Wide ratio gearbox

Joined
Oct 28, 1999
Messages
30
Likes
0
#1
I am keen to get back into off road riding after 1 year of concentrating on other things. I had more than 1 KDX and a DRZ400 previously, but I am very interested in a KX/CR/RM for this round. My question is, just how 'wide' are the enduro bikes wide ratio boxes. I did a test ride on a ktm exc 200 and 250, and both felt top end wise not really any faster than a KX/CR. Wat are your experiences concerning top speed runs ?
 
Joined
Mar 15, 2000
Messages
396
Likes
0
#2
KDXer said:
I am keen to get back into off road riding after 1 year of concentrating on other things. I had more than 1 KDX and a DRZ400 previously, but I am very interested in a KX/CR/RM for this round. My question is, just how 'wide' are the enduro bikes wide ratio boxes. I did a test ride on a ktm exc 200 and 250, and both felt top end wise not really any faster than a KX/CR. Wat are your experiences concerning top speed runs ?
I own a 2004 YZ250 two stroke and a 2003 KTM250exc.

4th gear on the KTM is same as 5th on YZ, both numerically and in top speed as recorded by my ICO enduro computer.

Buy the KTM.....
 

fuzzy

Subscriber
Joined
Jul 26, 2002
Messages
447
Likes
0
#4
The real benefit to a wide trans is having a granny first and still having MX or greater top speed...
 

KaTooMer

Subscriber
Joined
Jul 28, 1999
Messages
435
Likes
0
#5
fuzzy said:
The real benefit to a wide trans is having a granny first and still having MX or greater top speed...
True - the first two gears on the 2-stroke KTM's are the same whether it's an MXC or EXC. The disadvantage (in my mind, at least) is the wide EXC gap between 2nd and 3rd. I always felt that 3rd gear on my old EXC was too high for most of my trail work, but 2nd gear wasn't quite high enough. I've solved that on my MXC and my KX by going with a 14/50 sprocket combo. For some, that's a bit tall for 1st and 2nd, but it gives me more workable 2nd and 3rd gears. But the wide ratio trannies still have more top end speed. So it's a tradeoff. In a perfect world the 250/300EXC would be a 6-speed, with 1st-5th being the close ratio of the MXC, and 6th gear being "overdrive".
 

fuzzy

Subscriber
Joined
Jul 26, 2002
Messages
447
Likes
0
#6
the first two gears on the 2-stroke KTM's are the same whether it's an MXC or EXC
Yeah, I never realized that until I looked at your spreadsheet. It's slightly more informative than KTM's website :)

My WR had that same EXC gap syndrome. I re-geared in the other direction which made a 1st gear worthy of pulling a stuck jeep out, but 3rd is sweet now. Since the dang thing would probably hit close to 100 with the stock gearing I had some top to lose. I think the 5th gear could be taken out and sold as new...

I've read about folks swapping the WR450 5th gear (and some the whole WR trans) into the new YZ250's. They can then re-gear to suit and the 5th will make a nice overdrive gear.
 
Last edited:
Joined
Feb 28, 2004
Messages
153
Likes
0
#7
Hey guys, I found another old thread to bring back to the top. I know MX bikes werent built for all out top speed, but I love going fast and would like to drag race other bikes if it ever came to that. What I want to know is how much faster would the top speed get with each tooth you go down on the rear sprocket, or up on the front sprocket? And how small can you go on the rear sprocket. If stock is 49, is there a 48, 47, 46, 45, 44, ...?? I am also wondering what the top speed is right now on my BONE STOCK 03 YZ250. Also, what is the stock gearing on my bike, is it 14/49? Thanks for the replies. Mike :ride:
 
Joined
Aug 15, 2000
Messages
224
Likes
0
#8
Mike's 2003 YZ250 said:
What I want to know is how much faster would the top speed get with each tooth you go down on the rear sprocket, or up on the front sprocket? And how small can you go on the rear sprocket. If stock is 49, is there a 48, 47, 46, 45, 44, ...?? I am also wondering what the top speed is right now on my BONE STOCK 03 YZ250. Also, what is the stock gearing on my bike, is it 14/49? Thanks for the replies. Mike :ride:

I don't have the '03 specs, but if they are the same as the '04, and I think they are, (stock gearing is 14/49) your YZ probably will not go much over 70 mph, if that (but opinions will of course vary).

