Clutch plate setup on the 250 CSR

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Re: Clutch plate setup on the 250 CSR

Postby Ozmadman » Mon Sep 04, 2017 3:08 pm

I have found a picture I took of my sprocket. Note the larger section that extends a small way down the sprocket, this end goes on the crank towards the engine which then allows it to go fully home as it fits over the step in the crank. As you tighten the nut it should make contact (with or without shims) with the inner track of the outer crank bearing and pull the crank over to remove any end float. I would suspect that as yours is you still have end float in the crank even with the nut fully tightened?? this is wrong and is allowing the crank to move side to side as the engine runs. You don't need any end float as that side of the engine is running in two roller bearings and the crank needs to be pulled up tight against them. As I said earlier the end float you have prior to doing that nut up is now gone but leaving a gap of about 0.020" (not critical as long as there is at least that the allow for expansion of the timing bush) at the other end on the crank.
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Clutch plate setup on the 250 CSR

Postby clanger9 » Mon Sep 04, 2017 6:29 pm

Paul is right. If the sprocket is round the wrong way, then it doesn't take up the crank end float properly. This is potentially much more damaging than chewing the alternator rotor a bit! I can understand why they're often fitted the wrong way round because it really does look weird when fitted correctly.

Sometimes you'll find a bodged spacer behind the reversed sprocket where someone's attempted to "correct" the end float issue. Basically, fit the sprocket the right way around, tighten it up and check that it's properly aligned with the clutch sprocket (and any end float should disappear). Any chain misalignment can be fixed by shimming the front sprocket, but provided everything else is correct then you shouldn't need any shims.

On no account fit shims or other bodges behind the clutch. That needs to be done up tight on the shaft or it'll just work loose.
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Clutch plate setup on the 250 CSR

Postby Ozmadman » Mon Sep 04, 2017 7:48 pm

clanger9 wrote: Basically, fit the sprocket the right way around, tighten it up and check that it's properly aligned with the clutch sprocket (and any end float should disappear). Any chain misalignment can be fixed by shimming the front sprocket, but provided everything else is correct then you shouldn't need any shims.
Mine didn't need any..bearing in mind someone had also tried to "shim" the end float by putting those shims inside the engine on the crank, had sheared off the woodruff key on the crank that located the breather rotor that fitted between those two bearings and then decided to leave the rotor out all together. It was a hellava job trying to get what was left of the key out of the crank.
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Clutch plate setup on the 250 CSR

Postby pecon » Tue Sep 05, 2017 1:48 pm

I had a closer look at my sprocket and found that it does seem to be fitted back to front. However what is puzzling me is that when I reverse it the sprocket rubs against the casing. It looks as though there should be something between the bearing and the sprocket to prevent this?.
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Re: Clutch plate setup on the 250 CSR

Postby clanger9 » Tue Sep 05, 2017 2:43 pm

I think that's the right way round (not 100% certain from the photo). The "extended" part of the sprocket centre should face outwards towards the alternator rotor.
DSCF1066.JPG


Are you absolutely sure it's rubbing on the casing?
If so, you may need to fit a (small) shim - these are alluded to in the manual, but aren't available anywhere as a part...

I made some from easily available DIN 988 shims: viewtopic.php?f=15&t=17322&start=10#p155684
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Last edited by clanger9 on Tue Sep 05, 2017 2:54 pm, edited 1 time in total.
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Clutch plate setup on the 250 CSR

Postby Ozmadman » Tue Sep 05, 2017 2:54 pm

Or maybe the bearing isn't fully home in the casing? I thought mine was touching but it wasn't, it is pretty close though
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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