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Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 7:38 am
by cfairweather
Tip: If you ever have a #35 slow idle jet that is really plugged and you can't even get an "E" string to go through the hole, use a #80 drill bit.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 12:03 pm
by Sidecar Bob
I always chuckle when people recommend using an "E string" like that because it would be difficult to be less specific.
To start with every guitar has 2 strings tuned to E but 2 octaves apart so the low E string is 4 or 5 times the diameter of the high E but on top of that string sets come in a number of "gauges" (thicknesses) from extra light to heavy and the sizes provided in each set depends on the manufacturer so the high E can be anywhere from 0.008" to 0.016" and the low E from 0.038 to 0.056".
I won't get into the custom sets some people use that include strings made for other instruments that are outside those ranges but you get the picture.
BTW, if you do use a guitar string to clear out carb passages please make sure that you file the end square (this will require a fine file and probably clamping the string between 2 pieces of wood so that the file doesn't bend it) because wire cutters will deform the cut end when they mash their way through it.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 12:17 pm
by cfairweather
You have got to be kidding. If a person can't figure out which "E" string to use, they have no business doing this simple task. The smaller diameter "E" string is just the right diameter and will work fine after you use a pair of dykes to cut it. You can use a micrometer or other precise measuring device to verify the diameter.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 12:44 pm
by Sidecar Bob
Most people should realize that you mean the high E but not everyone. Someone who doesn't know anything about guitars and asked someone who knows guitars but not carbs could easily hand them a low E.
Diagonal cutters will distort the end and form sharp points which can scratch things up. It may not make much difference the first time but it won't help things either.
And with the range of gauges available the B string from one set could be more suitable than the E from another set so it would make a lot more sense to specify the string's diameter than which note it is usually tuned to.
So which size string do you use?
Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 1:00 pm
by cfairweather
All of the high "E" strings I have used measure approximately .3mm. It is sometimes difficult to find a carb cleaner for this tiny jet. I have one, but most people don't. The #80 drill bit also works fine but I am sure you will find something wrong with that too.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Mon Jun 16, 2025 2:24 pm
by Sidecar Bob
0.008" = 0.2mm
0.016" = 0.4mm
Sounds like yours is right in the middle so it is probably a 0.012 string.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Tue Jun 17, 2025 8:57 am
by redglbx
The idle jet is a number 35 which in Keihin terms is .35mm or .0135 in “merican” ,,,,, I personally have a set of small pin gages that go down to .005in (don’t drop it), I use the .013in pin gages or lacking that the #80 drill bit.
Most sets of torch tip files/cleaners have a small .013in bit in their sets, Randakks used to sell these as a specialized tool but they are just torch tip cleaners.
To check this circuit I take the “straw” from a can of gumout and sand it down to a point, insert it into the idle jet and spray, it should come out of the little brass tube in the middle of the carb bore if it’s clean.
The only thing I’ll add and cannot emphasize it strongly enough is to protect your eye’s and no you can’t ask how I know this,,,, but it does hurt!!!
And as Cedric said a plugged idle jet will really only be evident at idle and up to around 2000rpm where the other jets start to feed fuel so it covers the miss up.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Tue Jun 17, 2025 12:58 pm
by Dirty Dave
Beating a dead horse, .012 or .013 is the high E on an acoustic.
Electrics are usually .010. Wimpy string bending blues/rock guys may go .009 or .008.
SRV's high E was a .013 but he tuned down a 1/2 tone.....
Really miss that guy.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Tue Jun 17, 2025 2:37 pm
by dontwantapickle
My guitar high E strings are all .007 , They fit thru the pilot holes.
I always cut them with wire cutters.
Deformed ends? Probably... but it has never been an issue.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Tue Jun 17, 2025 3:25 pm
by Sidecar Bob
Look at the cut end with a magnifying glass and ask yourself whether you want to push it through a precision passage.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Tue Jun 17, 2025 5:38 pm
by Lucien Harpress
Well, in order to muddy the waters even further, I started the bike this afternoon with the intention of re-setting the carb sync, and wouldn't you know it- she ran just fine. Putted right along on all four cylinders, carb vacuums as identical as you could get 'em, revved nice. Like nothing was wrong at all.
