Villiers Carbs and Originality.

[Brian Thompson]

It seems that often, bikes offered for sale on EBay and elsewhere have non-standard (from Greeves) carb setups. MY 24TCS Scottish is currently fitted with an S25/6 carb (as is correct for a TFS!) and a 'standard' air filter (with the sliding choke on the filter body) which is what was fitted when I bought it. Also, the rod operated choke (strangler) has been removed and the hole for the rod blanked off with an appropriate sized screw.

This setup seems to work well (if it aint broke etc...!) and gives easy 2nd. kick starting with the choke slide closed and a good tickle (flooding.) However, as I intend to gradually put the bike back to standard spec, but with 'sensible' mods so the bike can be 'used' as intended, I've sourced parts accordingly for when I decide to rebuild the bike. These include an '1800' air cleaner to replace the 'standard' item currently fitted (see pics below.) I was also going to refit the rod 'strangler' assembly, but was given the following advice by Villiers Services.

The rod/strangler has been known to drop down during off road use and obviously this will choke/kill the engine, sometimes when you least want it too...! For this reason many trials riders leave the rod and strangler assembly off and balnk the hole as mentioned previously, fit an '1800' air cleaner and just flood it when starting.

Also, I note that there are two possible specs (not counting the S25/1 with the choke cable arrangment) for a 32A carb;

S25/6 Choke bored to 1", with strangler, rod operation; 32A and Starmaker. (What I currently have, minus the strangler, and correct spec. for a TFS as already noted.)

S25/2 Standard carb body with strangler and rod operation; 32A and 37A.(The correct spec. carb for my TCS.)

I was wondering if the correct S25/2 carb might give slightly better torque being a smaller choke size, and if there is any point/advantage in trying to find one to replace what I already have?

Any thoughts from our experts on these points would be interesting to hear.

Thanks,

Brian.

[Brian Thompson]

Carb sizes etc.

Thanks for the response John. (While I was posting this it appears to have gone though...)

Re the question of bore sizes on carbs, when I ran my old Ducati SD900 Darmah, I was considering going down the route of high-lift 'Imola' cams and 40mm Delortos (standard was 32mm, for better low end/mid range torque as befits the models more 'sports tourer' role), but as I noted in a previous thread an old (since passed) journalist aquaintance and Ducati enthusiast (Don Upshaw) put me off it, as the cams he fitted to his 900ss made it really lumpy on the road, and he said it was the worst thing he ever did to it. As such, probably better for top end/track use so I kept it as it was for 'useability' reasons.

All this ties in to my understanding of the relationship between venturi/airflow and torque, although as we discussed on the other thread you mentioned re this somehwhat strange Villiers carb spec (1" bore), I guess the difference may be pretty marginal in this case. But still, it must have been done for some reason or another.....

Interestingly, as an aside, I note that the latest big Ducati engines (i.e. 1299 Panigale) are now so massively oversquare that they can only run properly at low engine speeds with complex electronic engine management for this very reason. That's the price you pay for going all out for top end power I guess, in order to build a big twin to compete with the jap fours. I've never ridden one, but from write ups I've seen, even with all the trickery they seem to lack 'drive' in the mid/bottom. Strange when you think that's surely the whole point of a big v-twin.....

Brian.

[John Wakefield]

I moved my post to here http://www.greeves-riders.org.uk/for...5471#post25471

[Brian Thompson]

Fair play John, no worries.

Brian.