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Do I need a new clutch?

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carg3

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A few weeks ago I noticed the tachometer needle jumping when going over 5k RPMs. I took my bike for a quick ride today and noticed the tach doing the same thing but around 3k RPMs, also it feels as if the bike is working harder to keep speed and sometime it would just rev up as if I was disengaging the clutch.

I'm pretty sure these are all symptoms of a bad clutch but wanted to confirm here just in case.

I have a 1972 bike with around 13000 miles.

Thanks
 
Assuming you're using the correct oil for a wet clutch and you've got it all adjusted so it's allowing things to fully engage, it sounds like it's time for new friction plates.

I went w the CycleX 5 plate setup with extra holes drilled in the hub and all the channels filed, and have no complaints. It's smoother and more consistent than the oem arrangement ever was.
 
dirtdigger said:
Im not a fan of oil with moly even if it is motorcycle oil. Especially in the old bikes it can cause clutch issues
Click to expand...
Agreed. I didn't even consider Liqui Moly as anything more than the brand name. The bottle pictured mentions wet clutches but I can see how actual moly additive could cause slipping.

Fwiw, I use Valvoline 20-50 conventional motorcycle oil in my K4... 4T, wet clutches, JASO MA2, and all that. Seems to be really good stuff.
I use VR1 in a '50s flat tappet engine for the high ZDDP (zinc) level. I found Valvoline's product sheets to be about the most informative when researching oils for that application so I went back to them when looking for motorcycle oil.

https://shop.valvolineglobal.com/pr...V1WO4SX24Gl2lsxsuHB25dRVbWVB2f56KeH&Size=1+QT
 
Hmm, it seems like that could be the issue. I always thought that was just the brand name too. I know it is a good oil, but maybe not for these bikes. I have put around 600 miles since I got the bike running after sitting for the last 20 years. 600 miles doesn't sounds like enough mileage to me to go from working fine to clutch slipping.

Well, live and learn I guess. I've already bought the new kit so I'll replace it anyway and switch to a different oil.

Thanks,
 
carg3 said:
Hmm, it seems like that could be the issue. I always thought that was just the brand name too. I know it is a good oil, but maybe not for these bikes. I have put around 600 miles since I got the bike running after sitting for the last 20 years. 600 miles doesn't sounds like enough mileage to me to go from working fine to clutch slipping.

Well, live and learn I guess. I've already bought the new kit so I'll replace it anyway and switch to a different oil.

Thanks,
Click to expand...
If it's a high molybdenum content causing the slipping, your friction plates would be toast anyway as they're absorbent.

And on that note, be sure to soak the new plates for a day or so in whatever oil you decide to go with.
 
I've installed the new set and the bike is running great. I also checked the thickness of the old friction plates and they were all within spec at around 3.48mm in average.

The oil was definitely the cause of the issue.

Thanks for all the help.
 

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