[Dnorton1]

Hey all, lately I’ve noticed an annoying rap like sound getting louder, I can hear it all the time now except at high rpms, I was confident at the beginning that it was the clutch but the other day I started second guessing that theory, so I pulled the primary clutch and fired it up, and sure enough, no noise at all, but what I don’t understand is why? I have 4 cfmotos in the family and they all make a little noise (from the primary) but nothing like this. I’ll try to post a video of it running when I had it apart to set the valves, you can’t miss the noise, it only has 600 miles on it and I did put heavier weights in it but I see nothing wrong, loose or dirty, there’s not much to these. Any ideas? Or just drive it and enjoy it? Still works perfectly

[NMKawierider]

What many people don't realize is that combustion engines do not run at a constant RPM like an electric motor. Upon compression the engine slows down slightly, then during initial charge detonation, which is a few degrees before TDC, it slows even more. Then when it makes it over TDC it speeds-up quickly for a few degrees then smooths-out during the rest of the power stroke depending on the throttle position. Watching this on a scope looks almost like a hart beat on a heart monitor. Just a quick blip but it's there. This means everything connected to the crankshaft is also effected with this "pulse"...including the clutch. Now, part of the clutch is fixed to the crankshaft but part isn't...the movable part. Any side play it might have will cause that free part to bang back and forth during this pulse. These clutches have shoes or guides or something that takes that play out and allows that part to move. Once those guide pieces get enough wear...from either normal operation or that side ways hammering they tend to wear faster and faster. Yours..sounds like they are getting due to be replaced. If it were mine I would do two things. One, replace all the guides. They will be #8 in this photo. The next thing I would do is take each slider and weight and weigh them. They all must be within .05 grams of each other. The closer the better. Very important as this not only effects the clutch operation..ie heavier ones push more then light ones and effect the plate angle...causing those guides to wear faster, but an out of balance clutch kills engine main bearings as well as effects other engine parts. Good luck. Do it soon.

   

[Dnorton1]

Wow! Nicely put sir, I actually understand what you explained, I will order those now, it’s still apart and I’m going away for an xtra long weekend, alpha sports has been great for me on delivery time, so hopefully when I get back I’ll have them, and check the weights to make sure there the same, thank you once again NMK and all the others on this site, I’ve learned a ton of shit from you guys!

[NMKawierider]

Wow! Nicely put sir, I actually understand what you explained, I will order those now, it’s still apart and I’m going away for an xtra long weekend, alpha sports has been great for me on delivery time, so hopefully when I get back I’ll have them, and check the weights to make sure there the same, thank you once again NMK and all the others on this site, I’ve learned a ton of shit from you guys!

Welcome. Also check how the sliders are fitting in their slots. They can also start getting some play as well. The cam plate is supposed to just touch those at idle to help keep them from rattling but...under the right conditions everything can wear a little. If the guides seem still tight, check the cam plate and sliders even closer.

[Dnorton1]

Update. The new guides got here pretty quick, just had a chance to put it back together, but not before I checked the weights, they were not all the same, even weighed the sliders and they were not the same either, so I made them all within .01g of each other with the sliders. Problem solved! Clutch is nice and quiet now, hopefully it lasts a lot longer now that it’s much more balanced. Thanks again for the advice

[NMKawierider]

Update. The new guides got here pretty quick, just had a chance to put it back together, but not before I checked the weights, they were not all the same, even weighed the sliders and they were not the same either, so I made them all within .01g of each other with the sliders. Problem solved! Clutch is nice and quiet now, hopefully it lasts a lot longer now that it’s much more balanced. Thanks again for the advice

Your welcome. Enjoy...and your engine will thank you for the balancing with much longer life.