TT carb set up

Hi Ian

I have a 500 Inter with a brooklands can on it and am running a TT carb. My notes show I am running:

Main jet: 320

Slide no.: 5

Needle jet: 109

I started with the needle in the middlegroove (3) but kept fouling up plugs so have dropped it as far as it goes (1 notch at a time), is that 1 or 5?

I have no mention of where the pilot assembly is but I just turned it back and forth until I had the best pick up from tick over when blipping the throtle.

Over all the bike runs very well like this, look at the plug and it is running a bit rich still but as I have been running in I decided this was preferable to running it weak. It pulls very well throughout the rev range (not that I ever thrash it so cant really comment on full throttle). It occasionally fouls the plug up if I get stuck in traffic but open it up once you get out the town and it clears in no time. Now that I have 1K miles on the clock I may investigate weakening it off a little more, but it was certainly a good starting point.

Good luck

Andy

The other thing to mention is that the first think I had to do was drop the fuel height as it kept flooding. This can be done by carefullybending the clips on the float, or by putting an extra fibre washer under the float chamber to lower the hole lot.

Hi Ian

My carb still drips a bit when the bike isn't running but stops as soon as you get it started. Also, because of the downdraft it drips worse when it's on the stand as this lifts the back wheel up and increases the angle...

I seem to remember the tuning notes I had saying that TT carbs do drip until the engine is running, I'll see if it can find them to confirm that though.

Andy

There is some debate here about leaking carbs. And some methods of stopping it.

Good luck

Andy

Previously ian_bradley wrote:

Hi all My 1949 inter is on the the road after a year of fettling ,the carb needs sorting .The books and a service manual I've read state Main jet 350 Needle jet 109 Needle position 2 Then I read Irving's tuning for speed which said needle position 4(and the main jet &needle jet the same )which I think should be a weak mixture .is it a case of turning the pilot air assembly a number of clicks anti clockwise to richen the mixture to get a good tick over point and a good mixture . The bike has a brooklands can on that will change things? Cheers Ian

It is worth remembering that your 1949 Inter, lucky you, was set up to run on he awful 72 RON Pool fuel which was controlled by the Petroleum Board until 1953. This fuel needed lower compression ratios than pre-war ,less ignition advance and different air/ fuel ratios.So I imagine that the handbook reflects that era. Modern 95 RON unleaded will behave very different properties and will require both different ignition timing and jetting. I don't know whether post 1953 inters had TT or GP carbs. If TT, then the settings for a post 1953 might be a starting point.

I bought this book when I was building my engine and it was fantastic. It's mostly taken from other books but its updated to allow for current fuels etc and its got all the info in one place. It gives 3 different values for ignition timing depending on the compression ratio you are using. I'll look it up for you if you aren't sure about ignition timing. But with carburation I think its just a case of looking at the plug and tuning it to your specific bike.

Sorry Ian.

I have no idea, but I wasn't aware they came in different lengths.

Andy

It's a fantastic thing to ride Ian. Can we see a picture?

I dropped the fuel height on mine the other night to stop the leaking and hopefully weaken it off a bit. Took it for a ride round the block and it seemed good. I was meant to be taking it to Warwickshire over the weekend and doing 300 miles or so on it but that didn't happen. My dad got knocked of his 1920 Henderson by a car last Thursday so the holiday got cancelled and a real test of the changes will have to wait. 1000 miles on from rebuild though and it's a superb bike.

Im off to France on my ES2 on Thursday so the Inter is under the cover for another week or two. I'll let you know how I get on with it and if I end up messing around with jets.

Andy

Hello guys you do not run your machine with too weak a mixture as this leads to other problems like burnt valves or a hole in the top of the piston , it will not harm the engine to run just a little on the rich side as this will help to cold the engine, my Great Uncle Freddie Dixon run his bikes on DOPE and he use to take the needles out so it ran rich as dope cools the engine , and it was he that re -designed the carburettor to how it is to day, and try laping Brookland at 103 mph with No brakes like My Great uncle Freddie did,

I understand it mustn't be too weak. But my inter is running too rich and does foul up the plugs occasionally. I'll keep and eye on the plug and make sure my piston and valves stay in one piece.

Andy

Previously andy_marks wrote:

I understand it mustn't be too weak. But my inter is running too rich and does foul up the plugs occasionally. I'll keep and eye on the plug and make sure my piston and valves stay in one piece.

Andy The mixture may be correct but if you are running a race cam its possible reversion is messing things up.