The engine on my recently acquired SYM 150cc “Wild Wolf” seemed to have a slight misfire. I did the usual maintenance stuff in hopes of solving the problem: put some of that fuel-system cleaner into the gas tank, changed the air filter and fuel filter. Better, but not quite right. Took it to a mechanic. He opened the carburetor, did some cleaning, some carb adjustments. And then he adjusted a set-screw (initially hidden beneath a rubber boot) on the crankcase.
I have noticed this rubber boot before, never knew what was beneath it. The mechanic pulled it off to reveal a set-screw held in place by a locking nut. Please see the photos:
Adjustment screw with rubber boot in place
With rubber boot removed
I have no idea what this thing is, or what it does. Asking my mechanic wasn’t very fruitful - I’m not even sure he knows the Chinese name for it, let alone English. I’m baffled as to just what this set-screw adjusts, let alone how to know when it’s adjusted properly.
I’ve never seen anything like it, but judging from the position it could be the timing adjustment. Back in the old days you could adjust the position of the points relative to their operating cam using a screw accessible by opening the crankcase. This might be a more sophisticated version. Just a guess. Or it might be the misfire regulation screw, similar to the crash frequency adjustment found on more modern scooters.
I THINK its a manual cam chain tensioner, but I’ve only had the CG125 engine (as in the Zing, Grand King, Hartfords) which, being a a pushrod version of the CB125 engine used in the Wolf, wouldn’t need one. So I’m not sure.
[quote=“Ducked”]I think its a manual cam chain tensioner, but I’ve only had the CG125 engine (as in the Zing, Grand King, Hartfords) which, being a a pushrod version of the CB125 engine used in the Wolf, wouldn’t need one. So I’m not sure.
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Hi Ducked. Yes, your included parts diagram looks very much like what I’m seeing, and I’m sure you are right. Thank you for this!
Now that I know what the thing is called, I did a google search. Came up with a few links that explain what a cam chain tensioner is and why it is important:
correct. Old school design, but correct I believe.[/quote]
You say “old school design” like its a BAD thing.
I suppose it can be if (as is often the case) previous owners have never adjusted it, but you could have a lot of grief with neglected or faulty hydraulic tensioners as well, and I have (on a Ford Sierra DOHC).
My Lada had a manual cam chain tensioner and it took about a minute to adjust it once
a year.
Given the choice I’d go for a pushrod engine or a gear driven camshaft. I can’t imagine that I’d pine much for the performance difference between the CG and the CB 125, whatever it is.
Actually I admit that I have no idea what it is. The Wolf is so reliable that it is a very rare occasion that I ever have to do anything to mine, other than routine maintenance. I would agree however that it does appear to be a cam chain tensioner adjusting screw.
