The original Gurtner carburetors fitted to Mobys can be a sod to sort
once they're worn, so an alternative is the Dellorto SHA carburettor.
The advantage to this carb is it's readily available for a reasonable
price and, for the less discerning there are Chinese copies that are even cheaper!
I have an original Dellorto 15/15 fitted to my SPR50, this was as a result
of not being able to get the original Gurtner to play.
Once an appropriate inlet is fitted, they need a 19mmOD/15mm ID
one available through several French suppliers,
the carb was simple to fit and tune. Yes I did say tune, unlike the original ones Dellorto's have
different jets available allowing for that fine tuning and
smooth running that we all crave from our bikes.
The Chinese alternatives have a bad press, but the ones I have came from a
Pit Bike company and are lever choke models, making them easy to fit but needing
the side panels leaving off, not a problem on the projects they were used on.
Again they are 'tune-able' and need a suitable inlet.
The main jet in both types is a 5mm item that can be replaced, I bought a 'set' of
jets and use them to get the carbs set up for the particular engine they're fitted to.
One thing I do need to mention here is that I have these carbs fitted on either
high compression engines or upgraded (that is 67cc!) ones.
If you want an easy(ish) upgrade then this is the way to go , and either version
or manufacturer is good to use.
One last note, on filters, make sure the one you choose fits.
I have standard filters on two carbs and a cone filter on the third,
the wide round filter that came with the carb below is too long, so...