Tuesday, 22 May 2012

Lovely to look at. The Moto Guzzi 750S3

This Guzzi S3 is on eBay right now and has prompted a bit of a geek-fest on the Guzzi owners' club forum. When did Guzzi start chrome plating bores? It matters because if the plating's going, going or gone you could knacker the hard-to-find round barrels. Not difficult to check by lifting the head on the OHV Guzzi, but is it necessary?

Geek that I am I had to check...Ian Fallon's book (which Ivar de Gier proof read and he assures me is the most accurate English language Guzzi reference) says "The ...1974...850T..as usual at that time had chrome bores" Then later on "Nigusil (replaced chrome) from 1980...used for the SP (Spada)..(and the) T4". All my books refer to Nigusil (Guzzi's patented silicone/nickel bore plating) but I'm sure mags at the time spelt it Nickasil which suits English (if not Italian - no K over there! Hence Chianti red wine, not Kianti..)

So it seems from at least 1974 (ie just after de Tomaso's take over) to 1979 Guzzis had chrome bores, then from 1980 on Nigusil/Nickasil. But there's something else I can't get a definitive answer on - the S3 was basically a sleeved down T3 (certainly same engine cases with the sump filter and a T3 camshaft) so I guess it had a chain drive to the cam (gears were used on the V7 Sport). The swan necks had gone by the S3 too, but the original owner of this bike fitted them anyway. Good man.

Lovely as the S3 is to look at (I painted a 400/4 this colourscheme in the 70s!) it was really the start of de Tomaso's cost cutting. Heavier and less powerful than the Sport, contemporary road tests struggled to get much over 110mph out of the S3, a good 10mph less than the Sport. The seller's looking for offers around £8500 which looks value when you realise only 950 were made, but really a Sport or Le Mans is worth the extra. If you've got it. Unless you already have a Sport and Le Mans, and want the set. The S3 wasn't a bad bike, it just wasn't as great as its predecessor and was up against the new Ducati 900SS and BMW R90S. But at least it kept the sporting V-twins coming out of Mandello, and with pleading from genius Lino Tonti, de Tomaso was persuaded to make amends with the Le Mans. More info in back issues of Benzina.


  1. The 1972 V7 GT850 California I owned had a V-belt drive in front of timing gears to a generator nestling between the cylinders on top of the motor. The S3, as you can see, has on alternator on the front of the crank, suggesting that it's the T motor with camchain

    1. Further to the above, I question whether this S3 is a 1976 bike. The series one Mk 1 850 Le Mans appeared that year. I now own a series two Mk 1 made in 1977. However mine no longer has chrome bores because it's wearing 5mm bigger holes thanks to Spada Nikasil barrels taking it to 949cc with bigger 40mm DellOrto pumpers. (To be pedantic, Nikasil is a trademarked electrodeposited lipophilic nickel matrix silicon carbide coating). I've also got a timing gear conversion to get rid of the camchain and Dr John camshaft.

    2. Here you go: "The S3's pushrod-operated 90-degree V-vwin engine was heavily based on that of the V7 Sport, sharing its bore and stroke dimensions of 82.5 x 70 mm (for a capacity of 748cc), its 9.8:1 compression ratio, and most mechanical parts. But Guzzi had made some changes, most notably incorporating a proper oil filter in the crankcases (the Sport made do with a mere strainer), and replacing the earlier model's helical gear camshaft drive with a cheaper chain and sprockets." I note also that it only had 30mm carbs

  2. Yup, bit more digging says the V7 Sport lost the gear drive cam/oil pump in 1973 so affects late Sports (engine 33448 on)as well as the S and S3. That was when AdTomaso started cost cutting. Seems all the Tonti framed/alternator equiped V-twins had 30mm carbs til the Lemon got 36mm jobs and (like the Convert) cast iron cylinder liners. Love the sound of the second commenter's Le Mans, btw