Air/Fuel adjustment or Sync Adjustment??

[cmyoch]

When I found out one of my coils was shot I acquired a set from a fellow member on here that lives nearby. He had a parts cache the helped me out of a pinch. This was several years ago and I don't remember if they were from the same year or not. They are early coils because I remember the wires were not detachable.

[WingMan71]

I regret to report that the bike did not run any better after this. I walked away from it for a couple months due to aggravation. Last week I pulled the carb rack AGAIN and started the cleaning process again. I dipped all my brass parts in the carb can while I shot cleaner and air through all passages. Everything is reinstalled with the exception of one air screw. The head snapped while tightening. I have a replacement on the way from ebay ($10 shipped) I also sourced fresh air screw o rings and manifold o rings from the local Honda shop as a precaution. I'm determined to get this to work. I've invested enough time in it and I know the bike runs good when in tune.

I regret saying that I have 1100 carbs on my GL1000. I didn't do this, it just came that way. Someone did this 20 years ago for some reason. I know they work, I just need to get them dialed in properly. I posted yesterday to see if anyone else has this setup. I am setting my air screws at 2.5 turns out and starting from there. I really do not look forward to adjusting air screws.

A couple of important things on your carb rebuild.

1. When you cleaned the jets, did you remove them to clean them and spray carb cleaner through the circuits in the carb body with the jets out?

2. Did you remove, clean, and SIZE the pilot jets? These jets have the smallest holes of all (typically .013") and they have to get completely clean and fully open. Plus you should "size" them with a wire of the correct size to make sure that they are fully open. I know, some inexperienced carb builders say to never stick a wire into a jet. Well, that's just not so. If it is then why does even Honda make a tool specifically for this purpose with various sized wires that are to be used to make sure a jet is clear and fully open. Some folks take to using an "E" string from a guitar to do this with the pilot jets, and that's OK, but just be sure that the end of the wire you're running through the jet has no sharp barbs on the end of it that will cause it to stick. Getting the tool is better. Mine is a "K&L Carb Cleaner Wire Set" that I got on Amazon for $10.00.

3. I would use 3 full turns out as a starting point on your pilot (idle mixture) screws. That's the typical starting point recommended by site guru Mike Nixon (retired Honda service tech). On my '76 GL1000 mine ended up at 3 & 1/2 turns out for best throttle response and no hanging idle.

Hope that helps. Hang in there, you'll get it!

[BustedKnuckles]

3. I would use 3 full turns out as a starting point on your pilot (idle mixture) screws. That's the starting point recommended by site guru Mike Nixon (retired Honda service tech). On my '76 GL1000 mine ended up at 3 & 1/2 turns out for best throttle response and no hanging idle.

Hey WingMan,
Can you post a link to this? Is that 3-1/2 turns out for all carb models? I set mine to mfr's recommendations (2 turns), but the PO had them set at 3. I would like to see the logic there.

[WingMan71]

Hey WingMan,
Can you post a link to this? Is that 3-1/2 turns out for all carb models? I set mine to mfr's recommendations (2 turns), but the PO had them set at 3. I would like to see the logic there.

Hey BustedKnuckles,

I found that info on the site somewhere, I would suspect that it was in the Guru's Corner. Wish I had bookmarked it.

And NO, all carb models are definitely not the same. Even different carbs for the same size engine, e.g. GL1000, do not have the same recommended pilot screw settings. I have purchased a number of carb rebuild books for various sized Honda engines from Mike Nixon and they are the best available.

The OP's problem is even more complex because he has GL1100 carbs on a GL1000 engine. That said, making the pilot settings a bit richer than factory settings is almost always best.

The reasoning behind the increased pilot screw setting recommendations from Mike and other Honda professionals is that Honda has purposely jetted their engines extremely lean at idle. That is the reason almost all Honda motorcycle engines have air-cut valves on them. When backing off the throttle quickly and the throttle butterfly valves shut quickly the mixture is then really lean. In order to keep the engine from backfiring due to the lean setting of the pilot jets, Honda installed air-cut valves that cut part of the air supply when the throttle snaps shut fast like that. Cutting that extra air momentarily richens the A/F ratio thus preventing the backfiring. If you actually get your pilot jets set properly rich enough there is no need at all for the air-cut valves. In fact, on the CB750s that I have rebuilt I always increase the pilot screw settings and then defeat the air-cut valves since they are no longer needed. Bikes run much better at idle that way, have better throttle response and no hanging idle caused by too lean an idle mixture.

