EV007 VM ENGINE

What is the correct way to adjust the decompression lever? - Bob Hodgkins 3/1/2001

The exhaust valve lifter (at the timing chest end) simply rests on its stop when the cable is slack, which gives a small but adequate clearance from the exhaust cam follower. Then as you turn the lifter it rises and takes up the clearance then lifts the follower a few thou, but only a few thou. So you need to do two things - with the engine up against compression (so that you know the exhaust valve is fully closed) turn the lever by hand and check it moves through about 10 - 20 degrees of arc before contacting the follower. (You won't be able to turn it further by hand). This is just to check yours hasn't been wrongly assembled or modified in some way.
If OK, take all the slack out of the cable using the adjuster that is screwed into the lower pushrod cover tube flange. When you operate the lever on the handlebar you should feel it move half way with little resistance then the other half with quite a squeeze, and you should be able to turn the engine over tdc without feeling compression.
If your lever is sloppy, or cable spongy, etc then you can tension it to pre-load the lifter but it is essential to check that, at tdc on compression, you can turn it about 10 degrees by hand against its spring before it starts to lift the rocker. - TW 3/1/2001