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#557067 - 08/06/14 5:08 pm Do you run without intake balance pipe?  
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bonneville15 Offline
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I just removed the choke cables, lever and the choke slide from the carburators and was messing with the balance pipe. Removed the pipe and plug the intake manifold niples. Fire the bike and she was not happy at all. Misfired, pucking, coughing. Place the balance pipe back on and now is normal.

What is that balance pipe for and, how much that affect the caburators? Does is go rich or lean without it?

This is done on a 77 T140.

William


ASE Automotive Master Tech.
Never regret anything in your life because at one point, that was what you wished for.
Always tell the truth, even if your voice shakes.
1977 T140V
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#557070 - 08/06/14 5:23 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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It usually has little effect.

It makes the bike less sensitive to out of balance carburettors.


Amateur Loctite enthusiast.
#557095 - 08/06/14 7:01 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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It suggests that your carbs are not well synchronized.

#557115 - 08/06/14 8:55 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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have you plugged the holes at the top of the carbs where the choke cable used to enter?
If not then recommend that you do so.
HTH

#557166 - 08/07/14 7:38 am Re: Do you run without intake balance pipe? [Re: Tridentman]  
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Old Cafe Racer Offline
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OZ
Put the choke slides back in or else you have a very large volume of air void space above the venturi's which drastically reduces vacuum signal above the jets, especially when cracking the throttles at lower openings.
If you don't need chokes then tap the slides M4 and fit screws down through the tops with small O rings to seal/self align the slides and loctite the threads to ensure the slides don't eventually work down the slots.
Removing the slides is like fitting slides with much bigger cut-aways but it also affects the mixture all through the whole range in my experience.

davy

#557169 - 08/07/14 7:52 am Re: Do you run without intake balance pipe? [Re: Old Cafe Racer]  
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Originally Posted By: Old Cafe Racer
Put the choke slides back in or else you have a very large volume of air void space above the venturi's which drastically reduces vacuum signal above the jets, especially when cracking the throttles at lower openings.
If you don't need chokes then tap the slides M4 and fit screws down through the tops with small O rings to seal/self align the slides and loctite the threads to ensure the slides don't eventually work down the slots.
Removing the slides is like fitting slides with much bigger cut-aways but it also affects the mixture all through the whole range in my experience.

davy


Not in my experience.


Amateur Loctite enthusiast.
#557210 - 08/07/14 12:22 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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I would imagine that if the carbs are tuned using the balance pipe then if the balance pipe is removed and the holes plugged then the carburation will be upset. However, if the carbs are tuned without the balance pipes I cannot see any reason why they cannot achieve a good level of balance on tickover and have not heard any sound theory why a balance pipe would improve things. On the contrary, it complicates the issue as each carb depends to a degree on the tuning of the other carb as well.
As far as I can tell, the balance pipe on the inlet manifold has about as much value as the one on the exhaust pipe except that the exhaust pipe has the advantage of a little extra mutual mechanical support.


1971 T100R
1970 T120
#557212 - 08/07/14 12:22 pm Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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What Davy says makes sense since it is that very same issue that gives the Monobloc a slower throttle response than a Concentric. I suspect this is why Keihin put a gate type of choke in their roundslide carbs to remove the void in the slide.

But my guess is you did not plug those balance nipple holes very well and you have a serious air leak. Your symptoms are what I would expect if you simply left the balance tube off and did not plug the nipples.

regards,
Rob

#557214 - 08/07/14 12:26 pm Re: Do you run without intake balance pipe? [Re: Snakeoil]  
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Originally Posted By: Snakeoil
What Davy says makes sense since it is that very same issue that gives the Monobloc a slower throttle response than a Concentric. I suspect this is why Keihin put a gate type of choke in their roundslide carbs to remove the void in the slide.

But my guess is you did not plug those balance nipple holes very well and you have a serious air leak. Your symptoms are what I would expect if you simply left the balance tube off and did not plug the nipples.

regards,
Rob


I'm not saying it doesn't make sense. I'm saying I doubt that it is apparent.

I also seriously doubt that you, Rob, can discern a difference in throttle response, between Monobloc and Concentric on the same bike.


Amateur Loctite enthusiast.
#557281 - 08/07/14 7:23 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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John Healy Online content
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Triton have you ever ridden a bike with a flat side carburetor?


#557284 - 08/07/14 7:47 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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Davy is right about the extra volume. One of the tricks I learned from the Japanese gamble racers was to fill the void left by the choke slide with epoxy or JB weld in order to increase responsiveness. Note that the slides used in the Mikuni round-slide carbs have a flush bottom.....


