1974 850 commando project

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Aug 25, 2010
My dad has given me his red 1974 850 commando. He put it away around 1980. He rode it consistently before that and a few times after but stopped in 1987. He moved a few times and it has sat under his current house in the crawlspace since 1992. We pulled it out yesterday and I'm hoping to get it running. He no longer wants to ride it but doesn't want it to sit any longer. It has only 3800 miles on it.

I know there is a lot of work ahead of me. This is my first time working on a bike but I'm familiar with engines and don't mind putting the time and labor into fixing this thing up. We had a few worries about a bike sitting for so long (seized engine, varnish in tank, etc). I was able to pull the clutch and kick the kickstart (so the piston isn't frozen in the engine). However, I'm not getting very good (if any) compression.

I was curious if anyone had any tips as to where to start on this project. My manuals are on the way but in the meantime I'd really like to dig into cleaning up the bike and analyzing my compression issue. There's some rusting in spots (some more than others) but the bike is in relatively good condition.

I also wanted to introduce myself and thank you all for the wealth of information I've already gathered from reading past posts. Thanks in advance for any help you can give me. I'll post pictures as soon as possible.

Sounds like a complete tear down to start with, sad to say. All the rubber parts and gaskets are probably toast. It'll just make your life a steady hell of break down if you get it running without starting over. :cry:

I agree with Bob, the best way is to ensure you get a satisfactory bike is a complete teardown and rebuild. With low mileage, hopefully you'll have few parts to replace, notably the gearbox which can be expensive. However, you will need to tear it down to replace the suspect layshaft ball bearing with the essential roller version.

1st you're doing it right by getting the factory manual and parts book, also avaialble on line. 2nd photograph everything. As you're not familiar with Commandos, it pays to record all of the bike before you pull it down and progressively as you remove the various sub-systems. 3rd have both AF and Whitworth spanner kits. AF is on the chassis stuff and Whitworth on the motor and transmission. 4th, get lots and lots of small plastic picnic boxes and zip lock food bags to store the respective parts and fasteners as you remove them and label them with a felt pen. 5th, look at the parts book as you remove stuff to recognise what you are removing when it comes time to order new parts. Good example is the rear hub you won't believe the number of shims, washers, spacers and seals just in that alone and why they ever did it.

Last of all is to keep in contact with this forum and post lots of pictures, easy when you've got the hang of it and it helps us to help you when you;ve got the parts book reference and a photo to identify.

Good luck and have fun and don't forget the endless beer supply.

I'm certainly not the best mechanic (maybe the worst) on this forum, but my 74' 850 (12K miles) sat for 25 years mostly in my garage, exhaust system off and rags stuck in the exhaust ports. I turned the engine over every couple of years just to make me feel better about it. Last year I put about $4K of parts into it, the obvious like brakes, cables, cush drive, new exhaust, front wheel (really rusted - back was protected by chain oil leakage), rebuilt forks. Carbs rebuilt and boyer added vernier isos also added.

Believe it or not, before the boyer was added and carbs rebuilt it started 2nd kick. Put it on the road in March. Only 2K on it till now but seems to run perfectly. The only thing that has gone wrong to date is a leaking head gasket - who would figure that a head gasket that had never been torqued for 36 years would leak! My point is that you may not have to tear the whole thing down to have a good running Norton.
how are you determining compression ? have you removed valve covers to ensure the valves are moving too -

when dad parked it how did it run and did he do basic oil changes etc..

while a complete teardown is not a bad thing - you didn't pick this thing up from some unknown owner, so i'd check a few things before really dismantling the thing -

