I checked the comp. on 3 Raptors today. Mine goes a bit better then the other two even if we swap pipes, with all three at the same carb settings. We checked the comp. and mine and one other was 100PSI, one was 160PSI and this is the slowest one?? I have heard there is some sort of decompression switch in these but not sure as to how it works? If anyone could give me any info I would greatly appreciate it .

 

The Decompressor is a centrifugal weight attached to the cam sprocket.

When the engine is off, or at very low cranking speeds, the weights do not rotate fast enough to keep them from being pushed out to their driving position. When that happens, a "mini cam" (located inside the cam shaft) rotates from the weight movement and causes a small pin to protrude from the engine cam core. The pin is located on a cam lobe for one of the intake valve rocker arms. The pin causes one intake valve to remain slightly open and thereby relieve compression so the starter can spin without issue.
The compression release can be a problem for riders with tall gearing who ride tight technical woods or track rides. At low rpm, the release can and will cause the engine to stall. On my race engines, I remove the system and I have not had a problem starting even with a very large piston.

 

I thought this is how it worked. I was going to check and see if there was a difference in cranking RPM, Do you happen to know at about when this occurs. I think I remember reading 800RPM someplace but don't remember where?

 

I think it varies as your different compression results tend to show. That is why I think there is no place for the release on the machine.

If you want to check your static compression, I suggest you install the gauge and try a brief bump start. It will turn the rpm (hopefully) faster than the starter and cause the release to close. I guess you could also remove the valve cover and use some temp wire or ?? to hold the weights out. Who knows??

Note that if you remove the system, there will be a major oil leak unless it is done correctly!