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Post by humanshield on Jul 29, 2018 18:48:49 GMT -5
Do you have a tachometer?
I got the exact same gear set you did. The noise is bearings. I ordered new bearings and will install them soon. The gears meanwhile have quieted down and smoothed out considerably. But I still have a bad bearing.
As far as top end.......
so far I've only tried 7gr and 6gr rollers. (I didn't have any 5gr or 4 gr rollers on hand)
They should be here next week some time and I'll try those.
I'm actually glad to hear yours is doing ok. Probably just means I need lighter rollers. Dexameth had also said it would take lighter rollers.
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Post by golfmech on Jul 29, 2018 19:04:30 GMT -5
Rollers definitely help. I don't have a tach I wish I did. I have a new issue though. after changing to a larger tire today I lost 1-2mph off my top end kind of the opposite affect I thought it would have so now I'm really considering going to a 50mm bbk. I feel like I've gotten as much speed I can out of tuning and now it's just down to a power issue
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Post by humanshield on Jul 29, 2018 20:18:37 GMT -5
You know, maybe that's it. My scoot already had 12" wheels. Maybe the 2.88 will work with 10" wheels but not 12" wheels? (with 4 or 5 gram rollers)
My motor with 50mm BBK "should" have more torque to push the taller gears. But it also depends on compression. I keep mine around 170ish.
With stock gearing my top speed according to GPS was 47.5 (tucked and zero wind) Now it's 40. But the RPMs are 2000 less
I'm installing 5 gram rollers when they get here. Will let you know the results.
I'm also still considering dropping back to a 3.12 final gear ratio 15/51 gears.
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Post by golfmech on Jul 29, 2018 22:50:45 GMT -5
I'm bouncing 39-40 top speed now. before the tire swap it would bounce 41-42. I switched from a 100/60-12 tire to a 110/70-12 tire. I really need to figure out my Final drive ratio I'm almost certain the other two gears are different from yours since I had to modify the new set to fit. I'll count bell housing rotations to tire rotation and figure it out tomorrow. I'm still amazed you had a top speed loss because even with my current setup I'm at a 5mph gain than with the factory gears.
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Post by humanshield on Jul 30, 2018 9:50:53 GMT -5
have you seen this? Pretty darn cool. Tire Size Comparison CalculatorYou went from a 16.72" diameter tire to a 18.06" diameter tire. The gears just can't push it apparently. What you really need is a tachometer so you can see the RPM's at different speeds. My goal is to hit 50 around 7,800RPM. My 5 gram rollers are out for delivery so I might be able to try them later today (mail arrives here around 5pm) Here's my Tach I installed a few years ago...still working perfectly.  
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Post by humanshield on Jul 30, 2018 10:00:11 GMT -5
I just found this post of mine while searching for my tachometer pictures...... Now that I have a reliable tachometer I can see what rpms I'm pulling at speeds. 38 mph (actual) = 6,000rpm 44 mph (actual) = 7,000rpm 13 inch wheels 130/60 tires This is very puzzling. Seems I had pretty much the RPMs and speed I wanted with the stock gearing back in 2015  And I have 13" tires. not 12"
Now I'm wondering if all I really needed was a new belt? The rollers were fairly new and variator is the same.
Now I'm probably gonna have to go drop $200 and go buy myself a press.
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Post by humanshield on Jul 30, 2018 13:53:33 GMT -5
honestly I just wacked the old gear out with a hammer then used a vice to get the new gear started and a hammer again to drive it home.
Ya know, it surprises me that you didn't mushroom out the shaft doing this  |
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Post by dexameth on Jul 30, 2018 16:03:07 GMT -5
If he was using a brass punch then it would damage the punch before the gear shaft... I've thought about that technique but worried myself. I normally took a $20 bill and my gears to a local car garage and a couple hours later I'd go scoop them up. Most garages would tell me their press was too large so I just went from one to the next until I found a good guy.
