The importance of o-rings
I was blessed to wrench in some heavily-trafficked Honda dealerships in my early years. I somehow quickly commanded the lion's share of the shops' Gold Wing work, along the way developing certain must-dos on services. For example, every time I did a maintenance service I unbolted the intake manifolds and replaced their all-important o-rings. Every time. Ever since then I have had the part number (91301-371-005) etched into my brain from those many years of asking for it from the parts dept. I include these o-rings in the shipment of carbs back to my customers even today. Another critical o-ring point are the two large diameter thin wall o-rings under the aircut valve. I usually glue them to the valve as I know most folks remove the valve during carb reinstall and I want to make it not as easy to lose the o-rings as it might otherwise be. But perhaps the most important o-rings in GL1000 carburetors are those on the primary and secondary main jets. I replace these on every rebuild because they are the first line of defense against fuel mixture issues, seeing as how the jets are a slip fit into their cast aluminum towers. These o-rings are extremely hard to find by themselves, by the way. This is because, as is usual with Honda, they are very odd sizes, 3.2mm x 1.1 and 4.2mm x 1.1. As I say, pretty unique. The ones in the kits are crap, no surprise there. And none of the half-dozen o-ring houses that have sprung up in recent years have them. However, there are three retail oulets for these parts imported from Japan, among them Amazon (what don't they sell?) and the best probably being Cycle Recycle in Indiana, who has them for just $1 each. OR-4604 and OR-4609 are the part numbers.
Timing is everything
It really is. No disrespect intended, but Robert Overby did not discover the split ignition timing technique. Though he wrote about the procedure in the June 1995 issue of Wing World magazine, he was 20 years late to the party, and for that matter was likely not yet born when the method was first endorsed immediately after WWII by BMW for use on their boxer twins. Thus it's no surprise Honda dealer techs were practicing this technique on the GL1000 from almost the Wing's very beginning in 1975. It's a great method, and bottom line, even mandatory. Dynamic timing just isn't as good. But before attempting points ignition timing on the venerable Wing, there are a number of things you need to know. First, tension the camshaft belts as carefully as you can, that will help. But even perfectly-tensioned belts will not prevent the forces of the engine's valve springs and their effect on the left side cam from varying ignition timing. The problem is simply built-in, so do the best you can. I have gone so far as hand-stoning the ignition advancer's lobe. But though the timing improves, the performance benefit just isn't there. Second, be aware that the longish advancer-mounting snout on the end of the left cam has been shown to often be bent, and this of course adds to ignition innaccuracies. Finally, realize that none of the parts inside the ignition points housing are mounted concentrically with one another, and on top of that the mounting surface of the points backing plate is anything but a precise fit. Thus movement of any part in the housing during ignition adjustment takes place eccentrically as well as omnidirectionally in relation to the camshaft, so that each succeeding tweak upsets the previous adjustment. Maddening, if you let it get to you. Pros though, through much experience, know how to deal with this.
Pilot screw adjustment
The four-cylinder Wing's carburetors were made smaller almost continuously throughout its production. In 1975 the carb's venturi was as big as it would ever be. Three years later in 1978 it would shrink, and in 1980 it shrank again when the GL1100 emerged. Finally, the carbs shrank still more on the 1984 GL1200. The reason? Honda changed their idea of what kind of bike the Wing was supposed to be, after initially positioning it as a quasi-sportbike (yes!, check out the period Honda ads) and quickly repurposing it in response to America, Honda's biggest market, redefined the Wing as a luxo-tourer. The fact is, due to their being substantially oversized, the GL1000's carburetors, absent an accelerator pump, very badly need one. For this reason, most knowledgeable techs are liberal with the GL1000's idle mixture screws, adjusting them richer than factory spec to at least partly compensate for the lack of good airspeed at idle, and as a result mimicking an accelerator pump's benefit. Over-rich effectively provides the only available fuel compensation when the bike's biggish throttles are yanked open from idle, and as long as it isn't overdone, presents no drawback in terms of idle performance.
Alternator connector repair
Many folks bemoan the Wing's tendancy to melt its alternator connector, but few realize why it happens. More importantly, how to repair it correctly, and how to avoid its recurrance. You almost have to have a history with the Honda product, and to some extent all vintage Big Four (Japanese) vehicles, to fully appreciate the issue. And guess what? It's not alternator heat. It's not system load. And it's more a defective manufacturing process than it is a bad part. The fact is, wire crimping is the problem. The combination of the crimped-on wire terminals and open backed cannon plug adds up to create the problem. Exposed to the elements through the old-school plugs, the crimpings steadily oxidize, ultimately increasing resistance that in turn creates the heat that melts the plug, sometimes dramatically. The fix? Address the two issues. Clean and solder the terminals and back-fill the canon plug with grease. If necessary, replace the melted cannon plug, sourcing it from one of the half-dozen online suppliers. The problem will be in the past never to return.
One thing I have noticed about GL1000s and 1100s, no one seems ever to properly maintain the spark plug caps. On every one I see these days, the caps are practically falling off the wires, and three out of the four are deteriorated to the point of reading 20K, 50K, or even infinity. Each time the bike gets its 3,000-mile service, one cap should be removed from the rubber seal joining the two caps, unscrewed from its wire, the wire nipped back 1/16", and before reinstalling it onto the wire, the cap should be resistance-tested. New they are 5K ohms. As they age their resistance increases, and should be replaced at 10K. After testing, reinsert the cap into its rubber seal, and remove its neighbor and repeat. Removing and servicing only one cap at a time ensures you won't mix them up, which would result in load bangs instead of a properly running engine.