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Down on power at top end?
I don't wish to continue hijacking the "gas mileage" thread any longer, so I'll start a thread of my own.

Background: 1986 GL1200 Interstate, ~39,500 miles. I got this bike from a friend last August. I've run about 10 tanks of fuel through her since then. I was getting ~20mpg (US) and things were getting worse. That improved to about 36mpg (US) by cleaning the binding rear brake.

I still feel that the bike lacks power. I've never ridden a well-tuned GL1200, so I'm basically going by top-speed to assess my state of tune. I'm topping out at ~95 mph. When I get the revs up, she vibrates too much. I'm now suspicious that I have a slide diaphragm that is cracked or a sticking slide. The bikes starts up well, idles well, seems to pull from a stop pretty well.

What I've done:
* Compression test (dry): ~180 all around, quite even, looks good.
* Plugs: Correct NGK plugs, gapped correctly, look maybe slightly lean, which I think is normal for this era machine. Good condition.
* Ignition: Starts, idles, runs well, plugs look good. I'm gonna assume things are pretty much in order. Not sure about vacuum advance mechanism or vacuum hose.
* Air filter: Almost brand new.
* Carbs: The bike sat for a couple months with Stabil in the fuel. She started right up, but ran a little rough, and REALLY was low on power. I ran a can of SeaFoam through her. After riding about 100 miles with SeaFoam in her, she really just WOKE UP suddenly, and I swear she lifted the front wheel an inch or two! Seems to have lots of grunt down low. Idles well, starts well on choke and when warm without choke.
* Timing belts: Don't know, but assume that they were changed close to service interval, as prior owner(s) were enthusiasts (lights and chrome enthusiasts, anyway). I'll change them soon.

Where I am now:
Vacuum Tee between #3 and #4 carbs was cracked, so I replaced it, and the two hoses going towards #4 and the anti-afterburn valve. The forward-facing hose to the slow air cutoff valve seems pretty stiff, but I can't really get to it without pulling the carbs, so I just made sure the tee fit in properly (used a long-handled needle-nose with a curved tip).
Pulled the carb cover on #3. One of the screw heads was already gone, so I slotted the shaft with the Dremel, and used a screwdriver to get it out. That diaphragm looks good, if a slight bit stiff (compared to the rebuild kit I used on my old Jaguar SU carbs a couple years ago). Definitely not cracked. I'll check #4 (maybe tonight).
No, I have not yet synchronized the carbs. Whatever this problem is seems much more severe than carbs that are slightly out of sync.

Questions:
1) How do I get the slide diaphragm to stay put while I re-install the cover?
2) Can you get a screwdriver on the carb cover screws on cylinders #1 and #2 carbs without pulling the whole fairing?
3) Has anyone had a sticking slide that exhibited this behavior (low power at higher RPM & too much vibration)?
4) Has anyone had a cracked, ripped, or leaking diaphragm that exhibited the same behavior (low power at higher RPM & too much vibration)?
5) Is there a trick that allows you to drop the bowls and clean the jets, etc. without pulling the carbs?
6) This seems pretty severe, so I doubt that it could be a simple carb sync issue. Also, bike starts and idles well, whereas the problem is at higher RPM. Has anyone had carbs that were so far out of sync that they had these symptoms?
7) Is there a trick to get to the vacuum advance hose and replace it (just to be sure)?
8\) Any other ideas?

Thank you,

Ed
1986 Honda GL1200 Interstate
Reply
#1 03-26-2009, 08:51 AM,
It is not a big deal to pull the carb rack especially if you're looking for hard to find problems like you have. Consider the age of your carbs and how many inexperienced owners have touched your carbs then have a look here; <!-- m --><a class="postlink" href="http://www.randakks.com/Master%20Price%20Catalog.htm#11">http://www.randakks.com/Master%20Price%20Catalog.htm#11</a><!-- m --> and order the carb book and a carb kit for your 1200 and then tear into your carbs and make them like new so you can ride with peace of mind for many thousands of miles. The fact that you stated that there was a broken screw on the carb leads me into thinking that this is the best approach. The book will tell you exactly what to do in great detail and then all that is left is to check your timing belts.
Ed (Vic) Belanger - 1954-2015
Founder of gl1200goldwings.com

Reply
#2 03-26-2009, 10:35 AM,
Actually Vic, I was going to suggest going the other way. One tooth off on cam timing exhibits the same characteristics. It's less painful than removing the carbs, and he'll at least know what going on up front.
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#3 03-26-2009, 10:56 AM,
Thank you Vic & GL,

My gearhead buddy here at the office is making fun of me: "Waaa! Waaa! I don't wanna take my carbs off!" Truth is, my bike is rideable and plenty of fun, so I'm reluctant to screw around with it and have a few days down-time.

I know that all three of you guys are right, I've just been trying to find that "simple" problem, but it keeps boiling down to "just do the whole job" and then it will be done, and I'll be good for years to come.

I'm already into the carbs, so I'll go that route first. I've seen this post http://www.gl1200goldwings.com/viewtopic...rbs#p31521 that breaks down the job. Any more pointers?

Thank you,

Ed
1986 Honda GL1200 Interstate
Reply
#4 03-26-2009, 11:22 AM,
glhonda Wrote:Actually Vic, I was going to suggest going the other way. One tooth off on cam timing exhibits the same characteristics. It's less painful than removing the carbs, and he'll at least know what going on up front.

