Down on power at top end?

[edbikerii]

Thanks Vic. No, she really has no power. My buddy, who has also been riding bikes since he was a kid, rode her yesterday. He described her as "can't get out of its own way", and "feels like it has a governor", and "it is almost as if opening the throttle doesn't do anything at highway speeds". Oh, there's definitely something wrong.

I've got belts and hose in my lap right now. I don't know if I'll complete the job tonight, but I'm gonna start ASAP.

Thank you

Ed

[edbikerii]

Hey guys, I stumbled upon another post that I think may be relevant.

I've got these chrome carburetor tops (carb covers, whatever), that were installed on my bike when I got it. They look identical to those in the attached picture.

I noticed this post in which EdZ posted that he has had trouble with aftermarket chrome covers causing vacuum problems:

<!-- l --><a class="postlink-local" href="http://www.gl1200goldwings.com/viewtopic.php?f=1&t=4180&p=35710&hilit=vacuum+carb+tops#p35710">viewtopic.php?f=1&t=4180&p=35710&hilit=vacuum+carb+tops#p35710</a><!-- l -->

Anybody else seen these problems?

I don't have the original covers or I would have already changed them back, just to eliminate this as the cause.

I'll try to contact Ed Z directly as well.

Thank you,

Ed

[admin]

Have you tried raising and lowering the slides manually? If the chrome caps are restricting air/slide movement you'll feel it with your fingers.

Try this fellow to see if he can ship you a set of stock caps: <!-- m --><a class="postlink" href="https://id212.chi.us.securedata.net/whiteys-classic-wings.com/merchantmanager/">https://id212.chi.us.securedata.net/whi ... ntmanager/</a><!-- m -->

[edbikerii]

Thanks Vic,

I did raise and lower the slides manually when the carbs were off the engine. Everything seemed unremarkable, but I don't really know what to look for. On my old Jaguar with SU carbs, I could block off the vacuum port and the throttles would stay open until the vacuum was released. Any such port on these carbs?

I shot Whitey an email, as I didn't see the parts listed on the site.

Thank you,

Ed

[edbikerii]

Update: I checked the fuel pump. I got nearly 80ml in 5 seconds, so it is good.

Thank you,

Ed

[Ed Z]

Might want to check and verify that the carb tops are on correctly... There is a notch on the underside of the cover that has to line up with the port on the carb... The aftermarket tops I had did not line up well with the ports and therfore did not work well... I just buffed the heck out of the old ones and all is good now (looking good too)...

[edbikerii]

Thanks Ed,

Do my symptoms sound similar to those you have experienced when the holes didn't line up right?

Thank you,

Ed

[Ed Z]

Not real sure.. I didn't even ride the thing with them... Just goosing the throttle in neutral told me something bad had changed... I put the originals back on and it was fine again...

[edbikerii]

Eureka!!!

So, I bought a set of used carbs on eBay from PinWall (good service, I've bought from them before, and they were good that time, too). These carbs had OEM tops. I also have a set of OEM tops on its way to me from Whitey's (thanks for the link, Vic) for my new spare carb bank.

I refitted the OEM carb tops and dammit, this bike has POWER now!

I cannot believe the performance improvement! I figured she should have more power, but I didn't expect the power to improve ACROSS THE BOARD! I thought she was powerful at lower RPM before, but now she is nearly frightening! WARP SPEED. I'm really impressed with Gold Wings now! The biggest bike I'd ridden before was a 1340cc fuel injected Harley Road King that I rented for a weekend, but that bike could not hold a candle to the mighty Gold Wing's performance.

Thanks to everyone for all the advice and encouragement, especially Vic, GLHonda, and Ed Z (who had the same problem).

For the record, I'm also dumbfounded by the stupidity of this issue. I should have known it would be something so dumb. Some previous owner of my bike had also installed a chrome brake lever meant for some other bike, and used a grinder to make it fit. He then failed to notice (or care) that one could easily pull the brake lever all the way to the bar, and that the front brake was less than 50% effective. I should have expected that the same guy would have installed these chrome carb tops and failed to notice that the bike was down maybe 50% on power! Funny, the bike wouldn't stop, and it wouldn't go. Sure had a lot of chrome and lights, though!

So, in case it might help someone else, I figured that I'd compare the chrome vs. OEM carb tops and figure out why the chrome ones suck for so many of us.

I filled an OEM cover with water, and then poured that water into one of the chrome covers. The chrome cover still could have held maybe a couple CCs more water, but that difference did not seem significant.

I measured the diameter of the sealing surface of the two covers where the radiused edge of the cap flattens into the sealing surface (which seals against the diaphragm's circumference). On the chrome caps, the diameter was 66mm. On the OEM caps, the diameter was only 63mm (see pictures). The inside diameter of the groove where the diaphragm's ridge sits is ~62mm, and the outside diameter is ~68mm (the groove is about 3mm wide).

So, I believe that the problem with these chrome caps/covers is that the inside diameter of the sealing surface is too large, allowing vacuum to escape around the outer edge of the diaphragm. This causes the pressure difference across the diaphragm to be lower (partially equalized), so the slide does not rise as fast or as far as it must when the throttle is opened. Essentially, these carb tops are designed improperly for our carbs. I don't know who the manufacturer of these carb tops is, as there are no markings on them. I will promptly throw them into the garbage can, in order to prevent them from ruining some other innocent GL1200 ever again.

Thanks everyone!

Ed

[admin]

Excellent report Ed. I'm so glad that you finally got it all working properly. You might want to check a few other things like moly 60 paste on the rear splines, lubricant in the final drive and the fork oil just in case the PO messed up there as well. If you haven't done so flush all the hydraulics and install new DOT 4 every 2 years.

[Guest]

Glad you finally nailed it!!! I was thinking about dressing my rear carbs with chrome tops. Looks like I'll polish them instead. I've always maintained that given the age of these bikes, and the fact that they've been touched by fourteen pairs of hands, the single biggest mistake one can make is "assuming the guy who worked on it before you, knew what he was doing". Good job.

[edbikerii]

Thanks, Vic.

When I put the new rear tire on her last month the rear splines got their moly 60, and the final drive got checked.

I took care of the DOT4 when I cleaned out the brakes (shop did rear) and the clutch.

I'll check the fork. I was told that the fork seals were done just before I got the bike, so now I'm worried about the quality of that work. Jeez. :cry:

Thanks again for all your help!

Excellent report Ed. I'm so glad that you finally got it all working properly. You might want to check a few other things like moly 60 paste on the rear splines, lubricant in the final drive and the fork oil just in case the PO messed up there as well. If you haven't done so flush all the hydraulics and install new DOT 4 every 2 years.

[edbikerii]

I just cleaned up the OEM caps with ScotchBrite green pads, and then used Eagle One Mag & Aluminum polish for the final touch. No, they aren't mirror-finish like the chrome, but they look more business-oriented than the chrome. I guess the bare aluminum may be more susceptible to corrosion over the years, but I'll hit them occasionally with WD-40 and see how it goes. Unlike a certain PO, I'd rather have the bike run well than look good!

Thanks for all your help!

Glad you finally nailed it!!! I was thinking about dressing my rear carbs with chrome tops. Looks like I'll polish them instead. I've always maintained that given the age of these bikes, and the fact that they've been touched by fourteen pairs of hands, the single biggest mistake one can make is "assuming the guy who worked on it before you, knew what he was doing". Good job.