If you go to Mike Nixon's site and read his white papers on Honda carbs, you will not regret it. Even after wrenching on bikes for over 50 years I have learned so much from Mike and his site. Great guy with years of professional Honda experience. Here's his site:

http://www.motorcycleproject.com/

Cursor down the home page to Tech Articles and then start reading the articles under Carb Corner. You will be greatly enlightened and educated about Honda carb technology. The wealth of information on his site is just staggering. You could read for a month and not take it all in.

***

[gltriker]

WingMan71 said, "The wealth of information on his site is just staggering. You could read for a month and not take it all in."

AMEN!

[cmyoch]

I regret to report that the bike did not run any better after this. I walked away from it for a couple months due to aggravation. Last week I pulled the carb rack AGAIN and started the cleaning process again. I dipped all my brass parts in the carb can while I shot cleaner and air through all passages. Everything is reinstalled with the exception of one air screw. The head snapped while tightening. I have a replacement on the way from ebay ($10 shipped) I also sourced fresh air screw o rings and manifold o rings from the local Honda shop as a precaution. I'm determined to get this to work. I've invested enough time in it and I know the bike runs good when in tune.

I regret saying that I have 1100 carbs on my GL1000. I didn't do this, it just came that way. Someone did this 20 years ago for some reason. I know they work, I just need to get them dialed in properly. I posted yesterday to see if anyone else has this setup. I am setting my air screws at 2.5 turns out and starting from there. I really do not look forward to adjusting air screws.

A couple of important things on your carb rebuild.

1. When you cleaned the jets, did you remove them to clean them and spray carb cleaner through the circuits in the carb body with the jets out?

2. Did you remove, clean, and SIZE the pilot jets? These jets have the smallest holes of all (typically .013") and they have to get completely clean and fully open. Plus you should "size" them with a wire of the correct size to make sure that they are fully open. I know, some inexperienced carb builders say to never stick a wire into a jet. Well, that's just not so. If it is then why does even Honda make a tool specifically for this purpose with various sized wires that are to be used to make sure a jet is clear and fully open. Some folks take to using an "E" string from a guitar to do this with the pilot jets, and that's OK, but just be sure that the end of the wire you're running through the jet has no sharp barbs on the end of it that will cause it to stick. Getting the tool is better. Mine is a "K&L Carb Cleaner Wire Set" that I got on Amazon for $10.00.

3. I would use 3 full turns out as a starting point on your pilot (idle mixture) screws. That's the typical starting point recommended by site guru Mike Nixon (retired Honda service tech). On my '76 GL1000 mine ended up at 3 & 1/2 turns out for best throttle response and no hanging idle.

Hope that helps. Hang in there, you'll get it!

Wow, thanks so much for the advice. I'll answer these in the same order...

1. When I cleaned the carbs, I pulled all the jets, sprayed carb cleaner and used high pressure air to blow them out. I pulled the pressed in jets also. 3 of the 4 were blocked solid. I sprayed and blew through all the areas in the carb bodies where the jets were held.

2. I cleaned the pilot jets with a wire pulled from one of my wire brushes. The wire was thin enough to poke through the hard deposits. I did not size them though. I didn't think about that. I was hesitant pulling them using the drywall screw method but it worked. I have them reinstalled in the carb bodies. I have a tip cleaning set but the smallest tip cleaner would not fit. I'll have to look at the sizing of it to verify.

3. I have my air screw in route to me as we speak. I broke the head off of one of them when reinstalling. Luckily, it did not break off flush with the carb so I was able to remove it with a pair of pliers. The other 3 are set at 2 1/2 turns so I'll bump them to 3 turns before installing. I bought new o-rings from the Honda shop and they are a little tight as I tightened the screws. I'm being extra cautious as I set them.

I also purchased new o rings for the manifolds to help eliminate the possibility of air leaks. I'm doing my best to make what I have work. I wish I could travel back 20 years or so (for many reasons) and speak to the prior owner of this bike to get the full history and most importantly find out why the carb switch was done.

[robin1731]

snip................
The other 3 are set at 2 1/2 turns so I'll bump them to 3 turns before installing.

Could have left them at 2 1/2. You will need adjust them once the engine is running and up to temp anyway. Use the idle drop method to set them.

.

[BustedKnuckles]

I think the idle drop is the only way to go in your situation. Those factory settings are only certain if your cams match your carbs, you have a custom application on your hands. Running it lean will cause you trouble, best to play it safe and start with them backed out further than you think (3 or 3.5 turns out), then do the idle drop.