When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
#557287 - 08/07/14 7:58 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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Standard practice when racing was to fill in the choke void after removing the slide. Some blokes used to mess about with filling the bottom area up as well and shaping it, you do have to fiddle about with jetting etc to compensate though.



#557290 - 08/07/14 8:04 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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Quote:
Note that the slides used in the Mikuni round-slide carbs have a flush bottom


Not exactly. There is no cut-out for a slide, yes in that sense they are flat, but they have the same recess as a Concentric MKI and MKII.

These make the bottom of the slide, well sort of flat in an effort to improve throttle response. And yes, you certainly have to play around with the jetting as they do increase the signal on the needle and main jet:

http://www.thunderproducts.com/u_f_o.htm


#557319 - 08/07/14 9:58 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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bonneville15 Offline
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John Healy:

Have you ever used those ufo discs?? It looks interesting enough to try a set.

Does anybody knows if removing the pipe will make it go rich or lean ??


ASE Automotive Master Tech.
Never regret anything in your life because at one point, that was what you wished for.
Always tell the truth, even if your voice shakes.
1977 T140V
#557388 - 08/08/14 9:03 am Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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Well TT, after messing with mine without chokes slides and the tops sealed for 12 months I had an epiphany and fitted the chokes and all the bad flat spots went away, especially off idle when cold.
Your experience might be different from mine but if it was then some other factor was at play.
In my experience the difference was night and day and was like fitting accelerator pumps.

davy

#557395 - 08/08/14 9:49 am Re: Do you run without intake balance pipe? [Re: Old Cafe Racer]  
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Ok,time for an experiment...I'm looking at this guy's bike with a flat spot at low speed. No choke .Newer Concentric single carb with a number 3 slide and the engine is tuned properly....I just filled the choke hole in the slide with epoxy and leveled it off,did not fill the whole depression. When it's cured tomorrow,see if it makes a difference.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#557533 - 08/09/14 8:39 am Re: Do you run without intake balance pipe? [Re: John Healy]  
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Originally Posted By: John Healy
Triton have you ever ridden a bike with a flat side carburetor?


I don't think so.

I have filled the air slide hole on throttle slides and used Mk1.5 throttle slides with the base of the hole blanked off, as well as normal throttle slides with and without air slides fitted.

Here's a thing though- when the throttle slide is near closed and the air slide is fully up, there is a large open volume under the air slide. That's what makes Old Cafe Racer's recommendation to leave the slides in seem strange.

Last edited by triton thrasher; 08/09/14 8:42 am.

Amateur Loctite enthusiast.
#557541 - 08/09/14 11:16 am Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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I reassembled the Concentric with the choke hole in the slide neatly filled with epoxy. Just the choke hole,the "teacup" was left as is.
I would say there's a slight improvement in engine response better at low RPM. This is a good running but high mileage 1965 6T engine.The modification might be more noticeable on a higher tuned engine....Or for those using E10 gasoline...I use non ethanol gas...


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#557678 - 08/10/14 11:04 am Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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Originally Posted By: triton thrasher
It usually has little effect.

It makes the bike less sensitive to out of balance carburettors.

That has been my experience. I have never tried riding my bike without the intake balance tube, but I do use those connections for carb synchronization. I made up a Y connector for use with a vacuum gauge. When I pinch off one side, perhaps the RPM drops just a little, but it really has only a very slight effect.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#557710 - 08/10/14 5:51 pm Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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Originally Posted By: triton thrasher
Originally Posted By: Snakeoil
What Davy says makes sense since it is that very same issue that gives the Monobloc a slower throttle response than a Concentric. I suspect this is why Keihin put a gate type of choke in their roundslide carbs to remove the void in the slide.

But my guess is you did not plug those balance nipple holes very well and you have a serious air leak. Your symptoms are what I would expect if you simply left the balance tube off and did not plug the nipples.

regards,
Rob


I'm not saying it doesn't make sense. I'm saying I doubt that it is apparent.

I also seriously doubt that you, Rob, can discern a difference in throttle response, between Monobloc and Concentric on the same bike.


which bit doesn't make sense?

As for the balance pipe, removing that and not plugging the holes is as bad or worse than having an air leak at the flange, I swear you could pipe those balance spigots to a 3rd carb or fuel injector! Sounds silly but there is one hell of a suction from those balance spigots. After using cylinder heads with and without them, I much prefer not to have them, darn things are a pest to seal.

As for the Monobloc/Concentric comments, and the concentrics do give a better throttle response than the Monobloc, when the throttle is opened it takes less time for the pressure to equalise in the tea cup of the slide on the Concentric than the Monobloc, the result is an improved throttle response. Things that also do this are smaller ports and snappier valve durations.