I need to get it on the road to confirm (and I WILL be keeping a very close eye on my ignition, because at this point anything this intermittent I have a hard time believing is carb-related), so we'll see how that goes.
(In reference to the jet-related discussion, all my jets were clear, including the pilot. Nice clean shot of brake cleaner went through it no problem, along with the related idle passages. So like I said- I'll be keeping an eye on the ignition.)
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I did a healthy ride around the block today after work, and everything was back to normal. Either I busted something loose with my last carb clean, or it is an intermittent electrical issue, OR it's just an old bike having an off day. Either way, I'm happy she's behaving.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Thu Jul 10, 2025 9:25 am
by 4dub
Lucien Harpress wrote: ↑Tue Jun 17, 2025 5:38 pm
Well, in order to muddy the waters even further, I started the bike this afternoon with the intention of re-setting the carb sync, and wouldn't you know it- she ran just fine. Putted right along on all four cylinders, carb vacuums as identical as you could get 'em, revved nice. Like nothing was wrong at all.
I need to get it on the road to confirm (and I WILL be keeping a very close eye on my ignition, because at this point anything this intermittent I have a hard time believing is carb-related), so we'll see how that goes.
(In reference to the jet-related discussion, all my jets were clear, including the pilot. Nice clean shot of brake cleaner went through it no problem, along with the related idle passages. So like I said- I'll be keeping an eye on the ignition.)
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I did a healthy ride around the block today after work, and everything was back to normal. Either I busted something loose with my last carb clean, or it is an intermittent electrical issue, OR it's just an old bike having an off day. Either way, I'm happy she's behaving.
I have a 76 with the original carbs, rebuilt last year with Randakks kit. I too have the same issue from time to time, #1 cylinder not fueling as well as the other 3 are at idle. It’ll run around 300 degrees on the exhaust outlet while the others are 460ish degrees F. I’ve taken the carbs off before and went thru the #1 carb extensively, to find no issue. I have replaced the coils with Dyna 2.2ohm coils, new wires, and new NGK resistor plug caps. The ballast resistor and points are still in play, no electronic ignition.
In my mind, he’s absolutely a fueling issue, not ignition. The bike idles fine, no popping as you are experiencing. The only way I found out the issue is just taking temp readings on the exhaust at a random time.
As soon as the main jet comes into play, all exhaust temps are within 10 degrees of each other.
It’s a mystery to me, but it runs well so I keep riding it. Maybe one day the problem will get worse and show itself in a more drastic way.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Thu Jul 10, 2025 11:14 am
by Rat
My solution to these kinda probs ... fill with nice fresh gas ... ride 200 miles ... fill with nice fresh gas ... ride ...
Gord
Re: Yellow '76 Carbs, Back On The Bench
Posted: Thu Jul 10, 2025 6:51 pm
by Lucien Harpress
Thankfully, 200 miles is, like, two days for me.
. I've been getting more seat time since I melted my Valkyrie, and so far so good. I'll definitely keep an eye on things, but at this point laying down miles seems like the best plan.
Re: Yellow '76 Carbs, Back On The Bench
Posted: Fri Aug 22, 2025 9:20 pm
by Lucien Harpress
Decided to drop a follow-up, just in case anyone finds this thread later. Since the end of this thread, I ended up replacing the battery. The signal beeper was getting a bit anemic, and it'd been a while since I'd changed the battery. While it's only been a minor improvement, since putting the new battery in the idle has seemed to settle down and become a bit more steady. As I said, it's minor, but definitely an improvement. I doubt it was all of my problem, but I'm sure it was part of it.
. I've been getting more seat time since I melted my Valkyrie, and so far so good. I'll definitely keep an eye on things, but at this point laying down miles seems like the best plan.