'96 1500 bogging down


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spiralout
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Motorcycle: 1975 GL1000 (gone)
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1996 GL1500 SE

'96 1500 bogging down

Postby spiralout » Tue Jun 10, 2014 5:52 pm



Hi all. First, a little history. I have a new to me 1996 1500 SE. The bike sat for about 3 years with gas in the tank and bowls. When I purchased it, it would only crank and run on the SE circuit and the vacuum slides were frozen. Proceeded to do a carb overhaul using Randakk's kit and ended up replacing one slide that looked like it had been melted with some kind of solvent. The other slide looked fine, no tears or pinholes. Pulled the tank for a clean and derust (most pita job I've ever done, btw). I rebuilt the petcock, also. Checked the condition of all the visible vac lines while I had the carbs out and all seemed to be ok. After reassembly, the bike fired up and ran and idled great, no surging and no hesitation whatsoever. I put about 100 miles on it over the course of the next three days and it ran so well, I was proud of myself considering this was my first 1500 carb job.

Ok, now to my problem. 3rd day putting around town, low on fuel, it started acting like it was running out. Got it to a gas station for a fill up, but it still had trouble getting the RPMs up after. With a quick twist of the throttle, there's no problem, but a slow roll on coming off idle and it bogs down so bad it lurches and tries to die. The carbs were cleaned really well. I've overhauled numerous sets of 1000 and 1100 carbs and these weren't nearly as dirty as some I've done. The floats were set dead on 8mm and the pilots set to 2.5 turns out. I've synched them already but haven't adjusted the mixtures yet due to not having the D shaped tool. I used a modified 7mm socket to remove the pilot screws for the cleaning but don't have anything long enough to reach now that they're installed. In hindsight, I should have cut slots in them while I had them out, dang it.

I've noticed that the vacuum slides don't move as much as I expected when I twist the throttle fast and don't move at all when I give it throttle slowly. Both are free and slide easily when pushed with a finger though. I tested both before reinstalling the carbs, and both responded to vacuum. Oh ya, the accelerator pump is squirting great, too
Here's a vid of the symptoms. Take note that when I roll on the throttle gradually from idle, I never let the RPMs back down, it's doing that on it's own. I'm either holding steady throttle or giving it more. Any advice or suggestions?





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virgilmobile
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Re: '96 1500 bogging down

Postby virgilmobile » Tue Jun 10, 2014 8:50 pm

Those pesky vacuum lines....
Under the carbs is a rubber mat,under the mat is a suspect vacuum line.
I found that EVERY vacuum line that had a sharp 90` bend were very weak.One actually sucked shut when running the bike.
Also,it seemed that each one attached to the intake tubes( rear ones) had hardness and cracked.I trimmed them back a bit.There's 4 of then on mine.2 on each side.Feel around for them,there kinda on the back side.
Inspect the vacuum lines where they connect.If there hardened, they will be easy to move.

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virgilmobile
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Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: '96 1500 bogging down

Postby virgilmobile » Tue Jun 10, 2014 8:53 pm

By the way,whatever chemical was used that damaged the slide could have been sucked into the vacuum lines.....probably not to good for them either.

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curley
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Re: '96 1500 bogging down

Postby curley » Wed Jun 11, 2014 8:52 am

the fuel petcock is vacuum operated ...sits in front of the gas cap...under the center section under the radio....at idle (high vacuum) it will remain open... as you open the throttles(low vacuum) it does what a petcock is designed to do...shut off the fuel. Cycle Max ( in Ohio) has a rebuild kit...if you have a vacuum tester ( like from Harbor Freight) you can test the petcock before tearing into it...best test ( at least for me) was to take it up on the freeway...as I increased the throttle getting on the freeway ramp ....the bike felt like it was running out of fuel...hope this helps

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WingAdmin
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Re: '96 1500 bogging down

Postby WingAdmin » Wed Jun 11, 2014 12:29 pm

curley wrote:the fuel petcock is vacuum operated ...sits in front of the gas cap...under the center section under the radio....at idle (high vacuum) it will remain open... as you open the throttles(low vacuum) it does what a petcock is designed to do...shut off the fuel. Cycle Max ( in Ohio) has a rebuild kit...if you have a vacuum tester ( like from Harbor Freight) you can test the petcock before tearing into it...best test ( at least for me) was to take it up on the freeway...as I increased the throttle getting on the freeway ramp ....the bike felt like it was running out of fuel...hope this helps


If you have a T or something you can use to bridge the two fuel lines, you can use it to bypass the fuel petcock, then clamp/plug the vacuum line going to the petcock. If that solves the problem, you know the petcock is the issue.

I wonder also if main jets are clogged, and a quick twist is delivering fuel from the accelerator pump, which makes the engine run fine?

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spiralout
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Re: '96 1500 bogging down

Postby spiralout » Wed Jun 11, 2014 1:02 pm

Thanks for the replies. The vac line under the rubber mat with the 90 degree bend was the first one I checked after reading of so many failures. The end was still soft and the bend seemed in good shape so I didn't replace it.

