lcrken
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- Joined
- Mar 15, 2009
- Messages
- 5,037

We've had some good information lately in a couple of other posts on belt drives, but I thought I'd post this one separately to address a question I've had for a while. I'm particularly hoping for answers from folks who've used the Gates Poly Chain Carbon or Polygrip GT3 belts, like G81 Can Cycle (John) and comnoz (Jim).
I've used HTD belt primaries for decades, and been very happy with them, but they do have some disadvantages. From my standpoint, the principle one is that I need at least a 40 mm wide belt for the higher horsepower Commando engines, and that doesn't allow easy fitting of the stock alternator. I never cared much on the race bikes, which don't use a alternator, but now that I'm more involved in street bikes, it's a real disadvantage. The newer belt designs, i.e. Gates Polygrip GT3 and Poly Chain Carbon, need to have pulleys with the GT2 tooth profile, at least according to Gates. I've seen at least one Commando primary drive using HTD profile pulleys with a GT2 profile belt, and it seemed to work OK.
So, my question is, does anyone know if it is practical to use the newer profile belts with the older HTD pulleys? The reason I'm asking is that I suspect that Gates might be guilty of telling us they aren't compatible for business reasons, not engineering ones. And I could be wrong on that. Anybody with experience in this area willing to offer up some real world data? If we can use the newer belt technology on existing HTD drives, that would be a real plus.
FWIW, I'm not interested in the alternate trapezoidal belt drives. I tried them decades ago on a race bike, and had disastrous results.
Ken
I've used HTD belt primaries for decades, and been very happy with them, but they do have some disadvantages. From my standpoint, the principle one is that I need at least a 40 mm wide belt for the higher horsepower Commando engines, and that doesn't allow easy fitting of the stock alternator. I never cared much on the race bikes, which don't use a alternator, but now that I'm more involved in street bikes, it's a real disadvantage. The newer belt designs, i.e. Gates Polygrip GT3 and Poly Chain Carbon, need to have pulleys with the GT2 tooth profile, at least according to Gates. I've seen at least one Commando primary drive using HTD profile pulleys with a GT2 profile belt, and it seemed to work OK.
So, my question is, does anyone know if it is practical to use the newer profile belts with the older HTD pulleys? The reason I'm asking is that I suspect that Gates might be guilty of telling us they aren't compatible for business reasons, not engineering ones. And I could be wrong on that. Anybody with experience in this area willing to offer up some real world data? If we can use the newer belt technology on existing HTD drives, that would be a real plus.
FWIW, I'm not interested in the alternate trapezoidal belt drives. I tried them decades ago on a race bike, and had disastrous results.
Ken