Carb Questions - still


Information and questions on GL1500 Goldwings (1988-2000)
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bri720a
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Carb Questions - still

Post by bri720a »



98 Gl1500se - I wish I knew more about carbs, so help me with my education :D and what I should be looking at next.

Last time I asked - yes the slides were sticking, fixed that issue and solved a lot of my drivability issues.

Now, still idles great and no more high rpm surging.

While driving, - slow acceleration 1/6th or less of the throttle it will accelerate fine all they way up. However from 1/6th to 1/2 or so throttle it bogs pretty bad, doesn't want to take off and will not pick up/very slowly pick up speed and rpm. When I hold the throttle in this range it really struggles to gain any speed/rpm (runs crappy). If I give it more then 1/2 throttle it will take right off without a problem.

I am guessing this is a slow speed jet problem - I did rebuild the carbs, soaked them and put in new jets, etc. So I am at a bit of a loss as to what needs to be checked/fixed etc.

Fuel delivery, petcock, etc is all working well (I have tested). It will go down the road without a problem. 8-) It is just that 1/6th to 1/2 throttle issue. :x I have run a considerable amount of seafoam and techtron through it, helped a bit but it seems to no longer making a difference.

Any suggestions you can give will help tremendously.

Thank you in advance again for your assistance!!
Brian


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bellboy40
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Re: Carb Questions - still

Post by bellboy40 »

You say you replaced the jets. Where did you get the jets? If from an aftermarket supplier, there is a good chance they are not the correct size. You should be able to clean up the original jets so they would work. If not, I would get new ones from Honda.
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ct1500
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Re: Carb Questions - still

Post by ct1500 »

So were these slides stuck closed or open? Sounds like that made a miniscule dent in your running problems. RPM range when problems occur is more informative, turn of throttle settings are meaningless, you might be running on half an engine if one carb is messed up. What idle RPM does it run at? Most folks will start jacking with the sync screw to make an engine run somewhat, was that done?
Follow this for "Lean Carbs" just a drip or two of spray out of straw to begin with while running.
AND SOME MORE SPECIFIC TESTING

A good quality carb clean spray (Cyclo) non foaming with straw is a valuable diagnostic aid and I keep a can in the bag. Do not mash on the spray valve, just a lite touch with increasing pressure if needed.

Bike dies on the road: While cranking spray a little in air intake, if bike wants to fire, fuel problem confirmed.

Vacuum leaks?: Spray a little around suspect area, if idle increases or smooths out found source of leak. Pinch off vacuum lines at source to confirm for downstream leaks.

Lean carbs?: Spray a little directly into its individual intake, idle increases or smooths out lean carb confirmed.

Rich carbs?: Spray a little directly into its individual intake, idle decreases
rich carb confirmed within reason.

Quick confirmation of pilot adjustments: Consistent idle (RPM) response when a little spray is introduced to each individual carb intake.

High speed miss?: Spray a little into intake stream, if smooths out and picks up lean condition confirmed.

Avoid overuse around composite parts. (1500 slides for sure) Starting fluid is too volatile and messes things up. When revving the engine you want to confirm vacuum slides are moving in tandem on the 1500 and that all air bleeds are free and clear with good accelerator pump shot.

Other bikes can use sync gauge ports for rich or lean checks. Control the uncovering of ports when screw removed idles up it is rich, spray directly in for lean check while sealing area around straw with your fingers.
Last edited by ct1500 on Fri Mar 19, 2021 5:44 pm, edited 2 times in total.
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bri720a
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Re: Carb Questions - still

Post by bri720a »

Carb slides were sticking closed, not moving or moving very minimal.

RPM - while going down the road it does good from 800 (idle) to about 1250 or so. from 1500 to 3000rpm is the "dead zone". It does run but no power, bogs down, not enough to die but will not pick up any speed and with a steady throttle up to about half open it will not pick up RPM.
Once it is above 3000prm it seems to have 100% power, pick up and acceleration.

I synced the carbs, both at idle and stay synced up through RPM range when sitting on the center stand. AF screws are both right about 2.5 turns out.

The diagnostic checks are perfect and I will preform them to double check everything.

