I found this neat site where you can load all the info on bikes primary gears, sprockets and tranny ratios and it will give you overall ratios. Really helps tell you what sprockets will be needed when converting a 6 speed KTM to 5 speed for MX.
FYI: It looks as though most 250's (new and old)and older 400's were set up with around a 20 to 22 overall gear ratio for first gear. Im running a 13/54(20.37)combo on my 70's 400's. I am converting a 74 250 and think I will go with 12/54 (22.07). For reference a 98 250 SX came geared at 19.88 and a 2007 came at 20.45.
125's seem to be down around 30 to 35. A 75 RM 5 speed came at31.08 and a 76 RM 6 speed came at 35.15. A 98 SX came at 30.04 and a 2007 SX came at 30.03.
This is really cool as you can also tell the gaps between gears to help you get it just right, and also compare other bikes and brands. I spent hours on this site!
Go to //www.nightrider.com and click on Motorcycle Performance, then click on Gear Ratios in the lower right side of this page.
I meant to put this under Penton Talk!
Quotequote:Originally posted by Mike Lenz
I found this neat site where you can load all the info on bikes primary gears, sprockets and tranny ratios and it will give you overall ratios. Really helps tell you what sprockets will be needed when converting a 6 speed KTM to 5 speed for MX.
FYI: It looks as though most 250's (new and old)and older 400's were set up with around a 20 to 22 overall gear ratio for first gear. Im running a 13/54(20.37)combo on my 70's 400's. I am converting a 74 250 and think I will go with 12/54 (22.07). For reference a 98 250 SX came geared at 19.88 and a 2007 came at 20.45.
125's seem to be down around 30 to 35. A 75 RM 5 speed came at31.08 and a 76 RM 6 speed came at 35.15. A 98 SX came at 30.04 and a 2007 SX came at 30.03.
This is really cool as you can also tell the gaps between gears to help you get it just right, and also compare other bikes and brands. I spent hours on this site!
Go to //www.nightrider.com and click on Motorcycle Performance, then click on Gear Ratios in the lower right side of this page.
Hey Mike, Running a 12/54 ratio on a 250 will give you a bike that will bring the front up very easily in third gear. On my 76 MC 5, I ended up running a 13/54 combination to smooth it out a bit, and it allows me to run gears 1st through 5th, instead of 2nd to 6th.
1976 MC 5 Original Owner
1982 Suzuki PE 175
2002 KTM 200 EXC
1976 Husqvarna 175GP
1979 KTM 250 GS (Project)
1981 KTM 250 (Project)
I want to run 2nd thru 5th to get rid of missed shifts between second and third and also because I cant gear my bikes up enough using first for me, even with 15/40 gearing which is what I run with a six speed for MX. Runnibg 12/54 using second thru 6th will be much taller gearing.
Hey guys here are the numbers for the 70's KTM motors to put into the gear ratio calculator.
Engine sprocket: 25 (20 on 125 and newer 175)
Clutch sprocket: 69 (72 on 125 and newer 175)
Transmission sprocket: This is the counter shaft sprocket your using
Raer wheel sprocket you are using
Tranny Ratios are:
2.571 first
1.777 second
1.333 third
1.041 fourth
.884 fifth
.75 sixth
.724 sisth on 125 and newer 175
Plug these numbers in and you will get your overall gearing.
Hey guys here are the numbers for the 70's KTM motors to put into the gear ratio calculator.
Engine sprocket: 25 (20 on 125 and newer 175)
Clutch sprocket: 69 (72 on 125 and newer 175)
Transmission sprocket: This is the counter shaft sprocket your using
Raer wheel sprocket you are using
Tranny Ratios are:
2.571 first
1.777 second
1.333 third
1.041 fourth
.884 fifth
.75 sixth
.724 sisth on 125 and newer 175
Plug these numbers in and you will get your overall gearing.