Problems with compression test.

[Hammermechanicman]

This thread took a left turn a long time ago.

 

[BVT]

What motorcycle are you working on. Compression releases are still on some current production motorcycles. I would recommend getting a better-quality compression tester also. Depending on the motorcycle you're working on you may be able to find a service manual online or got to one of the online motorcycle parts stores and look at the parts diagrams and find the camshaft, look and see if it has any type of a weight on it that would be the release. the other thing to check is (again depending on what motorcycle you are working on) the valve clearance.

 

[lbrac]

Never seen a mechanical ACR on a multi cylinder 4 stroke bike. Honda did have one on the XL500S. It was a 500cc 4 stroke thumper that pretty much killed off the 2 strokes used in flat track racing. Back in the heyday of big single racing 2 strokes it was common to have a compression release activated by a lever on the handlebars. Wasn't used for starting but rather modulation of power while holding WOT.

Manual 2-stroke compression releases were used for braking, when the drum brakes back then would wear out in one enduro, sometimes before it was over. Disc brakes solved that problem.

 

[Hammermechanicman]

Buddy of mine raced flat track back in the day with a big 2 stroke single. Once up to speed he held the throttle wide open all the time and used the compression release to modulate power in an out of the turns. Keeps the engine revs in the powerband all the time. Brakes? What are brakes? I helped him in the pits sometimes. Those guys had more balls than brains.

 

[lbrac]

Does #2 cylinder miss at all rpm ranges? Idling or gradually revving through the rpm range while sitting still; riding while coasting or under different loads/power levels? If it misses only at a certain rpm range or loads/power levels, it might help identify which fuel circuit in the carb is at fault, assuming that is the cause for the miss. I worked at a Yamaha/Suzuki dealer in 1983-84 and never heard the mechanics or parts people mention anything about a compression release on your model, or any 4 cylinder models of that time frame. Nearly all had electric starters, and most had done away with kick-starters.

A parts guy there had a friend w/ a new HD who would dare different people to try to kick-start it, and we got a lot of entertainment out of that. If you weren't serious about follow through, it would throw you over the handle bars when it kicked back. They tried it with me and, to their surprise, I cranked it on the first kick, despite being a relative lightweight. But unknown to them, a friend of mine had a 450 Husky that I was used to kick-starting.