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Discussion Starter #42
Engine vacuum is not RPM related, it is load related. The higher the load the lower the vacuum and vice-versa. But I am thinking that valve would be designed to open on very little vacuum since it needs to be open at WOT which is your lowest vacuum event.
I took the valve apart and found the problem with the fuel flow not shutting off after shutdown. The forward seal was stuck (likely from time) and would not move enough to fully open or fully close. I ordered the kit this morning, but it turns out the rubbers were just fine; the rear larger seal was a little oily or fuel soaked, but I cleaned it off. I'll go ahead and replace it when the kit comes in.

I also noticed that the little air hole on the bottom was clogged up from corrosion. So I cleaned and air-blew it dry. The valve works like a charm now. Start the bike and then disconnect the vacuum line (plugging it of course), and within about 2 to 3 minutes, the carbs run out of fuel and the engine shuts down. Re-insert the vacuum line and fuel flows as it should.

But now I know without any doubt that the carb float on the left side is not closing. I replaced the fuel filter and now that the fuel is flowing well to the carbs, it only takes a few minutes of idling and the engine begins to chug and want to stall. Gas it a few times and the exhaust smells like raw fuel. So the carbs will have to come off.

Now I'm convinced that my jerking issue is fuel/spark related. The left carb is dumping too much fuel from a failed float needle, and fowling out the plugs (possibly). Whether the plugs are firing sufficiently or not, it is clear by the way it behaves that the engine is running too rich, which would explain the 28mpg that I'm getting. Once you get going down the road, the rich condition is being blown out the pipe and seems to run normal; especially well above 2,500 RPM's. Come to a stop light and she idles perfect for about 2 minutes, then starts chugging again from too much gas.

So, next week my friend and I will remove the carbs and I will rebuild them, change the float needles and needle seats, replace the jets with the correct ones (someone put larger main-jets in the carbs), and see how it does. However, with the carbs out, I will also remove the coils and wires to ohms test them and also inspect the coils for damage/cracks.

I'm certain that this will solve the jerking problem.

On a side note, when I had the carbs out last year, I noticed that one of the CV cups was scratched/chaffed. Wouldn't this cause a drivability issue if the cup was sticking?

Joe
 

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Discussion Starter #43
Update:

Carbs are removed and I found a few jets slightly clogged, but nothing major. I have a rebuild kit with new jets, seals, and idle mixture screws. So all will be good.

Inspection revealed my suspicions that the left carb float needle was not cutting fuel flow (flooding) even with engine shut off. Now that my auto-fuel petcock is functioning, the fuel that remains in the fuel hose after shutdown drains into the left intake manifold. When the carbs were removed, you could visually see a puddle of fuel in the left intake manifold; not a severe puddle, but enough to know that the float needle was failing. I measured the float height and it is waaaay off at about 6mm. If you recall, I set them at 7mm in error, but will correct it to 8mm. The right carb float needle was just shy of 7mm, but it was sealing.

The left carb also had torn seals around the jets, so I wonder if fuel may have been seeping in there as well; I'm not sure if that would make a difference or not. At any rate, the rebuild kit comes with new seals.

I performed a primary and secondary ohms check of all the coils, wires, and wire-caps, and all appear to be good. I haven't yet checked for proper voltage levels so I will be doing that next to ensure that each of the coils is receiving proper voltage.

At this point, it appears the jerking was a fuel-fowl issue from the left 3 cylinders due to a failed float needle and improper float height. I will be cleaning the carbs, and installing new jets and idle screws, with new seals. So that should solve the flooding issue after shutdown.

With regards to ignition, it's possible I may have a problem with the center coil, but more testing will be needed to confirm any voltage or ohms issues. Right now, the primary ohms test of 20 to 26 ohms is passing on all 3 circuits. I measured approximately 23.5 ohms on the right coil, 22.3 ohms on the middle coil, and 24.6 ohms on the left coil, so all appear to show proper primary ohms resistance values. However, as indicated, I will be testing for ample voltage to each of the coils since the wires on this bike appear to be corroded. Yet at this time, I believe the primary issue is carb related, and so SHOULD solve the jerking issue which I now believe is a misfire issue involved with excessive fuel.

