75 Goldwing Carb Sync

[RobbyMoto]

I'm having issues syncing the carbs on my 75 Gl1000. I'm sure this is not the first time this topic has been brought up on this forum. However, previous posts dont seem to address the issues I'm seeing.

I've spent a couple hours getting the bike to run this good but it's still bad. From a cold start, I have to nurse the choke until I find a sweet spot to keep it from hanging up at 4000 RPM or stalling out. After warming up for about 5-10 minutes, the idle is still... unpredictable.

I have a dial type gauge from Amazon. I can get all 4 cylinders pretty close at idle...

The vacuum reading at idle is 2-3 in. mercury. Does that seem ok? I dont find any documentation about what the vacuum readings should be, only that they should be the same on all 4 cylinders.

but when I blip the throttle...

it bogs down for a sec and then revs up to about 3-4k RPM and hangs up there sometimes and sometimes not. The vacuum readings are all different by a couple inches at the higher RPM. Sometimes it stalls when it comes back down.

Compression test is ok. 135 psi on all 4 cylinders.

[RobbyMoto]

Well I found A problem, not sure if it's the only problem.

There is a leak around the intake boot/ carb holder on cylinder 1. When I spray a drop of starter fluid there it revs up high. I sprayed fluid around the other parts of the intake and no change in RPM, just that one spot.

Ideally I would replace the rubber boots but they're unavailable. I was going to try this fix, using 4 boots for the GL1500. Has anyone done this?

viewtopic.php?f=13&t=53194

[RobbyMoto]

UPDATE:

fixed the leak on cylinder 1 but it didn't fix the issues.

[cfairweather]

Did you rebuild the carbs? It sounds like your idle circuits in the carbs are plugged. The off-idle pilot jet mod should be done too while you have the carbs out.

[RobbyMoto]

Hi cfairweather. This is actually a continuation of this thread... viewtopic.php?f=3&t=71794. I started a new thread because that one is old and I'm coming back to this project after a couple months away from it.

I did a lot to this bike, including rebuilding the carbs with a randakks kit. I made sure to clean out the slow jets, idle circuits and everything. I had the carbs separated and I'm wondering if I didn't reassemble the linkages incorrectly.

I've been trying to adjust it and it just isn't happening. It revs up randomly when I start it and hangs at about 3000 RPM. Can I just take off the intake headers and put a feeler gauge in the butterfly valves to get it back to baseline?

Could this be caused by sticking slides? When I had the carbs out, I made sure the slides were operating smoothly but I didn't polish them.

[Rambozo]

You might want to post a list of things you have done in order. I looked through some of your old posts and lost track of the order of operations.
After you cleaned and sealed the gas tank, did you clean out the carbs? I saw you had a lot of gunk in the tank.
Have they gone through an ultrasonic cleaner? Based on some of the photos, they need it.
Typically, you use a pin gauge or drill bit shank to set the butterflies. Flat feeler gauges don't really work for concave radii.
Did you check the function on the bench before installing them? Things like float level and linkage function are more accessible off the bike.
Sticking slides will make the mixture go super rich, this will be obvious on the spark plugs and exhaust temp.

It really sounds like it's time to pull the carbs and start over, making sure they are clean and functioning properly on the bench. Take the time to run cleaner and compressed air through all the passages and compare each carb. If they are different, you have problems. Go over the linkage and make sure it moves smoothly and returns to the stops sharply. Check for bends, binding and excessive wear. Lube all the links. I like PTFE spray as it is dry and won't attract dirt. Also

[RobbyMoto]

Here is the order of operations, the best I can remember...

- changed oil
- changed belts
- new coolant
- rebuilt top end of left side engine (replaced bent valves)
- replaced broken rocker arm on left
- took out carbs and rebuilt them with Randakks kit
- put carbs back in but engine wouldnt stay running
- determined that the gas tank had a lot of corosion and rust/ gunk in it
- removed gas tank and lined with por15
- old fuel pump leaking so replaced with OEM pump
- took off rusted out OEM exhaust and put HM431 exhaust (this is from '78 gl1000 I believe)
- took carbs out a second time, cleaned with ultrasonic cleaner, cleaned out sections I had missed the first time. Sorry, I don't know the proper terminology but...
- idle jets under the rubber plugs
- removed the little pucks and cleaned under there
- cleaned out jets on the little brass elbows off the side of the carb bodies
- pretty sure I got everything. Carb cleaner, shop air, ultrasonic, then shop air again.
- replaced control cables (throttle, clutch)
- rebuilt brakes front and back
- set static timing but couldn't get it perfect. New points I bought were wrong size so I cleaned off the old ones, put them back in and set the timing as close as I could get it.
- fresh non-ethanol gas
- put carbs back in and this is where we are at now.

[RobbyMoto]

Also I should add, the carb linkage is very snappy when disconnected from the throttle cables, but is a little sluggish to return when connected. Can this cause the issues I'm seeing?

