Ask The Editors: Decompression Depression

Can I just ditch the whole thing?

Dear ATVC: I lost the spring on the decompression lever when I replaced my valves. Can I run the ATV without the decompression lever on the camshaft? Would doing so cause problems?

Well without knowing the make/ model ATV and corresponding design of the decompression system, let’s start by getting the universal answer out there right away: Yes, running it without will likely cause top end trouble. Here’s why:

A compression release works by slightly opening the exhaust valve. By allowing much of the compression present inside a cylinder to be eased out of the exhaust tract, positioning the piston to top-dead-center becomes much less difficult.

We’re not certain which spring you lost- but assuming it is the one that returns the decompression assembly to the off position, and thus allows the exhaust valve to fully seat once more, you would be operating your machine with severely compromised cylinder pressure at all times. Not only would this cause power loss but it would also put your valve and piston at risk of damage as well.

Throughout the years there has been a very wide array of cylinder decompression designs. Everything from handlebar-activated cable systems to a release lever affixed directly to the head. We have heard tales of those who removed the cable assembly successfully but even they were forced to leave the system in tact at the cam for the reasons stated above.

Some designs are less likely to result in damage when run incomplete than others but were it our ATV, we wouldn’t take that chance. Hit up the dealer and order the missing spring.


Ask The Editors: Decompression Depression