Tuning 2017-01-25T14:54:00+00:00

Tuning

Now you’ve got one you might as well make it go….

Cams are very different on a Parilla – just one lobe to open both valves. They have a hard time.

This pic has been slightly doctored to enhance the cam profile & show the differences in lift & duration.

The ’54 Fox cam is on the extreme right. No sooner is the valve open than it is shutting again.The 175 Turismo usually has an unmarked cam with a lift of about 5mm & no duration (i.e sharp-topped). This can usefully be changed for an S if you can find one. These have about 6 mm lift & a bit more duration/overlap.

The 175 X1 & SS seem to have the same lift at 7mm but a different profile. The X1 having more duration & a more sudden opening. I

The 250 X1 has even more lift at 8mm, you may notice this cam is from a gear drive engine, the others from chain drive.

This only starts to work at about 5k but produces good power up to about 8.5k.

Suck it in….

This diagram compares the touring version to the racier X1

It all amounts to valves opening earlier & closing later – more chance for the gas to get in but only really efficient at higher rpm

Good condition S & X1 cams are hard to come by but there are some being made.

See the Parts section….

You won’t impress the concours judge with this one.
Fit a decent carb. Amals are cheap & wear out in 10k miles but have the advantage of working very well & being a doddle to tune.

An SS1 looks wonderful but it’ll cost the same to fit it with a new needle & spray tube as a complete Amal Concentric & a few spare jets….and the bike will start, tick over & go 100% better than with a knackered old Dellorto.

Blow it out….Unbaffled pipe with Chiuisninininino

The Parilla engine responds well to a straight pipe or reverse cone mega. The pipe shown is a little too long & could be trimmed to advantage.
The bike is very noisy with the open pipe. Certainly the most noisy single of its size. This can be tamed – a little – by a moveable baffle. See the full size version of this pic to make it out properly. Known as “silenziatore chiusino” (they can be found in Italy) the baffle can be lifted by a cable operated by a choke lever on the bars. You can see my control just under the back of the petrol tank.