I’ve had my beloved Moto Guzzi V35II for quite a long time and I really think that I am one of the rare people who own an oldtimer as a primary and an only bike. This year Guzzi turned 40 and there is no better birthday gift than a (unplanned and not-entirely-needed) engine ‘renewal’.
Full restoration was not needed, and despite the massive peer pressure, I decided not to give in and get the fresh paint job, change the instrument cluster or anything else that would ruin its originality.
The engine ran smoothly, never let out a tiniest particle of smoke, only occasionally produced an unidentified sound. The latter was the reason why we decided to disassemble the engine to see what might be the cause of that mysterious tapping coming from a secret place somewhere deep in the engine.
It did stop and the cause was never discovered.
But what was discovered was that the piston rings needed to be changed pretty much immediately. It is actually quite surprising that there was never any smoke coming out from the exhaust, since ring end gap clearance should be somewhere between 0.20 to 0.30 mm, and it was between 2 to 3 mm. Even if you don’t know a thing about piston rings and end gap clearances, it should be pretty obvious that it’s way too much.
The cylinders were also a bit worn out, so they were bored out and cast-iron cylinder liners were pressed in (instead of Nikasil). This is the only deviation from the original, but we decided that it is better and more affordable. Cylinder heads were resurfaced and valve seats were ground. When it comes to pistons, we installed new gudgeon pins. This is when Guzzi prepared a surprise for us. Relying on the specifications, we bought 18mm gudgeon pins, but it turned out that we needed 15mm pins. Also, piston rods are lighter than expected. The conclusions will be discussed later in the text. Camshaft and crankshaft were inspected and I can say that they are perfect as new.
Clutch friction disc was quite eroded, so we got it renewed at the company called Comet. The flywheel was adjusted so that the engine timing could be set up properly. Here, we encountered another surprise. We had already had a clutch that was supposed to fit perfectly, but no, it didn’t. My clutch is significantly thinner and lighter than one would expect for Moto Guzzi V35II. The flywheel itself is also different and lighter than expected.
Furthermore, all seals and radial shaft seals were changed, a new timing chain was installed, and the quirky starter was repaired. We also installed new wiring just in case, even though the old one was fine.
The carburetors were thoroughly cleaned and all jets were replaced with the originals. New fuel taps were installed so that everything would flow smoothly. The brakes were rebuilt with new seals.
When everything was finally finished, the spectacular first start finally happened. It did start, but it was immediately clear that we need to deal with the ignition pickups. If you have ever worked on that, you probably know that it is the job for the patient. Tune-up and try, tune-up and try. And we did tune-up and we did try and we finally succeeded. And now it starts perfectly!
Max, the main engineer of our racing program who you already met in the previous post was in charge of all precision work, and my dad Zdenko and Neven were in charge of the assembly. I also tightened a bolt or two.
Guzzi’s engine is now like-new, but we never actually found out why certain parts are basically lighter than expected. You might say that somebody just put it like that, but if you’re just a little mechanically inclined, you’ll know that you can’t just put it like that and expect it to work. You’d need to change a bunch of other parts and it just doesn’t make sense.
The only google-drawn conclusion is that these parts are lighter because of speed, since it was probably built for the police and hence needed to be faster.
We will continue our research until we solve the mystery behind that, and in the meantime, I’ll just continue bragging about my bike. That’s what already do anyway. Just joking guys. Or not 😀