[robin1731]

I think the idle drop is the only way to go in your situation. Those factory settings are only certain if your cams match your carbs, you have a custom application on your hands. Running it lean will cause you trouble, best to play it safe and start with them backed out further than you think (3 or 3.5 turns out), then do the idle drop.

Idle drop is the only way to go period. Factory settings are lean. All engines are different whether same everything else or not. If a person doesn't do the idle drop, on any bike, not just Honda or GL, you're not getting the carbs/idle the best it can be.

.

[BustedKnuckles]

I think the idle drop is the only way to go in your situation. Those factory settings are only certain if your cams match your carbs, you have a custom application on your hands. Running it lean will cause you trouble, best to play it safe and start with them backed out further than you think (3 or 3.5 turns out), then do the idle drop.

Idle drop is the only way to go period. Factory settings are lean. All engines are different whether same everything else or not. If a person doesn't do the idle drop, on any bike, not just Honda or GL, you're not getting the carbs/idle the best it can be.

.

Agreed. I go with the recommended baseline to get close, then finish it off with an idle drop. All engines are different, moreso after 40+ years.

[maury]

Early in the posts to your question, someone posted that another person was helped with this idle drop/high idle by Pistol Pete. I AM THAT PERSON.

The problem I had was once to operating temperature (fan cycling), the idle would climb and stay there. I had exhausted MANY hours and posts about this. So I sent my carbs out to Pistol Pete (he said it was one of the best rebuilds he has seen), Pistol checked them out, made some adjustments and sent them back to me. When I put them back on, the same problem occurred. I called Pistol and he explained that although he does / did place the carbs on an engine to test them, he did not ordinarily take them up to full temperature and that's when he told me what to try.

Pistol Pete first asked if the idle changed when pushing down directly on any of the sync assembly screws. It did, the idle went from 2,500 to 1,000. When I let the pressure off the sync screw top - idle climbed right back up to 2,500. So this is what he had me do....... take a screwdriver, rest it against the side of the carb (just below the vacuum cap) then VERY slightly bend out the upper arm of the "C" shaped tab on the carb sync screw/assembly (See pictures below). If you're not familiar with the sync assembly there is the top tab that the screw passes through with the lock nut on top of it, then below that a spring (with washers in proper position) and the lower tab that is actually shaped like a "C". Do NOT pry on the top tab with the screw going through it, ONLY the bottom "C" shaped tab. When I first did pry on the tab, I could see it flex slightly and I stopped. The idle did not drop from 2,500. At the suggestion of Pete, I again applied a bit more pressure, could see the tab flex again ..... and then...... MAGIC !!!!!!!!! Idle dropped to 1,000 and when throttled up............dropped perfectly to 1,000.
The sequence he had me use (if I needed to do more was).......
First - Carbs # 2, 4 sync assembly (between carbs # 2 and 4)
Second - Carbs # 1, 3 sync assembly (between carbs # 1 and 3)
Third - Sync assembly that adjusts right side carbs to left side (to the outer side of carb # 4)

I did not have to touch the second and third above at all.

I felt for a long time that there was a binding/sticking somewhere but did not feel, see or know where it might be. My guess is that as the engine heats up the heat causes a slight expansion of the butterflies or sync assembly and then at the sync assembly there is a very slight bind/friction. All I really know is that it worked and I'm thankful after chasing the "Mysterious Honda High Idle" for months.

carb1.jpg (43 KiB) Viewed 465 times

carb2.jpg (34.44 KiB) Viewed 465 times

PS - After rebuilding a couple sets of carbs. I can tell you without a doubt, that if you're not putting the disassembled carbs and pieces into a GOOD ultrasonic unit to clean them........... they are not really clean. It is amazing after using cleaners, brushes, wires, etc. then put them in the ultrasonic with distilled water / little dishwashing soap, turn it on and just watch crud come out of every orifice...............Just my opinion mind you.

76 LTD - rebuilt and beautiful
75 Finally finished !!
2013 Goldwing ALL dressed out!!
Austin, Texas

[gltriker]

That remedial procedure was exceptionally well explained and with supporting photos, to boot!
Thank You, Maury!

[cmyoch]

Yes, very nice post. I definitely learned something here. I contemplated an ultrasonic cleaner but a GOOD one is a little spendy. Then again, you get what you pay for.