Concentric carb setup

Barry, 32mm seems rather big for an ES2 although I have known of this before. Just changed the settings of my 530cc ES2on a 928 and runs the best it ever did: Now has No 4 slide, 270 main jet and needle in the middle. I think the needle jet was 106.

On the other hand my standard bore Poor man's Manx uses a 930 Mk 1 but the inlet was worked on to suit. I assume you have done this. The carb plug colour is right but difficult to say if the running could be better because of the very high gearing: 22 teeth on the engine sprocket and 20 on the gearbox. Yes it pulls it and max revs around 4K. Carb settings are No 3 1/2 slide and 230 main jet. Can't remember the rest.

Both carbs have mesh / belmouth on.

If your engine is std, Barry I would honestly think about fitting a 928 28mm and settings as above. Works very well for me. Both my ES2engines are 1959. The ES2runs the standard ignition and the PMM on Boyer, both 12 volt conversions and both use a Champion N5cplug.

You need first to get your main jet sorted, get a selection of main jets and fit the largest jet, then take it for a spin and on a fast uphill section give it full throttle and if it 8 strokes then its too large, if it does not 8 stroke but by reducing the throttle opening slightly it goes faster then its too small. Once you have it 8 stroking then go down in steps of 20 on the main jet until it stops 8 stroking and you have the correct main jet within 10. Better to have an 8 stroking main jet than a lean jet so starting high numbers is best. Once you have the main jet sorted you can move on to the rest of the settings.

If you don't know what 8 stroking feels like leave out the main jet completely and go for a run, wide open throttle and it will 8 stroke. Below full throttle the bike will run fine without a main jet.

Hi Barry, your gearing is standard but with a 932 I wouldn't like to suggest any settings. As John says, the bike will run without a main jet BUT does start having effect over 1/2 throttle.

With the 928, which is around the equivalent of the std carb size I was using a 3 1/2 slide and was way too rich for what I was doing. (I use a 20 tooth G/ box tooth gear to give a slightly more relaxed cruising speed while using the std 20 tooth engine gear. The No 4 slide fixed that.

As said above, the 930 carb was different again so using this logic your carb set up doesn't sound a million miles off, always he problem when deviating from standard.

What you haven't said is how it is running (If it is running) with your current set up? Another thing I find is that if your bike starts easy from cold, on a cool day with no choke then your pilot settings might be too rich, but this only governs the first little bit of throttle.

Ride it at the speed where it is not giving enough power. Close the choke a bit - if it gets better, try a larger main jet. Turn the petrol off. If it goes better just before the engine runs out of fuel, try a smaller main jet.

When I fitted a 930 to my 626cc 1958 19S, I just duplicated the original 1 1/16" Monobloc settings and throttle cut away. It seems to work just fine and the bike pulls a 21T gearbox sprocket and 20T engine sprocket easily.

Fine Albert, but I'm not sure about the monoblock equivalent settings on a 932, which works fine on a 928. Still, worth a try I guess. All I can say is that I had to come down in slide and main jet sizes with a 930. While the plug colouris right I can't confirm the pulling power (As said before) because of the tall gearing.

A 930 would be a good size choice for a 19S, especially a big bore. My ES2 is 530cc. You'll just have to experiment Barry.

Hi Neil,

I used those settings as a starting point on my 19S as I figured on having to tweak the carb a bit anyway to dial it in. I have been told that the Monobloc actually flows better than a concentric, bore size for bore size. The 930 was given to me and my old instrument was pretty well shot, so I figured "what the hey, let's give it a whirl!" It seems to work as I've seen 90 per on the bike (Briefly!)

regards,

Albert

This is true Albert, but I think the difference in the flow is marginal and so you have a like for like, more or less, given the concentric nearest equivalent.

I actually like the concentrics, I have them on all bikes except the 276 on my 16H. I still think Barry would have been better off with a 928, a 270 main and a No 4 slide...Job sorted with just the needle to suit. Then again, I don't know if the inlet has been opened out to suit the 932? Back to the experimental in that case.

Previously neil_wyatt wrote:

hi chaps,as your on the carb line, im doing a 55 19s that has a 51 engine in it. I would like to fit a monobloc and was wondering if anyone does a flange adapter to fit the original tube inlet tract.A freind said he thought that triumph head fittings were the same thread. anyone had any experience of this. Thanks,colin.

This is true Albert, but I think the difference in the flow is marginal and so you have a like for like, more or less, given the concentric nearest equivalent.

I actually like the concentrics, I have them on all bikes except the 276 on my 16H. I still think Barry would have been better off with a 928, a 270 main and a No 4 slide...Job sorted with just the needle to suit. Then again, I don't know if the inlet has been opened out to suit the 932? Back to the experimental in that case.