Vintage Dirt Bike Q & A

I have a 1979 cr125r when I pull in the clutch whether the bike is running or not, it will not disengage it out of gear? The cable operates fine and pulls the lever on the engine all the way. so I am thinking it is something internally. but what is my question.

I'm not sure of your knowledge about the internals so don't take offense if I am not answering at your level. I also assume you don't have a bent actuator somewhere.

Your clutch is made up of alternating plates of smooth steel and friction material similar to what is found on brake pads. The friction plates are directly connected to a drum<clutch basket> that is rotated by the gear drive from the engine. The clutch shares oil with the transmission for cooling and is designed to work while immersed in oil.

There is a slotted shaft that goes through the center of the drum to drive the transmission. The steel plates have teeth that engage the slots.

With the clutch pulled in, it releases the spring pressure that forces the friction material plates attached to the drum to move away from the steel plates attached to the shaft, in theory, letting them rotate past each other.

In practice, Honda used ~semi metalic friction material in their friction plates: Little chunks of bronze in there. The combination of [smooth, oil, bronze, spring pressure forcing the plates together] does you in.

It's a lot like trying to pull two sheets of glass that have a thin sheet of water<oil in this case> between them apart. Thing is there is no force to move the plates apart! Honda and everyone else just relies on the absence of pressure to let the plates float apart.

The bronze in the friction material does not help the situation as it frequently corrodes the plates together if the bike is stored for any length of time. Doesn't take much, just a little discoloration will do it.

Anyway the drill for getting the clutch loose is put it in 2nd gear and with the clutch pulled in, VIOLENTLY shove the bike back and forth.

A method I use because I live in the country is to bump start the bike and ride it for 5-10 minutes with the clutch pulled in. As things heat up and stress on the bike due to hard acceleration with my lardbutt on it, the clutch eventually frees itself.

Worse case is you have to drain the oil and remove the clutch side cover. Once you have the clutch exposed, you just pull in the clutch and move the plates appart with a screw driver. Note that if you forget to do a single plate the clutch will still be stuck. This is a last resort type thing that I only do when I find a bike that has been sitting for 10 years or so. The clutch baskets are made out of the worse possible metal, worse then you find in a kids cap gun, and will bend or break if you so much as look at it wrong.

Your clutch basket might have notchs in it.. The plates may be hanging up..

_________________
Frankie
75 Honda 250 Elsinore
Findlay, Ohio

I tore into it anf found the clutch plates are stuck together and look like they need to be replaced so thats what I am going to do is buy a clutch kit with springs .gasket and a repair book. the job of replacement looks fairly easy thanks for your input.