Internal Changes and Modifications

These cases were cleaned by hand with brushes and degreaser from MachineryCleanery. No bead blasting to ruin the original patina and casting marks. All bearings used are SKF except for the crankshaft main bearings which are genuine. Custom machined main bearing sleeves from VeeTwo, the only way to go as there are many very minor variances in the sleeve diameter. Important to have perfectly sized main bearing sleeves to allow the correct crush on the main bearings to prevent slipping. This slipping is evident particularly on the primary ( left side ) of engines. The factory tooling at the time wasn't terribly accurate or consistent in its results when the case halves were machined then matched and stamped.

There were two types of cases used sandcast and diecast

Flywheel Lightened

The flywheel was lightened by 1kg, original weight of 2kg. Helps the engine rev a little quicker without totally sacrificing torque.
Excess material is removed from the main body of the flywheel not the outer diameter.

Oil to Rear of Transmission

Oil to the rear of the transmission case has always been an issue. The right crankcase rear cylinder oil return gallery is modified to allow oil to drain and spray the transmission. Hole diameter is 6

Dipstick Tricks

Oil dipstick modification. Rare earth magnet ( 6mm diameter x 3mm thick )
A cable ferrule ( with a smear of epoxy inside ) is fitted over the magnet and secured by a shallow countersink drilled in the dipstick shaft and punched. Click on the 2nd image for a better view.


If the hex on your beloved Agip dipstick has been defaced here is a stylish and useful repair provided you're handy with a lathe.

Oil Improvements

Oil Gallery Magnet.
In conjunction with the dipstick the oil gallery plug located on the RH crankcase is also fitted with a rare earth magnet. Secured with epoxy adhesive and a 12mm internal circlip ( after machining a retaining groove ) this magnet also collects ferrous particles.

Importantly, this is located on the suction side of the oil flow, protecting your oil pump and crank from particles which have made it past the sieve.

Requires checking/cleaning only once a year or every 10,000 kilometres.

Shown above is the stock rubber oil gallery plug, this is what is supposed to seal to the end of the oil sieve. A new plug is to the right, a used one to the left. After time they harden and flare as shown no longer performing any useful function. That is apart from the less than perfect fit even when new.

The alloy insert shown to the right is made by RYE and with orings seals perfectly as well as allowing the use of either a roundcase or squarecase sieve without modification. Simple to fit with failsafe function make this upgrade essential.

Available from Mdina Italia

Pistons

Original 750GT pistons were Borgo, Mondial pistons were fitted to the 750 Sport and 750SS.
this engine is fitted with Mondials. Whilst the sizes of the bores are the same between the models, the different makes of pistons require rings specific to the type used. The piston pins used are a light tapered type. The Sport pistons provide a higher compression ratio.

Piston markings on the Mondial piston tops differ, however all will have AEC marked on the underside. Click on the images to see the underside of the piston.

Clutch and Throwout Lever

The clutch on the roundcase is prone to slipping, this can be cured by fitting a Surflex S1425 clutch kit. Consists of new friction and plain plates ( 8 of each ) and includes heavier springs.
These don't slip and also reduce the weight of your clutch plate assembly by 920 grams, that's nearly 2lbs for the metrically challenged.
The new friction plates are alloy and smaller than the original. You can use stock clutch springs if you find the new springs too heavy.

Fitting Notes
1. One of the friction plates has bent tangs. This plate is fitted first ( against the clutch basket ) with the tangs facing outwards towards the cover.
2. One of the plain plates has bent tangs. This plate is fitted last against the pressure plate with the tangs facing inwards towards the clutch pack. See this image

The clutch throwout lever can be lengthened to reduce lever effort at the handlebar.The increase on mine is 16 mm ( approx. 3/4" ), some folk make that increase up to 40mm. Involves cutting and welding the extension into the original lever.

NOTE : The cover on the left is from a sandcast engine, note the different selector pin coupling having a female end. These early bikes were fitted with Ducati widecase single parts on the selector box as the twin parts hadn't been developed at the time. This is not shown in the parts book .

Alternator Conversion

It's well known that the alternators in the roundcases were marginal, especially with headlamp on, riding around town. There is an excellent article written by Willy Gonnanson here

My method of improvement was slightly different, using a rotor from a '91 to '96 belt drive Ducati and a stator from an S4 or similar. This conversion requires machining of the rotor as well as milling the alternator case to accept the wider stator. The result is a stunning 13.2v @ 1200rpm, rising to 13.9v @ 3000rpm and above. This is achieved with the headlamp lit. You must also use a modern voltage regulator, ( Shindengen SH 548 ) shown in the electrickery section.

Click on the image of the stator for a larger image to show the relieving of the webs in the cover to allow the routing of the wiring. The quality of the wiring and insulation is superior to that of the original as you would expect. The rubber sheathing of the replacement stator was removed and a thinner plastic sheath fitted in its place to allow clearance through the wiring plug and gland in the cover and keep the original appearance. As this stator also has shorter wiring than the original a subloom ( with heavy gauge wire ) and join was fabricated to keep the regulator in its origial position. The join is under the tank and can't be seen. Careful measuring of the components was required for clearance issues. I deliberately haven't provided dimensions as other rotors can be used as well as stators. You can't use the stator from the '91 to '96 belt drive bikes, it is way too deep.
It's well worth a visit to a motorcycle wreckers to see what can be found, my conversion cost less than $300Au in total.

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