Thank you,
Brian
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ct1500
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Re: Carb Questions - still

Post by ct1500 »

What often happens in the case of idle circuit problems is that the owner jacks up the idle speed which raises throttle plate opening to begin drawing fuel off the main jet circuit so it will idle somewhat. As fuel demand increases with engine load the normally contributing idle circuit is non-existent and the engine cannot run correctly at higher RPM on fuel from just main circuit.
You need to diagnose what the problem is, 90% of the time it is lean running from carb problems.
A sync is never a cure for a poor running engine, it is the icing on the cake after all else is perfect. Syncing a poor running engine screws things up even more as you are dialing up one bank of the engine to compensate for a deficiency elsewhere. Testing with carb clean is the way to go, finding whether it is rich or lean. Bottom of air box is left in its location with vacuum hoses attached underneath with cover and filter out. Can even test with injecting spray riding down the road at problem RPM.

A properly tuned 1500 engine can idle all the way down to about 450RPM before it finally stalls. What RPM is your engine idling at and how slow can yours get maintaining a decent idle quality?
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bri720a
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Re: Carb Questions - still

Post by bri720a »

It will idle down to 450-500rpm before stumbling (the bottom line on the tach).
When the carbs were out I had synched them on the bench and once running an hooked up to the gauges. It was less than 1/8th of a turn to make them exact.

I will pull the top off the air cleaner and test with the carb cleaner to get a better idea what's happening.

Thanks again will update soon.
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ct1500
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Re: Carb Questions - still

Post by ct1500 »

Sounds good so far, you way ahead of the pack, maybe too much? :D Do check with the spray while riding (crotch the spray can) and give her a whiff down each throat at problem RPM to see what happens and identify if it is one side, the other or both.
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DenverWinger
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Re: Carb Questions - still

Post by DenverWinger »

I agree with ct1500, but while the air box is open just try blipping and working the throttle some while watching the carb slides. should be nice and smooth, and work more-or-less together. Might still be sticking a tiny bit but open up nicely when you hit the throttle hard?
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Swagonmaster
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Re: Carb Questions - still

Post by Swagonmaster »

Verify that the two slides are positioned the same, if the diaphram isn't indexed to the slide and to the carb housing the slide winds up turned slightly (or more depending). Other than that as mentioned above the main jets not being correct would be very possible and if you wind up pulling the slides again make sure that the needles are seated properly.
Right now while driving try turning up the fuel enrichment lever and see if the engine picks up a lot, it will of course pick up the revs some normally but if its real lean it may pick up the pace even more.
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bri720a
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Re: Carb Questions - still

Post by bri720a »

Here is a video I just made.

I did try squirting a little carb cleaner when it was bogging. I could not tell any difference when I gave it a very small shot of it. I am about out so need to get some more and do it while on the road so I can better tell what's happening to be sure it is not making it better.

As you can see in the video - slow roll on (especially at the end of the video) revs up fully. When giving it a bit quicker it takes off fine then Boggs. I can pin the throttle and it will take a while to catch. Of course under load on the road it is much worse.
It's hard to see in the video but there us a good and even accelerator pump shot of gas.

Please let me know if I can give any further explanation. Thank you for your help and assistance!!



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ct1500
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Re: Carb Questions - still

Post by ct1500 »

Revving in neutral and then from idle to wide open only tells one just so much, we used to call that a speed tune when a guy is hoping something blocking his carb will dislodge itself. One needs to study what is going on with an engine at all operating RPM not just idle to wide open especially considering the carbs have three fuel circuits being the idle, main and secondary main which are the slides. From the one second clip that I saw, it got down to idle speed. :) I like to see a problem engine idle for a bit, then a slow roll on of throttle, slow roll off, quick roll off, a quicker acceleration and so on listening to the engine for backfires, surges, uneven running, intake noises, etc. all part of diagnosing. The engine then is running on just idle and main circuits (no slide action), slides only open and provide more fuel under moderate to heavy engine load. With an engine stationary I never rev up to more than 4000RPM or so and then just briefly. Drive it on the road like grandpa would not going over 2000-2500RPM and on level ground through all the gears. This operating condition will not call the slides into action which you will watch them stay closed. How does it drive then? Slow it down to 1000RPM in fifth gear then first time very lightly and next time heavy accelerate, it should pull up to speed, what happens? On a problem 1500 I can spend 2-3hrs diagnosing plus plastic removal time which system is at fault from compression checks, engine mechanical defects, fuel delivery, carb, spark, emission devices, electrical, road testing, spark plug condition etc. Your eyes and ears are foremost in gathering clues. During a normal driving road test what RPM does the problem start, what RPM does it go away. Does it get progressively worse with RPM. No need to race track it at all. The faster you ride it the less time you have to make observations. Your wide open problems are probably there in some subtle form during normal riding. Verify and verify again.
Along with carb problems the 1500 can have shot air, vacuum hose misrouting, air jet solenoid, AIR injection problems to name a few which affect the mixture entering engine. The GW 1500 is one of the most difficult to diagnose and repair bikes ever made. ;)
We will continue to plod forward on the assumption it is lean running because 90% of the time that is the culprit.
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bri720a
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Re: Carb Questions - still

