81 kz305 valve adjustment makes extreme differance

Bike was getting hard to start and stalling at idle. I checked compression and found left cyilinder 30psi and right cylinder 150psi.
Found left intake valve adjustment tight, (no gap). loosened tappet screw about 1/4 turn to get proper gap. Compression increased to 160psi. WOW. I never thought a valve staying open by so little would cause such a big change in compression. Bike starts and idles as it should now.

Geeze man, there is this thing called "maintenance" for a reason.  I'm truly stunned that people don't bother to follow the manuals recommendations.  

Yep, that'll do it.

These are mechanical devices. They will work as long as certain parameters fall within a fairly broad range, as you saw (30psi vs 150psi), but they will work best when they are within a certain narrow range - as you also saw.

Nessism post=876254Geeze man, there is this thing called "maintenance" for a reason.  I'm truly stunned that people don't bother to follow the manuals recommendations.  

Geeze man, that's quite an assumption.
Any idea why a valve would go tight and remain partially open when valve gap was checked/adjusted and within spec just 2,700 miles ago. The nut on the adjustment screw was tight, so I don't think it slipped.