Rob's 750 build thread

[Ironracer]

I'm starting this thread to document my project build. While parts continue to flow in from the man in the brown truck and the increasingly exasperated mail lady it's going to be a case of evaluating what I've got and what new parts I need to order to make things work.
I'm trying to get as much used stuff as possible and it's starting to come together.

Tonight I'll start stripping down the donor engine for its top end, cylinders and rods and whatever other parts are common between the earlier engine with tach drive off the timing cover and the later version with points there. The A-N parts lists have been very useful working out which parts are the same and which I need to source.

I have a Yamaha XS650 36 spoke front wheel and disk from another project with a nice shouldered rim to match the rear and I'm torn between getting a Commando wheel or just using what I have and making up spacers for it.

Also, I made my first rookie mistake. Not being totally familiar with the gearbox other than general shape I bought what was being sold as a Commando box which turned out to be an AMC box. So now I have a Commando housing and mainshaft to mate with the internals from the AMC box. I hadn't really intended to do a gearbox rebuild but in for a penny in for a pound...

 

[o0norton0o]

I don't have a lot of time this morning because I have to get to work, but I did a yamaha cast alu wheels conversion, both front and back. There were a lot of modifications necessary. The yamaha disc in the front will be an inch wider in diameter than the lockheed disc. You can't just cut the disc down because the disc's bevel will foul the lockheed caliper, so you need to make a bracket to reposition the caliper or adapt another calper.

You'll also need to change the bearings in the front wheel to work with the norton front axl, at least that was how I did it, because the axle diameter and the yamaha wheel bearings didn't correspond.

In the rear, I used the yamaha axle with the yamaha wheel, then widened the axle slots of the norton swingarm to 17mm to fit the yamaha wheel. I also moved the brake cable shackle to the other side of the swingarm and made a long cable to loop over the wheel and down the right side of the swingarm to operate the drum brake on the yamaha rear wheel which is on the right side of the bike, unlike the stock norton drum on the left side.

Then there's the spacers to figure out, and you'll need a ~40 tooth sprocket for the new yamaha rear wheel. (I got mine at sprocket specialists in utah somewhere, I think)

 

[L.A.B.]

I'm starting this thread to document my project build.

Thread moved to Rebuilds section

 

[grandpaul]

Thread moved to Rebuilds section

hee hee I WAS going to mention to the O.P. that he ought to ask to have it moved...

Thanx.

 

[Ironracer]

Oops, I totally missed that whole section! Thanks

 

[Ironracer]

Looking at the front wheel situation, I decided to keep the Yamaha wheel for another project and build a Commando wheel instead. Picked up a billet front hub, now waiting on spokes and rim.

Last night I started stripping the engine. Not as bad as it could have been but I was disappointed to find some damage on the back of the left rod. It doesn't seem to correspond to anything so I'm thinking that at some point a piston skirt broke and gouged it up.

 

[Ironracer]

Forks stripped. No oil and the internals of the right side are pretty rusty. Maybe too rusty to bother with?

 

[gortnipper]

Yeah. Ouch.
​

 

[mdt-son]

Forks stripped. No oil and the internals of the right side are pretty rusty. Maybe too rusty to bother with?

If you are lucky, the damper body may clean up. The remainder of the internals is trash. Watch out for corrosion of the slider. The bore may be pitted and the threads on top weakened. If so, just discard it. More interestingly is the left side - if damper rod is even slightly pitted, just discard it. Corrosion will damage the damper cap and ensure it leaks. Damper caps may be restored to better than new function, pls. read Jim Schmitt's web page on this topic. New damper rods should be made of stainless steel!

-Knut

 

[grandpaul]

That rod shows evidence of lots of metallic trash swirling about inside the engine till it blew. You are bound to find more trouble deeper in...

 

[Ironracer]

Grandpaul I concur. Luckily this is a donor motor for various bits and pieces, it'll be interesting to see what else I find but I'm still bummed about the rods.

mdt-son the damper body is badly pitted on the inside. The other one looks a whole lot better, it had a bit of oil residue.

Scrap...

Usable?

 

[Danno]

Looking at that rod, it seems extremely fortunate it didn’t break at the gouge, wreaking even more havoc.