Joe
 

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Discussion Starter #44
Mission Accomplished!!!

Man she runs so smooth now and accelerates much stronger than before, and without the fuel smell I would often get. The left car float was not functioning and the float height was too short at about 5mm, although I thought I had set them at 7mm 2 years ago when all of this first began. I set both floats at 8mm.

The o-rings on the left and the right carbs were bad for the jet caps. I'm assuming this may have allowed too much fuel when not needed for both the slow and fast jets. If I understand the caps correctly, there is a fuel hole on the very bottom. The first jet to receive fuel is the slow jet (I think). The fast jet will get fuel also, but not quite as much as the slow jet during low RPM ranges and loads. When more fuel is demanded, and the RPM is much higher, sufficient fuel will travel through the jet caps to cover both the slow and the fast jets. I've never seen this kind of setup, but I assume that is how they function.

Unfortunately 2 of the left cylinder plugs are fuel fouled; they still spark but not near as strong as the other plugs. So out of curiosity I switched them out just to make sure it wasn't a coil or wire issue, and it's definitely the plugs (2 of them). I assume the very rich condition fouled them both out and so I will have to replace them AGAIN! LOL And I didn't even get 6,000 miles on those damn plugs. Seems like Honda plugs are so touchy when it comes to fuel fouling. Run them rich too long and at high speeds, and they go bye bye. Never happened to me in my truck. Then again I rarely have rich conditions.

So then, now on to the front forks wobble problem.

Thanks for all of your help guys!

Joe
 

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...they still spark but not near as strong as the other plugs.
I assume the very rich condition fouled them both out and so I will have to replace them AGAIN!
If they are still sparking and not causing misfire I'd clean them up best you can and simply screw them back in and let the properly running engine clean them the rest of the way...
 

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Discussion Starter #47
If they are still sparking and not causing misfire I'd clean them up best you can and simply screw them back in and let the properly running engine clean them the rest of the way...
They still spark and it appears to have gotten better. I ended up having to order a gas cap instead of replacing the plugs again. :ROFL: Never rains but it poors.

When my bike shut off a few days ago, I assumed it was the gas cap so I tried to blow it out with an air hose, which was stupid on my part; I blew out the internal seals. I can even tell you what color the rubber diaphragm was. It was red. So now my gas cap will not hold pressure; just bleeds air. I can't believe the damn thing costs $80 bucks.:frown2:

Joe
 

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Discussion Starter #48
Summary of repairs: Correcting stumble/jerk problem below 2,000 RPM

Now that I've acquired more experience on the GL1500 carbs, I believe I can now decipher what was causing the problem.

The carbs had two main problems:

1. Sticking float needle valve
2. dissolved jet cap o-rings which control the high and low speed circuit.

It is my opinion that my fuel related issue of only getting about 28 to 32 mpg had to do with a combined factor of failed float needle on the left carb, but more the dissolved jet cap seals which control the low and high speed circuits (jets). I believe the lack of o-rings on the jet caps was preventing the proper metering of fuel since fuel was entering behind the jet caps and feeding uncontrolled/non-metered fuel levels for mid range power. With the RPM's below 2,000 RPM, the high speed jet was receiving too much fuel in conjunction with the low speed jet due to the dissolved o-rings. This became obvious to me when looking at the jet-cap itself, as it has a specific hole size to limit the amount of fuel entering into the cap, which supplies metered fuel to both the low and high speed circuit. Thus at about 1,500 to 2,000 RPM's, too much fuel was entering the intake and causing a misfire, which also fouled out some of the plugs. By rebuilding the carbs and installing replacement o-rings for the jet caps, the engine now responds quite well below 2,000 RPM, albeit with a slight hesitation upon throttle roll-on, until the fuel has a chance to catch up; the accelerator pump momentarily supplied sprayed fuel to handle the tiny delay, which when combined, makes for a smooth transition of power. Thus below 2,000 RPM, the slow speed jet feeds fuel to the engine until RPM exceeds 2,000 RPM at which point the high speed jet supplies fuel.

