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2 Questions: carb balance tube & straight through mufflers #144731 07/10/08 2:21 am
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Alan in TN Offline OP
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1978 T140EBX; box stock, contact breaker ignition, dual AMAL Mk II carbs; added Norton style “peashooter” mufflers this spring.

Question No. 1: This question has to do with the small quarter inch balance tube that runs between the carburetor bodies to smooth the pulsations during engine running (I am assuming).

In the past I have had problems keeping a piece of fuel hose on the small nipples that stick out of the carb body. I have used the ¼ inch black fuel line plain; I have tried same with Goop to bond it. The best success I have had was with a piece of 3/16” urethane fuel hose and a little dab of Goop to help bond the ends to the nipple. After the heat cycling from riding it is unstable also so I will have to replace it soon.

When I studied the parts catalog breakdown of the carburetor it appears to me that these brass nipples are a threaded item that screw into the carb body (probably a pipe thread with taper). If this is the case I am wondering why these nipples couldn’t be unscrewed and a more purposeful item be designed and threaded into the port and this would hopefully end this particular headache. Something in the way of -03 SS braided hose and fittings to make it leak proof or even a more rigid piece might work. Unless – in reality these small parts are simply brass tubing dressed to a diameter and then pressed in with a light interference fit.

I feel certain that others have addressed this issue successfully and I would be very appreciative if those members would share the method of success on this critical area.

Question No. 2: Since I installed these peashooter style mufflers which are a straight thru design compared to the stock cigars which a baffled and I assume chambered does this imply that I will be running leaner in the third to two thirds throttle position and therefore will have to either make a change with jetting or adjust the pilot jet position? I don’t want to end up as a dog chasing his tail.

Many thanks in advance,

Alan

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Re: 2 Questions: carb balance tube & straight through mufflers #144732 07/10/08 3:41 pm
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Ibsnortin Offline
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I'm not sure why you're having the hose problem. Couple of easyway outs: tiewire to tube and/or bellow the end of tube.

I've never put the peashooters on a Triumph but about any change you make will most likely make it run rich. My experience with open reverse cones on a triumph is they want to run really ratty just before coming on the cams at best. Reverse cones must be "tuned" to gain performance. What most people don't realize is that even on a 4 stroke the exhaust system is part of the exhaust valve. The reverse cone is basically an amplifier that has to be tuned to make music. When dealing with the exhaust you are dealing with both reflected and inverted pressure waves. You want a reflected wave to hit the exhaust valve pocket timed to help scavange the spent mix and to help keep fresh from escaping.

The only reason I went there is the number of people in the past who change out a factory exhaust system and can't understand why they are running worse with open pipes or reverse cones.

My experience with most systems is at sea level, to drop the needle one notch and drop the main jet 10 or 20 points (AMAL).

Should be real close. Remember you only run on the main jet at WOT. Adjusting the needle will give the most noticable results. Then do the main on a lonely stretch of road or track.

Mike

Re: 2 Questions: carb balance tube & straight through mufflers #144733 07/10/08 3:52 pm
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SBoyd Offline
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" the small nipples that stick out of the carb body"

Alan
On the T140E with AMAL MKII's, the balance tube runs between the intake manifolds, right behind the cylinder head, 2 inches in front of the carbs.
Ordinary NAPA fuel hose works perfectly.

I wonder if someone has messed with yours. The only tubes connected to the Amals are the vent tubes that must not be connected together.
(based on the two T140E's that I have in front of me)

????????

>>sb


Stop the insanity.
Re: 2 Questions: carb balance tube & straight through mufflers #144734 07/10/08 3:58 pm
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SBoyd Offline
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Alan
As for the peashooters, if you're talking about the EMGO replacements that are intended for T140's, I also have a pair.
They are straight through (very loud).
Looking through the muffler, there is a 1 5/8 inch perforated pipe that runs front to back, straight through (not reverse cone meg.).
They may or may not make your bike run leaner, you'll have to take the readings and be the judge of that. They did not change my tuning. I've taken them off 'cause they're too loud for my neighborhood.

>>sb


Stop the insanity.
Re: 2 Questions: carb balance tube & straight through mufflers #144735 07/10/08 4:34 pm
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RF Whatley Offline
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Alan -
Nearly zero experience with 1978 models, but the 1/4 inch ID black neoprene fuel hose I've been touting here on BB.C has done a dandy job on all Bonneville models 1977 and prior. The intake manifold spigot to which the hose fits should be a 5/16 OD, so you should have to squirt some WD-40 on the 1/4" hose to slide it on, and then it stays put all by itself. I'm with SBoyd and wonder if yours haven't been swapped out.

