Fuel flow limitations of the concentric carb

[muskrat]

Now, now fellas. I failed English at skool. Thank heavens for spell check. Only problem it's in US and not proper English . As long as it's understandable, most of our non-English speaking members do really well . Just as well we don't have audio as I wouldn't understand a word TT (Scot) or Charterlea (Irish) says .
Glen. I have a concentric on my '51 A7 and it works very well compared to the 276. There is a clearance issue putting one on an A10 plunger I think.
Cheers

[RichardL]

Now, now fellas. I failed English at skool.

Me too.

[Triton Thrasher]

Now, now fellas. I failed English at skool. Thank heavens for spell check. Only problem it's in US and not proper English . As long as it's understandable, most of our non-English speaking members do really well . Just as well we don't have audio as I wouldn't understand a word TT (Scot) or Charterlea (Irish) says .

Some people tell me I talk like a vehement Ulster person, so probably best not heard anyway.

The stylism of spelling "bloc" is French, I think.

[bsa-bill]

yep the typed word lacks a knowing smile I'm afraid,  smiley's help tho (that's though TT   )

being half Scot half Anglo it's only right I end up talking Geordie - like

[Triton Thrasher]

Yebbut- repeatedly mis-spelling a trade name that we're very familiar with is not like getting "cemetery" or something wrong.

It's more like spelling "Ireland" or "Australia" wrong.  Someone would point that out.

Anyway, the guy is quite right to fit a Monobloc, because I like them.

[nimrod650]

important to who bee ess aye oaner

Ok now you're in your own dream world.

Anyway I hope the change of carb does the trick.
[/quote]you started it

[jachenbach]

Back to the carbs: unit BSAs and Triumphs had both dual and single concentrics. Back in the 1980's I had both (Bonneville and TR6R) and honestly never noticed an appreciable difference. Maybe I just didn't ride fast enough.

[RichardL]

Maybe I just didn't ride fast enough.

Sort'a getting us back to Earth. All this talk about not being able to get from 90 up to 100 MPH is not really applicable to my own riding goals, the biggest of which is to put as much time as possible between rebuilds while going fast enough to keep it fun. Of course "fun" is different for everyone.

Richard L

[nimrod650]

were the monobloc float bowl extension as fitted to many bikes a way to solve a starvation problem

[Rocket Racer]

 all the A65 single carb thunderbolts ran 928's
The carb size isnt whats stopping the A10 from getting past 90mph. It should be on par with your 650ss unless the latter is on methanol.

[duTch]

 

were the monobloc float bowl extension as fitted to many bikes a way to solve a starvation problem

 Is that a question...?

[bsa-bill]

were the monobloc float bowl extension as fitted to many bikes a way to solve a starvation problem

I believe so Nimrod650, others on stock bikes would just turn both taps on.
However I would think sportier elements might have tanks with one tap so go for the extension.

now for those who really know did fuel starvation come about because of not enough float bowl capacity at full revs, or when banked (left/right) or a bit of both, ( yep it's not something I ever encountered other than the day before payday )

[BSA_54A10]

Yes ,
I rather think the float bowl starvation bit is another extrapolated urban myth.
AFAIK the only documented case of it happening was at Daytona where the bikes get near horizontal on the bankings and yes they did suffer fuel starvation problems.
So because we ride just as hard & fast as Daytona racers naturally we had all suffered from starvation every day on our way to work so we all desperately needed the extendd float bowl.

Now FWIW my old ( long departed and truely killed ) A10 never ever had a fuel flow problem and it was running a monoblock
It was also regularly clocked well over the ton on the Friday & Saturday night Bomborah Pt road drags.
Mr plod gave me a summons for doing 122mph under the airport tunnel so me thinks this whole thing is a bit of a Furfy.
It could possibly be a problem when running on dope as you shove a whole lot more in a lot quicker than petrol, but in my 5 years running that bike, not enough fuel was never a problem.
I was running Fleet 100 ( 105 octane with 10% nitro benzene ) while the bike had the 11:1's in there, but then again, that brew was all it would run on.

[worntorn]

all the A65 single carb thunderbolts ran 928's
The carb size isnt whats stopping the A10 from getting past 90mph. It should be on par with your 650ss unless the latter is on methanol.

It's the ability of the standard Concentric MK1 float needle and seat to flow fuel that Jim C found to be the limiting factor with his dyno testing. 35 hP was about tops without modifications to needle and seat for more fuel flow to the bowl. My Concentric is unmodified as yet so I suspect it may be the problem.
To clarify on the need to reach 100 MPH or more- this isn't something I would subject the old bike to more than once or twice, just to make sure original as designed performance is available.
The need to have good passing power is important for safety reasons. Right now it doesn't have as much passing power as I think it should, using the 650 ss as a yard stick. The two bikes have the same overall gearing and weigh about the same amount.


Glen

[RichardL]

Confused about fuel flow vs. horsepower. Wouldn't sucking all available fuel out of the bowl just kill the engine or lead to so much coughing that you had to let off the throttle? When accelerating full out with an engine built for speed (say 50 HP, for example), wouldn't you be using the full 50 HP right up until you ran out of fuel, at which point you'd drop to zero HP?

Richard L.