When it starts to take off, if I force the linkage closed it still doesn't help.

How do I check to make sure they are all the same on the bench?

What size drill bit do I use to set the butterfly valves?

Is there a way to adjust #3 or do I measure that and set the rest to match it as closely as I can?

[RobbyMoto]

UPDATE:

I took off all of the intakes and adjusted the butterfly valve clearances with a 0.015" wire, inserting it between the top of the butterfly and the throat of each carb. I adjusted all 4 to be as close to each other as possible. I also put 4 new stainless hose clamps on instead of the old clamps before reinstalling the intakes, thus eliminating any leaks. I tried spraying a little starter fluid around the intake boots and o-rings and it had no effect on the idle.

The butterflies were all pretty close to each other before I adjusted, but when I reinstalled the intakes, the idle was more stable. It doesn't take off randomly anymore and hang up around 3K RPM like before.

There is still a lag in throttle response however. When I twist the throttle, the engine bogs down before revving up. If I do a quick snap on the throttle, the engine will stall. I tried playing with the linkage, forcing the throttle this way and bypassing the throttle cables and sleeve. It was a little more snappy but still bogs down. Also the throttle linkage on the carb doesn't always return to it's seat. I think this is caused somewhere in the throttle cables or the throttle sleeve because I remeber when I had the carbs out for cleaning, the linkage was very snappy returning to it's seat. (I did lube the new cable before installing but maybe need to replace the throttle sleeve.) This is a problem but I don't see how it would cause the engine to bog down like it does. Doesn't this seem like a fuel mixture / delivery issue?

The vacuum readings change as the bike warms up. Everything looked good on the gauges initially (all 4 at about 5" mercury) but after running a couple minutes, cylinder 2 needle started flapping around wildly. Adjusting the sync had no effect on the vac reading. As the engine continued to warm up, cylinder 2 settled down and cylinder 4 vac reading started to go crazy with the needle flapping around across the full scale of the gauge.

Also I should mention the bike is hard starting, which I was chalking up to being old and cold-blooded but maybe it is a symptom of something else with the carbs?

I really don't want to take these carbs out a third time but it seems to be leaning that way. Anyone have a checklist to go through when bench testing these carbs? Does Randakk's video cover bench testing procedure? Like how to make sure the linkage is operating correctly? Thank you!

[Rambozo]

Check that the accelerator pump is working and giving a good shot of fuel when you crack the throttles open.

[RobbyMoto]

Oh good idea! How do I check that?

[cfairweather]

Glad you are making some progress. The hard starting and the "lag in throttle response" will be improved by doing the off-idle modification. This is easy to do and you do not need to remove the carbs to do this. Simply replace the air jets that are in in the brass elbows with smaller jets, about #97. The only problem is that you won't be able to find that size . The best way to get the size you need is to start with #60 air jets from a cheap GL1000 carb kit and use a #62 drill bit to make the hole the correct size. If you do not have a #62 drill bit, check with Harbor Freight or eBay for micro bits. If you do not want to try and figure this out, send me a PM and I will help you. I have some #60 jets and the correct drill bit.

To get to the jets, simply pull off the rubber tubes and you will be able to unscrew the old pilot jets.

The suggestion about the accelerator pump is not valid for the 1975 GL1000 as it does not have one.

[RobbyMoto]

Thanks cfairweather. I will PM you.

So if I understand correctly, these air jets in the brass elbows are connected to the 3 holes under the puck in each carb?

I removed and cleaned out these passages and replaced with a new puck but I used gaskacinch to hold them in place. Considering how sensitive these carbs are, do you think this could be causing the intermittent issues?

What is the correct way to hold these pucks in place while you reassemble the carbs?

[cfairweather]

The pucks are kept in place by the float bowl bowl and gasket. You should not use gasket sealer on the puck. The air jets in the brass elbows are called "Pilot Jets" and they provide air to the idle circuit. Yes, the passage does connect into where the puck is and also to the #35 idle jet. This circuit is very easily plugged and when this happens, the cylinder will act like it is dead at idle. The two most common places that get plugged are the #35 idle fuel jet and the emulsion tube that stands up in the venturi near the butterfly. Hope this helps. I drilled out 4 jets for you and sent you a PM.

[RobbyMoto]

Thanks cfairweather. I will try the new air jets and hopefully that fixes the off-idle issue.

[UncleLumpy]

I seem to remember that the gauges we used had restrictors in each line, this would slow somewhat the responses from the vacuum gauges.
Does your set have them?

[RobbyMoto]

Yes. They have restrictors. I had all 4 dialed in correctly.

