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Carbs or AAU?
#753062 10/16/18 11:32 pm
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My 68 T120R starts first kick, ticks over like a clock, runs like s%#t (low power & backfiring) until 3.5K then...BAM....lights off and runs like a new bike the rest of the way on up. When I back off and the Rs drop below 3.5K she turns back to s#%t- (low power and back firing) Opening the throttle up does not help. Maybe make it worse. Down shift to get the Rs back above 3.5 and...BAM...she's new again. Last year I installed new AMAL premiums and set them up so...??? I've double checked the sync and air screw setting (1.5 seams about right). I've checked for air leaks and can't find any. Plugs are sooty around the rim with medium brown electros. I bought a new Pazon Surefire IE thinking it may be a bad AAU. But before I rip out the existing ignition system on an Easter egg hunt I'd like to know what you guys & gals think might be going on.
Thanks in advance for your help!
Randy


68 T120R
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Re: Carbs or AAU?
Randy Richardson #753097 10/17/18 8:46 am
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Coil, that's right on the money for the primary to secondary windings!
if it was a Boyer I'd also think black box, cos its around where the advance begins in earnest, but I understand that a Pazon is more progressive?

Re: Carbs or AAU?
Randy Richardson #753099 10/17/18 9:07 am
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In your right hand is a diagnosis tool called the throttle, mark it with tippex at 1/4, 1/2 and 3/4 and go for a ride, once your bad running kicks in vary the throttle opening and look at the marks. If the symptoms vary with different throttle openings then its carb related and the markings will tell you to look at cutaway 1/4, needle position 1/2, main jet 3/4 and above. If there is no change with different throttle openings then its more likely electrical and start with coils. ht leads etc. If opening the throttle makes it worse then sounds like wrong sized main jet or its unscrewed and in the float bowel.

Re: Carbs or AAU?
Randy Richardson #753126 10/17/18 2:44 pm
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I may have caused confusion mentioning the Pazon. I have not installed it yet. - The bike still has the original 6CA ignition system (points and mechanical AAU). The points, plugs, and condensers currently have about 500 miles on them. The poor running appears to be exclusively related to RPM. Below 3.5K it can barely pull it's own weight regardless of throttle position. Above 3.5K it runs like a new bike regardless of throttle position. At the beginning of the riding season I removed the AAU, cleaned it and lubed it with light oil. Both springs (looked?) good, but I don't know how to test them. When doing the static timing I rotated the cam to full advance to set the point's "break" point. but when I released the cam it didn't return on its own. That didn't seem right- but when I did the dynamic timing with the strobe the timing mark advanced and returned normally with RPM. I suspect the problem is with the AAU and, if it is, the Pazon will fix it. But I don't want to install the Pazon until I understand what's wrong now.


68 T120R
Re: Carbs or AAU?
Randy Richardson #753134 10/17/18 4:08 pm
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Hi, Randy: The AAU is probably just fine, as it's returning when the bike is running...…….that's how I remember mine working on my '70. I wouldn't mess with it.
Jim

Last edited by Class Clown; 10/17/18 4:08 pm.
Re: Carbs or AAU?
Randy Richardson #753166 10/17/18 8:28 pm
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My guess is that what you are perceiving as the problem clearing up at 3500 RPM is actually the carb transitioning in that particular gear. I think you may have too lean a cutaway in the carb slides.

Ed from NJ

Re: Carbs or AAU?
Randy Richardson #753313 10/19/18 1:06 am
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Did the bike run right in the past? Did it just start acting up on its own? Did you change something then it startedacting up?

My first thought was aau. Further comments make me doubht it.

Things I have seen that could be the cause are

Needle loose from clip.
Main jet unscrewed
Coil but not in this case.
New carbs with spray tube installed backward.

But my real opinion is a loose wire. Whenever I see a problem rpm related I look for a wire making contact at some vibration pattern and not at others. Hope you get what I 'm trying to say


Rich (last remaining member ThreeMustGetBeers)
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
72 commando
75 commando
couple of beesas a ducati
and a Honda?
Re: Carbs or AAU?
Randy Richardson #753314 10/19/18 1:14 am
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What Richrd said about needle & clip ^^

I had a needle clip break once, the bike acted as you describe, Randy.


Kurt

-- Don't believe everything you think.
Re: Carbs or AAU?
Richrd #753347 10/19/18 2:07 pm
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Hi Rich
Thanks for your reply! You very well might be right about the wire thing. I once had a bad fuse holder cause some weird problems.
Two years ago I replaced the wiring harness with a new POP harness and also swapped out the zener / rectifier with a Podtronics....So???
One year ago I replaced both of the carbs with new AMAL premiums...So???
This year I removed, cleaned and lubed the AAU , replaced the plugs, points, and condensers, clutch cable and kickstarter pinion gear spring...So???
Ed at "E&V Engineering" is going to check it out for me tomorrow and have no doubt (based on past experience) it won't take him long to figure it out.
I'll keep ya posted.