You should be able to easily find 48 & 47 teeth sprockets. Smaller than that aren't as popular but they do exist, I run a 45 on my CRF in some races. You should also be able to fit a 15 tooth counter sprocket on your bike...



An easy calculation on the gearing changes is dividing the # of teeth changed by the original. So if you go from 49 to 47, you changed gearing (and top speed) by 2/49, or slightly more than 4%, going to 15 from a 14 counter is a much bigger change, 1/14 or about 7%.

If you wanted to find the max. top speed your YZ is capable of 15/45 gearing will probably get you there, this is almost 17% taller and should get you into the 90mph range (but opinions will vary on this also).


Hope this helps.
 
Joined
Feb 28, 2004
Messages
153
Likes
0
#9
Excellent reply. The bike stock has so much torque down low, it just seems to make sense to take away some of it there and add it to the top end. It pulls a wheelie with so much ease in the first 3 gears, I figure I wouldnt mind giving up some of that and at the same time add some speed to the high speed runs. I guess its all in what you like to do with the bike. Great reply, I look forward to reading some more. Oh, by the way, I dont disagree that the top speed is only 70mph or so, but I read in another thread somewhere on here that it was more like 77. I hope its more like 77. :laugh: Mike :laugh:
 
Joined
Mar 16, 2003
Messages
50
Likes
0
#10
Im willing to bet that almost all MX bikes that roll off the showroom floor wont go much more than 75 MPH stock...a friend of mine is a police officer and has a radar gun that we used to clock a few different bikes. My 426 with stock gearing(14/49) did 78 MPH on asphalt...when i put a 15 tooth front sprocket it jumped up to 85. With 15/47 it did 88. His YZ 250 did 74 completly stock, but after a gear change did 91 but was a nightmare to start off in 1st gear. I guess it all depends on what you want to do with it...you can make an MX bike do 100MPH, but your going to suffer when the going gets slow!!
 
Joined
Feb 28, 2004
Messages
153
Likes
0
#11
Jeffro, very good info. This is the kind of info I am lQQking for. Do you by any chance remember what gearing your friend with the YZ250 had when he went 91mph?? Is 15 the biggest you can up to on the front? When you say it was a nightmare to start off in 1st gear, was it really that bad? You mean it couldnt even pull a wheelie anymore in 1st gear? Thanks for the replies. Mike :cool:
 
Joined
May 4, 2004
Messages
2,431
Likes
0
#12
fuzzy said:
Ive read about folks swapping the WR450 5th gear (and some the whole WR trans) into the new YZ250's. They can then re-gear to suit and the 5th will make a nice overdrive gear.
Aren't the YZ250's already 5-speed? Or did you mean the YZ450? I'm curious because I have a 450 and would like to get 5th gear back.
 
Joined
Mar 16, 2003
Messages
50
Likes
0
#13
You could easily still pull a wheelie, but its like taking off in 2nd or 3rd gear...if memory serves me correctly he was running 15/46. As for the gear up front...the 15 tooth is the biggest i could run without having to eliminate the case guard and if i ever threw a chain with it removed, it could spell disaster. For me, 15/49 is plenty fast enough for most desert riding, and still enough get up and go to ride fast motocross tracks.
 
Joined
Aug 15, 2000
Messages
224
Likes
0
#14
YZ165 said:
Aren't the YZ250's already 5-speed? Or did you mean the YZ450? I'm curious because I have a 450 and would like to get 5th gear back.

He is talking about the YZ 250, it is a 5 speed but the WR 5th gear is about 12% taller. The WR and YZ 250 gears should be interchangeable...