A secondary issue was the lack of fuel at times due to a failed auto-fuel petcock likely caused by the use of ethanol based fuel. Albeit the bike has been running on ethanol since before I purchased the bike. The bike is roughly 20 years old, and has taken a long time for the ethanol to begin dissolving much of the internal rubberized components of the fuel system. Thus what caused my engine stumble and eventual shutdown last year on Thanks Giving day (and a few days ago) was a flimsy open/close diaphragm on the petcock valve to where at times it would open just enough for cruising, or else close altogether and cause a stall.

The spark plugs were fouling due to excessive fuel, which would also cause a spark-knock issue when insufficient fuel was metered causing a lean condition.

Thus in summary, the failed jet caps due to destroyed o-rings, a sticky float needle, and a failing auto-petcock also leading to spark knock and plug fouling, contributed to the pre-2,000 RPM jerking, poor fuel economy, and a nasty gassy smell. Since all of these repairs, the bike now runs quite smoothly and I appear to be getting approximately 38 to 40 mpg; only time will tell. Since repairs, engine speeds are now smoother and much more peppier. However, my GL1200 which I am still restoring, seems to be much quicker off the line, with a hell of a lot of torque compared to the GL1500. I suspect this is due to the GL1200 Interstate being a much lighter bike.

Hope this information helps. If anyone has a different opinion, feel free to contribute. I hope this will help others who experience the pre-2,000 RPM jerking/stalling issue.

Joe
 

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my GL1200 which I am still restoring, seems to be much quicker off the line, with a hell of a lot of torque compared to the GL1500. I suspect this is due to the GL1200 Interstate being a much lighter bike.
+1 on that. I think my 1100 would beat the 1500, the 1100 even beats stock Hardleys! :grin3:
 

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They still spark and it appears to have gotten better. I ended up having to order a gas cap instead of replacing the plugs again. :ROFL: Never rains but it poors.

When my bike shut off a few days ago, I assumed it was the gas cap so I tried to blow it out with an air hose, which was stupid on my part; I blew out the internal seals. I can even tell you what color the rubber diaphragm was. It was red. So now my gas cap will not hold pressure; just bleeds air. I can't believe the damn thing costs $80 bucks.:frown2:

Joe

I would have just used it as is Joe,
on my '94SE I purposely drilled a hole in the gas cap, and that stopped a lot of my problems.
I lived in Phoenix AZ then, and high temps were causing problems....
we were getting 125* days for a week at a time, and the '94 was my Daily Driver to work and back then.
 

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Discussion Starter #52
Hi all! Sorry I've been offline for a while. Wanted to give you all a follow up.

Apparently finding a new gas cap is difficult since they are no longer making them. Local Honda shop stated that they were on back-order, and usually that means no more production. I did however find a used one fully functional for $20 bucks, so that problem has been solved.

Also, the IX-9 plugs came in last week and I switched them out. I then took 4 of the best older plugs and installed them on my GL1200 and they work just great.

Loving the IX-9 plugs; i noticed a real different. Mid-range to max RPM pulls strong. The bike doesn't jerk anymore. However, if you lug it under 1,500 RPM's, there is a slight hesitation which I suspect might be my accelerator fuel pump. I rebuilt my carbs a few weeks ago, but that was one of the items I did not replace. I checked it and it sprays fuel but only if you snap the throttle hard enough. Normal throttle roll doesn't seem to spray much fuel, but then I never have a hesitation issue under normal throttle roll; only during throttle snap will it hesitate under 1,500 RPM.

Other than that, the front-end wobble is my next task. I've determined that the head bearings are bad. Honda wants $320 bucks to replace the head bearings. So I've decided to order the special tabbed socket needed for the job, and I will replace it myself.

Joe
 

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Considering the price of the socket and the amount of work needed to do the job I would be glad to pay the dealer 320.00 to do the job and get a guarantee! And that is using OEM parts.
 
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