68 T120R
Re: Carbs or AAU?
Randy Richardson #754066 10/26/18 12:07 am
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I want to thank everyone for your help and let you know what the fix was. I'm totally embarrassed to post this!!! I would no way admit to this if not that I hope someone else learns from my bone headedness. It was the pilot air screw adjustment. I rented a covered trailer, transported my bike 100 miles south to E&V engineering. Ed did a quick check of the valves, points, timing, floats & jets. Everything okay. We started it and let it warm up. He listened to it running then turned each air screw in from 1.5 turns out to 1 turn out. Runs like new!


68 T120R
Re: Carbs or AAU?
Randy Richardson #754067 10/26/18 12:15 am
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Can't buy that.


Rich (last remaining member ThreeMustGetBeers)
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
72 commando
75 commando
couple of beesas a ducati
and a Honda?
Re: Carbs or AAU?
Richrd #754340 10/28/18 1:06 pm
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You are right!
It's still doing the same thing.


68 T120R
Re: Carbs or AAU?
Randy Richardson #754359 10/28/18 4:01 pm
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I seem to recall similar symptom(s) on my bike a few years ago. It was a loose jet holder in one of the carbs. After I got off the slide/needle jet circuit, the bike would run just fine, but once I was on the pilot/needle taper/slide circuits, it ran like sh!t....

Cheers,

Steve


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

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
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Re: Carbs or AAU?
Randy Richardson #755030 11/04/18 3:27 pm
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Took the advice to used throttle as a diagnostic tool and did a test ride
The results were: 3.4K RPM is like a bad/good switch regardless of throttle position
I think I'm going to install the Pazon I have sitting on the shelf and see what happens.

Bike is all stock or reproduction stock except for Podtronics and AMAL premier carbs.
Compression= 150 PSI on both cylinders. New plugs and air filters. No air leaks.
Marked thottle at 0, 1/4, 1/3, 3/4, and WOT.
Once warmed up bike is a a one kicker and ticks over evenly at 1200 RPMs.

TEST RIDE:
One mile section of country road with a gentle hill in the middle of the run.
Going up hill
1/8-1/4 throttle: Low power with occasional spitting and backfire.
1/4 to WOT throttle: Same as above until RPMs creep up to 3.4K then BAM!
Full power runs great.
Going down hill
Kept throttle at 1/4. Low power, occasional spitting and backfire
until RPMs reached 3400 then -BAM!
Full power, runs great.
On level road
Opened throttle to 3/4 and let RPMs slowly climb through low power to 3400 RPM.
BAM! Full power. Rs quickly climbed to 5K. Throttle retruned to zero.
Let Rs drop to 4K then throttle was returned to WOT. HUGH punch back up to 5K.
Returned throttle to zero.
Let RPMs drop to 3.5K then returned throttle to WOT. HUGH punch back up to 5K.
Returned throttle to zero.
Let Rs drop to 3K then returned throttle to WOT. VERY low power to 3.4K then
BAM! Full power back up to 5K.
Back home. Looked at plugs. L= tan electrode dark interior. R= light tan electrode and interior.


68 T120R
Re: Carbs or AAU?
Randy Richardson #756798 11/22/18 2:55 am
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Winterized the bike tonight, pulled the gas tank and found the drive side coil had moved rearward-
which caused the spark plug wire to rub on the gas tank wearing a hole in it's insulation. Might have
stumbled on the culprit- won't know till spring though. Will keep ya posted.


68 T120R
Re: Carbs or AAU?
Randy Richardson #757110 11/25/18 8:41 pm
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Good rule is when the problem is related to throttle position its carburation. When it is rpm related it is electrical or timing.

There are exceptions but this has prooved out many times in my shop.


Rich (last remaining member ThreeMustGetBeers)
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
72 commando
75 commando
couple of beesas a ducati
and a Honda?
Re: Carbs or AAU?
Richrd #772122 04/27/19 8:42 pm
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After several "That's got to be it"...and wasn't... the problem is finally fixed! Not 100% sure what fixed it but I think it WAS probably the AAU after all.
Here's the final leg of the journey- for your entertainment.
1. Found a coil had slid back and the spark plug wire was rubbing against the gas tank...That's got to be it....NOPE- Still running the same.
2. Found the wire from the alternator was hanging on by a strand or two at the connector (not charging battery) ...That's got to be it...NOPE- Still running the same.
3. New points, plugs, condensers and timing...Hoping that- That's got to it...NOPE- still running the same
4. Re-sync'd the carbs...getting desperate and hoping that just maybe That's got to be it...NOPE- Still running the same
5. Okay- now at the end of my rope- I ripped out the re-pop harness, the points, AAU, and coils... made my own harness and installed a new Pazon EI.
Runs like a new bike!!! Not to be fooled again a put on two hundred miles before posting this and she's still running GREAT!!! HAPPY HAPPY HAPPY.
Plugs are sooty- but I'm not touching anything else for now. It's just SOOOOOO nice to be riding a great running Bonneville again!

