1975 850T Survivor Project

[cmice]

Hey all - just got myself into a "barn find"/"ran when parked" project.  Last registered in 1985, last operated in 1991.  Apparently a stuck clutch is what took it off the road.  P.O. did a favor and drained all the fluids, fogged the cylinders, and stored it inside - so far, all the fasteners are coming out without too much of a fight.

Bike is pretty much all there, with the exception of the H-pipe and mufflers.  I'm not sure the Wixom fairing is going to stay or not, but it is growing on me.  Is a non-filter model, so that's fun.

Other things to fix are: broken steering stop, scored forks, bent crash-bar, and tired rubber (including tires).  If there's anything else you spot from the photos, do let me know.

I'll post my first question to the collective under this post.

Next up is to pull the heads as they are chrome bores and I'm pretty sure they're up to no good.

[cmice]

Pulled the flywheel cover out, and the ring gear has seen some action.  What do you suppose caused this?  Inside of the bell housing is unmarred, so I think the thrust-bearing/end-play is ok.  Looks like maybe the starter hit the ring gear while the engine was running and spun against it for a bit?

Use it, or bin-it?  Whaddayathink?

[Antietam Classic Cycle]

If the steering stop is broken off and the crashbars are bent, then I would check very carefully to make sure the frame isn't tweaked. Those are both good indicators that there is frame damage. I have three Tonti frames here that wobble side-to-side on a flat surface.

With only 23k miles in 50 years the chrome is going to flake from the cylinder bores if you run them. Sitting around is the worst thing for them. IMO, there is not such thing as "good chrome bores" - it's not "if" they will flake, it's "when". Replace them now before they destroy the engine.

The ring gear damage likely happened from a tankbag or something else accidentally hitting the starter button. It will probably work okay as-is, but a replacement wouldn't be a bad idea.

[cmice]

Today's update - figured I'll pull the conrod caps off and see what it looks like there as a quick assessment of how he's been treated. Mixed news.  The bearing shells look distressed but the crank journal looks great - at least on the center web anyway.  But the distressed shells mean the crank should come out and get checked, along with the front and rear mains.  Off comes the front cover.

By the look of the incorrectly folded folding-locks and the boogered up stake-nut on the crank-drive sprocket, someone has been in here before and without the right tools.  So here's hoping whoever it was treaded lightly.  Some additional good news is no stripped threads or helicoils anywhere - so that's a bonus.

Rubber finger tensioner was tensioning air - so chain and chain tensioner are in order.  The flywheel was incorrectly indexed to the crank for some reason, so that's going to need some additional investigation when it comes time to time-everything-up again.

So, let's pull the cylinders off and see what we're dealing with.  And,  whelp, I'd already budgeted to change the cylinders and pistons out, so this isn't a shocker - but chrome has left the building.

[cmice]

Ok - today's update.  Made a rear main bearing puller - worked like a charm.  Here, again, mixed news.  First, the crank looks great so that's a relief.  The rear main bearing looks "ok" and I would probably run this, but curious what others think.  Unfortunately, front main doesn't look as good and I think he's a goner.  Again, what do calibrated eyes think here?

[Antietam Classic Cycle]

"Looks" are one thing, the micrometer tells the tale...

[cmice]

Ok boys and girls, always remember to clean out your crank.





A sort of rubberized slug of chrome dust and who knows what else came out - almost in one piece, but it broke apart into lots of chunks when I tried to extract it.

The bung plug was in only finger-tight, despite being "staked" and came out with only a faintest hint of thread damage (just at the very top where the stakes are). So he's going back in, but sealed and sent home properly this time.

[Antietam Classic Cycle]

This is from a '71 Ambassador with 98k miles on it.

[cmice]

While it seemed I've gone quiet, I've been doing quite a bit of work behind the scenes.  With the motor completely apart to assess the bearings, it was time to start building the shopping list...and that covered a lot of ground....

First-up was the re-plate vs. buy-new decision on the cylinders since my chrome has definitely failed and bare aluminum was showing, plus the bearing damage as a result.  I followed Charlie's math to look at re-plate vs. new, and indeed, buying new pencils out to the best eventual outcome.  I checked with the two usual places for re-plating, and one would come in about $100 cheaper than buying new (still no pistons or rings), the other would come in at $20 more expensive than buying new (with no pistons or rings).  Plus shipping back and forth, when you add up all the nickels, buying new sets gets you the most bang for the buck.  In the end, I flipped for 83mm Gilardonis which included pistons, pins, piston rings, and head gaskets.  Existing con-rods will be re-used; question as to whether the small-end bushings need to be mic'ed and reamed to size for the new pins, or close-enough and just run it?  Do the rings need to be gapped or do they come pre-gapped? (I'll check them regardless)

Speaking of conrods, that leads us to the great bearing replacement.  The chrome seemed to have done a number on the conrod big-end bearings and the front main bearing.  The rear main looks fine, and the journals all mic out to standard size and look great.  The rocker pins also look fine, as did the cam jounrals.  The cam bearings looked not great, so a *very* gentle touch-up with 1000 grit cleaned them up - called it close enough, we'll leave them alone.  Can these ever be replaced?  Seems like if you could find plain bearings the right size, a line boring machine would make this not too bad a job.

