Britbike forum

looking at a 75 850

Posted By: Pete Suchawreck

looking at a 75 850 - 09/04/18 10:31 pm

Hi all, contemplating a 75 850, Owner says 29,000 miles, everything works including the starter. Some small paint problems original paint , red.
original mufflers, etc. Said the bore was recently honed, new rings. Valves need to be re-adjusted. He said he will take $4200.
I'm not familiar with Nortons-what should I look for and what are thoughts on the 75's in general?
I have a Triumph 750 along with other vintage bikes.
Thanks, Pete
Posted By: Rohan

Re: looking at a 75 850 - 09/05/18 7:30 am

One of the known problems with the Mk3 was that some of them seem to have had soft cams - so if it needs the 'valves adjusting', this might be an indication that all is not well in this dept ?
Other possible problems with Commandos are the usual worn swingarm bushes, soggy rear dampers, worn isolastic rubbers, and rubber components in general, worn seals in the brakes, and general wear and tear.

At that price, if that was here, that price is a pretty good deal.
You could spend a handful of cash, and have a good Norton.
Its not that difficult to do all the work yourself even.
And, it may have been well kept and a genuine mileage, and quite rideable already.

The electric start later Mk3 is one of the more sought after models too.
Let us know how it goes.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/05/18 11:44 am

Thanks for the info Rohan. The owner said the valves need adjustment because he had had honed the cylinders but not gotten to adjusting the valves before getting hurt.
He did say he had a rebuild kit for the front brake.
My understanding is the stock starter is weak. I see some alternatives such as the 4 brush starter and a modified Japanese starter.
Posted By: bill50cal

Re: looking at a 75 850 - 09/05/18 11:49 am

the swingarm bushes almost never wear but the cradle does and that is where 99% of them have a loose swingarm at. this was corrected on the MK111 cradle

Originally Posted by Rohan

Other possible problems with Commandos are the usual worn swingarm bushes,

Posted By: Rohan

Re: looking at a 75 850 - 09/05/18 11:06 pm

You are probably right, I've heard of that.
But I replaced the bushes in a used Mk1 that I had, they were decidedly loose and a shade or 2 oval.
The OIL in there needs to be kept topped up, greasing them is death...

Good that the owner says its just adjustment needed for the valves.
Keep a watch that the clearance(s) don't need continual adjustment though.

There is a lot of chitchat about upgrading the starter. I've not had one...

Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/06/18 7:56 pm

Well I'm looking at it tomorrow so we shall see. Thanks for the input-pictures if I buy it.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/10/18 8:34 pm

Brought it home. Guy had 15 cats and it was in his living room...the stench!!
Had a loose rocker clearance with the adjuster all the way in so we pulled the head and cylinder.
Cam and followers are perfect, loose exhaust valve guide, other sloppy. replacing the valve springs, guides, and exhaust valves.
The cylinder was just honed, new rings, good pistons. Bike is mostly original including the mufflers. Except for the cats it is clean
Starter works, I have lights and spark. Lucas RITA ignition.
The head gets dropped off tomorrow for the valve guides.
Posted By: kevin roberts

Re: looking at a 75 850 - 09/10/18 8:56 pm

i've never thought my norton commando was stinky.
Posted By: Tridentman

Re: looking at a 75 850 - 09/10/18 9:00 pm

Kevin--they say that you can never smell your own hole.
Posted By: Hillbilly bike

Re: looking at a 75 850 - 09/10/18 10:36 pm

I rode with Pete to look at the Commando...It was a creaky old house and it did reek of cat urine.. The bike owner was disabled somewhat from a work accident 10 years ago...He mentioned taking a massive doses of morphine and oxycotin daily,..The floor was sagging , cats were giving us the stink eye,there were smaller unusual bikes scattered around all had something important missing....Like we had timed jumped onto a Fellini film...The bike was a good deal for the price ..We moved some junk out of the way and ramped the bike from a hallway , out the door into Pete's truck...While on the ramp being handled by Pete and me.the tire slipped sideways and the bike leaned over and the doped up guy flew like a flash over to help...he said he did an extra dose of morphine just encase he had to help...We got something to eat, day dreamed about the waitress, got gas a half hour later and the bike still smelled like cat urine...But every thing the guy said about the bike seemed true...
Posted By: Rohan

Re: looking at a 75 850 - 09/10/18 11:00 pm

After such an epic tale, we gunna get a pic !?
Posted By: Triless

Re: looking at a 75 850 - 09/10/18 11:06 pm

Apparently, pre MK3 gearbox cradles were prone to wear in the swingarm pivot area. Maybe this place was the inspiration for the Harry Chapin song. Pete should check that area in case the cats have been in it !
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/11/18 2:28 pm

I have to upload pics to a server before i can post. The bike has spark-cleaned the damn thing three times and it still smells a little. One valve had excessive clearance so we pulled the head and cylinders. Cams and followers beautiful, head not so much.
Posted By: kevin roberts

Re: looking at a 75 850 - 09/11/18 2:47 pm

Originally Posted by Tridentman
Kevin--they say that you can never smell your own hole.


richard, there are so many disturbing possible replies to that observation that i'm going to just let it alone.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/11/18 4:01 pm

Tony and I pulled the valves out-the intakes are good, exhausts are burnt.. One exhaust guide was wobbling in the head. At the machine shop now to replace the valve guides then new springs and exhaust valves. Pushrods look fine too.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/12/18 2:10 pm

[Linked Image]
Here she is pre teardown
Posted By: bodine031

Re: looking at a 75 850 - 09/13/18 1:41 pm

Heavy doses of Fa-Breeze!!! Nice score

The shop that's doing the guides I hope know's WTF he's doing. Not to recut the seats to deep or face the valves so u can shave with them. Installed spring height springs get loose as the valves get sunk deeper into the seat
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/14/18 3:23 am

Thanks! The shop comes recommended. Owner has a '75 as well. I will have to shim the springs to the correct height,first time I've had to do that.
Got a front brake upgrade for it. Rotator cuff surgery in a week so she'll be sitting for a bit-me too.
Posted By: kevin roberts

Re: looking at a 75 850 - 09/14/18 3:38 am

bulllshit, peter. just tell your body you won't stand for it.

when i was 16 i broke a metacarpal in my first-ever motorcycle wreck. they put me in a rigid splint, but i couldn't twist the throttle anymore, so i broke the splint in two at the wrist.

now i have fond memories of my teenage years every time i look at my bent hand.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 09/25/18 6:20 am

I've done that Kev smile
Heard You got some new record-congrats! Typing with one hand presently...
Posted By: ricochetrider

Re: looking at a 75 850 - 11/02/18 8:44 pm

I'd say you got a pretty good deal on that bike! Of course soon you ll have more in it than you'll ever get out of it! HA HA...

Seriously tho, best of luck with A: the new bike and B: your shoulder. Take this advice from a guy with staples (R shoulder) & screws (L shoulder)- LET IT HEAL PROPERLY. You'll only get one chance to heal it right, and if you blow it you'll live to regret it. Don't ask how I know.
Posted By: Pete Suchawreck

Re: looking at a 75 850 - 11/03/18 1:50 pm

Thanks ricochet! As Hillbilly says "I only count the original cost of the bike. The rest is just maintenance..."
Tony came over yesterday and we started it up-11 years later, after a complete top end job, new rings and a lot of cleaning.
My arm is six weeks out, been slowly working on the bike as I can, getting one hand creative w/nuts and bolts.
I'm not rushing the arm- I plan to vintage motocross again this summer-gotta be ready!
On to the front and rear end and trying to save the gas tank.
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