Got Flakes?

Early 2017 Update
It was a matter of time before the cylinders came off for inspection, and a persistent minor leak on the right was the reason this moment finally came.  I had re-torqued the head a few times already with no change, so after a little procrastination I got some new gaskets on order and got to work.

At first glance I thought all looked OK, until I noticed some scoring on the back side of the piston.  Then it was clear that one of the rings was ground into the groove near the exhaust side and the piston was scored.  A check of the corresponding cylinder bore location revealed an unsettling mark.  Crud, the chrome had flaked off in an area about the size of a 'Tic Tac'.  This cylinder is toast.  And a little scary at how close it might have been to failure, had I not checked.

Options ranged from sourcing used jugs, to NOS cylinders, to new Gilardoni cylinders.  And with or without pistons? Rings? Since an eBay search showed several reasonable used items, I decided to go the cheapest route (my usual!) and buy used. Including the pistons, which is good, as the scoring on my right piston has gone a little far for comfort.  I hope the photos and descriptions live up to the condition required to use them.  More when they arrive and the installation is done.

Follow-up: the used cylinder arrived, with chrome bores in very good condition.  And, the piston with which it is matched is in good shape, and the rings are free from obvious wear and move freely in their grooves.  Wrist pin also looks great; that was popped into the freezer for later installation.

Both needed a lot of cleaning, however; mud wasp nests and corrosion from the cylinder and carbon from the piston head.  My soda blaster was put to use as well, helping to strip decades of build-up; a water bath then neutralized the soda and all was dried.  Following the thorough scrub and cleaning (and aluminum paint on cylinder fins), it was time to install the piston, gaskets and put the head on.  I'd never held the 'beating heart' of a motor in my hands before, so was a little nervous about putting this all back together.  I further did not expect the wrist pin (a press fit) to be so snug.  A tool had to be made to press the old one out and the new one in (and installing it fresh out of the freezer overnight helped as well).  Below photos show the tool in action pressing the old one out, and then the parts of the tool.  Next time I will use a more robust bit of PVC tubing, but this worked well and I got the new piston installed without too much effort.

The head bolts had to be torqued properly before the valve clearance adjustments could be made.  While cold, the head was bolted down in a star pattern until very snug, but just under full torque.  At roughly 24 hours, the head was torqued to 34 pd/ft.  Then again, roughly 24 hours later the head was re-torqued to the same 34 pound feet.  Valve clearances were then both set at 0.006" (slightly tighter than Guzzi spec, I know).  Other note, both were at first measuring tight from prior setting, as evidence that the new gaskets are (obviously) not quite as compressed as the old ones were.  A day later I took the 850T out for a ride; it started quickly as usual and settled into an idle.  It rides at least as well/normally as before; revving easily no smoking or oil leaks.  Hooray!!

wrist pin pressed through the rod, and cylinder about to be dropped down onto base gasket

Sorting Stuff Out

Nov 2016 - what's next for this Moto Guzzi?

So, with the bike reassembled and the project goal accomplished, I've had the opportunity to put about 250 miles on the 850T.  A few things quickly became apparent, as one might imagine; nothing unusual or troubling, just the routine experiences and observations which come from daily living with such a mechanical entity.  While I can live with it just fine as is, a little attention to the following will enhance the reliability and rideability.  The forks are quite undersprung and the front disc brake is very poor, like a block of wood against steel.  I also found a small leak at the base of the right cylinder and the rear drive leaks as well (minor leaks are a major reason for maintaining a clean bike so, first, you are aware of a potential problem very early and, second, you can more quickly pinpoint the source).  Minor issues are par for the course on a 40 year old bike - note, I do not expect it to handle like any of the other decades-newer bikes in my stable.  Nonetheless, these are correctable, and things that I'd like to sort out.

The first thing is getting the cylinder leaks taken care of (leaving tiny, misted droplets on my boots after a 30 mile ride).  Some brief research implies that this is normal for big block Guzzi's, and should be rectified by re-torquing the cylinder heads.  After sorting through various forum exchanges I determined that the torque needs to be at least 32 lb/ft and no more than 34.  Unfortunately I only have a torque wrench in inch pounds, which tops out at only 3/4 of this range.  Oh well.  Pictured below are the rockers under the valve cover over the left side cylinder.  Another 'unfortunately', the rockers have to come off for access to two of the six bolts holding the cylinder head down.  It was not difficult or all that time-consuming, but I had put it off for a few weeks as the first time doing anything carries with it a little trepidation.  I could feel that the six bolts loosened fairly easily (not easy, just easily enough) - judging that they needed more torque and not having a torque wrench, I simply marked each bolt with a tiny scratch so I could confirm that it had been snugged a tad (technical unit of measure) more than before.  All buttoned up again, the left side is ok but the right still has a little pool of oil collecting on the lower inside.  I've since borrowed a larger torque wrench to get to this job again shortly.  Ugh.

The next thing to warrant attention are the fork springs, since I'd like to correct the saggy feel and dive before addressing the disc brake.  I'd removed and serviced the forks during the rebuild, and put the stock springs back in; whether they ever were in the first place, they are not quite up to the task now.  I called Progressive earlier in 2016 looking for springs with a heavier spring rate for this bike.   I purchased the recommended springs (0.68 kg/mm) but they were 60mm too long.  Or at least they were 60mm longer than the stock springs and I was sure that they could not be compressed enough to fit.  Past 90 days from purchase I could not return them, but the tech told me they could be cut down a few inches.  Consulting Guzziology, it was noted that a spring should generally not be much more than 1.5 inches above the top of the damper shaft at full extension (or spacer length if setting preload).  The stock springs sit at exactly the top of the shaft when not compressed.  Feeling that the Progressive springs would be stiffer than stock, I elected to cut the Progressives down leaving about 1.5 inches.  This was a mistake!  Whether they are stiffer than stock or not, I still cannot really say.  The sag is better and they are compliant and not springy, they still sag several inches under bike and rider weight and then bottom out under heavy braking.
To Resolve - the cut piece can actually be used as a spacer; either with the stock spring or the Progressive.  Although the total length of the Progressive spring may be prohibitively long.....  I just hate to take these on and off in a trial-and-error fashion.  But I cannot identify what the spring rate of the stock spring is.... Ideally, for a bike weighing about 500lbs and a rider (me) weighing about 200lbs, a spring rate of 0.95kg/mm is called for.

above = stock spring (420mm); below = Progressive after cut (total 480mm)

And last, the seat.  I somehow knew that this saga would end with me actually fabricating a seat for myself.  After the shop which made the first cafe seat (too low and interferes with rear fender) promised to replace it, and then waiting another 2+ months, they won't do it.  Options include buying a stock seat just for the pan, or using the cafe pan I have.  I can't use the seat that came on my project as it is not original and was fabricated from aluminum, thus it doesn't hold its shape well and presents problems for attaching the seat cover.  So cannibalizing my new cafe seat for the pan will be my approach.  I also think I can cut off the top of the foam to retain the shape of the cafe seat, as they did quite a good job of this (and it requires patience and skill, two things I have only in limited supply).
Two dense foam pads from Home Depot (gardening kneelers) will serve as the base on top of the pan.  Then the cafe padding, then I bought a roll of 1/2" foam to cover and smooth the underlying layers.  From eBay, I found a Moto Guzzi V7 replica seat cover that has the words 'MOTO GUZZI' in block letters across the back.  The hump is not the same, but close enough that I'm confident that it will fit (and still look "cafe") with a little tuck here and there and extra foam if necessary.

slightly photoshopped to show where it would sit higher after modification