STRIPPING . . . . . an 850 MK3 engine

Hi Lads,

I picked up a complete spare MK3 850 engine a while back and I'm only getting to the stripping stage now!

The exterior of the engine is in a very sorry state but so far it has come apart without any major struggle.

I have the head & barrels off, there was some water in the bore but it was mixed up with lots of oil so a gunky goo all over the internals which seems to have preserved the metal (no major rust on important surfaces yet!)

It looks like the engine was 'cut out' of it's frame. The exhaust was cut just before the exhaust collers & there's a small part of the swinging arm still attached to the rear loop which has been cut off from it's main mothership!

My theory is that the bike was in a breakers after a crash & somebody just wanted the engine & cut it from the frame, all the cables have also been cut.

Now to my question:

The LH piston has a 'B' stamped into it's flat top head, is this a STD out of the factory piston? I can't see any + markings indicating an overbore?

Any info. appreciated :mrgreen:

And now the pics

click said:

The LH piston has a 'B' stamped into it's flat top head, is this a STD out of the factory piston? I can't see any + markings indicating an overbore?

Click to expand...

Is there another 'B' mark on the top of the barrel?

Hi L.A.B.,

Had a quick look, don't see a 'B' stamped on the top of the barrel but I still need to clean it a bit more. Does the 'B' tend to be on the fin area or the mating area?

What is the significance of the 'B' on the top of the barrel?

Around the base of the barrel it does have the word BIRCO cast into the barrel with the number 063850 (I think this is just the usual standard casting marks for an 850 barrel?)


Many Thanks

Kevin

click said:

Had a quick look, don't see a 'B' stamped on the top of the barrel but I still need to clean it a bit more. Does the 'B' tend to be on the fin area or the mating area?

Click to expand...

On the joint face, probably?

click said:

What is the significance of the 'B' on the top of the barrel?

Click to expand...

Probably a piston & bore grading code I should think?

Boy that's one for the ATF-Disel-Acetone or Strongarm soak to go further. Looks like a hole in the water into which one pours money but leaves life long memory. My slightly brain injured state makes visions like yours float to mind falling to sleep for a twitch that repeats back annoyingly. ugh.

Few more pics below.

The primary cover was damaged & had most of its screws missing.

VERY rusty inside!, lots of penetrating oil & left it for a while.

Somebody had already attempted to take the alternator off, most of the nuts were missing from the alternator mount bolts and the ES alloy support.

Got the rotor off & stripped the grungy clutch plates out. The clutch basket is moving freely after a bit of persuasion.

The crank end sprocket is stuck fast! I have a puller on it & I've been tap tapping away on the sprocket to see if it will budge but no luck so far.

I tried a bit of heat with an electric heat gun but still no luck. I might try some flame heat tomorrow, with my fire extinguisher beside me!!

Thinking of bringing the bottom end to a petrol station jet wash & blast all the grime away before I go any further!

hobot said:

Boy that's one for the ATF-Disel-Acetone or Strongarm soak to go further. Looks like a hole in the water into which one pours money but leaves life long memory. My slightly brain injured state makes visions like yours float to mind falling to sleep for a twitch that repeats back annoyingly. ugh.

Click to expand...

:mrgreen: :mrgreen: :mrgreen: :mrgreen:

It's really just a learning project, it's rare that you can work on an engine that I don't actually plan on using

So far, although cosmetically it looks crap, all the fasteners have been it good condition i.e. no gorilla mechanic has been at them (I was one of them when I was younger!) All the nuts/bolts feel like they were at the correct torque.

The pistons might be STD size (need to measure bore etc.) which could mean it's a low milage motor :mrgreen:

The clutch centre does not seem to be notched & might be a bit better than the one on my running Norton.


What I hope to get out of this is:

1. An education on the stripping/rebuilding of Norton Commando motors (nothing like practical hands on learning)

2. Have some good used spares, head, barrels, crank, crankcases, gearbox + hopefully a few other bits & bobs.

3. My Mk3 has a 920 conversion which I love, lots of torque but I might consider bringing it back to a standard 850 & hopefully I'll now have the bits to do this :mrgreen:

Hotbot, don't loose any sleep over this one, I don't plan on getting this baby back on the road any time soon :mrgreen: Sleep well my friend!

