73 Commando 850 help!

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concours said:
Shrapnel is correct, for using the wheel/trans/kicker/crankshaft to break the pistons loose, near TDC/BDC gives the most mechanical advantage to the crank. At 3:00/9:00, the PISTON has the upper hand, not the crank. :idea:
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Excuse me, I could have sworn we were just talking about tapping on the pistons to brake them free not using the kicker or wheel so you can see why I disputed BDC as a benefit. As for the rest of the doom & gloom, I'll stand by what I said. Who would want to risk their pride and joy's bearings, cam, etc. etc. for the bragging rights of saying you got rusted up motor running for a few years before you needed to split the cases and do some serious $$$ work? I'm talking your own "pride & joy", not your neighbor's lawnmower.
 
It's great to hear from both camps, you guys have been awesome and super responsive.

I'm letting the soak work it's magic, if that ever happens.

Sure if it's in bad shape , I'll tear it down further. As for now, I have patience. It's only been soaking a few days. I'll give it at least a month before I explore other options. Again , thanks to all of you for all the info and tips.
Yes I agree it's not lawnmower, it's a Norton and should be treated accordingly.

Are there any special tools I should aquire for a potential tear down in meantime?
 
also, do you think a product like this http://www.evapo-rust.com/ would work any better to free the engine? ive used to to remove rust from gas tanks with great results. i actually dissolves the rust to liquid, without and abrasiveness.
 
This one took a week-long soak in PB Blaster to free up.

73 Commando 850 help!


73 Commando 850 help!


73 Commando 850 help!
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If it's froze, you need to pull the head anyway and it makes the freeze-up easier to deal with.
 
"Nothing wrong with deliberate speed on this one. If it breaks free and turns through rather easily, hell , why not have a go at it. "

Because the iron oxide/aluminum oxide will likely tear up the other expensive parts that WOULD have been serviceable if torn down, cleaned, inspected before attempting to start. Cam, lifters, oil pump come to mind.
 
Understood concours but we do not know the degree yet so if it were to break free and turn freely the contamination is minimal and can be easily dealt with through an oil change or two. Most if not all the iron oxide would go the way of the exhaust port. If it looks like anything even close to what Danno and others have depicted then it's a no-brainer, tear it down.

The Norton engine can and does tolerate a lot of cr*p and corruption. Take a look at the magentic drain plug or sludge trap of any Commando (filter or filterless). The roller elements are generally very tolerant of contamination and cams sh*t the bed typically due to poor quality.

Just to be clear, if we want to guess, my guess is that it will need a teardown but maybe the OP will get lucky but I am not betting on it.
 
jzmax22 said:
It's great to hear from both camps, you guys have been awesome and super responsive.

Are there any special tools I should aquire for a potential tear down in meantime?
Click to expand...

One thing about this group is there are very few full on arguments. Differences of opinions, yes. Picture this whole discussion happening in a pub. There would be serious talk, good information, some BS, lots of good natured ribbing and lots of laughs. The take-away would be positive without any torn shirts or black eyes. As for tools, at the very least, for now, you'll need a set of 3/8 th drive Whitworth sockets and Whitworth combination wrenches too. And a book! I like the factory manual but there are others too. "Knowledge is power". Right off there are some tricky nuts and bolts holding the head on. Again, get a book. And good luck, Stay in touch. -Pete
 
Engine being stuck aside, when i was removing the Primary chaincase , i was unable to remove the drain plug screw, its stuck and the slot is chewed from years of people trying to remove. I have a plenty big enough slotted driver to fit snug, just unable to break it free. any advise on that? it to has been soaking in pentrating oil.
 
Heat will work best here, steel screw in alloy case and the alloy will expand more if the heat is even and not localised releasing the steel. Replace with stainless version.
 
I think what you are describing is one of two inspection plugs on the side of the primary. One is to allow adjustment of the clutch while the other is to observe the ignition timing marks for timing purposes. My guess would be to use very moderate heat on the case (cover) and an ice cube in the center of the plug and then see if it will break free. A screwdriver tip, although it may be a tight fit, will certainly upset the alloy and tear things up a bit. If I recall correctly, the original tool kit had a spanner for maybe the shocks or something and the back of it had a large crescent shaped tab that was meant to fit into these slots. A slow steady force is what will be needed as it is usually the o-ring that is bound up.

Hope this helps.
 
Sounds like work and it is but chaincase caps are subject to big screwdriver gnawings to the alluminum so I made steel slot toolage by getting oversized bar stock and wheel grinding it down until it just snugly fit the new caps . Kinda fun mini- project to do.
 
Dances with Shrapnel said:
I think what you are describing is one of two inspection plugs on the side of the primary. One is to allow adjustment of the clutch while the other is to observe the ignition timing marks for timing purposes. My guess would be to use very moderate heat on the case (cover) and an ice cube in the center of the plug and then see if it will break free. A screwdriver tip, although it may be a tight fit, will certainly upset the alloy and tear things up a bit. If I recall correctly, the original tool kit had a spanner for maybe the shocks or something and the back of it had a large crescent shaped tab that was meant to fit into these slots. A slow steady force is what will be needed as it is usually the o-ring that is bound up.

