Who built this one? GL custom in Oklahoma

[CrazyJerry]

Looks like so much fun! I'd like more info on disabling the air cutoffs, please. I know I read about it on Mike Nixon's site, but haven't actually seen it done...

Track T 2411,
The actual disabling is quite easy to do on a GL1100 Rack. Each carb's air cutoff cover must be removed (two screws on each cover). For those screws in tight quarters, this can be done with a phillips "bit" and a pair of needle nose pliers, etc, to remove those screws. Once the covers are off (easiest done one at a time IMO), inspect the air cutoff valve - if it's in good shape - great! If not, I'd suggest replacing them with new or very good used ones. These need to remain in place for sealing reasons.
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In the pic below, note the stock O-ring (that allows for vacuum to operate the valve). This will be removed from the stock location and replaced with the same size solid rubber disc that can easily be cut with scissors and a thin piece of rubber (of approx the same thickness as the original O-ring).
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Press or vaseline the solid disc in where the original O-ring was, and reassemble the air cutoff cover (the air cutoff spring remains in place as it was. This will forever keep pressure on the air cutoff valve against it's seat to seal off that part of the circuit.) The solid disc will ensure vacuum cannot activate the air cutoff valve (and pull it off its seat by overcoming the spring pressure holding it in place.) The new installed rubber disc in the photo has a gob of vaseline on both sides so it looks more like a ball than a disc.
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Here's a previous pic that shows a non-vaselined disc, and has the air cutoff spring where it should be just before the cover goes back on:
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If the bike was running/idling perfectly before the modfication, it will do so following the modification providing nothing else was adjusted or disturbed.
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~CrazyJerry~

[CrazyJerry]

I'm thinking that I now know how you came to have the name "CrazyJerry"! Just sayin. Enjoying this thread a lot.

[5speed]

your "diving" pic is hilarious.
what is the purpose of blocking the air cutoff valve?

[robin1731]

what is the purpose of blocking the air cutoff valve?

Inquiring minds want to know.

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[CrazyJerry]

your "diving" pic is hilarious.
what is the purpose of blocking the air cutoff valve?

Eliminating a future failure point. As these cutoff valves deteriorate with age, they can be (and are) problematic. Their only necessary function is related to a deceleration condition whereby they assist in negating afterburn, and the associated popping noise out the exhaust. The preventive action basically means we don't have to worry about these failing anymore, and driveability remains unaffected.
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A very good explanation of all this can be seen at the following webpage:
https://www.motorcycleproject.com/text/ ... _more.html
(Be sure to view the link labled: " Keihin Idle Circuits White Paper.")
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~CrazyJerry~

[robin1731]

If replaced during a carb rebuild the failure rate is very low. Contrary to what that link implies, it isn't like we have guys on here all the time talking about them failing if they were replaced. And if they are old and fail chances are you need a full rebuild anyway. As most quality kits come with the air cutoff valve assemblies one may as well install them. IMO

And if you are going to eliminate them why not build a real block off? Putting the valve and spring piece back in could also lead to a failure in the future. If you are to believe the link.

Just my thoughts.

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[CrazyJerry]

If replaced during a carb rebuild the failure rate is very low. Contrary to what that link implies, it isn't like we have guys on here all the time talking about them failing if they were replaced. And if they are old and fail chances are you need a full rebuild anyway. As most quality kits come with the air cutoff valve assemblies one may as well install them. IMO

And if you are going to eliminate them why not build a real block off? Putting the valve and spring piece back in could also lead to a failure in the future. If you are to believe the link.

Just my thoughts.

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Failing is one aspect... Working as intended can be another entire issue and assumes everything upstream is in excellent working order all for the purpose of what actually? If we can eliminate an unnecessary function - seems like a win-win going forward.
- The blocking disc disables the cutoff valve so it's not likely to fail if it just remains static.
- The spring in place allows for the correct blockage during normal operation, so why build a block-off when the correct piece will easily do the job as intended during normal operation?
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Alternatively, if one ever wishes to return to the stock setup/function of the air cutoff valves, the procedure is as simple as replacing the solid rubber disc with the proper O-ring. No harm - no foul - and non destructive to the carbs.
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~CrazyJerry~

[robin1731]

As I stated, we rarely hear of someone having issues with them. I think the Keihin engineers knew what they were doing. So I wouldn't call it an "unnecessary function ".

[rcmatt007]

I just replaced mine.... after 41 years and only because I was doing the carbs

[CrazyJerry]

As I stated, we rarely hear of someone having issues with them. I think the Keihin engineers knew what they were doing. So I wouldn't call it an "unnecessary function ".

The Honda suspension engineers likely knew what they were doing too....
But I like this one better!
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~CrazyJerry~

[Track T 2411]

No intention of 'stirring the pot' but, from what I understand, the air cutout circuit is needed to overcome the overly lean condition that occurs on deceleration, which, according to Mike Nixon's 'white paper' is the result of the lean factory idle settings required to meet the emissions standards of the era. The proscribed 'idle drop' method of tuning basically says adjust until the engine likes it, then lean it out a half turn. The 1100's carbs even have stops installed to prevent enriching the mixture. Mike's contention is that when tuned 'properly' the air cutout becomes redundant. If bypassing the system didn't still require a good diaphragm be in place, it would save a fairly significant expense, especially on the 1100's, which require four diaphrams.

[ericheath]

I don’t think Mike’s White Paper article is available any more. But this one is: https://www.motorcycleproject.com/text/ ... _more.html

Defeating the valve is going to make it cackle and backfire during deceleration, but according to Mike it isn’t going to hurt anything. My hybridized beast with 1200 carbs or V65 carbs adapted have no air cut for enrichment and thus backfire. If I don’t want it to, I simply pull the “choke” a bit to enrich the mixture enough to quiet down, or just not downshift.

[CrazyJerry]

I don’t think Mike’s White Paper article is available any more. But this one is: https://www.motorcycleproject.com/text/ ... _more.html

Defeating the valve is going to make it cackle and backfire during deceleration, but according to Mike it isn’t going to hurt anything. My hybridized beast with 1200 carbs or V65 carbs adapted have no air cut for enrichment and thus backfire. If I don’t want it to, I simply pull the “choke” a bit to enrich the mixture enough to quiet down, or just not downshift.

What it will do is cackle and pop due to afterburn, and being a cut-down chopper with straight pipes - it better do all that and then some!
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~CrazyJerry~

[CrazyJerry]

Last week the only joy I knew was a dish washing liquid, but this week's GL1100 engine tear-down has changed all that!
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The intake was removed last week due to a carburetor issue and has since been fixed.
The newer pewter metallic paint on this engine is excellent.:
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Next we drain the cooling system. Radiator removal is a snap when there's no fairings :
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While laying on the floor, it was a good time to give that water pump a quick look. No wiggle and at the impeller, it looks like it may have been put on yesterday:
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Let's pull those heads and let's see what secrets are hidden beneath them!
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The right side is not exactly "pristine":
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Look at the lovely pitting on the ceiling of #3!
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The right side head gasket (which was seeping anitfreeze between the block and head) appears not to have sealed very well. It practically fell off under its own weight:
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Once again luck befalls this project as the left side looks to be in superior condition as compared to the right side. Can we use the words "factory fresh" or "like new"? :
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Well, at least the gasket on that side didn't just fall off!
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Time to go stimulate the GL1100 parts economy!!!
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~CrazyJerry~

[Track T 2411]

Well, I've seen worse looking cylinder walls...
The water pump looks like it was installed yesterday, probably because it was... The original pump had a bakelite impeller. Newer units are metal, like yours...