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Old 05-02-2010, 01:35 PM
meowy84 meowy84 is offline
Motorized Bicycle Elite Member
Join Date: Jul 2009
Location: Canada
Posts: 238
Default Clutch Spring Adjustment and Modification?

I'm getting my first engine ready for the initiall install. It's a PK80. I'll be doing the usual intake/exhaust matching and folloring some of the threads some light port work just to clean up the casting flash, etc. I'm also wanting to give the clutch some attention. My clutch was initially stuck from sitting in the box as so many others report so I took the clutch cover off and while depressing the clutch arm gave the pressure plate a slight whack with a rubber mallet which freed it up.

Anyways, my first question is this: I'm not going to assume that it came properly adjusted from the factory so anyone know what the general pressure on these clutches should be at to prevent slip? Some have reported them being so stiff that the arm breaks. Since it was raining this morning and I didn't want to run out to the garage I decided to "scientifically" test this out in my livingroom (redneck, I know LOL) using whatever I could find, mostly new and full jugs of cooking oil for weights by hanging them off the clutch arm on the engine. Anyhow, it takes about 11 lbs of initial pressure to start the arm moving (and that's when I ran out of "weights") but I figure with another 6 lbs the clutch on my engine is fully depressed. So all in all it takes 17-20 lbs of pressure to fully depress/disengage the clutch on my engine as it came from the factory. This is nowhere near to breaking the clutch arm as some have reported. I suppose once I put the thing together and ride it I'll be better able to tell if the clutch is slipping or not and make some finer adjustments. But in the meantime I'd love to hear some inputs.

Now, the second question concerns the actual clutch adjustment. I know there's a way to adjust the main clutch spring preload from outside the engine but I plan to disassemble the thing to grease the innards anyhow so I'll be adjusting the spring then.

To illustrate what I'm talking about look at the front bicycle wheel. Once you adjust the preload on the bearings with the bearing cup there is another nut that you tighten against the bearing cups on both sides of the wheel so things don't loosen up. BUT WHAT ABOUT THE CLUTCH? Once the spring is adjusted, what actually keeps the adjustment collar from backing off a thread or two over time from the constant spring pressure on it and all the engine vibration since there is no lock nut behind the adjustmant collar to lock it in place? (see my attached amateurish illustration Manic Mechanic has a way better diagram). Mind you I haven't disassembled my clutch yet so maybe I'm missing something here.
Attached Images
File Type: gif clutch2.GIF (6.8 KB, 282 views)

Last edited by meowy84; 05-02-2010 at 02:10 PM. Reason: syntax
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