I'd love to try a set of flat slides as John mentions, at some point I probably will but for now, personally I find the concentrics work quite well and not too difficult to set up.

2c


beerchug
#557714 - 08/10/14 6:20 pm Re: Do you run without intake balance pipe? [Re: Allan Gill]  
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Originally Posted By: Allan Gill
Originally Posted By: triton thrasher
Originally Posted By: Snakeoil
What Davy says makes sense since it is that very same issue that gives the Monobloc a slower throttle response than a Concentric. I suspect this is why Keihin put a gate type of choke in their roundslide carbs to remove the void in the slide.

But my guess is you did not plug those balance nipple holes very well and you have a serious air leak. Your symptoms are what I would expect if you simply left the balance tube off and did not plug the nipples.

regards,
Rob


I'm not saying it doesn't make sense. I'm saying I doubt that it is apparent.

I also seriously doubt that you, Rob, can discern a difference in throttle response, between Monobloc and Concentric on the same bike.


which bit doesn't make sense?

As for the balance pipe, removing that and not plugging the holes is as bad or worse than having an air leak at the flange, I swear you could pipe those balance spigots to a 3rd carb or fuel injector! Sounds silly but there is one hell of a suction from those balance spigots. After using cylinder heads with and without them, I much prefer not to have them, darn things are a pest to seal.

As for the Monobloc/Concentric comments, and the concentrics do give a better throttle response than the Monobloc, when the throttle is opened it takes less time for the pressure to equalise in the tea cup of the slide on the Concentric than the Monobloc, the result is an improved throttle response. Things that also do this are smaller ports and snappier valve durations.

I'd love to try a set of flat slides as John mentions, at some point I probably will but for now, personally I find the concentrics work quite well and not too difficult to set up.

2c


We're very much at cross purposes.

Nobody said anything doesn't make sense. Nobody said you don't have to block the manifold spigots if you, for some strange reason, remove the balance tube.

I'll try to clarify in the next post.


Amateur Loctite enthusiast.
#557715 - 08/10/14 6:23 pm Re: Do you run without intake balance pipe? [Re: Old Cafe Racer]  
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Originally Posted By: Old Cafe Racer
Put the choke slides back in or else you have a very large volume of air void space above the venturi's which drastically reduces vacuum signal above the jets, especially when cracking the throttles at lower openings.
If you don't need chokes then tap the slides M4 and fit screws down through the tops with small O rings to seal/self align the slides and loctite the threads to ensure the slides don't eventually work down the slots.
Removing the slides is like fitting slides with much bigger cut-aways but it also affects the mixture all through the whole range in my experience.

davy


I disagree that removing the choke slides causes a problem. Thousands of them have been thrown away!

I do agree that the holes for the choke cables should be plugged if you remove the chokes.


Amateur Loctite enthusiast.
#557719 - 08/10/14 6:49 pm Re: Do you run without intake balance pipe? [Re: triton thrasher]  
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Originally Posted By: triton thrasher


I disagree that removing the choke slides causes a problem. Thousands of them have been thrown away!

I do agree that the holes for the choke cables should be plugged if you remove the chokes.


Well, I disagree based on my back to back test one day apart on the same single carb engine two days ago. A slight increase in throttle response off idle like when the carb circuits go from pilot jet to slide cutaway. Perhaps an increase in vacuum signal...
Your results may vary ...


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#557732 - 08/10/14 8:11 pm Re: Do you run without intake balance pipe? [Re: bonneville15]  
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Re: removing and filling choke slide section on AMAL mk 1s

I think the results will vary based on the overall condition of the carb, if the slide is a poor fit the increase in vacuum will be smaller. It did make a large difference on my single carb T'Bolt but it was not my only change so the combination of more open exhausts, bigger inlet valves and a little port tweaking make up the overall difference. Certainly on mt T100R it richened it up considerably requiring the fitting of 105 needle jets but that was with smaller carbs (26mm) and they were new.
I remember doing the mod years ago when racing which is why i do it now but i don't fill in the slide base part as you have to shape it and fiddle extensively with jetting etc.

Last edited by NickL; 08/10/14 8:12 pm.


#557764 - 08/11/14 12:38 am Re: Do you run without intake balance pipe? [Re: bonneville15]  
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Compadres:

I did removed the choke slides and the bike still feels pretty much the same. Maybe need a little tweak. The balance pipe I will leave alone because will take to much adjusting with no reasonable gain. I would like to try those UFO discs but looking at the prices I might pass.

William


ASE Automotive Master Tech.
Never regret anything in your life because at one point, that was what you wished for.
Always tell the truth, even if your voice shakes.
1977 T140V
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