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Hi guys. I have a 13t front and a stock 40t rear on my 250L. My calculations put the speedo at -7.5percent right? That's what I should set the DRD for? I just installed it and have yet to go for a drive due to snow here in nh. Is that what you guys are running? Thanks

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I come up with 7.15 percent, but I think your thinking is correct. I don't have a speedo correct yet though, so can't say for sure. I plan on getting one soon so I'll follow this post to see so I know when I get mine :D I also am running 13/40, for now.

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how do you calculate the factory speedo error? I have mine set for the 13/42 but I think it is still slightly off.

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You can go to the 12 O'clock labs calculator.  http://www.12oclocklabs.com/sdrd_calc.htm

 

The more accurate method is by entering trip miles and gps miles for at least a 60 mile ride, but the sprocket difference will get you pretty close, but make sure you enter the correct tire size too.  The H5 is the model for the CRF250L.

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I did mine with a top speed test. I ran a GPS app on my phone to compare with what the bike said.

Mine came out as -11.6% with 13/42's and a 4.50X18 rear tire.

It is very close as I match the speed signs on the street. I have not ever checked it against the GPS again tho. 

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I came up with 7.15% based solely on the tooth difference. 13t is 7.15% smaller than a 14t, so in my mind it makes sense that it's 7.15% off with everything else being equal.

 

With a 13/42 I get a 12.15%, again based solely on teeth count. 13t is 7.15% smaller than a 14t, and a 42t is 5% bigger than a 40t. Add them together and you get 12.15% But it's been a LONG time since high school, so my math might be wrong haha. 

 

EDIT: apparently there's a part in the formula I am missing though. The link dkappelm gives a 11.6% difference, based solely on tooth count. Shows you what I know. Ha!

Edited by Old Goat Ninja

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The more accurate method is by entering trip miles and gps miles for at least a 60 mile ride

 

Using trip is not accurate! Trip and speed meters can have even 5% difference, mine did.

 

If you want to calibrate the speed accurately, you need to do GPS max speed run like gnath suggested. There's no reason to have accurate trip meter since it doesn't give you the tickets.. ;-)

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Use whatever method trips your trigger. The trip meter method worked fine for me and uses various speeds. Mine corresponds well with the speed warning radars from 30 - 70 mph.

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Use whatever method trips your trigger. The trip meter method worked fine for me and uses various speeds. Miy speedometer corresponds well with the speed warning radars from 30 - 70 mph.

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Maybe works for you, maybe doesn't, doesn't mean you shouldn't use the most logical and correct method. If you have GPS, it's much faster to test max speed instead of driving 60 miles.

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The funny thing was when I did mine ..... my top speed displayed was 88 mph ....  :lol:

(GPS showed 79 mph)  stage 1 kit with 13/42's and new tires. 

 

640px-Digital-speedometer.jpg

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All the methods will give you close to the same conversion factor as long as you use the 12 o'clock labs calculator, but when you have the opportunity you should verify with either with GPS or radar. The speedo DRD is a great little device though I installed mine when the weather was nice for riding, so I just enjoyed the ride.

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One would assume pretty much anybody has a GPS in their phone these days. :) I used "GPS Essentials" for Android, it records the max speed and also maintains a nice history graph where you can verify it (just relying on "max speed" value alone might have some temporary hiccups which you wouldn't know without seeing the history).

 

So yes of course verify in any case even with radar. My one and only point was, do not use the trip function as on many bikes trip and speedometers and calibrated differently AND GPS trip'o'meter might be funny depending where and how long you drive? Too many ifs that way. But sure, use a tape measure if you want, if it results in the correct verified speed later.. ;)

 

And eh well if you do have bike mounted GPS, it's few seconds to see the difference..

Edited by Hege

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LOL. The trip meter uses the speedometer, but could definitely be inaccurate if you are spinning the rear wheel.

 

Eh yes, but how hard is it to understand that they work differently and may have different compensation figures straight from factory? This is common knowledge, just google.

 

I guess no point continuing with this. I'm just telling from my own experience, I wondered why the figures don't match up when I did it with my trip meter. Then googled, then felt stupid. Maybe this helps someone else to go for the "correct" way and not wonder unnecessarily.

Edited by Hege

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DRD users, how the heck do you access the bikes connection??? I can barely see it let alone get my hands on it to make connections!

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Thanks for your input on cam timing Willy. That was exactly the kind of info that I was looking for.I definitely don't want to make my bike more difficult to ride in the technical stuff. I had to laugh when I read your comments about the front tire and the handlebars.My first ride on this bike I lost the the front end at low speed and twisted the bars!Thanks to you as well Bryan for the comments on your experience with the FMF Megamax.I wonder if I could expect similiar results with the Powercore IV squared?

I had mine installed but I saw a YouTube on it ... long needle nose and a long screwdriver and skinny hands .... search YouTube ... I am mobile right now otherwise I would search for you ...

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DRD users, how the heck do you access the bikes connection??? I can barely see it let alone get my hands on it to make connections!

 

 ... long needle nose and a long screwdriver and skinny hands .... 

pretty much what gnarth said.

when i did mine i loosened up the gas tank just to make my life easier. from the right side of the bike i took a long  flat head screw driver to push the connector off of the metal tab its on. i also had those surgical tweezers so i could grab the connector and pull it to where i could access it on the left of the bike. 

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I had mine installed but I saw a YouTube on it ... long needle nose and a long screwdriver and skinny hands .... search YouTube ... I am mobile right now otherwise I would search for you ...

 

 

pretty much what gnarth said.

 

gnarth ......  :lol:

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I don't have small hands or long needle nose pliers. :thumbsdn:  My EJK arrives today :thumbsup: so I will probably loosen and lift up the fuel tank as others have done. Maybe that will help me with access. Sucks to have to disassemble the whole bike to make a couple snap-together connections.   :cry:

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