Hope this helps.
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Its the drain plug on the on the left side of bike on the bottom of the chaincase. The three larger ones come out no problem.
 
The "drain plug" you are referring to is actually the level plug. Applying heat is a good idea; the plug has enough meat on its flanks that you should be able to get a vice-grip on it, a tool of last resort. I'll admit to having 6; what ever they touch gets binned!

Regarding you current problem with stuck pistons: You may free them, one way or another, but they should be considered wall hangers. I would further suggest that you plan on complete disassembly of the engine, careful inspection and measurement of all sliding surfaces/bearings; a jewelers loop will help you see into small places.

You may also want to have a good look at your portfolio and see if any of your positions are ripe for profit taking or loss balancing; the Norton is a demanding mistress. If you do not have the time to renew or re-skill your mechanical talents there are a number of shops that can help out.

be kinda cool to wheel (under its own power) this magnificent mechanical marvel up to your dad's place out of the blue and surprise him, single malts all around.

Good luck
 
jzmax22 said:
Engine being stuck aside, when i was removing the Primary chaincase , i was unable to remove the drain plug screw, its stuck and the slot is chewed from years of people trying to remove. I have a plenty big enough slotted driver to fit snug, just unable to break it free. any advise on that? it to has been soaking in pentrating oil.
Click to expand...

Sharp center punch, near the perimeter, 45 degree lean (lefty loosy :idea: ) one hit wonder.
 
I had an 850 that had stuck pistons. After removing the head, I removed the base nuts and through bolts, pulled the barrel/pistons clear of the base studs and simply wiggled the barrel to the right and left (after a good 3 days of PB Blaster soaking). I stuffed the lower end with rags to protect the rods and used as little force as possible. It took about 5 minutes of movement to free the pistons from the barrel.
Using a bore scope earlier I had determined that the real estate inside the cylinders looked like a moonscape and knew that I would be completely disassembling the engine; I hope you aren't still thinking that freeing the pistons will promote a starting process; consider that any open valves may also be stuck; bending breaking them won't be doing yourself any favors.
 
RoadScholar said:
I had an 850 that had stuck pistons. After removing the head, I removed the base nuts and through bolts, pulled the barrel/pistons clear of the base studs and simply wiggled the barrel to the right and left (after a good 3 days of PB Blaster soaking). I stuffed the lower end with rags to protect the rods and used as little force as possible. It took about 5 minutes of movement to free the pistons from the barrel.
Using a bore scope earlier I had determined that the real estate inside the cylinders looked like a moonscape and knew that I would be completely disassembling the engine; I hope you aren't still thinking that freeing the pistons will promote a starting process; consider that any open valves may also be stuck; bending breaking them won't be doing yourself any favors.
Click to expand...

I think teardown is where I'm heading next, after inspection through the plug hole, it looks as though the exhaust valve? is stuck open on the left side of the bike.

Besides the shop manual, which I have , is there any detailed documentation with pictures available out there for me as reference.
Thanks again for all your guys input, it's been very helpful.

Where to start.

I would bring it to a shop if I had the funds to do so, I don't, so I'm taking this on myself. I'm still learning about Brit bikes. Any help is greatly appreciated. Thanks again
 
Old Britts have a comprehensive technical section, you can review which work and mods to do.

http://www.oldbritts.com/ob_tech.html

There is always at least one valve open, hence why one piston locks up first if exposed to damp air. The valve may not be stuck, you can see if it's stuck or just open by removing the exhaust rocker cover and loosening the tappet, the valve is stuck if you get clearance right away.
 
jzmax22 said:
I think teardown is where I'm heading next, after inspection through the plug hole, it looks as though the exhaust valve? is stuck open on the left side of the bike.
Click to expand...

An open exhaust valve is not unusual and I am not sure how you determined it was stuck open. The exhaust or intake can be seen in various stages of open depending upon where the engine is stuck in the cycle on that cylinder.

If the pistons are near BDC as you had indicated earlier, and if the engine was in good order when it last stopped, the left cylinder with the open exhaust valve would be at the end of the power stroke and/or start of the exhaust stroke and the right cylinder would be at the end of the intake stroke and/or beginning of the compression stroke. The RH exhaust rocker should have some slack and the RH intake should be slightly open (no slack in the RH rocker).

Pulling the head should be telling. A few pictures will be helpful once you get the head off. Have you pulled off the oil/penetrant you loaded into each cylinder? Any milky liquid or other indications of water or chunks or color of rust? Might as well get that stuff out before pulling the head in order to avoid the mess and combustible hazards.
 
jzmax, give us an idea about your skillset, it'll help us give better advice. You said "new to British bikes". What kind of work have you done on other bikes? Valve adjustments? Chain & sprocket replacements? Brakes? Most challenging project?
 
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