compression test

[lunatic]

I've searched the forum and found that several members are saying 210 psi cranking. I have the triumph service manual and it says nothing about cranking psi, unless I missed it? I can only muster 185psi in all cylinders. Only reason I am doing this is I want to get a base line before changing out the pistons and camshafts. The bike was running fine and did 152hp just last fall on a dyno.

During the test I had the spark plugs,coils,throttle bodies, injectors and exhaust off during the test. I had it on a heavy duty battery charger, so it was cranking over very fast. The engine was cold at room temp. I am also at 2,200 elevation. The gauge is a snap-on, not some cheap gauge. All cylinders tested at 185psi.

Why am I getting such a lower numbers? Is it elevation, testing at different temperature? .......

 

[Neville Lush]

Change the Schrader valve in the end of your gauge hose and try again.

 

[R-III-R Turbo]

When you say spark plugs off during the test - did you leave the other hole in that cylinder empty for the test?

 

[John Miller]

It is a low compression engine after all. To check for ring sealing quality you can squirt some engine oil into each cylinder and crank it for a while then check again - if the pressures come up significantly then you have ring sealing issues. Honestly 185 PSI is good for a stock engine at your altitude. Just make sure you are at WOT with secondaries fully open when cranking it.

 

[TheKid]

I thought 185 consistently sounded good

 

[R-III-R Turbo]

My carpenter 240 motor did 212-210-205psi front to rear cylinders, practically at sea level (25331 miles)

Same motor did 205-205-205psi at 100m above sea level (19333 miles) but that was a different gauge. 165psi when the throttle was closed.

Stock motor did 209-200-200psi (18670 miles) at 100m above sea level

I noted when the battery was less than spectacular, i might get 150psi.

 

[lunatic]

Change the Schrader valve in the end of your gauge hose and try again.

Installed a new schrader valve, didn't make a difference. I'm pretty sure the gauge is accurate....I think my low reading is because of the elevation and cold motor. All the cylinders tested 185-186psi again.

 

[lunatic]

Im done with the compression testing. Im going to start tearing into the motor. It is what it is....

 

[lunatic]

When you say spark plugs off during the test - did you leave the other hole in that cylinder empty for the test?

I pulled one plug out of each cylinder so it would turn over faster when running the starter....

 

[TheKid]

Im done with the compression testing. Im going to start tearing into the motor. It is what it is....

Keep us posted.