As for carb settings, set the timing and put in some NGK B7ES or Champ N3C plugs. Get it to idle good and then go run it WFO for a main jet reading. All you need to know about this is in the AMAL Tuning manual found at the top of the threads in the "British M/C in General Forum". With all the new fuel formulations, I really wouldn't trust the setting anyone achieved several years ago.

:bigt:


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: 2 Questions: carb balance tube & straight through mufflers #144736 07/10/08 4:47 pm
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SBoyd Offline
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Just a Reminder RF and Alan.
The T140E calls for an N5 Champion (the chart under the seat is a leftover), that would likely be the best plug to jet with.
The NGK equivalent is between a B5ES and a B6ES.
Either will do with the B5ES being hotter.


Stop the insanity.
Re: 2 Questions: carb balance tube & straight through mufflers #144737 07/10/08 4:54 pm
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RF Whatley Offline
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See !! There's proof I told the truth. I have very little experience on 1978 models!

laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: 2 Questions: carb balance tube & straight through mufflers #144738 07/10/08 4:57 pm
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JubeePrince Offline
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Not sure if this applies to your bike Alan, as the T140E has the parallel ports, but on my splayed port head, if the hose is not long enough, it can come loose....I think somewhere around 5-6" in length is enough to keep the hose pressed against the manifolds (on the splayed port head) helping to hold it in place......

Try a slightly longer piece and see if the tension against the carbs with the added length doesn't help hold it on....

HTH,

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: 2 Questions: carb balance tube & straight through mufflers #144739 07/10/08 10:25 pm
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Steve in Tulsa Offline
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On the parallel port head the nipples screw into place. Keeping the hose in place requires making the tubing a little longer - a shorter radius curve in the tubing works well. And you could add a clamp, wire tie etc. if needed. A piece of picture wire works well.
The mufflers on the 78 atrocious. ANYTHING runs freer than those. I put Contis on my 78 way back when and immediately it woke up. They are straight through center line with a almost full length perforated tube. The main issue was the main jet which went from 190 to 210. But the air box is gone and I run UNI foam filters.
HTH


Steve in Tulsa
Re: 2 Questions: carb balance tube & straight through mufflers #144740 07/11/08 4:20 am
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Alan in TN Offline OP
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Ibsnorton, SBoyd, RFW, JP & Steve

Re: Q1 My bad; ya’ll are correct, the balance tubes are on the intake manifold. I seem to make this mistake often. I will check the diameter to see if they have been messed with. I will re-check my technique and that should help me get this problem fixed for good. Thanks for the suggestions on ways to fix this problem.

Re: Q2 I was worried that I may be creating more problems with this style of muffler but then if EMGO has made them for the T140 then I can feel some relief that I won’t have to go through an extensive jetting session. If I get the motor timed and running good I can do the plug chop as a check that the jetting is correct. Overall I’m glad these mufflers are a move in the right direction. I don’t mind working on tuning the carbs to the pipes once it is running OK.

I still don’t understand why the E version uses an apparent hotter plug than the others. Was this some tactic to satisfy the lab coats at EPA similarly with the horns inside the filter box and the exhaust crossover tube?

Thanks guys for the help.
:bigt:

Alan

Re: 2 Questions: carb balance tube & straight through mufflers #144741 07/16/08 4:19 pm
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Peter Jones Offline
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T140E uses hotter plugs as the parallel ports allow for cooler combustion temps.

Re: 2 Questions: carb balance tube & straight through mufflers #144742 07/16/08 6:12 pm
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Alan in TN Offline OP
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Thanks Peter. Details like this are good to know about the engine and the overall bike.


Alan :bigt:

Re: 2 Questions: carb balance tube & straight through mufflers #144743 07/17/08 4:39 pm
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RF Whatley Offline
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IMHO the change was driven by several needs:
• Getting more power without redesigning the entire engine
• EPA combustion standards
• DOT noise standards
• Etc

A costly change like this rarely has one parent.


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: 2 Questions: carb balance tube & straight through mufflers #144744 07/17/08 8:15 pm
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Peter Jones Offline
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Wierd how "environmental" measures forced manufacturers to make their engines less efficient confused


At least we are able to fettle our bikes to correct their emasculation (dunno about the future though)


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