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Post by billwill on Mar 29, 2024 18:47:18 GMT -5
Working on the scoot (1999 Zuma) this week and have been battling some issues getting up to top speed (for the entire build). I’ve done the typical things like check tire pressure, brake drag, pulley travel and trans tuning, etc. When I was checking rear wheel free spin today noticed what I thought was the rear brake dragging. It may have gotten more significant over time without me knowing, but comparing to my other scooter, it is indeed significant. Not like the rear brake is applied, but enough to make me look into it. It’s my understanding that the rear wheel should spin pretty freely and if you give it a good spin, will continue for several more turns. In my case, it would only free spin for about less than a quarter turn. Come to find out, it actually wasn’t the rear brake but the gearbox. Taking apart the gearbox, I notice the rear hub will spin freely with the cover and primary gear off but when I put it on and tighten specifically the bolt in the top left corner, this introduces significant friction and drag. At first I was thinking I had pressed the secondary on too far, and I may have, so I pressed it apart a bit. I also thought I may have installed the washer and spring washer wrong but even removing those completely there is still drag. Current primary gears are Doppler 15/50. Any ideas here? Could something be bent or a bearing worn? Really stumped with this. Some pictures of the current state of affairs, if anyone can notice anything off:      |
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Post by 190mech on Mar 30, 2024 4:10:07 GMT -5
Seems like one of the shafts is side loading a bearing, try each shaft one at a time to find the problem. A second gasket may help, a small amount of side play should be on all the shafts.
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Post by 90GTVert on Mar 30, 2024 5:25:30 GMT -5
Sometimes it can be as simple as shimming or gasket thickness. If I tighten the bolts and it won't spin freely, the first thing that I try is removing the shim if there's one in there. If that makes it spin well, then I leave the shim out or use a thicker gasket.
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Post by billwill on Mar 30, 2024 6:36:42 GMT -5
Seems like one of the shafts is side loading a bearing, try each shaft one at a time to find the problem. A second gasket may help, a small amount of side play should be on all the shafts. I thought about trying a new gasket but didn't know it was common to run more than one. That may help, thanks. Sometimes it can be as simple as shimming or gasket thickness. If I tighten the bolts and it won't spin freely, the first thing that I try is removing the shim if there's one in there. If that makes it spin well, then I leave the shim out or use a thicker gasket. Yep, tried all combinations of no shims, only one of each and both and still the same result. Stacking gaskets may do the trick. I pressed the primary out and wanted to just feel the bearing for that in the gear cover and it definitely feels "chunky." Here's a vid of me spinning it. Can you tell me if this looks like it's shot? Thanks guys. |
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Post by 90GTVert on Mar 30, 2024 6:57:25 GMT -5
You can try cleaning that out and lubing it with a little gear oil to see if it changes. If a bearing is suspicious to me, I'm changing it while I'm in there though. They aren't cost prohibitive enough to take chances on.
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Post by billwill on Mar 30, 2024 10:02:04 GMT -5
You can try cleaning that out and lubing it with a little gear oil to see if it changes. If a bearing is suspicious to me, I'm changing it while I'm in there though. They aren't cost prohibitive enough to take chances on. I’ll try that and see if it helps. Whatever the case, I’m chasing top speed right now with this thing and with a high revving race setup, can use all the performance I can afford. Just broke down and ordered a Polini gearbox cover. Was reading up on it and apparently it lubricates better and is one of the best for low friction, free spin. Really hoping this ends up being what has limited my top speed. I’ve done extensive tinkering with the transmission and testing different contra springs, rollers and pulleys. I was only seeing a max speed of about 60-62mph with the mxs race cylinder. This setup should be good for mid to high 70s. |
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Post by snaker on Mar 30, 2024 10:35:44 GMT -5
Watched the video and yeah, it sounds bad.
You call it the primary gear bearing. Is that the input shaft (that the CVT driven pulley rides on?)
If so, that bearing spins as fast as the engine bearings, faster if the CVT crosses the 1:1 ratio.
So yeah, that bearing spins fast, and needs to be very healthy
A lot of rigs have a bearing in the CVT cover that supports the other end of that input shaft
I don't notice a shaft end stub on yours (if your showing the input shaft)
Again, if so, your input shaft has more stress on it than some rigs have.
Even more important to have a healthy bearing there.
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Post by billwill on Mar 30, 2024 12:49:21 GMT -5
Watched the video and yeah, it sounds bad. You call it the primary gear bearing. Is that the input shaft (that the CVT driven pulley rides on?) If so, that bearing spins as fast as the engine bearings, faster if the CVT crosses the 1:1 ratio. So yeah, that bearing spins fast, and needs to be very healthy A lot of rigs have a bearing in the CVT cover that supports the other end of that input shaft I don't notice a shaft end stub on yours (if your showing the input shaft) Again, if so, your input shaft has more stress on it than some rigs have. Even more important to have a healthy bearing there. Yep that’s the one. And yeah my vento triton has a bearing in the cover. I was eying up the Polini cover too and it makes sense why it is so expensive now. They actually have a specific nut that holds the clutch on that sits inside of a third bearing on their case cover. Glad I just went ahead and ordered the Polini gear box cover. Might snag the Polini cvt cover down the road too. |
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Post by oldgeek on Mar 30, 2024 16:28:48 GMT -5
Looks to me like the Primary bearing is not entirely seated, that would cause side loading when the cover is tightened up. Try bolting it up with nothing but Primary shaft installed and see if it alone still binds.
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Post by billwill on Mar 31, 2024 8:04:24 GMT -5
Looks to me like the Primary bearing is not entirely seated, that would cause side loading when the cover is tightened up. Try bolting it up with nothing but Primary shaft installed and see if it alone still binds. I was thinking this too but it is apparently normal for it not to sit flush with the cover. Even with it not bolted up, the bearing doesn’t spin too freely. It could be that it is just not fully seated and having bolted it up this way caused the bearing to wear funny. |
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Post by oldgeek on Mar 31, 2024 8:24:40 GMT -5
Looks to me like the Primary bearing is not entirely seated, that would cause side loading when the cover is tightened up. Try bolting it up with nothing but Primary shaft installed and see if it alone still binds. I was thinking this too but it is apparently normal for it not to sit flush with the cover. Even with it not bolted up, the bearing doesn’t spin too freely. It could be that it is just not fully seated and having bolted it up this way caused the bearing to wear funny. I agree it does not sit flush with the cover, but yours appears to protrude more than is should. Could be just the way the picture looks. And yes that is what I was thinking, side load could cause weird bearing wear. |
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thatmint240
Scoot Enthusiast
Popping up the 2 stroke
Posts: 112
Location: Chicago, Illinois
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Post by thatmint240 on Apr 3, 2024 14:16:31 GMT -5
My rear axle bearing (not sure if thats the correct name, but the largest bearing that is on the axle for the rear wheel) started to seize and i had similar issues until i replaced it with a high quality one from All-Balls Racing. Just cross referenced the bearing number in the manufacturer repair catalogue.
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Post by billwill on Apr 5, 2024 7:13:15 GMT -5
My rear axle bearing (not sure if thats the correct name, but the largest bearing that is on the axle for the rear wheel) started to seize and i had similar issues until i replaced it with a high quality one from All-Balls Racing. Just cross referenced the bearing number in the manufacturer repair catalogue. Apparently this issue with bearings going out in the gearbox is rare but it does happen. I went ahead and replaced the gear cover with the Polini part. There was still some of what seemed like drag putting things together and tightening them down but with the rear wheel all back on and things fully put together, it is significantly less drag. It could have been some rear brake drag as well. The two videos below show the before and after. |
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