ADVrider

Go Back   ADVrider > Bikes > Old's Cool > 2 smokers
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-09-2015, 05:45 PM   #1
Highgear250 OP
n00b
 
Joined: Apr 2015
Location: mishitgun
Oddometer: 3
help with gearing

Greetings, I'm new so please forgive me if this is the wrong spot to post.

I have a 1978 Suzuki TS-250 I'm slowly transforming into an adventurous Cafesportbob.
I'm wanting to change sprockets I just don't know how far to go. The gear commander calculator keeps giving me results of NaN...

My goal is to make 1st and 2nd gear more useful while bringing 65mph down from 5k to like 3k. I believe it currently has a 15 front 45 rear
Highgear250 is offline   Reply With Quote
Old 04-10-2015, 09:03 AM   #2
Highgear250 OP
n00b
 
Joined: Apr 2015
Location: mishitgun
Oddometer: 3
Really hoping for someone to chime in here. I managed to get a rough estimate off gear commander by using the preloaded specs for a 1980 ts 185, I then adjusted the "current" to my 250 specs, and used "custom" as a test field. I came up with switching from my current 15/45 to a 17/38 will give me the rpm range I desire. Big question though, do I have enough torque to get off the line still?

The Ts is geared super low in 1st and 2nd so maybe. Any input is appreciated
Highgear250 is offline   Reply With Quote
Old 04-10-2015, 10:54 AM   #3
Tim McKittrick
Beastly Adventurer
 
Joined: Dec 2003
Location: Wasilla Alaska
Oddometer: 1,773
Gearing calculator aside, I suspect you are going to have rideability issues with a gearing change that drastic. The 250 just doesn't have the torque to pull the load at that speed, and you may find the machine will only be happy on level ground with a tailwind. In an ideal world you would want to match peak torque engine speed in top gear to your desired cruising speed- and I would suspect that your 250 is making peak torque at 4000-5000 rpm.

On my 1972 Yamaha RT2 360 I discovered that it would just barely accept another tooth on the countershaft over stock for highway cruising. This dropped RPM at 60 MPH to a more tolerable level but it now requires a downshift on steep grades. Were I in your spot I would start by increasing the countershaft sprocket by a tooth and road testing the result. You will likely find that it won't easily pull a 17 front even with the standard rear sprocket.
Tim McKittrick is offline   Reply With Quote
Old 04-10-2015, 11:01 AM   #4
phreakingeek
Studly Adventurer
 
phreakingeek's Avatar
 
Joined: Sep 2010
Location: VA
Oddometer: 585
Quote:
Originally Posted by Tim McKittrick View Post
Were I in your spot I would start by increasing the countershaft sprocket by a tooth and road testing the result.
As someone who's done a lot of sprocket swaps over the years, I agree with this strategy 100% I'd just change one tooth on the countershaft sprocket and ride it. It's not a ton of money if you decide to change to the 17 down the road...hell, some us even have a "highway" sprocket that we can switch to while out riding if we are looking like a long pavement run coming up. Takes all of 10 minutes to swap it out on my DR650.
__________________
“Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!”
-Hunter S. Thompson
phreakingeek is online now   Reply With Quote
Old 04-10-2015, 12:54 PM   #5
MATTY
BORDER RAIDER
 
MATTY's Avatar
 
Joined: Jun 2014
Location: THE BORDER ENGLAND
Oddometer: 515
Quote:
Originally Posted by Highgear250 View Post
Really hoping for someone to chime in here. I managed to get a rough estimate off gear commander by using the preloaded specs for a 1980 ts 185, I then adjusted the "current" to my 250 specs, and used "custom" as a test field. I came up with switching from my current 15/45 to a 17/38 will give me the rpm range I desire. Big question though, do I have enough torque to get off the line still?

The Ts is geared super low in 1st and 2nd so maybe. Any input is appreciated
I tend to agree with the one tooth on the front sprocket approach as above.
I know first is way low but 5k at 65 for a 250 two stroke with 22hp and only 20ft lbs of torque is not a lot of grunt to play with.
And its no lightweight either, if it were me i would be inclined to put up with he busy nature of the engine at speed. If you gear it up over stock you will lose the mid range power and it will die way too easy on inclines or headwinds destroying the way it goes now. 5000 rpm at 65 is revving a bit high perhaps but its not like its killing it and drop the cruise to 60mph it will be fine.
I tried gearing up my DT250 mx it did not work, i ended up going back to stock and the dt/mx is lighter and has more torque.
MATTY is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 03:08 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2015