Back in 1974, Moto Guzzi did their customers a real disservice by switching over from helical cut timing gears to a timing chain with a hard rubber block, which acts as a chain guide. In 1989 Guzzi switched over to a spring loaded chain tensioner, which is a bit of an improvement but is still not nearly as nice as the original set up.
As the chain doesn't run in a simple loop, chain life is usually on the order of 20,000 miles, and then wear progresses geometrically. If you've ever seen small bits of black rubber in your oil, such as in the rocker pins, the culprit is the chain wearing through that hard rubber block, which is comically described as the chain stretching device. In extreme cases, the chain will gnaw away at the crankcase and dig a trench in the case.
With a worn chain the valve and ignition timing is all over the place, and Old Paint don't run like she used to. The easiest way to check the condition of the chain is with a timing light. If the mark is bouncing around all over the place (and not from a hot cam causing a lumpy idle), the chain's garbage.
Owners of 850/1000 engines have a choice: either stick in another chain with an updated chain tensioner or go with timing gears from Agostini. Owners of 1100's (and I suspect all fuel injected models) are stuck with installing another timing chain, as the gears will bind on castings inside the crankcase. I should mention that I don't know at which point the spring loaded Guzzi tensioner loses its effectiveness, so perhaps 1100 owners have nothing to worry about, but eventually the part will lose its effectiveness, either through wear on the rubbing block or through spring fatigue.
Given a choice between gears and a chain/new tensioner, I'd go with the gears as they're easier to install, are a one-time shot and don't cost all that much more. The only bikes possibly that should stick with the chain and updated tensioner would be the late V7 Sport and early 850-Ts, as they don't have an oil filter to catch the aluminum sheddings from the gears during break-in, which could wreak havoc with the chrome liners.
The job can be broken down into several different parts: chain removal/gear installation, timing mark verification, torque heads/set timing, and finally engine filter change. Barring anything stupid like rounded off Allen heads, start to finish is usually on the order of six hours.
For tools you need: rotor puller, universal gear puller, 3/8" ratchet, 1/2" breaker bar, 17mm socket, 19mm socket and wrench, 27mm deep socket, 4, 5, 6 8 and 10mm Allen sockets, 4-inch extension (3/8" drive), 6 inch extension (3/8" drive), 10, 11 and 13mm wrenches, feeler gauge, valve lash adjusting tool, seal puller (optional), metal rod, gear holder, torque wrenches that read in inch/pounds, read up to 60 ft/lbs, and one that will go up to 110 ft/lbs, peg socket for the crank nut, 32mm deep socket for installing an 1100 crank nut (optional), small screwdriver, plastic mallet, hammer, brass drift, propane torch, degree wheel, positive stop piece, timing light, razor blade, dental pick and (hopefully optional) Dremel with cut off wheel and chisel, die grinder, Paramedics on stand-by.
For parts you need: gear set (obviously), timing cover gasket, timing cover seal (optional), sump gaskets, oil filter, 20mm crush washer, 2-8x20 Allens, two 8mm crush washers, engine oil, Loctite, anti-seize, valve cover gaskets, grease or gasket sealant for gaskets, head plug O-rings, contact or brake/parts cleaner, gasket remover, exhaust crush washers and pipe sealant.
The bike's clean; the work area's clean; you've got your stuff laid out and it's time to begin.
Remove the tank, valve covers and the timing inspection rubber. Place the bike on a secure stand, drain out about a quart of oil, loosen the frame Allens and the front engine mounting bolt, remove exhaust if required to remove timing cover.
Remove alternator cover (note wiring), remove alternator, put machine in gear and holding the foot brake down remove the alternator's center bolt. Insert rotor puller (don't listen to the Haynes manual - use the real tool!), thread in the alternator's center bolt, and holding the foot brake on, tighten up the bolt. If a reasonable amount of force doesn't pop off the rotor, put a block of wood on the rotor and give the wood a sharp smack with a hammer and the rotor will jump off the crank nose.
Punch out the front engine mounting bolt with a brass drift, remove the spark plugs, horns, tach cable and remove the timing cover with a few bops from mallet. Groan as gasket sticks to both mating surfaces.
Put engine in top gear and bonk rear tire forward until marks on timing chain sprockets align. If you're installing gears, jam metal rod in between sprocket and chain on left hand side. (If you're replacing the chain you'll need to use the factory sprocket holder as the metal rod will destroy the sprocket.)
Remove oil pump nut and washer. Here comes the hard part if the machine has never been apart before: bend back locking tab on crank nut, put propane torch on incinerate, heat nut up for at least five minutes until massive amount of Loctite finally melts and runs down the sprocket. Use factory peg socket to remove nut. Famous last words. On occasion, this nut will round off and then you need to very carefully cut a V-shaped wedge into this nut with a Dremel and bop it off with a chisel and hammer. This is not fun at all.
Put propane torch back on full blast, heat cam nut up until mass quantity of Loctite finally runs down the sprocket, loosen nut with breaker bar. Once it's loose, take the breaker bar and "shock" the jammed metal rod loose by jarring the cam nut clockwise. Remove metal rod, align marks on sprockets, re-loosen cam nut and remove nut and washer.
Using your universal puller, go from gear to gear and withdraw them from their shafts. All three sprockets have to come off in unison, so this can be rather tedious. Make very sure you do not lose oil pump's woodruff key. Remove idiotic "chain stretching device," hang up on wall for future laughs. I always plug the chain stretching device's holes with 8x20 Allens and crush washers; I don't know if this is necessary but they were plugged up before so evidently that's how it should be.
