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Post by KSR Moto on Sept 4, 2018 11:16:47 GMT -5
Which gears I need to replace from 10" case 139qmb to 12", to make the engine spin at lower rpms and getting higher speed?
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Post by gsx600racer on Sept 4, 2018 17:43:17 GMT -5
If you don't have the torque/power to pull taller gears(less rpm/more mph) chances are you will end up being slower than stock gears.
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Sept 4, 2018 19:26:39 GMT -5
Good starting point would be to tell us what your driving around top speed and RPM are. If you don’t have the power to pull lots of revs with the stock gearing, going to a lower overall ratio most likely won’t be of value to you. Second, I don’t understand what you are asking exactly. Are you planning to mount a 12
“ tire to replace a 10”?
In general, unless you have a fair number of mods on your bike including a BBK and bigger carb, I doubt that a switch in gearing will do you any good
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Post by KSR Moto on Sept 5, 2018 8:08:28 GMT -5
Good starting point would be to tell us what your driving around top speed and RPM are. If you don’t have the power to pull lots of revs with the stock gearing, going to a lower overall ratio most likely won’t be of value to you. Second, I don’t understand what you are asking exactly. Are you planning to mount a 12 “ tire to replace a 10”? In general, unless you have a fair number of mods on your bike including a BBK and bigger carb, I doubt that a switch in gearing will do you any good My scoot has a 44mm BBK, performance exhaust, pod filter etc It has a long case 139qmb engine with 12" wheels and I want to install gears form the same engine but with short case(10" wheels) to increase my output shaft speed My engine currently revvs too high, so I want to change gearing |
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Sept 5, 2018 8:47:21 GMT -5
OK, if I’m reading that right, you cuttingly have 12” wheels, and you are getting too many Rpms, and now want to go to a 10” wheel? Of course a 10” wheel would make your RPMs go up. In what speed range are you getting to many RPMs? The reason I ask is if taking off at WOT, your RPMs go too high, the first thing you would want to do is go to heavier weights/ sliders in the variator. If your in a comfortable RPM range (say 7500) while accelerating, but as you get to top speed your reving too high, (say 9000 at 45mph) then a different finel drive would be of advantage.
If your saying you are currently running a 12” wheel and plan on going to a 10” wheel, and your RPMs are already high, then going to a 49/17 final drive may be of value. I’m sorry that my mind is a bit clouded today from a few to many adult beverages, and don’t excatly understand what you are looking for. Again the RPMs at speed you are currently getting would be helpful. Example, let’s say you are going 45 mph at 8500 rpms. This would give a better picture of where your final drive ratio should be. Your RPMs when accelerating in the 5 mph to 35 mph range would tell us a bit more about if your weights are right.
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Post by KSR Moto on Sept 5, 2018 9:06:23 GMT -5
OK, if I’m reading that right, you cuttingly have 12” wheels, and you are getting too many Rpms, and now want to go to a 10” wheel? Of course a 10” wheel would make your RPMs go up. In what speed range are you getting to many RPMs? The reason I ask is if taking off at WOT, your RPMs go too high, the first thing you would want to do is go to heavier weights/ sliders in the variator. If your in a comfortable RPM range (say 7500) while accelerating, but as you get to top speed your reving too high, (say 9000 at 45mph) then a different finel drive would be of advantage. If your saying you are currently running a 12” wheel and plan on going to a 10” wheel, and your RPMs are already high, then going to a 49/17 final drive may be of value. I’m sorry that my mind is a bit clouded today from a few to many adult beverages, and don’t excatly understand what you are looking for. Again the RPMs at speed you are currently getting would be helpful. Example, let’s say you are going 45 mph at 8500 rpms. This would give a better picture of where your final drive ratio should be. Your RPMs when accelerating in the 5 mph to 35 mph range would tell us a bit more about if your weights are right. I have 9000rpm at 45mph, short case should have taller gearing to compensate for smaller wheel(10") I have a bigger wheel 12" but I want a 10" gearing to reduce my rpms |
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Sept 5, 2018 10:24:42 GMT -5
great! that makes it clear enough so even I can understand it. IMHO the the 49/17 final drive ratio would be an advantage to you. Note, you will need access to a press to change this out.
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Post by GrumpyUnk on Sept 5, 2018 11:00:45 GMT -5
Check the tech section searching for a post ... where the gears were changed without use of a press. FWIW.
Still too dang fast for me...
tom
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