I agree with you GL but I had suggested checking the timing belts much earlier in this thread therefore we can't make Ed drink the water we can only show him the path to it. I would consider the timing belts to be the top priority on a great running new to me GL1200 and I would consider the timing belts on a poor running GL1200 to be the first issue of maintenance above and beyond anything else. One tooth ahead on the belts witll cause improved low end performance while one tooth back lends it self to better top end performance and belt timing set right on gives you best all around performance. Belt condition and age are the main factors for considering the belts but if someone has already changed the belts they may have done a poor quality job in setting the marks right. BTW, if it was my bike and it was new to me I would change the belts simply as a precaution so I could be sure that I could rely on them. Old belts can look like new but they can fail instantly cause much expensive valve damage.
Ed (Vic) Belanger - 1954-2015
Founder of gl1200goldwings.com

Reply
#5 03-26-2009, 12:32 PM,
Yes, Vic, you did mention timing belts early on in the other thread. Seems the concensus is actually timing belts, with a strong recommendation for complete carb rebuild, too.

In other words, "just fix everything, dammit!!!" Smile. Well, I guess I can't miss with that approach! I've already rebuilt almost the entire braking system, yanked about 20 miles of silly aftermarket lighting and stereo wiring out, ABS cemented several cracked bits, replaced tires, loctited mirrors, and God knows what else. So, I "might as well" finish the job.

Alright, men, I'll go looking for the technique for the timing belts now. Can you hear me at the water fountain?

Thank you,

Edward
1986 Honda GL1200 Interstate
Reply
#6 03-26-2009, 02:21 PM,
Another question just occurred to me:

Is there any way to check the cam timing without actually doing the whole job?

Thank you,

Ed
1986 Honda GL1200 Interstate
Reply
#7 03-26-2009, 02:45 PM,
You'll have to remove the belt covers to see the timing marks. By that time you've already done the bulk of the labor which is minimal.
Like Vic, if it were mine, I'd just replace them while I was there.
Vic, I found your suggestion on another thread. While changing belts is an absolute with any "new to me" wing, I was thinking of it more from a diagnostic stand point.
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#8 03-26-2009, 04:56 PM,
admin Wrote:therefore we can't make Ed drink the water we can only show him the path to it.

That's kinda clever, "show him the path to water".....Mind if I steal that from you Vic? :lol:
Reply
#9 03-26-2009, 07:33 PM,
Alright, I'm drinking at the trough, starting with the carbs:

I've got 'em out and got #1 float bowl off. Why are there three jets? Other bike only had mains and pilots.

I've checked the two jets that screw in, and all are clear, including the horizontal passages through the emulsion tubes.

Now, how do I clean that third jet? It seems to be pressed or glued in, and not removable. On my other bike you could just pull the pressed-in jet out with a vise-grip, clean it, and then tap it back in with a small hammer. Can you do this on a 1986 GL1200 Interstate?

If not, what do you recommend for cleaning this jet & passage? Is this the pilot jet?
1986 Honda GL1200 Interstate
Reply
#10 03-29-2009, 02:14 PM,
I forgot to ask you earlier but when you say your bike lacks in top end power are you shifting at 7500 PRM or are you short shifting at 5000 RPM and expecting lots of power?

Only the pilot jet and main jet are removable, the needle jet is pressed in and unremovable. To get the needle jet clean boil the empty carb in water for about 10 minutes then with a glove pull the carb out while hot and blow the jet clean with compressed air both sides. If it's still clogged you may need to resort to using one bristle from a stiff paintbrush to poke it through. Note: using a piece of wire to clean the hole could result in enlarging the hole and a resultant mixture problem.
Ed (Vic) Belanger - 1954-2015
Founder of gl1200goldwings.com

Reply
#11 03-29-2009, 02:35 PM,
Thanks, Vic.

Nah, I don't short-shift. I've been riding smaller bikes than this for quite some time. I keep her revving pretty good.

I have noticed that the second screw-in jet (not the main) in #4 carb was clogged up a bit. Blew it out with lung-compressed air, and it is clear now. I'll go get some carb cleaner and shoot it into the pilots and see if/where it comes out. Then I'll try compressed air. Hey, if it's clear then I don't have to boil 'em, right?

Thank you,
Ed
1986 Honda GL1200 Interstate
Reply
#12 03-29-2009, 02:55 PM,
Ed biker, your bike should run 95 in 3rd gear, hope you find your problems soon.
joe
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#13 03-29-2009, 03:04 PM,
Oh, now I see the problem!!! All this time I've been trying to top 100mph in 5th gear!!! Wink

Kidding aside, thanks for the feedback. That helps me confirm mentally that there is, indeed, a problem.

joe turner Wrote:Ed biker, your bike should run 95 in 3rd gear, hope you find your problems soon.
1986 Honda GL1200 Interstate
Reply
#14 03-29-2009, 04:11 PM,
edbikerii Wrote:Thanks, Vic.

Nah, I don't short-shift. I've been riding smaller bikes than this for quite some time. I keep her revving pretty good.

I have noticed that the second screw-in jet (not the main) in #4 carb was clogged up a bit. Blew it out with lung-compressed air, and it is clear now. I'll go get some carb cleaner and shoot it into the pilots and see if/where it comes out. Then I'll try compressed air. Hey, if it's clear then I don't have to boil 'em, right?

Thank you,
Ed

To be honest, if you boil them in water it will really help loosen the crud. What happens with the boiling is that the aluminum and brass expand and contract causing some of the scale to fall off and since most of the scale was created by moisture the hot water becomes a solvent to the scale.
Ed (Vic) Belanger - 1954-2015
Founder of gl1200goldwings.com

Reply
#15 03-29-2009, 04:13 PM,


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