BannedCR500Riders.com

Compression release doesn't work as a check valve, if while you are riding you get some dirt or sand around the unit it could suck stuff in. an easy fix would to put on a water ballon (without the water), just like a normal condom, could save you some expence down the road
Cheap enough to change every ride I'm not sure if they will hold up to the heat? just something to consider.

Kuma wrote:Compression release doesn't work as a check valve, if while you are riding you get some dirt or sand around the unit it could suck stuff in. an easy fix would to put on a water ballon (without the water), just like a normal condom, could save you some expence down the road
Cheap enough to change every ride I'm not sure if they will hold up to the heat? just something to consider.

Interesting thought on the sucking...

It would not be hard to add a spring loaded ball as a check inboard of the valve.

Interesting thought here. I wonder if there is any documented occurrences of this?

I've made a retainer and added an extra spring to them when opened with a thumb lever, just so the preload of the activation lever didn't hang it open. This could be done any time.

It would have to be a complete piece of shit decomp.

Are those little Harley type ones a poppet valve unit , or not?

By poppet valve, I do mean just like a 4t valve and seat set up.

My auto decomps, have a poppet valve that is closed by vacuum. So, whilst the engine is off, the valve is open. When the engine is running, it is closed, at all times. It has a filter element in the breather ports that allow the diaphragm to move due to the vacuum and close the valve - it does not allow unfiltered air in at any time.

I've used them on bikes for over 25 years - never had dirt get into the engine, and I've drowned bikes, through the airbox being submerged, with no problems resulting, at all.

As I said, for a decomp to do what you say, it would have to be a complete piece of shit - either using some bizarre 'valve', or the old, exposed valve spring type. Those, belong back in the exposed 4t valve train era. Or simply a badly adjusted cable operated type, and not being able to close due to shit house set up.

agreed, we've sprayed these while running with brake kleen and either to see if its sucking vacuum, notta

My concern is not while it's running, but while you are riding, sand or dirt makes it's way into every nook and cranny, including the vent on the valve. When you open the valve to start, the motor takes it's first gulp. that shit could be pulled into the motor. I doubt that it would make it into the bottom end, should blow out the exhaust but it could get around the rings and cause a little wear and shorten the life span of the engine.
Bearoso's setup has a filter to prevent that.