1960 M8 inner chain case & clutch queries

[corbal]

Hi All

Bottom half of engine and gearbox now assembled and mounted in frame and about to fit inner chaincase with fairing to crankcase. The only gasket (in my set and listed) seems to be part 042169 which has 3 little ears and it fits around the outer boss face of the crankshaft bearing housing. Do you use Wellseal around the whole inner edge of the inner chaincase as well as the centre boss face or just metal to metal. I have incidentally scraped all these faces flat with engineers blue and a lapping plate so they do make a good joint.

Next problem!! - when I got the bike 18 months ago in a million pieces I discovered early on that the gearbox (traced through the club dating service) is from a Matchless 250, the clutch has 7 plates (as described in the manual for a std 250) and is Simplex. The primary chain I got with the bike is Simplex but the engine sprocket is a 22 tooth Duplex. I have just discovered that the clutch sprocket has 50 teeth and according to the manual should be 46. I really want to use everything I got with the bike because to me that's what I got and what was on it when it was stripped and left in a shed in 1975. I guess to make it work I will need to find a 22 tooth Simplex engine sprocket from somewhere. I would really appreciate any comments/advise - good news or bad - it will run again one day!!

Thanks Alan

[Tolly]

All the 350 lightweights have a duplex primary chain. This was a common "mis-modification in the past, as you know all the gears in the box are near the top and so require a gearbox full of oil. Because young lads back then didn't maintain their bikes very well oil level became low and nackered the box. The common thing was to go to a scrap yard and obtain another box and as they look the same as the 250 that was good enough. (Or so they thought). You will have to change the mainshaft in the gearbox to the longer 350 type and obtain another clutch hub. The probable reason it came off the road back then was because the PO had obtained a 250 gearbox and couldn't work out how to fit it and gave up.
Sorry to be the bearer of bad news but guess how I know?

[Ozmadman]

And just to answer he first part of your question, I just used Wellseal on both gasket faces when I put my inner cover back on. As for the gearbox, what has been said is correct. keep an eye on eBay or contact Steve Surbey at AMC Classic Spares for the parts you need bearing in mind that there are two 350 type main shafts due to a mod, both wil be ok, just make sure you get the correct clutch centre for the shaft you buy.

[corbal]

Thanks Tolly- the bike came from Kent but spent its early years in Cheltenham where it was originally supplied. I live next door in Gloucester. The last rider of the bike was my daughter-in-laws father but he died many years ago. He swapped it for a computer with his next door neighbour and it was him that stripped it but never got round to re-building it and after deciding to clear his shed out sold it to me. After the battle I had fitting the gearbox in the frame I hope I can use it.

Just in time - thanks Ozmadman - will use Goo on all joints. Not good news on the gearbox but it would be no fun if everything was straight forward.

Thanks All - Alan

[Ozmadman]

After the battle I had fitting the gearbox in the frame I hope I can use it.
Thanks All - Alan

Put it this way, it will all go back together and will work in 250 mode(the 350 isn't that much more powerful anyway) but the duplex chain was there for a reason. Having said that there are many older bigger engined bikes running a simplex chain with no problems so the choice is yours. Maybe if you treat it nicely and plod around at reasonable speeds then it will be ok?? if the chain goes though you will be back to square one. BTW the boxes are really simple to take apart and rebuild, reckon my 12 year old son could manage it so don't be put off by "having to replace the main shaft" discussions.

Paul