I've rebuilt the petcock as it wasn't holding vacuum and there were signs of leakage. When I disassembled it, the diaphragm was melted also, so I bypassed it until my rebuild kit arrived. The problem showed up while the petcock was bypassed and persisted after it was reinstalled, so that eliminates that. As far as clogged jets, they were meticulously cleaned during the rebuild, but I reused the old fuel filter after blowing it out the best I could. Seems like it would take a heck of a piece of trash to clog them as they are huge compared to GL1000 primary and secondary mains. It's idling rock solid, no missing or surging and runs fine over about 2k RPM. When I slowly give it throttle up until about 2k, it bogs down and has a horrible miss and will actually die sometimes. What now? Check the vac lines I can get to without pulling the carbs again? I AM NOT wanting to do that again until I've eliminated the other possibilities :lol:

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ct1500
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Re: '96 1500 bogging down

Postby ct1500 » Thu Jun 12, 2014 12:32 am

Unlikely it is a vacuum leak because it idles too well. Also unlikely is a fuel supply to carb issue because there would be enough fuel in bowls for the RPM to increase, it would take a longer amount of time for a lower fuel level to start to cause problems.

I would be looking for a main jet fuel pick up problem maybe from improper jet holder installation. Also on the list would be a misbehaving system of the air jet controllers or shot air. Check to be sure ECM is getting its vacuum signal also. Could be other things done wrong from previous work but a visual inspection would rule them out.
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curley
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Re: '96 1500 bogging down

Postby curley » Thu Jun 12, 2014 9:18 am

not an easy one to troubleshoot over the internet...
a) change out the fuel filter ( you may have a weak fuel pump)
b) does it run better with the choke "On"?...if so I would suspect a vacuum leak...check vacuum with a gauge...should be high and steady
c) check the out put of the fuel pump?...the pump only runs when the crank is turning...you could try and "jump it" (electrically) and see what the output is
d) WASG... float/fuel level is too low/stuck needle and seat/floats installed "upside down"
e) kinked or collapsed fuel line
f) what ever "melted" the internals of the carb/petcock was most likely added to the fuel tank...you may want to pull the pump/gas gauge assy and check it for damage...the pump has a plastic screen as well as a (rubber)fuel line that connects it to bulkhead fitting at the top of the tank.
hope this helps

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Mh434
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Re: '96 1500 bogging down

Postby Mh434 » Fri Jun 13, 2014 12:04 am

I'm going to go out on a limb here (having had the same symptoms in various bikes over the years), and suggest that fuel quality might be a big part of your problem. As you say, it ran great until you ran it really low on fuel & then fueled up, and then it ran poorly. I don't believe in coincidences!

If there was crud in the bottom of your tank & you got low on fuel, it may have been pulled into your carbs (hope not, as another cleaning would likely be needed!).

Or (and I believe this is a likely scenario) there was water in the fuel you brought on board. I've had that happen SEVERAL times, and the result was precisely what you have going on. I've had this happen both in summer AND winter, in motorcycles AND cars. In my case, every single time it was because I was forced, by circumstance, to gas up at a Shell station. Once, a few years ago, I only got a few miles & the bike just quit. I had it towed home, drained the tank into a clear container, and found that Shell had dispensed 2 qts. of water with my 2 gallons of gas...at premium gas prices. You don't even want to know what I drained out of my motorhome's gas tank, after taking on enough fuel to get home, at a Shell.

BTW, I use Chevron exclusively (except for the aforementioned emergent circumstances), as do all my friends, and as long as we stick to this rule we never have these issues. It may be different in the US, of course...

Before tearing it down, again, I'd seriously recommend trying some gas line antifreeze. It certainly won't hurt anything, and it may cure your problem outright...with low cost and almost zero work. What have you got to lose?

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spiralout
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Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: '96 1500 bogging down

Postby spiralout » Fri Jun 13, 2014 12:45 pm

Thanks for the advice, everyone. I decided to pull the plastics and do a visual check for anything obvious before looking for vac leaks. I've decided it must be the jets, but wanted to try ANYTHING before having to pull the carbs again. I noticed what appeared to be a unconnected vac line behind the right lower fairing, the one with the cornering light. The lose end was hanging down next to the right horn, but I couldn't find anywhere it should go, nor could I trace the other end. I figured it was probably some kind of drain hose, but cranked her up just to check for vacuum. No vacuum present, but I did notice something else. The symptoms were gone. Disappeared. It came off idle perfect, no bogging or hesitation at all. The only thing I did before pulling the plastics was take the top of the air box off to check that the accelerator pump was still squirting and the slides weren't hanging up. No clue. Still the same fuel in it, too. I did put my finger over the elbow in the front right of the airbox, the one that connects to the PITA hose underneath, but that's all. I'm gonna guess that it was trash in the carbs that cleared itself? I'm glad it's corrected itself, but hate the fact that it did this for 2 weeks and I didn't ever find the cause.

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ct1500
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Re: '96 1500 bogging down

Postby ct1500 » Fri Jun 13, 2014 3:44 pm

The hose in the right front is for the reserve tank overflow and is supposed to be open down below.

Did the bike ever have a backfire either in the exhaust or intake (popping) prior to the running problem?
This is what I do
Local and need repair help with your 1500, Valkyrie or ST please PM

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spiralout
Posts: 1049
Joined: Sun Feb 17, 2013 6:41 pm
Location: Alabama
Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: '96 1500 bogging down

Postby spiralout » Fri Jun 13, 2014 6:37 pm

ct1500 wrote:The hose in the right front is for the reserve tank overflow and is supposed to be open down below.

Did the bike ever have a backfire either in the exhaust or intake (popping) prior to the running problem?

I figured out that was the overflow today. As far as any backfires, none. It was the quietest, smoothest running bike I'd ever ridden. Ran like a sewing machine. And now it does again. I should have gotten a 6cyl Wing years ago. I had no idea about that sweet flat 6. By the way, this bike always seemed like a male instead of female to me and it got it's name today. Being Pearl Royal Magenta, I christened it Grimace, like the purple monster from McDonalds.




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