Although the different engine configurations imply different shaft-centre-distances and primary ratios, all Laverda SOHC 750s and 1000/1200 Triples use essentially the same chain - 3/8" x 1/4" x 76 pitches. Originally it was a triplex (three row) chain, but was changed to two single row chains in around 1982. Ideally the primary chain should be an endless riveted chain, but I have also used spring-clip chains without incident.
Lets look at the various good quality options currently available as of 2011:
The triplex chain is getting very hard to find in suitable quality for use in our engines. It is not a product which is in demand anymore, and as such manufacturers have gradually stopped producing it in the required quality. According to Andy Forsdick, the best remaining option is made by Spanish company IRIS (note, not IWIS), while Tsubaki also make a reasonable quality industrial triplex. The options below are a better bet however.
An interesting new product, brought to our attention by Andy, is this bush chain made by German company IWIS. It is of the type used as the camchain in some Mercedes Diesel engines and has quickly become referred to as "The Merc Chain". Utilising two rows of a normal set of triplex sprockets, I have tested this this chain in a race environment and has passed with flying colours. Many road bikes are opting for this chain as I write this, with no adverse comments as yet. Definitely a good option.
Worth noting is that if you have been running two simplex chains on the outer rows of your triplex sprockets, it might be a good idea to obtain new sprockets before utilising this option, due to the fact your outer rows of teeth will be slightly more worn than the centre row.
Similarly, later bikes which lack the centre row of teeth on the sprockets will require new sprockets to use the duplex. You can just use triplex sprockets from any Laverda dealer, and if you are keen you can machine the sprockets down to just two rows (delete the row toward the centre of the engine).
Two single row chains, as used by the factory toward the end of production, are also a good solution for the primary drive. The best two chains for this use would be the IWIS G67HP or the Regina C121HCS. Although I used the Regina product for many years and was very happy, it has become very hard to source of late. Thus, I am now using the IWIS product as supplied by Andy.
Note to Australian customers, all IWIS chains are stocked both by Redax in Qld and myself.
These engines use a gear primary drive, so for a change there is nothing to worry about there!