Ask the Editors: Why No More Compression Release?
Relic from the past?
You are indeed correct that manual compression release levers have become very few and far between but the reason for this has less to do with decreased cylinder and compression and more to do with another feature having gone extinct: The backup starting method.
We don’t think much about compression release – the process of manually propping the inlet and exhaust valves open until the motion of the piston cycling pulls them closed – because, on most modern ATVs, we’re no longer in a position where we have to pull a tough recoil or step on a stiff kick-starter.
Modern fuel injected ATVs are completely dependent upon their battery – not only in the starting process but to operate as well. Back in the carbureted era, it was commonplace for electric start ATVs to come with backup starting systems so that a weak battery wouldn’t put an end to the riding (thanks in no small part to the fact that fuel delivery was dependent upon gravity/ the battery only there to power the electric starter). Because tugging a recoil on a big bore engine could be back breaking work, the compression release took some of the difficulty out of the process.
These days its a jump start, tow from another machine, a new battery or bust. The pull starter (and the compression release lever) have become casualties of the forward march of technology.
They can still be found on some non-electric start models, however. Also automatic decompression cam technology exists as well on certain models, removing the human element from having to decide when to activate the lever.
