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Post by humanshield on Jul 27, 2018 14:09:57 GMT -5
Golfmech, I'm suspecting that you're probably not thrilled with results of your gear swap? Trying roller or slider swaps maybe?
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Post by humanshield on Jul 27, 2018 14:13:54 GMT -5
Did you remember to install the plastic washer? The gears with spiral cut teeth will tend to move in one direction, thrusted against the wall/bearing as the teeth mesh under pressure. If you left out the thrust washer or put it on the other side of the gear, you might get some noise. Did you turn the input shaft manually, or the clutch bell, to see how smooth it felt? If it is rough, take it apart again as it will not get better. I think if you look at the teeth as delivered you will not find they have rough spots that need to 'wear in' to become as quiet as before. If the teeth have damaged surfaces, they will not heal themself. They will always make noise. Compare teeth on the new gears to the teeth of the previous set. tom Yes on the nylon washer. Made triple sure it was in place.
I've ridden it now about 20 miles on the new gear set and already it's quieting down a bit. I think the noise I'm hearing is the bearings. I'm taking it back apart to check / replace the bearings. it was probably doing it before with the old gears, I just didn't check it before taking it apart.
I recommend to anyone changing the gears in the transmission to rotate the rear wheel without the clutch before removing anything just to have a baseline for comparison after you install the new gears.
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Post by humanshield on Jul 27, 2018 14:22:28 GMT -5
I don't think 2.88 gears are a good choice for even a 50mm BBK with cam. You need more engine power to push those tall gears. I've tried 6 gram rollers and still my top end is down from 47.5 to 42.6 (but at about 2,000rpm lower) I'm gonna try 5 gram rollers but I dunno folks..... I think the ideal gearing for a 50mm BBK with big valve head, A9 cam and a few other light mods is probably like 16/50 (3.12) and for a 47mm BBK with similar mods, probably 15/51 (3.40) Unfortunately (and to my surprise), neither is available. If I made this would anyone be interested ? I'd have to make at least 100 sets to make it worthwhile.
That gearset was a topic of debate for a while. I was always confused by claims of speed increase with deeper gears. I thought for a bit that perhaps the GY6 just didn't have the muscle to pull the stock gears to a good speed. Rather than just say it was wrong, I bought the gears myself and installed them on my SunL. Big surprise, I went slower. I did find that I was faster consistently, but not max speed for sure. I don't even know that most people would cruise faster consistently, because I'm and extreme example. I was 300lbs at that point, so I needed a lot more help than most would to keep speeds up. That's all documented in my SunL build thread. A while ago, that was the only gearset commonly available. Now you have a lot more choice and can get gears that really are good for higher speeds if you have the power to pull them. That's a big thing with scoots. It's not like my car with 500HP and 600TQ I can pull about any gears I want. You put some crazy tall gears in a scoot and you might find it can't even pull itself to go 40.
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mistab
Scoot Junior
BRRRAP BRRRAP
Posts: 7
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Post by mistab on Jul 27, 2018 14:31:20 GMT -5
I don't think 2.88 gears are a good choice for even a 50mm BBK with cam. You need more engine power to push those tall gears. I've tried 6 gram rollers and still my top end is down from 47.5 to 42.6 (but at about 2,000rpm lower) I'm gonna try 5 gram rollers but I dunno folks..... I think the ideal gearing for a 50mm BBK with big valve head, A9 cam and a few other light mods is probably like 16/50 (3.12) and for a 47mm BBK with similar mods, probably 15/51 (3.40) Unfortunately (and to my surprise), neither is available. If I made this would anyone be interested ? I'd have to make at least 100 sets to make it worthwhile. I'd be interested, I've got 2.88 gears in my 47mm setup with 7g sliders, and I pull ~7400-7500rpm at 42-43mph top end like yourself. They seem to be asking for just a little too much. I do wanna try 6g sliders though to see if it helps get in the powerband
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Post by humanshield on Jul 27, 2018 14:51:32 GMT -5
Note: I did find a source for a set of 16/50 gears in California. But they don't stock them and have to order them from overseas. They say about a month to get the gears after order.
$100 for the set
link16/50 Secondary Gear Set QMB139Anyone ever deal with this outfit?
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Post by humanshield on Jul 27, 2018 14:56:00 GMT -5
I'd be interested, I've got 2.88 gears in my 47mm setup with 7g sliders, and I pull ~7400-7500rpm at 42-43mph top end like yourself. They seem to be asking for just a little too much. I do wanna try 6g sliders though to see if it helps get in the powerband I'm surprised you can pull over 7,000rpm with 7 gram sliders. Does it take a while to get there? I have a 50mm BBK and cam and was pulling over 9000RPM with stock 14/52 (3.71) gearing but now with 6 gram rollers can only get 6500rpm but I didn't go that far. It just seems to flatten out there so I gave up pushing it.
Folks, unless you have a stroker QMB139 or some SERIOUS mods, 17/49 gears are not going to do you full justice imo.
Like I said above....and I welcome being corrected....
I think the ideal gearing for a 50mm BBK with big valve head, A9 cam and a few other light mods is probably like 16/50 (3.12) and for a 47mm BBK with similar mods, probably 15/51 (3.40)
You're gonna need some serious work done to push 2.88 (17/49) gears. A turbo charger might be advisable.
Again, I'm still gonna try 5 gram rollers (lightest I've tried is 6 gram), but my gut, set of the pants (haha) opinion is that 2.88 is a bit much for most of us.
