will england :: motorcycle notes and tips

About BMW Clutches and other Motorcycle Clutches


On Tue, 28 May 2002, Tom Baumen wrote:

> Some of you folks own or have owned BMWs.
>
> I have never had to put a clutch in any bike I have ever owned. I Have
> never worn one out. I came close on a BMW airhead but I don;t think I
> will ever wear out the clutch on the Concours.
> I seem to notice in used BMW bike ads a lot of folks have clutches
> replaced a relatively low mileages (40,000 to 80,000) compared to
> Japanese bikes. Any one have any insight as to why this is? Do K bikes
> need clutches too?

BMW bikes use a dry clutch like cars and trucks.  Most other bikes,
including the Concours, use a wet clutch.  Regardless of how much you slip
the clutch it is nearly impossible to burn up a wet clutch - the oil just
takes the heat off of it.

However, if you ride a BMW like a wet-clutch bike (lots of slippage on
takeoff, etc), you'll waste the clutch in a short time.

The key to BMW clutches is to ride it like you drive a car - clutch in,
shift gear, clutch right back out.  On startup, smooth quick release, no
slipping the clutch at the friction point.

Will


=== also ===


Conc clutch is a wet (runs in oil) multi-disc clutch.  In general, wet
multi-disc clutches can withstand lots of abuse.

BMW clutches are like car clutches, a dry (runs in air) single disc clutch.

Besides that, the Conc is geared relatively low - BMW's tend to be geared
rather tall, and to require a bit more clutch slippage to get rolling.

So in the context of the above, BMW clutches tend to fail for 2 reasons:

1.  Folks slip them more than on similar Japanese bikes due to tall gearing.
2.  The rear main seal on a BMW goes bad and oils the clutch and it's then
destroyed by slippage.

FYI - I've put clutches in 3 bikes.  A 1984 GPz-550 (cable was dragging, and
not allowing the clutch to engage as it should've), a 1978 BMW R100rs (wear,
at about 60k miles - it had the tallest gearing of any Airhead), and my 1994
BMW R11rs (at 75k miles, rear main seal went bad and oiled the clutch -
though that was an early Oilhead and the clutch was a bit weak anyway....).

I've never had to put a clutch in a car, but then I've ridden 300k miles and
I don't think I've drivven quite that far yet.

One more thing to remember - even here on the Cog List, there's a lot of
bikes that don't make it to that 40k-80k mileage you mentioned, for whatever
reason.  While many BMW's do, though I think that's partly a reflection of
higher purchase price making it easier to rationalize the repair on the
BMW's.

Best,

Doug Grosjean
Pemberville, Ohio


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