[P.H.C. Ritzen]

Hi,

Please check your gauges first, take one vacuüm point and connect all 4 the gauges to that one point, they all should read the same.
If the don't, please calibrate them, so you can be sure the reading is accurate.
Better option is trying to get a mercury unit.
As mentioned many times before, please be sure that your idle jets are absolutely clean (absolutely!!!), use a drill that is in mm the same as the number stamped on the idle jet when you are not sure, as it gives exactly the problems you describe, just as a leak in the intake manifold(s) will do.
Remember, that ultrasonic cleaning does not (not!!) open real bad closed jets, the implosion cannot reach the inner of the closed section of the jet hole, you must clean it mechanically.
Take care of the correct setting for the idle screws.
One thing i did not read yet, is that your advance unit in the ignition might be slow or frozen due to old grease or rust.
This will advance or retard your ignition too slow, or not at all, this can lead to problems of bad throttle response or "hanging" in revs when going back to idle.

Hope this helps.

[RobbyMoto]

UPDATE:

I worked on the bike this weekend and still couldn't get the throttle to respond snappily.

- Installed the new jets
- took off the intakes again and tried to reset the butterfly valves all to the same position
- Inspected all the vacuum hoses
- Inspected the throttle cables and linkage.
- Idle screws are all at 1 3/8 turns out as recommended in the Clymer manual.

The bike still has a hard start and sluggish throttle response. Wants to stall out when I blip the throttle.

I have some questions...

1 - Just how sensitive are these carbs anyway? Is it really that hard to tune these things in?
2 - Am I expecting too much out of this old bike? My prior experience working on bikes is with a modern v-twin. The engine warms up pretty quick and the throttle is very snappy. Is it realistic to expect this from the GL1000, or is this just the way it runs?
3 - What is the clearance I need to set between the butterfly and the carb throat? I have to turn the idle stop screw way in (almost all the way) to get any clearance whatsoever on Cyl 3.
4 - From looking at the plugs, cyl 3 seems to be running a little rich. Will the incorrect idle screw settings cause a sluggish throttle response? One cylinder flooding?
5 - The vacuum hose I have is 6.2mm ID and the Randakks article recommends 5mm ID. Could this small difference really have such a huge effect on the response?
6 - Has anyone used the Randakk's video? Does it cover these topics? I am thinking I should remove the carbs yet again, buy the DVD, and follow it. Not sure how to watch a DVD in the garage but that is
another problem.

Thanks for any thoughts on this!

[cfairweather]

There are many things that can cause the issues you are having. These carbs are very responsive and reliable one you have everything working like they were designed, but you must have everything perfect. The correct vacuum hose sizes you need are genuine Honda 5.5mm for the brass elbows and 3.5mm for the air cut valve. These fit perfectly. The Randakk video is a good, basic guide and I recommend watching it; however, it does not go far enough for me. I use clear tubes to verify the float level, fully polish the slides and other things to make the carbs work perfectly. Details on these carbs are very important. You seem to be worried about bench syncing the carbs and you really don't need to worry about that too much because you will be synchronizing the carbs with gauges which is the end goal.

You should take a look at the advance unit behind the points to make sure it is not sticking. The springs should fit snug, not too tight and not too loose. I also highly recommend you replace the points with a cheap electronic ignition and also replace the coils. You can get Dyna clone coils for about $30.00 ea and Dyna clone electronic ignition sets for about $40.00 on eBay. Installing both of these will allow you to eliminate the ballast resistor and the condensers. I wrote instructions on how to install these on the NGW Club web site and maybe on this site too. You must have your tappets adjusted perfectly and your timing adjusted perfectly before adjusting the carbs.

[RobbyMoto]

How do I check the float level with the clear tubing? Can this be done while the carbs are on the bike? Do I need some sort of adapter to screw into the float bowl drain? I double and triple checked the float levels when the carbs were off the bike but this would be another good check to eliminate that variable.

Also forgot to mention I did re-check the ignition. Static timing looks good still but I will have to check that advance mechanism.

[cfairweather]

You can make your own clear tubes and while it is possible to do this without removing the carbs, I don't recommend it because it would be difficult and you risk getting gasoline all over the engine and then a stray spark could start a fire. If you try this, have a fire extinguisher next to you. The level should be at the lower edge of the rim. See this thread on the NGW:
https://www.ngwclub.com/forum/viewtopic ... es#p823416
Again, you can make some simple clear tubes or I sell these on eBay. You will get it figured out as I can tell you have a lot of determination.

[RobbyMoto]

Sounds good. I think I need to bite the bullet and remove these carbs again. Someone in that NGW thread was using isopropyl instead of gas. Do you think that would work for bench testing the float levels with the clear tubes? Much easier to work with alcohol than with gasoline.

[Rambozo]

Due to the difference in specific gravity, the float level will be slightly different, but probably not enough to matter for Denatured Fuel Ethanol.

[RobbyMoto]

How sensitive is this engine and carb setup to exhaust back-pressure? The original exhaust that came with the bike was full of holes so I am running an HM431 exhaust, which I believe is the stock setup from a '78 Goldwing. Could this be a re-jetting issue?