1970 750 Commando Roadster bodge?

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Hi, I just bought an 1970 750 Commando to restore. Its my first Norton so I am a newby. The bike is fairly standard and mostly original, but had a nasty shock when I found the frame was twisted. :( Still while thats being sorted out I am checking the engine out. Most seems ok to me but there is a weird 'mod' on the crankcase behind the oil junction block.
I was going to post a photo here but cant yet. Anyway, someone has drilled a small hole in the case and put a screw in it. I cant see that in any parts book so I think its a mod.

Any ideas what it's for and what would happen if I took the screw out?
Thanks
Steve

PS can anyone tell me how I can post a pic?
 
Pic instructions are the top post on the main page.

Welcome. Does it have the halo around the headlamp?

Dave
69S
 
My guess is that you will have an oil leak if you take the screw out. I wouldn't worry about. Clean it up and reinstall it with a little red loctite.

Does it have the little nylon capped nuts on the lower fork triple clamp ?

Greg
 
DogT said:
Pic instructions are the top post on the main page.

Welcome. Does it have the halo around the headlamp?

Dave
69S


Thanks for the photo info. Yes it does have the halo.

and here's the pic.
1970 750 Commando Roadster bodge?


Steve
 
gjr said:
My guess is that you will have an oil leak if you take the screw out. I wouldn't worry about. Clean it up and reinstall it with a little red loctite.

Does it have the little nylon capped nuts on the lower fork triple clamp ?

Greg


Yes it has those too

Steve
 
I found something else. The timing chain was a bit slack. When I tightened it I saw that the chain had worn of the top of the tensioner top plate. Looks like the pinions are too close. Should there be shims behind them?

Steve

1970 750 Commando Roadster bodge?
 
Those are grub screws for accessing the oil ways. They were needed to secure endpoints after machining. Some cases have more than others. Locate them all, open them up and shine a light looking from other angles to see if clear. My new 210xxx cases have more than my 200xxx. One was particularly handy at the end of a way forward of the drain plug on the 72's.

Be very thorough. I have seen ring and piston bits in there. I collected about a teaspoon worth of shrapnel from a set. It was obvious why the motor fail. These bit were left behind after a rebuild by a PO.
 
cheen said:
Looks like the pinions are too close. Should there be shims behind them?

Not on the single chain models.

Maybe somebody fitted two thick cam chain tensioner plates instead of one thick (outer) and one thin (inner) plate.
 
Slacken the timing chain and see if the spindle shaft is loose in the casing. You should not tighten the cam chain without supporting this spindle.

When tightening the camchain without support, this spindle can pull over toward the cam. Yhis is because there isn't much surface area supporting the spindle in the case half. When the timing cover is put back on, the spindle is pulled back square which then tightens the chain waaayyyy beyond spec. by the the matching bore in the cover. This can be devistating if not corrected.

If this spindle is loose in its bore, you may need help. There is a oil hole in this spindle the should point down.

Many people have cut up an old timing cover keeping the dowel alignments and spindle bore, then cut access to the cam chain adjuster.

1970 750 Commando Roadster bodge?


1970 750 Commando Roadster bodge?
 
pvisseriii said:
Those are grub screws for accessing the oil ways. They were needed to secure endpoints after machining. Some cases have more than others. Locate them all, open them up and shine a light looking from other angles to see if clear. My new 210xxx cases have more than my 200xxx. One was particularly handy at the end of a way forward of the drain plug on the 72's.

Be very thorough. I have seen ring and piston bits in there. I collected about a teaspoon worth of shrapnel from a set. It was obvious why the motor fail. These bit were left behind after a rebuild by a PO.

That's a relief, thanks for that! There just seems to be one screw, and looking down the oil way it looks nice and clean.
 
pvisseriii said:
Slacken the timing chain and see if the spindle shaft is loose in the casing. You should not tighten the cam chain without supporting this spindle.

When tightening the camchain without support, this spindle can pull over toward the cam. Yhis is because there isn't much surface area supporting the spindle in the case half. When the timing cover is put back on, the spindle is pulled back square which then tightens the chain waaayyyy beyond spec. by the the matching bore in the cover. This can be devistating if not corrected.

If this spindle is loose in its bore, you may need help. There is a oil hole in this spindle the should point down.

Many people have cut up an old timing cover keeping the dowel alignments and spindle bore, then cut access to the cam chain adjuster.

Yes the spindle is a bit loose though not as bad as the one in the photo. I dont have a spare cover, so whats the best way to fix this? A new spindle or is there a way to replace the bush there? Or should I just make adjustments for the chain tightening when the cover is put on?
 
L.A.B. said:
Not on the single chain models.

Maybe somebody fitted two thick cam chain tensioner plates instead of one thick (outer) and one thin (inner) plate.


I checked the plates, one thin one thick as they should be. The chain is a bit loose on the cogs, could be the wrong width. I'll take it to my Norton dealer and see how it compares to his stock one.

Thanks
 
cheen said:
Yes the spindle is a bit loose though not as bad as the one in the photo. I dont have a spare cover, so whats the best way to fix this? A new spindle or is there a way to replace the bush there? Or should I just make adjustments for the chain tightening when the cover is put on?

Loose is one thing, sloppy is another. Many can slip in and out and this can be concidered "somewhat" normal, only because there are so many that are loose. This is another Norton engineering short coming, no big whoop if we are aware.

The one in the picture was very bad but usable when using the sacrificial cover to adjust the chain. I also invested it a 75 timing cover which has the inspection cover.

Sounds like yours is ok. Again, make sure the oil hole points down.
 
cheen said:
That's a relief, thanks for that! There just seems to be one screw, and looking down the oil way it looks nice and clean.

That's interesting. I have the motor out of my bike (138XXX) and there is no screw in the back of the crankcase. I am also very sure that the other bike (136XXX) doesn't have one either.

Greg
 
gjr said:
cheen said:
That's a relief, thanks for that! There just seems to be one screw, and looking down the oil way it looks nice and clean.

That's interesting. I have the motor out of my bike (138XXX) and there is no screw in the back of the crankcase. I am also very sure that the other bike (136XXX) doesn't have one either.

Greg
Notice the center punches for retainment.
The one that cheen shows is not on either of my cases. I'm sure there are other placements for these grub screws.

Not all cases have this one either and may be exclusive to the 72's. Bottom forward case fastener,facing front.
1970 750 Commando Roadster bodge?


This is Lower out side near oil pump mounting
1970 750 Commando Roadster bodge?


Inside timing cover.
1970 750 Commando Roadster bodge?
 
swooshdave said:
pvisseriii said:
This is Lower out side near oil pump mounting
1970 750 Commando Roadster bodge?

That the one that leaks on mine.

I guess you better slap on another Mike's XS Yamaha xs650 Reed type Positive crankcase ventilation Valve. :mrgreen:

If one is good......
 
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