YES. MEASURE IT UP AND YOU WILL FIND OUT WHAT SIZE THE PISTONS ARE. sOMETIMES there are different fit of new pistons and manufacturers tamp them A B C etc according to their size. when engines are assembled the pistons are fitted according to the best size available. [ due to tolerances and wear in tools, bores can be bigger or smaller [ in the thousandth of inches ] same with pistons. Hence possible that letter you were querying about.
As for the front sprocket, I have had to get a long tapered punch to belt the hell out of the sprocket near its centre to get one off [ . Make sure you have plenty of tension on the puller and also make sure you don't stuff the crank threads. When you shock the sprocket with that drift, it will come loose with a bang.

OMG click what a way to get your hands dirty first time inside a Norton. I figured you were old pro to take on that hunk of hunk of ... I'm thinking to put my spare stuff into a Combat but stumped on what to power with it, go cart or long tail boat, just nothing that flys.

hobot said:

OMG click what a way to get your hands dirty first time inside a Norton. I figured you were old pro to take on that hunk of hunk of ... I'm thinking to put my spare stuff into a Combat but stumped on what to power with it, go cart or long tail boat, just nothing that flys.

Click to expand...

I'm an old something, but not a pro :mrgreen:

HaHa... we are all "ol sometings", and some are older than others... Great project you have there and im a bit jealous.... Once complete with compitent DIY skills, as you may well have it will be a nice package to use or just have in the portfolio.. Good luck...

Mark 111 .

I've been working on trying to remove the crankshaft sprocket but still no luck :roll:

The puller has as much tension as I can muster + I've tried flame heat on the sprocket + lots of 'shocks' with a hammer & punches near the centre of the sprocket but still no luck.

I'm trying to figure out how to freeze the shaft so when I heat the sprocket the initial temperature differential is greater, its way too big to fit in the freezer I have, I need to find somebody with a freezer chest that won't mind me putting 60% of a Norton engine into it :mrgreen: :mrgreen:


More anon

Kevin

Click

A wee impact wrench at the local garage might be worth a shot!

J

auldblue said:

Click

A wee impact wrench at the local garage might be worth a shot!

J

Click to expand...

Thanks, I might try that later after I use some TNT :mrgreen:

If you are applying heat to the sprocket then you need to heat it as fast as possible so it expands before the crank does in order to release it.
Local garage or engineering firm may help if you don't have acetylcholine burning torch just be sure to only direct the flame at the sprocket and avoid the crank and doing it with the puller as tight as you can should do it trick.

Have you tighten the bolt and hit the bolt end,a sharp clout with a lump hammer should do the trick...sounds like you tighten the bolt and hit the sprocket? which aint effective. Put a copper disc on the shaft end to avoid damage...a coin will do nicely.

Allso when the bolt is tight, heat the bolt between the crank end and the puller, with your hot air gun, this expands the bolt , applying lots of force.

john robert bould said:

Have you tighten the bolt and hit the bolt end,a sharp clout with a lump hammer should do the trick...sounds like you tighten the bolt and hit the sprocket? which aint effective. Put a copper disc on the shaft end to avoid damage...a coin will do nicely.

Allso when the bolt is tight, heat the bolt between the crank end and the puller, with your hot air gun, this expands the bolt , applying lots of force.

Click to expand...

Thanks guys for your suggestions. I've been hitting the sprocket and the bolt which tightens the puller, at this stage I'm afraid I'll blow the crank out the other side of the cases :roll:

Good suggestions about the coin & heating the bolt, very clever :mrgreen:


More Anon.

I Had the same problem with my Mk3 engine , nothing would shift the crank sprocket , in the end I bought a hydraulic puller , loaded that up but it still wouldnt shift, until I thrashed the puller with a copper mallet, BANG the puller and sprocket came apart and shot across the workshop , stand well to one side if you follow this method!

OH My word click, you are giving me bad flash backs on my 1st Combat - operated so hard before me as show room sacrificial demo cycle it blacksmithed fused the sprocket to the the crank tapper. Broke 2 pullers, one the robust Norton factory puller like you have, not even hitting - just popped from tightening it between whacks, while i was catching my breath before another strike out.
Might try water ice or better dry ice inside the case around the crank then heat the sprocket till over frying pan hot 500's F and try again and again... You may have to open the puller holes to get more square on bolts aim or they may pop off in sprocket holes. No coin in the world can take the loads you will need so will moosh down and distort possibly un-squaring the puller to pop itself apart first. May have to acyl/oxy torch off most the sprocket in the end to salvage the crank. Ice inside and heat outside in cycles may eventually let the sprocket just pop off. My 1st one took a week and a few hundred interested minds on INOA, NOC and BI lists. The group mind focus does help, somehow alters reality and quantum entanglements magically to release impossible fusions like yours.