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Post by humanshield on Jul 30, 2018 16:21:36 GMT -5
Welp, My 5 gram rollers arrived and I tried them...... Barely any change. Not nearly enough. I can tell the motor is still lugging under the stress of trying to push these tall gears. I'm not gonna be able to get the engine's torque & horsepower dialed in optimally with these gears. So.... I'm going back to the 3.71 stock gears (14/52) and see why I was able to do 44 @ 7,000rpm back in 2015 and before all these changes I was like 7,000rpm @ 37mph. Probably just a worn out belt I bet. (grrrr) And this is with a 50mm BBK, Bigger valve head, cam and a few other light mods to the intake. Golfmech, since you don't have a tach, I'm gonna guess your engine rpms are too low which would account for your lower top speeds. You gotta get it so that it reaches peak horsepower and torque as it reaches top speed. 2.88 gears I think move the sweet spot too far uphill. (unless you go stroker and/or have insane compression) My advice after all this would be to steer clear of the 17/49 gear set unless you've done some really big mods to your scoot. Another option is to get a 3.12 set of gears (16/50) or 3.40 (15/51) If I can roll along at 40mph @7000rmp I'm happy. I should be able to since that what it was doing in 2015. I would definitely consider a change to 15/51 (3.40) without hesitation as that can be adjusted through the variator enough to compensate I would think. The 16/50 (3.12) gear set is getting awfully close to the 2.88 and I could stil end up with a slight mismatch in the gearing and power curve.
Changing roller/slider weights can help, but there are still limits to how much gear you can push with a given amount of torque and horsepower.
If someone has a set of 15/51 gears you want to sell shoot me a PM. That's what I'm looking for now.
This has been an educational journey. Hope it helps someone somewhere. And remember folks.......YMMV |
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Post by dexameth on Jul 30, 2018 17:10:35 GMT -5
So you still haven't tried a new belt??
All this great info and testing and still the old belt...
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Post by humanshield on Jul 30, 2018 17:33:08 GMT -5
So you still haven't tried a new belt?? All this great info and testing and still the old belt... If I had changed the belt BEFORE testing with the 5 gram rollers I wouldn't know if it was the rollers or belt that made the difference.
The belt looks fine. Not even sure it's a factor. Has maybe 1500 miles on it. The whole belt idea is just a last resort kinda thing.
Besides, if changing the belt will lower RPMs, that's the last thing I need right now. With the 2.88 gears RPMs are still down about 1500rpm.
Thinking out loud here...
The wider open the variator, the further the belt is squeezed out from the hub.....that's the equivalent of a larger front sprocket on a motorcycle....less torque more top end.The wider open the rear sprocket, the closer the belt to the hub, the equivalent of a smaller rear sprocket on a motorcycle. Less torque, more top end.
So a newer (or wider) belt will naturally result in better top end at lower RPM. As the belt wears, you lose top end and RPMs at the same speed will increase. Exactly what happened to my scooter.
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Post by dexameth on Jul 30, 2018 18:14:29 GMT -5
I mean, mine lowered when I did the up gear. So I lowered my slider weights to make up for it. I even played around with contra springs and found 1.5k to be ideal, help hold the motor in the powerband. I really think you can dial in these gears... Look at everything. Weights, belt travel, boss length, and springs.
Good luck man, as far as gears go I have found that short cae gears are one tooth off of lomg case gears. I swapped my short case gears into my lomg case when I got it and it was a tiny up gear, and I think it's exactly what you are looking for. If I had not let them rust I would give them to you.
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Post by humanshield on Jul 30, 2018 18:23:47 GMT -5
Seriously considering going to harborfreight tmrw and getting a 20ton press.
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Post by humanshield on Jul 30, 2018 18:24:56 GMT -5
I mean, mine lowered when I did the up gear. So I lowered my slider weights to make up for it. I even played around with contra springs and found 1.5k to be ideal, help hold the motor in the powerband. I really think you can dial in these gears... Look at everything. Weights, belt travel, boss length, and springs. Good luck man, as far as gears go I have found that short cae gears are one tooth off of lomg case gears. I swapped my short case gears into my lomg case when I got it and it was a tiny up gear, and I think it's exactly what you are looking for. If I had not let them rust I would give them to you. Thanks man.
I'm gonna post in the wanted section.
I REALLY would like to get a hold of a set of 15/51 gears
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mistab
Scoot Junior
BRRRAP BRRRAP
Posts: 7 
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Post by mistab on Jul 31, 2018 13:09:39 GMT -5
I've kind of been figuring out my problems with the 17/49 final drive gears. I swapped out my SSP-G performance variator, ramp, and glide keys for stock which brought back my top end RPMs. Definitely something wrong with the SSP-G variator, which I suspect is either a loose glide key, or defect in machining from the factory. It now gets to the top end smoothly and has a higher RPM when it gets there. Still a top speed of 43mph, but now at 8100rpm unlike the 7100-7300rpm before. I'm thinking of trying 7.5g sliders instead of the 7gs for more top end, or just going back to the stock final drive gears...
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