THANKS TO ALL OF YOU for your help along the way. It really helped and was sure good to have you guys to turn to. THANKS AGAIN!.



68 T120R
Re: Carbs or AAU?
Randy Richardson #772127 04/27/19 11:41 pm
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When troubleshooting problems like rhis, just keep reminding yourself:

If you can’t fix it with a hammer, it is probably an electrical problem


laughing


Never underestimate the human ability to elevate stupid to a whole new level!.
Re: Carbs or AAU?
Randy Richardson #772141 04/28/19 6:45 am
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Richard no disrespect but on a 4 stroke carb the angle of the spray tube is the same all the way round (flat) 2 strokes are different they seem to be the opposite way to what you think. We will ignore the triple type.

Glad the bikes running fine now but another good thing to check in the fifties would be at what point the bike reaches full advance. This will take someone working the throttle and someone on the strobe gun. New advance springs tend to reach full advance about 3000, I bought some from Eurotrash jambalaya in the states and they max out at 3500 (much stronger spring) given a tweak they reached full advance at 4K, for an A65 on modern fuel that’s about right IME, however the manual will show full advance for 2k and I believe that was in the bonnie ws manual.

I suspect the problem was either a coil or a broken wire in the loom (I think Richard said both of these) I’ve had 50 year old condensers still working better than new ones (bike starts first kick with old and second kick with new) and as long as the AAU advances correctly there is seldom an issue, although I have made one good one from 2 before now because of the slop one the shaft between one and another.... that won’t help tbh


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Carbs or AAU?
Randy Richardson #772146 04/28/19 11:06 am
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Ever see a Norton carb, Alan?

Re: Carbs or AAU?
Randy Richardson #772150 04/28/19 12:40 pm
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Allan, some norton carbs have notched spray tubes,


Rich (last remaining member ThreeMustGetBeers)
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
72 commando
75 commando
couple of beesas a ducati
and a Honda?
Re: Carbs or AAU?
Mike Baker #772850 05/06/19 8:04 pm
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Originally Posted by Mike Baker
Ever see a Norton carb, Alan?


Very aware of them Mike, selling AMAL’s I’ve had a few through my hands.


There are 4 spray tubes in total, yes the norton type has a cut away from it and the triple is like the 2t wth the top shaved off. But T120 carbs should be of the flat type


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Carbs or AAU?
Allan G #775375 06/01/19 3:31 pm
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I forgot to add a bad coil to the "That's got to be it" list. I replaced both of them with 2 new 12V coils- Nope, that wasn't it either.
Anyway- It's been about a month now since I replaced the harness and put in the Pazon EI (now with two 6V coils in series) and-
I'm very happy with it. Nice smooth acceleration all the way up the RPM range and she runs great at all throttle settings.
I really didn't want to change from points to EI but my Trump's a rider so I don't think the change was sacrilegious.
Kept all the old parts though in case the next steward of her wants to put it back.

After getting her running good with the Pazon I had a roller break apart on the primary chain. Fortunately the chain itself didn't break.
I replaced the chain, chain adjuster, clutch plates, clutch basket, thrust washer, rollers, rubbers, gasket and primary cover screws with allens.
I also tested the alternator's output through a 1-ohm resistor while I was at it and it's still putting out over 120 watts.
Fun project with a happy ending. Still running great and the clutch feels a little better-but that's probably just my imagination.


68 T120R
Re: Carbs or AAU?
Randy Richardson #775420 06/02/19 6:21 am
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You won't regret the Pazon Randy. Made a huge difference to my bike.

I know you've got the problem fixed but wondered if this might be battery, perhaps coupled with a weak harness ( which you have now freshly rebuilt).

3500rpm threshold seems like it might be where a sick battery breaks down but gets overcome by a fast spinning alternator, and after 3500 you're running on the alternators good efforts. Just a gut feeling.

Points are very tolerant to a sick battery, EI less so, but now you've rewired you might have taken some resistance out of the circuit so the Pazon is happy for now....

Winter here so must be summer for you. How's it running now?


'51 C11 in a '54 C10L frame. Back on the road...
'70 Triumph Trophy 500. Next on the bench for a refresh!
'72 Triumph Tiger 650. Back on the road...
Re: Carbs or AAU?
Randy Richardson #777864 07/03/19 2:25 pm
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Follow up-
Just wanted to let you guys know that I now have a little over 500 miles on the Pazon EI and the bikes' been running great. Happy-Happy-Happy.
Thanks again to all of your help / advice along the way


68 T120R
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