Perhaps beginning in late 1991, there has been an unused casting bulge inside the crankcase. This will foul the gears so it needs to be buzzed down with a die grinder before commencing gear installation.
Start oil pump gear onto shaft (note woodruff key, turn pump shaft with screwdriver to align gear with key), start crank gear onto shaft (note woodruff key alignment), start cam gear onto shaft (note cam dowel alignment). Punch marks on gears must be in alignment. Tap gears fully home with mallet and pay particular attention to the oil pump woodruff; if this is not fully seated, your oil pressure will be all over the place. Don't ask me how I know this one!
Lubricate gear teeth with light coating of engine oil, not assembly lube. The gears need to bed-in and will never quiet down if you use anything but engine oil.
Clean all threads (male and female) with contact or brake and parts cleaner, blow clean with compressed air.
Before the next step, two things: first, you're only supposed to use a LITTLE Loctite and second, using a formula that you have to melt to remove may not be the way to go when the cam and crank are drawing away all of the heat! Maybe they picked up 500 liters of Red Loctite at an auction years ago.
Also, you now have the opportunity to go with the 1100-style jam nut and washer on the crank instead of the old peg nut and lock tab washer. The 1100's flat washer may have to be ground down a bit for the 850 and 1000 cranks to get the jam nut to thread fully.
Place a drop of medium strength Green Loctite on each threaded piece, and with your fingers install oil pump washer and nut, crank washer and nut, camshaft washer and nut. Insert gear holder (usually comes with the gear set, although not always) and tighten oil pump nut (no torque spec given but I wouldn't go too crazy on this one as it looks as if it might shear easily)!
For the crank and cam nuts, pay attention to the gear holder as it'll try to walk its way out of the gears. If possible, have an assistant carefully hold this in place, but watch your fingers as the gears will slice them right off if given a chance.
Tighten up the crank nut (no torque spec given) and bend over lock tab if using old-style crank nut. Tighten up the cam nut to 108 ft/lbs and then hit each nut with one additional drop of Green Loctite which has a self wicking formula so it gets sucked right in there.
Replace timing cover seal (optional), remove gasket material from mating surfaces and install timing cover with new gasket. Put light coating of anti-seize on Allens and torque to 85-90 inch/pounds.
Reinstall front engine mounting bolt with anti-seize and retorque it and the frame rail Allens to 56-58 ft/lbs, reattach horns and tach cable, replace the exhaust gaskets and put the exhaust system back on, top up engine oil and it's on to step two which is verifying the timing marks.
For that you'll need a degree wheel, pointer of some sort and a positive stop piece. A positive stop piece can either be purchased or fabricated using a length of aluminum or brass attached to an old spark plug. The purpose of the positive stop piece is simply to stop the piston in its travel upwards in the cylinder.
Affix degree wheel to crankshaft using alternator's center bolt. Affix pointer with which to read degree wheel (safety wire attached to timing cover Allen works well).
Put machine in top gear, rotate rear wheel forward until piston on right hand side is on its way upwards on the compression stroke. Screw in positive stop piece and gently rotate rear wheel forward until the piston contacts the tool.
Loosen alternator center bolt and set degree wheel to 0 degrees TDC. Gently rotate rear wheel backwards until piston contacts positive stop piece and note reading on degree wheel.
A full circle is 360 degrees, so take the number of degrees on the wheel that it would take to make a full circle, subtract that and divide by two. For example, the degree wheel traveled 340 degrees before the piston made contact with the tool. 360 - 340 = 20 degrees divided by two = 10 degrees which is what we'll use from here on in to simplify matters.
Rotate engine forward, remove positive stop piece and slowly rotate wheel until degree wheel reads 0 degrees TDC. Rotate the rear wheel forward until you're at 10 degrees past TDC, and that is your true TDC mark. Reset degree wheel to 0 degrees TDC and note mark on flywheel. Do not be surprised if the factory mark is off by a few degrees on one cylinder! In some cases, both sides will be off. Duh.
Mark flywheel with punch and paint, and then rotate engine backwards with the rear wheel to where the static timing should be according to your owner's manual. Mark flywheel with punch and different color paint and then rotate engine backwards to where the full advance timing mark should be, then punch and paint once again.
Repeat process for left hand cylinder. V7 Sport auto advance springs will cut down on, if not eliminate, engine detonation. This requires the static advance mark to be put on at 8 degrees BTDC. The marks are there so it's now time to torque the heads, and I think you'll find that with the flywheel marks in the correct position, the valves will be considerably quieter.
Once the heads have been torqued and the valve covers are back on (anti-seized Allens to 90 inch/pounds, new gaskets, head plug O-rings), remove the degree wheel and pointer, reattach the alternator rotor, which needs to be torqued to 18-21 ft/lbs, reattach the alternator and wiring, put the plugs in and the tank on and then set the timing with a light. Don't forget to put the bike in neutral!
You then ride the bike for fifty miles, which is sufficient for the gears to bed in, drain the oil, drop the sump and strip it for cleaning (filter, mesh screen, pressure release valve), thoroughly clean the sump's passageways to ensure that all of the chips are out, put the pressure release valve back on with a little pipe sealant, smear the rubber gasket on the oil filter with some fresh oil and torque to 100 inch/lbs. Make sure to bend the locking tab back over for the mesh screen, stick on new gaskets, anti-seize the Allens and torque the sump to 90 inch/pounds, put a fresh crush washer onto the drain plug, dump in the oil, and you're done until you do the next bike!