Post by bri720a »

took it for another ride with air box off etc.
Slow roll of the throttle:
keep it under 2000rpm it will pick up speed and accelerate ok.
when taking it above 2000rpm it dies out and boggs very bad until it gets above 3000rpm (if I can get it past there). A squirt of carb cleaner when it is bogging in the rt carb makes it better, in the left made it worse.

I did check and no vacuum leaks under and above the mat, using carb cleaner.

I will be pulling the carbs again and re-cleaning the carbs. :) I would guess at this point this is where the issue lies.
Compression is good, plugs look good, air shot seems to work ok, slides work in sync and through the full range.
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Swagonmaster
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Re: Carb Questions - still

Post by Swagonmaster »

Since you will have the carbs off again make sure to compare the opening of the main jets, old and new. If you don't have a set of micro drill bits then a set of tip cleaners for an acetyline torch will usually do. If the new jet is the wrong size you can rebuild that carburetor forever and not fix the problem.
Under the main jets is what Honda calls the jet holder, I call it an emulsion tube, if you take it out you will see that it has a series of holes in the tube, it is very important that they not be stopped up at all, to the point that I always run either a drill bit or a tip cleaner through each one as they will affect the mixture.
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ct1500
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Re: Carb Questions - still

Post by ct1500 »

bri720a wrote: Mon Mar 22, 2021 3:50 pm A squirt of carb cleaner when it is bogging in the rt carb makes it better, in the left made it worse.
Congratulations :D It looks like you narrowed the problem down to the right carb or problem with right side of engine being lean. A few more observations need to be made before tearing things apart. Verify your vacuum hoses from carbs to air jet controllers are properly routed, top port of each carb goes to the same tee and air jet controller, likewise for bottom port. Find the common hose that goes from air jet controllers to sub air cleaner and pinch off with vise grips, run any better? Hopefully the large diameter hose that makes the gurgling sound bottom right front of air box is attached underneath of box. Put your thumb over the plastic port under air filter or hose itself if not attached underneath while running, run any better?
Above the throttle plate and below where the slide needle sits in the carb is where the main fuel jet discharge port resides. Rev it up and down good to about 3k RPM but not hard enough to open the slides, they remain closed. If they are opening you revving too much/hard. With a flash light if needed you should see atomized fuel (kind of looks like a fog) being discharged from the main jet ports. Since the right side is the one messed up you may not see that fuel/fog if it is a main fuel circuit problem. The look of the fuel being discharged should be identical between left and right carb. Likewise on the slides where the needle resides on hard revving you should see atomized fuel being discharged from needle port in identical volume from left and right carb when slide pulls back.
Now the spray into left carb making it worse could mean left side is spot on or is too rich and is where spark plug condition gives clues. Look for fuel dripping excessively out of main and slide discharge ports which is a sign of flooding.
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bri720a
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Re: Carb Questions - still

Post by bri720a »

Thank you!!!

It had looked like I was getting equal atomized gas from both main jets previously. HOWEVER it being dark outside and having to use a bright flashlight I was able to see that the right carb is not getting the same amount of gas from the main.

Some carb cleaner in the right spot and flushed a piece of crap out of the main. :D :D :D :D Now I have equal fuel flow from both main ports.

And it runs like it should all they way from idle on up through all gears both slow and quick acceleration!!!!!!! WoooHooo!!!! :D

Thank you CT1500!! I now know a bit more about the carbs and proper diagnosing them. (my weakest area of auto/bike mechanics)

I really really appreciate your help! Next time I am on the east coast I will make it a point to reach out and swing by. Thank you again.
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bellboy40
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Re: Carb Questions - still

Post by bellboy40 »

It is always a great feeling when you are able to find and fix a nagging problem! Congratulations. .👌


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