CentralCoaster

Front cylinder = 90 psi
Rear cylinder = 65 psi
Doesn't look good.

What should I expect? My chevy small block with similar compression ratio hits 150psi+.

I did this test twice, with throttle wide open, fresh battery, choke off, and spark plug in the other hole. (I know, I know, shoulda removed that.)

Problem is bike won't run. Has spark on both cylinders, I can smell fuel during cranking, starter fluid directly into carbs doesn't help.

I managed to get one or two random backfires out the exhaust during cranking.

The bike sounds different during cranking than it did before (when it ran). It almost seems like the valve timing is wayyy off or there's some serious damage in there. I tried stuffing a wad of tissue into the end of each exhaust pipe, it barely moved enough air during cranking to blow one out, the other didn't move.

History... bike ran great 4 weeks ago, I parked it to put on a new chain. Then it won't start no matter what. Tried fresh fuel, still no go. Did a valve adjustment a few thousand miles ago and also rechecked the manual CCTs adjustment.

It's as if I broke something just installing a new drive chain. I'm baffled.

I just wanna ride.

VTRsurfer

I was thinking CCT failure, but since you said you have manual adjusters and they check out, I'm stumped too.

But unfortunately your compression readings are way too low. I don't know how a drive chain replacement could have caused the valve timing to jump, especially with manual adjusters.

Have you checked the valve timing yet? I've never done it on a VTR, but it normally requires removal of the valve covers to check the cam timing marks with the crank timing marks. That would be the next step.

Good luck. If it didn't slip too much, the valves could still be okay. Cross your fingers.

CentralCoaster

Arggh. Yeah I guess I'll have to pull the valve covers again. I haven't heard any nasty valve crunching noises, and any contact would only be during cranking.

I tried checking the spark timing with the timing light through the side cover, but I don't know if the marks are intended for that. Although the spark is crank driven anyways I assume.

gboezio

Align the flywheel mark RT to the dot in the stator window and the rear should look like this.
On the front cyl, use the FT crank mark and the FI &FE marks and align to the edges of the cam cover seat surface.
There should be a 270° counter clockwise rotation (stator side) from the RT mark (cam aligned lobes up) to FT mark (cam aligned lobes up)
If this all checks ok it should start.
And yes remove that other cyl plug while testing, it will avoid pumping gas and messing the cranking speed.

CentralCoaster

I might just put it on the back burner and fix my other bike first. That one seems easier now.

bjorn toulouse