Ok, back to the update - given we're replacing the front main, that leads us to the topic of adding an oil filter.  The newer-style (with filter) front main bearing is cheaper and more available than the non-filter one; plus by adding a filter, we should be protecting all these expensive parts so this won't have to be done again by me or the next owner.  So new-style front main, plus a filter-in-pan off of Ebay, all that's left is the machining.  I didn't take a lot of photos, but there's a great writeup of the process here for those considering the change:

https://www.advrider.com/f/threads/moto-guzzi-early-big-twin-oil-filter-conversion.257513/

Just finished the machining today.  Hardest part, as others have found, is 1) having a 8mm drill long enough to do the deep oil passage (200mm will do it), and 2) the fixturing to hold the housing square with all the studs still in, and 3) having a machine tool with enough throat to hold this massive stack of parts plus extra-long drill (hint: the Bridgeport wouldn't accommodate just the housing with studs, let alone a Jacobs chuck and long drill).

Thankfully a friend has a habit of collecting old machine tools, including a 3-phase Rockwell gear-drive drill press - plenty of throat, nice and square and solid so nothing wiggles around while the quill spans a massive distance.  Little spooky working on that thing because if it snags on anything it will take your arm off.  All that's left is to fab the blanking plate for the old pickup, and then we can start putting the motor back together.

Lastly, earlier I'd posted a photo of the starter ring-gear and asked about how this could happen and whether to run it or not.  While I was browsing on eBay for a filter-in-pan sump, I found a listing for an "EV" flywheel and cover for cheap.  This alleged EV flywheel looked like a single-plate unit (which is junk) but figured what the hell - grab the assembly and if all I keep is the cover and ring-gear then great.  It showed up - and to my delight, it is completely unused and is not a EV flywheel at all, but a good-old multi-plate flywheel.  As an added bonus, the scale says the flywheel weighs in at 7.2lbs instead of the stock 9.2lbs(!) - so I guess I scored a lightweight LeMans flywheel by accident!  Gonna run that mofo for sure. :)

Next update should be about putting the motor back together - plus a fun side-quest in 3d-printing.

[Antietam Classic Cycle]

Existing con-rods will be re-used; question as to whether the small-end bushings need to be mic'ed and reamed to size for the new pins, or close-enough and just run it?  Do the rings need to be gapped or do they come pre-gapped? (I'll check them regardless)

Yes, do check small-end bushing i.d. and compare that with the specs in the factory manual. The new pins will be the same o.d. as the originals.

The rings are supposed to be "pre-gapped" but it doesn't hurt to check them.

There have been reports of a few of this latest batch of Gilardonis not fitting into the crankcase - the "spigot" of the cylinder wasn't properly machined and is too large to fit. Check this before you begin assembly. 

[cmice]

A little overkill perhaps, but CNC cut the blanking-plate for the original screened oil-pickup (ie. non-filtered flow), and installed.  I added nylocs on the back side just for safety, and we'll see if there's room once the crank is installed...I think there will be no problem. Now that all the machining on the block is done, and it is clean, we can start building it up again.

[cmice]

Short update for today.  Rear main lip-seal changed, and the rear main bearing is in the freezer waiting for the "big day" when the crank goes back in.

In cleaning up the rear main bearing, I forgot that there was still the old gasket stuck to it.  I don't know when whoever was in here was in here, but they used some sort of gasket sealant that got super hard and really stubborn over the last 30 odd years (can't be 50, surely).  Anyway, spent some quality time with a steamer with a brass-bristle brush attachment, and the almighty razor blade, and those stubborn things finally relented and came off nicely.  New gaskets will get hylomar - doesn't harden, cleans up easily, love that stuff.

New rear main lip seal went in with only oil - no sealant.  Old seal had I think shellac type sealant, and was a bear to get out. 

Some arbitrary engine shots.

[cmice]

Update from last post - freezing the rear-main is the bees' knees.  Dropped right in without a fuss.  Lip seal was a little stiff to get over the end of the crank, but gentle coaxing with non-sharp things got it to slip over and it went home with the gentlest tap of a dead-blow hammer.

Ok - today's question, and I'm sure it's a boneheaded one as it's been covered before....but this just doesn't make sense.

I'm reusing my existing conrods and kept track of how they came out (plus end caps, etc) - but I don't trust anything that's coming out of this motor now given someone else has been in it.  Looking at the oil squirt hole orientation, all the references say that the milled flats and the oil squirt holes should face to the right (which means one squirter points up, the other points down).


Oil Hole in question...


But that doesn't make sense if the role of these is to squirt the underside of the pistons.  It seems like both should squirt UP, but instead, all facing right means one side gets squirted underneath and the other squirts the sidewall of the engine case?  Am I overthinking it?  Using new bearing shells so previous run-in is ignored.


This is how I would THINK it would go, but this would be incorrect.


Also, looking at the two conrods, one side looks like something funny happened - unclear if this is from the factory or field related damage.  Is this just a manufacturing thing or is this rod suspect?  Underside of the cylinder skirt looks ok.  Thoughts?


Looks like a hand-grinder was taken to this???


[Post-lunch edit...] Everything I see says left-up, right-down.  I don't understand why, but that agrees with how they come out so that's how they're going back in.