New Guy and Bike

Hi, I've been reading the forum here a couple years now. I picked up a basket case 750 with hi rise bars 15 years ago. It was in the bargin paper I picked up going to work. He was asking $750 and I was the lucky first caller. It wasn't what I was expecting to see in the paper, much less get all excited and running to the phone as i'd have to scrape to get that kind of cash quickly. I got there after work and took a look at it. Its rough but forks, clocks, motor look good. It died from a broke gearbox. Guy selling it owned it a few years then sold to an employee who rode broke and abandoned it. Its been inside so oil soaked and no rust. So even though all my money was tied up racing and I didn't know anyone with british bikes, it would be sitting who knows how long, I bought it. He had 2 or 3 calls while I was there but stuck to the price and had me take a junk yamaha 250 enduro and ty 250 but no motor. I was pretty happy on the way home.

A couple years ago a friend who hangs out in my garage got interested in bikes. He sold the junk 250 enduro for $100 on craigslist so I gave him a 350-4 honda to fix. Hes been asking when i'm going to start on the Norton? So I got a gearbox off ebay to get the ball rolling. It has some damage but not bad. I stripped the motor. Serial no 150751. It has a roller and ball brng crank, vent on cam end, pistons with weakening slot, head look cut it measures .06" deep to the squish step, cam rods and journels are good. It was good after reading so much to see the parts.

I'll try some pictures. First is bike among others.



Motor



Cracks in ebay gearcase



Old blown up case

Gear box damage...get another case !

Gday edge, can only see one thing wrong with that trans case mate and that is its F@#ked well and truly! :mrgreen: Time to find anothery!

its not cracked between the two bearings so it should be ok.

Donald it's cracked around the bearing location, to the right of the picture.
Nobody in their right mind would use this! ........well i wouldn't!

Is there weld on the backside of that case?

If there is weld its going to be crap! a good weld would penetrate right through!!! plus no heat trace inside.

concours said:

Is there weld on the backside of that case?

Click to expand...

John Robert, I surely didnt think you would take my comment seriously.

Donald .OK banged to rights, anyway the case in question is the ebay case,not the dire looking one..so i retract all i have said!

uote="madass140"]John Robert, I surely didnt think you would take my comment seriously.[/quote]

Welcome to the forum. That is a treasure trove of a shop, lots of dusky jewels in there...

The e-bay case looks fine ,it even has a roller layshaft bearing in place (where is the internal half?). The left upper stud has cracked the case but not a stressed area . Clean and inspect that with brake cleaner.

Thanks for the welcome. You'll have to cut me some slack as my writing tends to cause confussion. The old blown up case is welded outside and was run again until a gear broke to pieces. Bearing clearance between kickshaft and layshaft is .015" or really sloppy. The cracks in the ebay case by stud are from a ham fisted mechanic. Layshaft roller brng is damaged and will be replaced. My first question is where can I find what the running clearance for all the sleeve type bearings in the gearbox should be. I'm measureing about .004" to .01" and guessing they could be .0015" to .002". I have a lathe, 660 bearing bronze and a sunnen hone. In the shop manual it tells about pushing new sleeves in and reaming to size but doesn't mention the actual fitted clearance. Or maybe i'm not looking in the right place for the info. Between the 2 gearboxes I think I have enough good repairable parts to make a good one.

e-bay case O.K. Use sealant around ham-fisted stud or pull it and weld whilst apart. Luckily not a stressed area. Just a sealing issue. Heat gun drops out old bearing then drop in frozen new (roller) one. Sleeve gears always worn, replace. Also delicate 1 st. gear bush. Good luck.

Amazing the thin web betwix bearings is not cracked, so ughly as the case looks other wise, likely just JBW to hold oil and rebuid and run a long time, if not racing and dropping clutch drag take offs is all. Btw Commando gb shells have a top DS notch that requires a thick washer to snug up on installs. This special Commando unique feature costs ~$250 extra to buy over otherwise identical Atlas shell, if it comes to spending decision time again. I find the Altas easier to install and remove than the real deal, so your call - after calling world wide vendors to verify this.

Hobot, whats a top DS notch? My 2 cases don't measure the same across the mounts. I'll gather info and post questions.

I think he's talking about the 'top drive side notch'. There's a thick 1/2" washer that fits between the gearbox and the cradle, inboard side. Sometimes it gets left out and then things get kind of skewed around and the chain rubs, cradle gets bent, etc. It's about 1/8" thick, maybe more. If you need a pic, I can find it.

Dave
69S