compression #'s and engine temp

[Guest]

Went for a ride today and bike felt like it had lost a little power. So, when I got home I did a compression test, 3 were at 140, 1 was at 150. Throttle wide open, fully charged battery. Just did a valve adjustment. This was an hour or so after I got back.
I added oil and they went up to 170 psi.
The last test I did, 2 were at 160, 2 were at 150.
I have never done a test with the engine overly warm/hot.
How hot should my engine be for compression testing?

[gs850cmc]

Sounds like good numbers to me, from what I have read on this site, you should check compression with the engine warm after a good run. Did you adjust the valves while the bike was still warm? From your post that is what it sounds like, I thought valve clearance check/adjustment should be done a minimum of 12 hours after last engine run.

[gearhead13]

Valve adjustment done stone cold. I do have high compression overbore Wiseco pistons in it, I though the numbers should be higher than 150 or so.
How warm is warm, hot to the point of burning yourself?

[rapidray]

When you say high compression, exactly how high are they? Also, the cams & where they are degreed & how much duration they have affects the compression. Give us more SPECIFICS please. Ray.

[gearhead13]

Supposed to be 10.25:1. '83 1100 cams degreed at 106 intake 108 exhaust. Could my cams be bleeding compression off? I was thinking of going 102-104 or something for more bottom end and midrange. I measured duration at 231 degrees @ 0.50" when i degreed them. They seem to have a really slow opening ramp because with zero lash, they had about~300 deg duration measured just as the valve started to move. Is that normal?

[SqDancerLynn1]

loss of power compared to what ? Maybe a bad tank of gas, carb pluged ?

[chef1366]

My numbers are the same.
I degreed my cams 110 110

[gearhead13]

loss of power compared to what ? Maybe a bad tank of gas, carb pluged ?

It could be other things, but the fact that i am down 10-20 psi compression means I was not imagining it. Checked all the plugs they all look exactly the same. If it goes down much further I will do a ring job.
The thing had 140 psi compression BEFORE I rebuilt it

[gearhead13]

I went on a 450km ride a little while back and kept the engine at 7-9000 rpm+ for 100+ km's. Could my valves have sunken into the head from the abuse I put it through, causing the lower compression?

[TheCafeKid]

I went on a 450km ride a little while back and kept the engine at 7-9000 rpm+ for 100+ km's. Could my valves have sunken into the head from the abuse I put it through, causing the lower compression?

I should hope they dont tulip that fast or some of us would be doing head refurbs every season. How many miles since the rebuild?

[gearhead13]

2500 or so kms since rebuild. Did a valve lash adjustment days before my trip.

[TheCafeKid]

How loose did you go on your valve adjustment? You sure you locked those adjusters down good and tight? Unlike the 8v, its possible for the 16v to actually go wider rather than only get tighter, if those lock nuts come loose. Just some things to consider.

[gearhead13]

The spec is .003-.005" I always go .004" mostly because I dont have a 3 or 5.

[jabberjoe87]

my compression is way lower than this my highest two are at 130 i think and one is 50 and one is 75!!!!

[mike_of_bbg]

my compression is way lower than this my highest two are at 130 i think and one is 50 and one is 75!!!!

If you're running stock pistons, your compression ratio is lower: <9:1 I think.

50 and 75 is pretty bad. I was getting around that on #1 and #2, because my crank was twisted about 20 degrees.