ET: Engine (Twin) GP for twin

[vibrac]

After a lot of soul searching I have come to the conclusion that 1-1/4 GP carbs are the best choice for a short circuit twin they keep maximum torque to under 5000 rpm and while 13/8 may be suitable for a single I think torque is where the twin will win
Anyway I thought the question was academic as 1-1/4 are not now made but sometimes things fall your way and I have located a pair of GP2 1-1/4 " does anyone know what sort of cut away on the slides would be suitable? perhaps needle and main jet ideas may help most of the stuff I can glean comes from the days when racing exhausts were not as restrictive as they are now.

 

[greg brillus]

Just remember on the slide cut away's that the slide number is in 32nd's of an inch not the usual 1/16th. A good start is look at the book specs for a Lightning running on petrol based fuels. 360 main, number 5 slide and so on. All the racing "Experts" at the track told me my 32 mm TT's were too small, but i found them to work very well.......Perhaps it was a tad rough out of some corners, this would have been a rich mixture low down, so a change in slide number (I think i had number 7's in there) was the reason. An 8 or 9 would have cleaned it up for sure.........remember mine ran on methanol, so different to what your settings will be. You can buy new TT's in that size from Burlen's I think..........They stock all the parts you will need.

 

[davidd]

I think the Flash with the 32mm 10TT9s used a number 7 slide. I ran a number 6 slide with the 109 needle in the middle most slot. At sea level I ran a 320 main jet. All on gasoline.

The new 10TT9s are 1-5/32" and are flange mount.

AMAL 10TT9 1 5/32"

AMAL 1oTT CARBURETTOR This is a high performance carburetter with improved reliability and starting. The mixing chamber body can be either of the spigot or flange type mounting. The remote float bowl application can be satisfied by using the Matchbox Type 510. Please call us on 01342 716 120

surreycycles.com

David