Front Sprocket Change And Odometer/Speedomter

I recently changed my 13 tooth front sprocket for a JT 12 tooth sprocket. Was on the highway today going 70 (or so I thought ) and getting passed by everybody. My wife was driving behind me and told me I was actually going 55. Anyhow, looks like my speedometer, and I'm assuming the odometer too, is way off now.

Just curious if a) others had this problem, b) how do the speedometer, etc, work on the WR250R, and c) what's the fix, if there is one?

Thanks!

Yeah, going to the 12 will knock your speedo off. A 12/43 combo with the 606's on bring the speedo to where it should be. You can get the SPeedoDRD from Brooks off his website 12O'clockLabs. Better yet, PM him (12oclocker). He can set you up.

Yep. Prior to changing the stock gearing you were already in need of a speedo fix.

The stock unit is roughly 7% off. The odometer was correct.

Dropping a tooth in front sent you even farther off on speed. Roughly to somewhere around 14% off.

The 12 O'clock Labs web site has a brilliant calculator that lets you plug in your gearing, the stock gearing, and even tire sizes so that you can get the most accurate idea of how far off you really are.

The changes I made to my X put me at about 22% off from reality.

granite4brains wrote:

...how do the speedometer, etc, work on the WR250R...?

Like most bikes designed these days, the (electromagnetic) speedometer pickup is off one of the transmission shafts.
This is why changing your gearing messes your speedometer accuracy up.

SheWolf wrote:

Yeah, going to the 12 will knock your speedo off. A 12/43 combo with the 606's on bring the speedo to where it should be.

Is this because the 606's are taller than the trail wings? Yesterday was my first ride with DOT knobbies and a 12T; did both mods at once. To be honest, I did not feel a major impact, i.e. quicker acceleration, from the smaller front sprocket. Your statement has me wondering if the taller DOT knobby offset the smaller front sprocket.

thanks guys! I'll definitely be picking up one of those SpeedoDRD thingys from 12 oclock labs. My buddy just bought a new bike too and we were wondering why our odometers were not comparing - I guess the factory default settings are probably a bit off for both of us - interesting to know.

well, I can't seem to accomplish much without some help from this forum

I just received my 12oclock SpeedoDRD thingy and I'm stuck on step 1: locate your speed sensor!

The manual kind of shows the generic location of it, and I thought taking off the seat and side panel might give access. Now I just see a bunch of wires and connectors and don't know what's what? I was able to succesfully identify the battery though

Anyhow, could anybody offer some helpful advice on this - I would much appreciate it!

EDIT: I may have found it. Right above my battery is a connector which appears to be the only that mathes the connector for the speedoDRD. When I attemp to trace it, it appears to be going to the back middle of the "engine" area, which matches the general location shown in the manual. Am I on the right track here?

Go here my man: click me

There are two connectors that look exactly alike.

One is the correct one, the other obviously is not.

Read through thread I linked you to. It's discussed and described perfectly there.

thanks motokid! That thread helped out a lot. Turns out I even guessed the right connector

Got it all installed and gonna take it out tomorrow and give it a test.

motokid wrote:

Go here my man: click me

There are two connectors that look exactly alike.

One is the correct one, the other obviously is not.

Read through thread I linked you to. It's discussed and described perfectly there.

link does not work.

Well - the thread is a little over a year old since that link was posted.

Seems the link was to a thread that no longer exists, or was perhaps moved.

I can't find it now.