® The GL1000 problem


Several years ago a customer sent me some vintage Honda carbs from Australia. I rebuilt them. He got them back, and a month or so later, due to his complaint, I paid for him to return them to me. Going over them carefully, I found nothing wrong with them. I then paid to ship them back to him. Subsequently, after almost a year of trying to help him, taking time from other work, to help him diagnose his issue-- in the end, the very end, he finally admitted to me, after nearly a year, that each time when I brought up the subject of ignition timing-- and you can believe I did bring it up a few times over the course of that year-- he had not been truthful when he said he had "checked" the ignition timing. In the end he admitted he had no idea how to adjust and service his ignition timing and another mechanic on his end had finally made the bike run right by servicing and adjusting the ignition. Well, at least he eventually told me.

There is something missing in the vintage motorcycle world today: an understanding of and knowledge about these motorcycles. No matter how passionate the owner, he almost always overthinks carburetors and underthinks ignition. And ignition on these old bikes is bedrock to their function. Just 2 degrees timing error, sloppy wiring, a bad mechanical advancer, poor quality aftermarket parts, lack of preventative maintenance on the high voltage side-- these are endemic while at the same time almost universal, and impactive on a level that just isn't believed by the non-professional. These are not old V8 cars on which you can set the timing by ear and it will be "good enough". The ignition's timing and general condition is the single most important aspect of these bikes' tuning. And user forums, by ignoring the specific issues, just make it worse because visitors to forums assume all they need to know is found there. Far from it.

And having a Dyna or other points replacement system does not change this. The Dyna is still driven by a floppy rubber belt, it is still subject to the other design shortcomings of the GL1000 engine, and most importantly, the Dyna and its derivitives bring to the table a whole new set of issues all their own.

Dividing the Dyna system in two, there is the low voltage side and the high voltage side. The low voltage side is the module, i.e. pulser plate or pickups. Not only does the plate have to be timed and this in a very unintuitive way that relies on watching the spark at the spark plugs instead of using a deadlight, but for some reason the Dyna produces stray, errant pulses in the middle of the timing, and this needs to be understood and taken into account. Then there is the fact that the pickups are not mounted 180 degrees to each other as they should be, so the timing has to be set on both pickups, not only one. Just like with points. And don't forget the uneven tension of the driving belt (even carefully tensioned, valve spring pressure alters its timing), which produces asymetrical ignition timing that cannot be adjusted away and also has to be compensated for. Again just like points.

But worst than these things, which are simply factors that anyone who knows the model takes in stride, are the issues on the high voltage side, that is, the ignition coils. Ninety percent of the folks who go Dyna put in the coils as well as the timing module. And here is where every installation goes awry. Aside from the fact that the Dyna ignition coils add little or nothing to the supposed advantage of the timing module, and aside from the fact that folks inevitably buy the wrong Dyna coil part number, and aside from the fact that folks are confused about the role of the stock setup's ballast resistor, the invariably poor quality of the Dyna coil installation introduces more-- not fewer-- glitches into the ignition system. Patently inexpert primary wiring work, unnecessary and inadvisable retention of the ballast resistor, and worst of all, the vintage Honda mechanic's horror of crimped, automotive type resistive spark plug wires. So that the part of the installation that is believed by many to be the easiest and present the least potential for issues ends up being nearly as challenging as the gotchas on the low voltage side, and from a percentage standpoint is virtually a given and thus cumulatively worse, so that this part of the installation inevitably requires the most time-consuming repair by the professional mechanic afterward.

So you can see why carburetor work on this model is fraught with after-the-fact issues that require time, effort, cooperation and education, and in the end it's a losing proposition, even if the customer is willing to listen to advice, which he usually isn't. Thus carburetor rebuilders, even the most qualified, are reluctant to do carbs for any points model-- the GL1000 is simply the "posterboy" for all points ignition Hondas; you can add CB350/400, CB500/550; and CB750 to this as they present many of the same challenges in their ignition systems-- because owners of these bikes just don't understand them and perversely won't accept direction from those who do.

Don't discount the benefit that knowing these bikes offers when it comes to tuning them. There is little that is intuitive about it, and even less that you will find on a user forum. Check out this video showing how a properly-fettled GL1000 should run and sound. GL1000 video


Last updated August 2021
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