You've come to the right place for help and inspiration. I know of at least one Norton person near Greensboro. Unfortunately, I've lost his contact info after a recent computer crash. I'm not too far down the road (Charlotte) and would be happy to ride up one weekend to help you get started. Feel free to send me a PM if you'd like. Best of luck!
Any old bike I've picked up over the years first gets basics, plugs, check points, clean carb, battery tested oil dumped and changed, check vale clearances. Get the bike to fire and see what happens. Usually a jaunt up and down the block can tell you how the bike is running and a lot of issues can be determined once it is running. Heck if it seizes you'll know it needed to be torn down for sure. If it doesn't you save a lot of time and money. I picked up a 64 duc that sat outside for nearly 40 years and it started fine and I still run it once in awhile without issues. I did a cosmetic job on it and am happy with it.
Tear it down completely and check everything. If a bike has sat that long, it needs a complete going through to be roadworthy and safe. With such few miles it hopefully won't need many new parts other than seals and assorted other rubber bits but you will be completely satisfied that the bike is perfect and you will have learned all about Nortons!! As mentioned above, the layshaft bearing should be replaced on these models because it WILL fail. Only a matter of time and it is dangerous. So fix it now. Peace of mind as we say. Nothing like completely restoring a bike for peace of mind. In the meantime, buy a modern bike you can ride so that you can take your time.
I would most definitely think about what needs to be replaced and repaired for safety's sake. 70 mph is not when you want to find these things out. I would also give a long, hard look at the electrical system. After all these years, that will fail you, I promise.
I recently got a bike back on the road that had been stored for 20 years. I wouldn't worry about tearing down the engine unless it developes some problems. But I would plan on at least taking things apart far enough to replace the isolastics. While you are messing with the rear isolastic, pull the swingarm and renew it as needed. Pull the gearbox apart and put in the layshaft bearing. It isn't hard to do and I did mine with the gearbox in the bike. I replaced the main bearing while I was there by making a tool to press it into the heated case.

Getting this far had the primary apart, so I serviced the clutch and checked the chain. It also had a lot of stuff out of the way so I was able to clean up the wiring. I pulled the timing side cover, renewed the oil pump and checked that chain. I put new seals into everything I touched, which was the main reason I was there, the old ones were brittle.

I rebuilt the stock master cylinder, pulled the front wheel and checked and lubed the bearings. I pulled down the rear and did the same on the bearings there.

I rebuilt the carbs.

This process was not difficult, but take notes and photos of how things come apart. Pay attention to shims and other bits in the primary so that you can put them back in the proper orientation. I have worked on lots of stuff over the years, but I am not a Norton expert. But this process gave me a good understanding of the bike and it solved most of my issues. As long as you don't find any major faults it isn't that expensive either. Once you have gone through this process you will be better equipped to decide what kind of upgrades and how much money you want to spend on your bike. Or so I think.

Good luck, this forum has lots of good information. Old Britts has the parts diagrams for quick reference. Dive in.


PS-post photos! Also it is kind of early here and somewhere between reading and writing I lost track of your compression issue. Yes, check those valves. If you have to pull the head. You will also read stuff about sludge traps and other delights that should terrify you into tearing the crankcase down and starting from the ground up. My thought on that in my situation is that I will end up in there soon enough through natural curiousity. My goal was to get the bike going and restore it later. But this is something that everybody has to decide on their own. If you think you are only going to take it apart once...better start from the ground up now.
rvich said:
You will also read stuff about sludge traps and other delights that should terrify you into tearing the crankcase down and starting from the ground up. My thought on that in my situation is that I will end up in there soon enough through natural curiousity. My goal was to get the bike going and restore it later. But this is something that everybody has to decide on their own. If you think you are only going to take it apart once...better start from the ground up now.

If bike really has only 3800 miles, sludge trap should be OK I would imagine. However, after rebuilding several of these old bikes, I don't take anything for granted any more. I think it is far easier to take it all apart once now than several times later on but as rvich says, you need to decide this for yourself. If the bike has low mileage, and was looked after, you shouldn't have much to replace but at least you will know for sure!
Do you know for sure it has only 3800 miles? My '69, I was very sure it had mostly the mileage I put on it. Bought it with about 4K on the speedo in '72, and put it away with 13.5K about '85. I did break down the crank cases recently and in the sump, there was next to nothing, the con-rod big end shells looked like new and this is with no filter. But I had decided to change out the pistons, but now I know what is in there. I'm not sure you can really tell how many miles are any bike that you buy, unless you know the seller, or open it up. Things can be very deceiving.

Get a can of Marvel mysery oil and a oil can, Valve covers come of easily. Start squirting that stuff everywhere in there. pull the plugs and squirt it in there. Turn over with CAUTION. Make sure the valve train is moving. Tap on the tappets and see if the valves will reseat. Make sure valve train is moving. Gearbox are usually fine. If it is turning the bottom is probably ok too.
But lets be real about this. It sounds like the source is reputable.
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