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1973 850 commando....

Classic Norton Commando Motorcycles.

Re: 1973 850 commando....

Postby concours » Thu Jul 27, 2017 7:16 pm

keso wrote:Ok.....update...a little more work has been done...but lots more needed...my intent is to get it running and try to keep it original....but have a couple of problem areas..we are rebuilding the front master cyl..and caliper...I need a brake switch(just see aftermarket..)..my original key switch is non functional..if we jumper it lights start working?..is there a was to "free up" this switch or should I purchase new?A bigger issue is when we cut the wire holding the exhaust nuts we saw that the head is somewhat stripped..the nut threads appear fine..any solution here short of getting a new head? Also both spark plugs were mismatched..a b7es..and a br8es...manual shows b7eb-11..which should we use?...Thanks in advance...


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Re: 1973 850 commando....

Postby Mr. Rick » Thu Jul 27, 2017 9:01 pm

Also both spark plugs were mismatched
I can see how one or the other might be mis-matched. But both? Gosh. :wink:
NGK BP7ES is a good place to start. Depending on what ignition you have, you might want resistor plugs BPR7ES. You cd spend more for BPR7HIX or BPR7EIX, if you think it wd help.

any solution here short of getting a new head?
Yeah, getting a new head wd be expensive. If the head is otherwise good, the exhaust threads can be repaired.. If it were me, I'd send it (with the nuts you plan to use) to someone expert like Jim Comstock, who wd evaluate the item in all respects (such as valve guide wear), and repair the threads as/if needed.
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Re: 1973 850 commando....

Postby keso » Sat Jul 29, 2017 6:57 pm

ok..ballpark on the thread fix?....need to tackle this problem first as it may take all my project money.....

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Re: 1973 850 commando....

Postby lazyeye6 » Sat Jul 29, 2017 8:44 pm

keso wrote:ok..ballpark on the thread fix?....need to tackle this problem first as it may take all my project money.....


Oh!, say $100 plus shipping. But while the head is off, get it checked out! No point in reinstalling a head that needs rehab, and that could cost $500 if done right.
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Re: 1973 850 commando....

Postby Mr. Rick » Sat Jul 29, 2017 11:30 pm

Keso, I don't think you told us how many miles are on this engine?
If it's 20K or so, new threads for the head might be all you need. But at 38k, mine was knackered; burned oil, blew smoke, was a bit*h to start and tune, needed new valves, guides, springs, etc. Not cheap, but not horrible either, had to be done. Along with a bore to 20 over, new pistons and rings, now she's a happy camper.
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Re: 1973 850 commando....

Postby cjandme » Sun Jul 30, 2017 7:16 am

Mr. Rick wrote:......But at 38k, mine was knackered; burned oil, blew smoke, was a bit*h to start and tune, needed new valves, guides, springs, etc. Not cheap, but not horrible either, had to be done. Along with a bore to 20 over, new pistons and rings, now she's a happy camper.

I might add that Comnoz will also do things like check the volume of both cylinders. Something I now believe the factory didn't keep such a close eye on.
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Re: 1973 850 commando....

Postby o0norton0o » Sun Jul 30, 2017 7:29 am

+1 on sending any critical repairs to Jim Comstock.

While any good machinist may be able to do rethreading a spark plug hole or some other simple machine work, just getting Jim to look at your head and give it his "OK" has a value that other machinists less familiar with nortons don't have... I had a single lifter delaminate on my commando without damaging the cam. Jim had me send him that pair of lifters so he could match them up to the lifter tunnel in one of his own spare barrels, which allowed him to fit the new lifters he was sending me to my barrels from 1000 miles away... He also sent me a tiny tube of assembly lube to make sure the lifters seated properly. He's a F*ckin' smart guy... who cares about getting shit right.

I also know a local machinist who is amazing. He's a motorcycle guy, but not a norton guy. I would give him most of generic machine work I might have because he's local to me, but some machine work, like threaded inserts in the exhaust port, or head work are best left to machinists who have that next level of intuition that only comes from being a "norton guy", like Jim....
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Re: 1973 850 commando....

Postby keso » Mon Jul 31, 2017 9:32 pm

Thanks for the insight..I have already contacted jim...300 for the inserts..the bike has only 9500 miles...every piece original...but the exhaust threads are not good..the nuts were wired tight..when the wire was cut they fell out...I know the bike sat for along time indoors..my mechanic friend is going to check compression to see what shape the engine is in...hate to do too much work..but want to do enough!!...insights?..

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Re: 1973 850 commando....

Postby Mr. Rick » Mon Jul 31, 2017 11:45 pm

300 sounds like a lot to me, but like my mother before me (who at 92 had fallen behind the times finance-wise by almost a whole decimal point) I consistently underestimate modern pricing.
You're on the right track. Find out discreetly what others charge if you can. And pay NO attention to someone who will not guarantee the work.

Good thing I wasn't there to see those wires being cut. I'd have been laughing out loud, and then feeling like an ass for finding your bad fortune humorous... :o
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Re: 1973 850 commando....

Postby gortnipper » Tue Aug 01, 2017 1:16 am

Mr. Rick wrote:300 sounds like a lot to me, but like my mother before me (who at 92 had fallen behind the times finance-wise by almost a whole decimal point) I consistently underestimate modern pricing.
You're on the right track. Find out discreetly what others charge if you can. And pay NO attention to someone who will not guarantee the work.

Good thing I wasn't there to see those wires being cut. I'd have been laughing out loud, and then feeling like an ass for finding your bad fortune humorous... :o


$300 sounds like good value to me. Lifetme fix. Priceless.
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Re: 1973 850 commando....

Postby cliffa » Tue Aug 01, 2017 10:08 am

Check it out here,

https://www.youtube.com/watch?v=ZPQc-mHtkiA

In my opinion very good value! Jim has done hundreds apparently. (make sure you send your nuts with the head, and he will match the threads).

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Re: 1973 850 commando....

Postby keso » Thu Aug 03, 2017 11:30 pm

Just a quick update...had a long talk with the owner who had the bike from 500 miles in 1974 til 9000 miles in the mid 80's..he was going to restore it but shedded it til the early 2000's that person shedded it also til I purchased it in the spring of 2017.He basically confirmed the mileage and that it had no bad issues(apart from a right side jug strip).He also has the original tool kit and owners manual!Still trying to find a Minnesota local guy to do the jug.....

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Re: 1973 850 commando....

Postby keso » Wed Sep 06, 2017 9:24 pm

New questions on this build...there is a 4 piece exhaust pipe lockring collet set..they are the originals..are the ok to reuse?...I am getting my exhaust ports fixed and am collecting needed parts..do these need to be new?Also..when looking at the bike on the right side rear there is a red wire terminal hanging..it appears factory..I have pics but cant figure out how to load them...any help guys?

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Re: 1973 850 commando....

Postby L.A.B. » Thu Sep 07, 2017 2:44 am

keso wrote:New questions on this build...there is a 4 piece exhaust pipe lockring collet set..they are the originals..are the ok to reuse?...


The collets should be ok to reuse, you should fit new sealing washers.
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keso wrote:Also..when looking at the bike on the right side rear there is a red wire terminal hanging..it appears factory.


Zener ground/return wire (ring terminal)?


keso wrote:I have pics but cant figure out how to load them...any help guys?


Look for: '[P] Add image to post' (in blue) on the left, immediately below your message reply box.
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Re: 1973 850 commando....

Postby grandpaul » Thu Sep 07, 2017 6:02 am

Make sure to read!
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