistent) and the calculated lobe centerlines, but was mostly concerned about the intake valves opening and closing so early or late. 8 degrees seems like a lot. Hence, my question about tightening the lash a couple hundredths. But if none of those numbers are concerning, i’m happy to leave it be.

I have some new parts, some used. The stock 447 camshaft was rephased, but not re-ground. The rockers and valve adjusters were used, but everything else in the head was replaced during the valve job. New valves, springs, keepers, guides, during the valve job and head work.