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mistab
Scoot Junior
BRRRAP BRRRAP
Posts: 7
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Post by mistab on Jul 27, 2018 15:02:11 GMT -5
I'd be interested, I've got 2.88 gears in my 47mm setup with 7g sliders, and I pull ~7400-7500rpm at 42-43mph top end like yourself. They seem to be asking for just a little too much. I do wanna try 6g sliders though to see if it helps get in the powerband I'm surprised you can pull over 7,000rpm with 7 gram sliders. Does it take a while to get there? I have a 50mm BBK and cam and was pulling over 9000RPM with stock 14/52 (3.71) gearing but now with 6 gram rollers can only get 6500rpm but I didn't go that far. It just seem to flatten out there so I gave up pushing it. From a dig 3/4-WOT it stays around 6300-6500rpm, and at the shifting point (16-18mph) the RPMs start coming up to 7k and eventually flattens out at 7400-7500 until max speed of 42-43mph
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Post by humanshield on Jul 27, 2018 15:03:30 GMT -5
I'm surprised you can pull over 7,000rpm with 7 gram sliders. Does it take a while to get there? I have a 50mm BBK and cam and was pulling over 9000RPM with stock 14/52 (3.71) gearing but now with 6 gram rollers can only get 6500rpm but I didn't go that far. It just seem to flatten out there so I gave up pushing it. From a dig 3/4-WOT it stays around 6300-6500rpm, and at the shifting point (16-18mph) the RPMs start coming up to 7k and eventually flattens out at 7400-7500 until max speed of 42-43mph Do you think your top end was higher with the stock gearing? Mine was. But the high revs were making me cringe
Also, is it at all possible your tach could be off or do you have a top of the line tach?
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mistab
Scoot Junior
BRRRAP BRRRAP
Posts: 7
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Post by mistab on Jul 27, 2018 15:09:06 GMT -5
From a dig 3/4-WOT it stays around 6300-6500rpm, and at the shifting point (16-18mph) the RPMs start coming up to 7k and eventually flattens out at 7400-7500 until max speed of 42-43mph Do you think your top end was higher with the stock gearing? Mine was. But the high revs were making me cringe I can almost gurantee you it would be, and I'd swap back to the stock gearing if I hadn't just changed the gear oil . That was why I went to the 2.88 final drive... I was over-revving at the top-end no matter what
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Post by humanshield on Jul 27, 2018 15:55:05 GMT -5
Ok. seems we're on the right track. Exactly why I did it too. Unfortunately, noone had posted enough information for folks like us to be able to make good decisions.
(That I could find through searching.....it may be there but I failed to find it. If it's there could someone provide links? Thanks)
Maybe this thread can get stickied like the BBK threads for posterity sake. We do need to change the gear ratio....but we need something closer to 3.40 - 3.12. 2.88 is just too much unless you're going stroker or really radical mods to up the output. did you see the link I posted above? There is a company overseas (Portugal?) making a 16/50 gear set. Problem is, I'm not sure anyone has tried it. It's $100 with no return. Who knows if it's even machined properly? No specs are available on it.
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Post by humanshield on Jul 27, 2018 16:41:58 GMT -5
Another thing I want to look into the is Primary gear set. It could be that a 2.88 Secondary would be ok if the Primary set was changed also. When I have time I'll investigate that
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Post by dexameth on Jul 27, 2018 16:50:37 GMT -5
I know we talked on the phone earlier, but I wanted to chime in. I had installed my 49/17 gears on my 50mm non-stroked motor a while back. It was 50mm, big valve head, A9, GY6 Carb and intake (24mm) with a Koso variator, 6 gram sliders and I was seeing 50mph easy. 7800rpm was average with this setup. Rear wheel was a 140/70-10.
After the 52mm + stroker I went up to 7g sliders, Polini variator and same carb/intake but the SSP-G cam instead of A9 since the bearings were toast. I take off and get right to 7500rpm and maintain it, and if I tuck I can get to 56mph at around 8500rpm. This rear wheel is a 130/70-12.
I think you should play around with variator weights and variator boss lengths... it gets crazy after a while but all the little things matter. Even 1mm difference in belt thickness can be a few mph's. I even bought the Naraku variator shim kit to really get picky. I am actually using the Polini variator with STOCK boss (noth the one it comes with) and added .5mm of spacers to it. I then added a longer 738x18x30 belt and it's AMAZING. The 729 belt sits too low in the clutch and limits my gear range and take-off.
Lots to think about man, sorry if I'm rambling on but I'm always here to help... when I can.
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Post by golfmech on Jul 29, 2018 15:46:24 GMT -5
Mine are smooth as silk did you buy the same set I linked? The only thing I can think that you might have done wrong is pressed the new gear into the wrong side of your existing gear... being that the gear is angle cut and not straight it does matter what side you press it in from.. I would pull it apart asap and make sure the angle of the pressed gears are both going in the same direction
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Post by golfmech on Jul 29, 2018 16:02:21 GMT -5
Humansheaild I am actually happy with the gear swap acceleration is still good and I gained 6mph higher average top speed. So for $29.99 6mph feels like a good deal. Now today I swapped to a larger rear tire and I definitely need to play with weights again. I know eventually I'm going to do a 50mm bbk with bhv but for now I'm just trying to squeeze as much top speed out of the 47mm as I can. I live in a rural area with long straight roads so acceleration isn't a top priority.
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Post by golfmech on Jul 29, 2018 16:14:03 GMT -5
Something is wrong if your top speed dropped how on earth does my 47mm gain 5-7 mph But your 50mm loose that much. If you bought the same set as me the SMM logo on the new rear gear should be facing out if it's not your running them backwards. Also I switched from factory 8 gram rollers to 4.5 gram. To help get the rpm's back into the power band.
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