Transmission work (Suzuki Burgman)

[The Atomic Ass]

I had an impromptu transmission overhaul session this afternoon, that upon 6 miles of testing, yielded some fruit that may get me closer to my current goal of 80mpg.

I had initially opened the rear cover merely to change out the very old, (19,500 miles), final drive oil. I ended with no sludge, but dark grey oil that was obviously done. Flushed the transmission and refilled with Royal Purple gear oil at 75w90. (For those that aren't familiar with the Burgman 400, Suzuki calls for 10w40 for the final drive). This final drive also has a vent tube, that for no reason I can figure goes into a small cubby hole on the transmission cover. It has no protection from the elements, and probably accounts for most if not all of the gunk in the oil. I placed a K&N style filter on the end of this hose, and I intend in the future to replace it with a sealed pressure relief system.

Then I figured, since I was already there, I'd go ahead and pop the cage off and inspect the belt. After getting that off, I figured, why not? I'll pop off the pulley's and have a look. A few hours later, I had the analog scale out, measuring the roller weights, which came out between 18.7 and 18.9 grams each. I glued 7 gram tire weights into the center of 4 of these to increase their weights to 26 grams, and now my speed/RPM ratio is much better. In addition to the lower RPM's, the transmission resists "downshifting" more when applying throttle, so I can accelerate with a wider throttle opening at lower RPM's than previously, which is what was giving me some grief on a few hills.

I ended up putting the old belt back on, as it's not cracked, shows no indications that it's going to break soon, and even if it does, I've got a new one ready to go in at a moments notice.

All in all, I have a slightly more-drawn out clutch lockup, (the clutch exists between the transmission and final drive), but significantly lower RPM's at most speeds, a 1mph higher clutch release under DFCO, and a noticeably, but not measured, coasting distance due to the new final drive oil. With only 4mpg remaining to my goal, I feel confident that my next fillup will yield the magic 80mpg.

[janvos39]

Sounds to easy to be true but I hope your are right. Something I will implement as well as you have your positive result.

[dcb]

That's a pretty good deal for $0.25 worth of fishing weights

[The Atomic Ass]

Originally Posted by janvos39

Sounds to easy to be true but I hope your are right. Something I will implement as well as you have your positive result.

I would tend to think the alterations you are making to your final drive would have the same effect, and that your taller first gear would make for basically the same clutch behavior. I think with the overall massive (in my eyes) change that it made for my clutch activation I would not want to go much farther towards making it harder to take-off. It doesn't want to start up a hill very well, but it's tolerable. I just try to avoid stopping on hills.

Given the option, I'd wish for all 8 of the weights to be around 26 grams, and were prevented from moving outward until the clutch locked up. That would really be the best of both worlds.

Though if I had an infinite amount of money, and no desire to rid myself of oil consumption, I'd probably vetter-ize and re-gear a BMW G 650 Xcountry. Ahh dreams...

[The Atomic Ass]

Originally Posted by dcb

That's a pretty good deal for $0.25 worth of fishing weights

Tire weights, actually. The stick-on variety. I bought a 4kg+ box of them some years back when I got my first bike and said ta' hell with the high prices for tire changes.

[janvos39]

Gear change mechanism is not ready, but I think I go testing the 5% higer first gear ratio first to get an idea of how the bike takes off. If that leaves room for heavier pulling I can do your 7 gram trick additional.

[MetroMPG]

Very cool, simple mod, Mr. Ass.

[The Atomic Ass]

As a further modification to the transmission, I'm now thinking about a manually actuated clutch to replace the centrifugal unit. Anyone know how I might go about this?

[dcb]

LOL, I was waiting for you to tell us

It's a belt, right? Put on a longer belt and an idler pully on a spring loaded lever that you can remove the tension with a hand lever (pully on bottom).

[The Atomic Ass]

Originally Posted by dcb

LOL, I was waiting for you to tell us

It's a belt, right? Put on a longer belt and an idler pully on a spring loaded lever that you can remove the tension with a hand lever (pully on bottom).

Doesn't work with the CVT. The CVT automatically tensions the belt between the 2 pulleys. And the clutch is on the OUTPUT of the transmission.

It's weird, I know.

Anyway, did not get the FE increase that I wanted, but I've also had worse than normal driving conditions, including one 13-mile trip that was just cold enough I think to trip my ECU into winter mode for the trip.