PR: Proprietary Items TT carb

[greg brillus]

It all makes sense....... It seems complex, but it relates to what we are doing, and backs up my theory about checking the levels when setting up these carb's........Of course when playing with methanol it affects things again........These big racing carb's were really designed to flow alcohol type fuels I feel, especially with the large float bowls. Now I'm playing with the big Gardner carb, that is in it's own league again.........

 

[chrisxball]

I think a lot depends on what ign' you use,
I made a huge mistake using an old Mag' converted to manual advance and retard.

Hi there, you mention that using a converted mag was a mistake, I'm interested to know why as this is the set up I have?

 

[Bill Cannon]

It all makes sense....... It seems complex, but it relates to what we are doing, and backs up my theory about checking the levels when setting up these carb's........Of course when playing with methanol it affects things again........These big racing carb's were really designed to flow alcohol type fuels I feel, especially with the large float bowls. Now I'm playing with the big Gardner carb, that is in it's own league again.........

Greg, I'd be really interested in your setting up of your Gardner. How about posting it as you go along?

Cheers Bill

 

[litnman]

Can the SG effect float levels? I know fuel temps do.

 

[Bill Thomas]

I raced my L/ning rep' for 7 years, It was not as fast as it should have been,
My road Special was much faster, But I did have 12 to 1 pistons and 36 mm Delloroto carb's,
In the road bike !.
But by the time I built the L/ning they had started messing with the petrol,
You could not get 100 octane leaded petrol at the road pumps anymore,
So I had to drop to 9 to 1 pistons,
Some of the racers cheated and used aircraft petrol, But I didn't want to go that way.

Others don't agree, But I think the BIG piston gives a lot of extra power.
If I had my time again, I would use a "D" Distributor, Even though I would have to carry a battery,
With dead loss electrics, The battery would still last more than a race meeting.

The old type mag' was a Bodge up of an 180 degree mag',
You can't have 2 strong sparks, With a 50 degree V Twin.
And when you convert it to Manual , I think it's even worse, I had it done by a top Mag' bloke.

If you could get a Scintiller Mag' they were different.
Good Luck, Bill.

 

[greg brillus]

Hi there John, yes definitely the SG has an affect on the levels.......its worse on alcohol fuels as you find the levels are higher than petrol........Similar but different to altitude.......Running at higher altitude results in a richer mixture, so this has to be taken into account when tuning. The big helper for me with setting up the Gardner is the use of a fuel/air meter........Actually mine is set for Lambda........I quickly found the ratio on my racer was way too lean, the needle in the carb more suited to petrol than methanol.........As an example, the needles for methanol are 4 mm diameter brass rod.......this has a taper machined down one face of the needle, this taper facing towards the inlet valve........On full throttle the needle width at that point was 2.7 mm across.......To get the full throttle mixture rich enough to be safe....... I had to shave the taper so that at full throttle the needle is 1.5 mm thick.........So to visualize this, imagine a circle at 4 mm in diameter, then cut this down so the circle looks like a capital "D" then shave the flat face down thinner until it is only 1.5 mm thick, that is all that is left of the 4 mm diameter needle on full throttle.......Remember as this is a road race bike i do run a large float bowl (SS1 Dellorto) this gives a more constant delivery to the carb, as opposed to a speedway engine or sprinting engine that would not use a float bowl at all on this carby, just the fuel hose directly from the large bore fuel tap to the carb fuel inlet fitting.........in this instance you need to be very careful not to open the throttle if the fuel taps are on and the engine is not running.

 

[Bill Cannon]

Greg, does your Gardner have fixed jet or fixed needle?

Cheers Bill

 

[litnman]

While lapping the needle/seat is helpful at times, the widening of the seat creates another problem. As the needle/seat wear, the float level rises requiring spacers between the seat and bowl. The fix was to install a new seat was a big improvement.

 

[Cyborg]

Every time I look at this thing, I’m tempted to take a stab at making a needle. There is also a taper attachment that comes with it, so jet needles might be possible as well? Haven’t really explored it. Shouldn’t even be thinking about it. Too many other projects.

 

[litnman]

I'm still tinkering with these old 10TT9 carbs, with the type 14 floats. Granted, these carbs were designed for racing and for alcohol fuels but I'm trying to make them work safely for street use. The issue is the famous drip that is almost necessary to get the fuel to the correct level. The needle and seat in the type 14 bowl is almost twice the size of that in the 302 float bowl. The bell type needle in the 14 bowl weighs considerably more than the needle in the 302 bowl. Two things come to mind that cause the drip. First is the size of the float and second is the size of the needle and seat.
I have been experimenting with materials to increase needle-seat pressure and can see some improvement.
Reducing the size of the needle seat has also shown to improve.
Ok, tell me how you dealt with the 'drip'.