Newb Commando restoration

cashman · Jan 31, 2017

I recently pulled my father's '74 Commando 850 out of my grandmother's garage, where it has sat since he stopped riding in 1980. He's been wistfully talking about restoring it for years now and I've decided to dive-in and get it running for him. Although I've got a fair amount of experience with riding motorcycles (~15 years), I'm an amateur when it comes to motorcycle repair. I've been doing my research and carefully planning this restoration but have a very basic question I'm hoping you all can chime in on.

Prior to storing the bike, my Dad drained all fluids, save a small amount of clean oil poured in the cylinders and crankcase. Before dismantling anything, I'd like to figure out how big a project this is going to be (i.e. - full engine rebuild?). Accordingly, I intend to run a compression and leak down test before doing anything else. My rather silly question is this - since the engine is essentially dry, is it necessary to do an oil/filter change before running the compression test to avoid damaging the piston rings and cylinder walls? Just squirt a couple tsps of oil down the spark plug holes? None of the above?

Any and all advice is appreciated. Thanks in advance. I'll upload a photo as soon as I can figure out how.

-Jon

htown16 · Jan 31, 2017

Yes dump a little oil in each cylinder. Don't be suprised when you get low compression readings on an engine that has sat for quite awhile and is cold. Rings are probably dry and won't seal well even if you add oil through the plug hole. Also you need the force of combustion to push the ring out against the cylinder wall. The other factor is bits of carbon can hold the valves off their seats. Meaningful combustion measurements are always done on a hot engine after a good ride.
It won't hurt to measure it the way it is now. If you get above say 100 psi cold the engine should start and run. But it probably won't tell you whether you need to overhaul the top end or not.

cashman · Jan 31, 2017

Thanks htown16. I appreciate the guidance. I'll give it a go and if I see anything above 100psi, I'll try to get her to fire up.

Nater_Potater · Feb 1, 2017

Being essentially lazy, I wouldn't go any further than checking that there's enough compression to blow my thumb off of the open spark plug holes while stabbing the kick starter. If it'll do that, it'll probably run at least enough to expose other potential woes. However, after sitting that long, I would venture to guess that what keeps her from running is plugged idle (pilot) jets in the infamous Amal carbs. Bone-up on Bushman's well laid-out steps at http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html before beating yourself up (as I did...)

Nathan

baz · Feb 1, 2017

before you do anything with this bike read up as much as you can ,ask questions on here even if they are silly ones it dosent matter its better than making a mistake!,as the bike has sat so long the pilot jets are bound to be blocked ,there could well be a ring of rust in the bores the isolastic rubbers may have collapsed etc there are many pitfalls with a commando but the good thing is now they can all be ironed out with modern ignitions /electrics /brakes engine work etc etc ,best of luck with it

Danno · Feb 2, 2017

If the engine turns free, don't get in a rush to open it up. Go through the carbs and ignition and put fresh fuel (tank cleaning?) and fluids and a battery in. Your subsequent attempts to fire it up will tell you how far you need to go to make it roadworthy. Once the engine is running, any leaks will soon become self-evident. You can also check out the integrity and function of the drivetrain and trans. When you are satisfied with the mechanical soundness, or have made necessary repairs, you can start on cosmetic work and serious cleaning.

N0rt0nelectr@ · Feb 4, 2017

cashman said:
I recently pulled my father's '74 Commando 850 out of my grandmother's garage, where it has sat since he stopped riding in 1980. He's been wistfully talking about restoring it for years now and I've decided to dive-in and get it running for him. Although I've got a fair amount of experience with riding motorcycles (~15 years), I'm an amateur when it comes to motorcycle repair. I've been doing my research and carefully planning this restoration but have a very basic question I'm hoping you all can chime in on.

Prior to storing the bike, my Dad drained all fluids, save a small amount of clean oil poured in the cylinders and crankcase. Before dismantling anything, I'd like to figure out how big a project this is going to be (i.e. - full engine rebuild?). Accordingly, I intend to run a compression and leak down test before doing anything else. My rather silly question is this - since the engine is essentially dry, is it necessary to do an oil/filter change before running the compression test to avoid damaging the piston rings and cylinder walls? Just squirt a couple tsps of oil down the spark plug holes? None of the above?

Any and all advice is appreciated. Thanks in advance. I'll upload a photo as soon as I can figure out how.

-Jon

When you can post some pictures. Being a primer member makes posting pictures a lot easier. Make sure they are 900 pixels or less.
We can all give you advise.
John in Texas

cashman · Feb 8, 2017

Thank you for the advice! This is going to be a slow build but I'll post updates of my progress and will definitely be asking for help along the way. Here's an initial photo of the Norton sitting next to my Triumph Thruxton.

Newb Commando restoration

cashman

htown16

cashman

Nater_Potater

baz

Danno

N0rt0nelectr@

cashman

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