Gyrobob
Serious Thumper
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Posers ain't motorcyclists
Posts: 2571
Newnan, GA
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Savage 1987 wrote on 03/31/12 at 06:29:41:Thank you everyone for the pictures, video, and suggestions.
With the linkage removed, when I operate the valve with my hand, I can definitely get it to travel further into the open position than I can get it to go with the foot lever.
I am beginning to wonder if the valve is actually open enough when I use the Ryca linkage and foot lever...and I just don't realize it.
What if I continue on with my project, assuming that I got the decompression linkage set up and operating correctly. When I get to the point of starting the engine up, am I going to do damage if the valve isn't open? What are the ramifications if I go this route?
I don't want to get hung up on this. I want to keep making progress (morale booster) so I can eventually finish and ride! All the decompression thing does is to lift the exhaust valve maybe 1/16" so the combustion chamber is not sealed for the first time the piston goes up on a compression stroke. Without raising the exhaust valve, asking the starter motor and gears to force that huge piston up and through a compression stroke is doable, but it puts a big strain on the starter motor and gears. Once the engine is spinning around, even if it isn't running yet, there is enough flywheel effect for the starter motor to keep things turning over even with the exhaust valve sealing properly.
So, the important thing is to just have the exhaust valve intentionally not sealing for the first time the piston heads north for a compression stroke. Therefore, it's not critical when you let up on the decompression lever. It's only a big deal to push down on the lever just before you hit the starter button, and hold the lever down for a second or so, or, if you want, until the engine starts.
The engine will run with the decompression lever pushed down while it keeps the exhaust valve from sealing. This is similar to a motor that'll run (poorly) with a warped or burned exhaust valve. Don't do this on purpose.
One thing you could do to verify the decompression function is working is to see if the compression chamber is sealed with the decompression lever pushed, and with it not pushed. There are lots of ways:
-- rotate the engine over with a wrench and compare lever up to lever down
-- put the bike in 5th gear, and have someone push you while you compare lever up to lever down
-- if the bike is on a stand (rear wheel free) put the bike in 5th gear and see if it is easier to turn the motor over with the decompression lever pushed
-- Take the spark plug lead off, push the lever down (raising the valve) and hit the starter button. If the motor turns over easily, the exhaust valve is lifted. If it does not, you have some troubleshooting to do.
-- if the lever is NOT lifting the valve, you will notice it's really hard to push the piston up through the compression stroke
-- if there is not much ambient noise, you'll hear air hissing past the lifted exhaust valve when the lever is held down while the piston goes up the compression stroke.
If, when you get your linkage all set up, you see the lever on the top of the cylinder head moving more than 20 degrees or so when you cycle the foot lever, you almost certainly are lifting the exhaust valve. If you see it moving as much as my ex-girlfriend was able to make it move in the video, you're okay.
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