Monday, June 10, 2013

SV650 Sticking Clutch

A few years back my buddy Randall had a problem with his SV650. The clutch wouldn't disengage. He'd pull in the lever and drop it into gear, and the bike would lurch forward. It acted like the clutch cable wasn't there at all. But then a few miles down the road it would work fine again. He brought it to me, and this is what I found:

This is the clutch basket. If you look closely, you can see there are nice shiny marks on the fingers of the basket. Running your fingers over these, the shiny areas are actually indentions,  and the dull areas raised ridges. What has happened is that this is a high mileage (50k) bike, and over time gunning the throttle has caused the clutch plates to slam into the fingers, which has create these shiny indentions. They don't look it, but they're deep enough at this point to occasionally catch the clutch plates, and prevent them from moving away from each other. The plates are firmly stuck in the indention. 

The correct thing to do is replace the clutch basket, and replace the clutch as well. However, the clutch in this bike was replaced less than 10k miles ago, and my buddy Randall was a grad student with no money. And since this is a blog that centers around budget motorcycle mods, here's the fix:

I'm painstakingly filing off material until the ridges are down to the same level as the indentions, and it's all completely smooth again. You can see I've completed one finger already, as the whole thing is nice and shiny. (leftmost finger) I did this filing for all the fingers, tossed it all back together, and was even able to reuse the clutch cover gasket. We even leaned the bike over in the grass so it wasn't even necessary to replace the oil.

Now, this fix is cheap, but there's a problem with it. It won't last forever. In fact, it won't last as long as the original clutch basket did. By filing the material down, there is even MORE slop in the clutch, which will cause the same problem to happen all over again -- and it will happen in fewer miles. So, it's a passable repair, that will probably get you another 20,000 miles. But it's not a permanent repair. Then again, nothing that has to do with your clutch is a *permanent* repair. They will all wear this way. 

That being said, my V65 Magna has 40 more horsepower than the SV650, 80,000 miles, and the clutch basket looks new. Different designs and different forces at work (and the V65 has a huge spring on the driveshaft that absorbs a lot of the immediate slamming force when hammering the throttle and dumping the clutch)

Anyhow, this is your technical tutorial for the day.

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