Vintage Dirt Bike Q & A

When I 1st start my 74 CR250M, the clutch doesn't seem to be working. When I attempt to put it into gear, its acts as though I didn't use the clutch. After the bike warms up a bit, it does work, but when the clutch is pulled, it acts as though its not completely disengaged. When the engine is not running, you cannot move the bike when it is in gear with the clutch pulled.

Any suggestions÷

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74 CR250M, bought new in 74, still stock, except for the new 36mm Carb, and proform exhaust.

Factory original 1974 clutch plates?

If so they deteriorate a bit with age. Old clutches used cork/brass filings that swell and corode. Once they start sucking up oil, they stick together like a drain plungers.

If it were me, first thing I would do is get a straight motor oil with no special additives. I'd then slip the clutch hard during a riding session so it work polishes the friction and pressure plates.

If it doesn't get loose, go to Dennis Kirk and pick up a new set of friction disks. They sell for ~$20-$50 depending on how much you want to spend.

Yes they are the original clutch plates. Yes, since I just got my carb issues straightened out, I haven't pushed the bike too hard... During the last ride, I did baby the clutch.. I will try slipping the clutch a bit during a hard riding session this weekend. It may just be a case of the bike sitting too long... (I hope).

I did change the tranny oil, and put in standard 10-40. I'll go for a little ride, change the oil, and then put it to the test...

thanks

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74 CR250M, bought new in 74, still stock, except for the new 36mm Carb, and proform exhaust.

If you do wind up changing the clutch plates may I suggest using the Barnett kevlar plates instead of the stock ones. They really last!

Dave at AMS Racing carries them.

Loren

By this do you mean a single viscosity or?? What do you recommend?

TIA,

Loren

An oil thread!

A 30 wt non detergent motor oil would be fine since the only thing it has to do is let the spongy parts of the friction plates wear off, then the oil gets changed. Hopefully there will be some friction material left.

Only thing I would stay away from is the oils advertized as increasing milage. I've had some bad luck with them making a marginal clutch slip.

Castrol is a good enough oil if cost and availability are concerns. A friend that used to work in a Honda shop says Castrol 20-40 is what they used when you brought your bike in for service. I change my oil often, every couple of hours of operation, so a long lasting synthetic wouldn't make much of a difference for me. If I ever get involved in a long hard ride I would use a synthetic like Mobil 1.

Another thing that might be happening is that your clutch basket may have indents where the metal pressure plates face up to it. This prevents the plates from moving apart when you pull in on the lever and releasing the spring force that holds the plates together allowing the clutch to disengage. Over time it is very common for this indenting to happen. If you have a vertical mill or are very very carefull with a flat file you can smooth down the surface of the basket where the plates engage it.

Loren