"Test Mule" '74 850 Monoshock build

grandpaul · Nov 3, 2009

They feel too glassy smooth, and the left side has never run from the time the new pistons were installed. So, just a quick pass with a finish grade hone to give them a bit of texture to trap oil for quick break-in.

Cookie · Nov 3, 2009

Good thing you tore it down! Waht about that pulled stub area? Weld up?

grandpaul · Nov 3, 2009

Already had a new set of bearing shells, so I just gave everything a mighty scrubbing and re-assembled the crank & rods. Nice and smooth rotation on the rods.

Cases modified & spiffed up, inside-

Cases, outside-

That's it for today.

Cookie - yes, the broken stud socket will get welded up and ground down, then re-threaded, tomorrow.

B+Bogus · Nov 4, 2009

grandpaul said:
Hmmmmmmm..... somebody at the factory forgot to set the locktabs on the crank nuts-

Only the finest British Gross Engineering Misconduct, and at no extra cost!

Good to see the crank journals can take the beating though - and that the locktabs aren't strictly necessary!

Looking forwards to the rest of the build :wink:

batrider · Nov 4, 2009

Did you reuse the studs and nuts holding the crank together or get new ones? Also did you have to do anything to the journals? Were they worn? It is great to have the detailed pictures. I've seen sludge traps that were completely packed solid with metal paste. Makes me want to take mine apart now...

Still can't believe this bike was running on one cylinder and they just gave up on it like that and walked away. It looks like they were actually running it that way for a while. They didn't know?

Russ

grandpaul · Nov 4, 2009

I re-used the crank fasteners with loctite.

There was no way to know that points post was broken without removing it, so I'm sure they fiddled and fussed, twiddled and cussed.

It's no fun riding a Norton 425 "quasi-thumper".

Cookie · Nov 4, 2009

In my college years for extra money I rebuilt scrap VW engines the dealership gave me. One that is frustrating just tends to get replaced as time is money. I imagine this happens with owners too.

grandpaul · Nov 4, 2009

Well, the gent I traded the Triumph parts for the Norton engine doesn't work with Nortons, so he just took the torch, chopped the engine out of the chopper frame and let it sit "in the back" till such a time as somebody offered him a trade. Worked out fine for both of us.

Cookie · Nov 4, 2009

I imagine it was the owner before who got sick of trying to fix it.

grandpaul · Nov 4, 2009

Got the case half back from the welder, just need to drill & tap it.

Goofing with the cam that came out of the engine, and a spare I have on the shelf; I need to find out which is the better cam, they are definitely different.

The one with more rounded lobes has a smaller base circle (0.880") and more lift - (0.330"), it's stamped with an "S", and then appears to be hand-scribed with a second "S". It has the tang slots and shouldered drillings for the timed breather.

The one with the more "pointy" lobes has a larger base circle (0.900") and less lift - (0.315"), it has no stampings whatsoever, and is from the 850 engine.

Can anyone shed any light on which would be the better cam to use on the 850 +.020 with stock carbs & 2-into-1 header?

Cookie · Nov 4, 2009

Nice job! Did he weld in a piece of stock?

SteveMinning · Nov 4, 2009

Hey Paul,

Really appreciate the forensic documentary on your engine. Any idea what caused the case to fracture around the bolt hole? Unless something struck it there I'd have to think that it was either way over-torqued or a casting flaw. Of course I'd expect an over-torque to just strip the threads out. Hmmmmm. ??

By the way; missed you at Barber. You missed a bit of rain but it was still a great event. Raced in light misting rain on Saturday, but perfect conditions on Sunday. Cindy and I slept in the paddock in our van and just had a wonderful weekend.

grandpaul · Nov 4, 2009

Not sure what happened originally, but there was a grade 8 bolt stuck in there. The remaining section of casting had ALMOST 2/3 of a thread circle, so it was holding to a degree. The welder just built up the area with weld rod, then shaped it down with a dremel grinder.

Sorry I wasn't able to get to Barber (or anywhere else on AHRMA's schedule) this year. maybe next year!

grandpaul · Nov 5, 2009

Well, I've switched gears again. My local salvage guy had a Suzuki TL 1000 theft recovery with a perfectly good front end (missing one brake caliper), so I decided to do the inverted fork on this bike, too. I dug around and found a like-new matched set of triple-pot Tokiko calipers, so it'll be a nifty setup. I might just forgo the Dreer front hub and have one made that will accept the Suuki (Sunstar) brake rotors without having to go to special bearings and disc spacers, bottom line will be a tad on the better side.

So, apart from a few tranny bits, and maybe a better crank, I already have enough (with my other client's spare frame), to build a mostly-stock 750 with Mark III disc brake front end, high Rider tank and bum-stop cafe seat. Why not?

dave M · Nov 5, 2009

This sounds exactly like my own twisted psychology, every time I finish a project even if the only parts left over are a broken right hand exhaust rocker and a front axle with a stripped thread I consider this to be a good basis for a new project!

grandpaul · Nov 5, 2009

Well, dave, you are a bit farther along (gone?) than I am, then.

I need to have at least one crankcase half and a clutch lever before I'll have a go at starting another project.

grandpaul · Nov 7, 2009

New parts received:

Cool braided stainless clutch cable (will probably end up on the Blue 880), tach cable, exhaust lugs, oil filter clamp hdwr, Dzus fastener for sidecover, footpeg studs, rear brake cable lug hdwr, oil banjo crush washers, primary cover nut, and sidestand rubber buffers.

Sidestand, rear brake cable, front engine mount bolt, swingarm cap assy with o-rings, oil filter, footpeg mounting nuts, primary gasket, and oil tank rubber mounts.

I love it when the new stuff starts arriving...

grandpaul · Nov 10, 2009

The Suzuki TL1000 donor front end parts-

Yokes with stem turned down to fit Norton steering bearings, and new steering stops welded in. Next stop - polishing!

grandpaul · Nov 10, 2009

Head face all cleaned up-

It's at the machine shop being media blasted, my best efforts couldn't get all the black paint off (or the RED paint under that!)

My homemade rocker spindle puller-

The big flat nut and small nut are used to pop them out of thier seat, the taller sleeve nut is used to draw them out if they won't simply pull out with a pair of pliers on the bolt head.

No worries!

grandpaul · Nov 10, 2009

Here's where it gets ugly. Somebody has decided to make a mess of the "RH" head stamping-

However, the casting is pretty clear, it's an 06-3807 (see previous photo of the cleaned up head face), standard on the '74 850; That makes it an RH10. I've gone ahead and cleaned off the head and re-stamped it with the appropriate RH10 stamping.

Stock 28.5mm intake ports may want to get opened up to 32 to accept 932s for the "warm" cam.

"Test Mule" '74 850 Monoshock build

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