Does a Scrambler 400 have a compression release? My friend's 400 won't fire and I suspect a top end rebuild, but a compression check might be a clue, if there's no release.

 

Do a compression check and anything below 80psi it will not run.

 

Hey PeterinAZ, good to hear from you. The 400 has a built in compression release in the form of a small hole above the exhaust port. Helps ease the starting, but doesnt really affect anything. If you tend to have spark and fuel, pour a capful of motor oil down the spark plug hole and try to crank it. If it tries to go or does go, then you need a top end job for sure. But a compression test should do it, and as 2many says, gotta have at least 80 to go.bubba

 

Thanks, Bubba. This Scrambler 400 has less than 30psi compression, so I've begun a top end rebuild. So far the cylinder walls don't look too bad, but haven't yet removed the cylinder. I'll probably find bad rings soon. If you recall, you helped me through the same job on a TB 250 last month. I've been down this trail before so I'll need less help. The 250 was a friend's son's, this 400 is the friend's . . . it's running in the family! When done, I think they need a lecture about why oil is a good thing.