New rear gears "cogging"... quickest way to wear them in?
by: upfartoolate - May 11, 2015 22:03:40 GMT -5
Post by upfartoolate on May 11, 2015 22:03:40 GMT -5
Hi, all.
Ok, so I had Jan Vos fabricate new rear gears for me a while back, and I finally got some free time to install them, along with hybrid ceramic bearings.
After I got all the new bearings in, I put in the new rear gears and hand-turned the wheel axle without the gear cover in place, just to be sure everything worked the way it should. It did. Those micro-polished and tungsten-sulfide coated hybrid ceramic bearings are slick.
But, when I put the cover on and tried to hand-turn the rear gears from the wheel axle, they'd turn a bit, and lock up! Thinking I'd messed something up, I pulled the cover, checked the diagram in the service manual, made sure the bearings weren't seizing up, and checked the runout on the gear shafts. It was all good.
So, I tried again... and the same thing happened. Going around to the left-hand side of the bike, I slowly turned the Gear #1 shaft (the shaft that the clutch mounts on)... I could distinctly hear and feel three teeth on the input gear shaft (Gear #1) lightly scraping against the gear teeth on Gear #2.
Confused, I tried again. I pulled the gear cover off, and turned the wheel's axle and the input shaft. All was smooth, turned very easily. Put the cover back on... three gear teeth scraping.
The cover off again, I turned the wheel axle as I squeezed Gear #1 and Gear #2 together with my fingers... ah, that was the problem... three teeth on Gear #1 had been ground just a tiny, tiny bit thicker at their bases than the rest of the teeth when the gear was fabricated. With conventional bearings, you'd likely not even notice since the bearing play would allow the Gear #1 and Gear #2 shafts to move a tiny bit. But the hybrid ceramic bearings don't have much play at all.
So, I buttoned up the rear gears, filled it with 200 ml of Royal Purple 70W-140 Synthetic Gear Oil with SynSlide, and spent the next 8 hours using a ratchet wrench and an electric impact driver, spinning the rear gears in both directions from the input shaft and the wheel axle in an attempt to wear-in those three teeth.
By the end of the 8 hours, I could turn the wheel axle by hand and it wouldn't lock up anymore, but I could still feel a slight "cogging" as those three teeth in Gear #1 engaged with Gear #2. The gear oil had a lot of "glitter" in it when I drained it.
I opened the gear cover again, and I could clearly see the three offending teeth... all the other teeth had minor polishing on the outer ~70% of the teeth face, but those three were polished all the way into the crevice between the teeth. The three teeth sit next to each other, so Jan Vos may have made a mistake when he began cutting the gear, or when he was finishing.
So... should I just ride it and let the teeth wear in? Will it damage the gears to do so? I plan on riding gently until this "cogging" is completely gone.
Ok, so I had Jan Vos fabricate new rear gears for me a while back, and I finally got some free time to install them, along with hybrid ceramic bearings.
After I got all the new bearings in, I put in the new rear gears and hand-turned the wheel axle without the gear cover in place, just to be sure everything worked the way it should. It did. Those micro-polished and tungsten-sulfide coated hybrid ceramic bearings are slick.
But, when I put the cover on and tried to hand-turn the rear gears from the wheel axle, they'd turn a bit, and lock up! Thinking I'd messed something up, I pulled the cover, checked the diagram in the service manual, made sure the bearings weren't seizing up, and checked the runout on the gear shafts. It was all good.
So, I tried again... and the same thing happened. Going around to the left-hand side of the bike, I slowly turned the Gear #1 shaft (the shaft that the clutch mounts on)... I could distinctly hear and feel three teeth on the input gear shaft (Gear #1) lightly scraping against the gear teeth on Gear #2.
Confused, I tried again. I pulled the gear cover off, and turned the wheel's axle and the input shaft. All was smooth, turned very easily. Put the cover back on... three gear teeth scraping.
The cover off again, I turned the wheel axle as I squeezed Gear #1 and Gear #2 together with my fingers... ah, that was the problem... three teeth on Gear #1 had been ground just a tiny, tiny bit thicker at their bases than the rest of the teeth when the gear was fabricated. With conventional bearings, you'd likely not even notice since the bearing play would allow the Gear #1 and Gear #2 shafts to move a tiny bit. But the hybrid ceramic bearings don't have much play at all.
So, I buttoned up the rear gears, filled it with 200 ml of Royal Purple 70W-140 Synthetic Gear Oil with SynSlide, and spent the next 8 hours using a ratchet wrench and an electric impact driver, spinning the rear gears in both directions from the input shaft and the wheel axle in an attempt to wear-in those three teeth.
By the end of the 8 hours, I could turn the wheel axle by hand and it wouldn't lock up anymore, but I could still feel a slight "cogging" as those three teeth in Gear #1 engaged with Gear #2. The gear oil had a lot of "glitter" in it when I drained it.
I opened the gear cover again, and I could clearly see the three offending teeth... all the other teeth had minor polishing on the outer ~70% of the teeth face, but those three were polished all the way into the crevice between the teeth. The three teeth sit next to each other, so Jan Vos may have made a mistake when he began cutting the gear, or when he was finishing.
So... should I just ride it and let the teeth wear in? Will it damage the gears to do so? I plan on riding gently until this "cogging" is completely gone.
MPH), and the gears get noisier. You can't hear the "cogging", just the spur gear whine. The only time you can hear the "cogging" is when the rear gears are completely unloaded (ie: the clutch has disengaged and you're coasting), you can hear a slight rattle-like sound that, as you slow down, becomes apparent is the gear teeth clashing a bit.