WR250 - Gear Ratio +More

I just picked up a 1992 WR250 to use the engine for an engine swap I have planned and need to get some definitive answers about a few things. After preliminary search I chose the WR over the YZ because of wider ration transmission (overdrive 5th) and the lighting coil.

I am starting to calculate for sprocket sizes vs. speed and am having a hard time finding the exact gear ratios for my WR250. I did find this thread (http://www.thumpertalk.com/forum/archive/index.php/t-728342.html) to find what the 3rd, 4th and 5th gears are, though I am not sure if that is correct for my 1992, but is also missing 1st and 2nd.

Can anyone tell me, or direct me to where I can find the exact transmission ratios for my 1992 Wr250?

Primary reduction, 1st, 2nd, 3rd, 4th, 5th.

The other information I am trying to find is part interchangeability between YZs of particular years. I have seen a few posts about this though the information seems to contradict each other or they only mention 94-97 WRs. Can anyone advise for certain what years of YZs are interchangeable with what year WR parts (mostly interested in motor parts)

Lastly, for the 1992 year, what were known fixes and or motor related (carb etc.) upgrades?

Any help or direction, or any other information aside from what I asked that I should know about the WR250 engine, is greatly appreciated.


1st 2.285

2nd 1.706

3rd 1.333

4th 1.050

5th 0.840

14/52 std gearing

mine has an eric gorr port job, fmf and reeds and its a super strong motor,power curve is different then my 04 yz 250 but still a blast to ride .

Awesome, thank you for the reply, very helpful.

This will be going into a street bike so I thought the more distributed power curve would be best. Hoping it is more like the early YPVS RZ350 bikes power range.

Looking for a few other pieces of information since looking around the web since posting this.

1. The factory carb model #.

I need to find a rebuild and jet kit..unless you have a suggestion for a better replacement carb. Can you verify it is a "Mikuni VM38"?

2. Stock Exhaust port angle, Transfer port angle, exhaust port volume and exhaust average temp. (Since the engine will be in a street bike I need to find/make a properly tuned pipe as the "FMF Fatty" that is on it wont fit in the frame/fairing. I am looking at 2 stroke pipe software such as http://www.mh-aerotools.de/airfoils/javapipe_en.htm and this is the information it asks for to get me in the ball park. I cannot check as the bike is in storage now about 45minutes away. rz350ssss.jpg

3. Is the redline on the WR the same as the YZs at about 9krpm or...? What is peak HP RPM for a modified bike such as yours?

4. What is the safe and danger zone operating temps for these? Hoping to setup a Trailtech Vapor gauge setup and would like to know to ensure street use doesn't melt this thing.

That's it for now I am sure I will have plenty more questions as this project goes on. Once again any help or direction is appreciated.


I can confirm the carb is a Mikuni VM series, 38mm sounds about right.

vm38ss, as for jets any dealer should have them in stock, just pull the old ones and carry them in and ask to match them to there's and select the size you need for your application.

rpm should be the same, just mainly different gear ratios as far as i know being the difference, i asked eric what he thought the estimated hp to be as i had no clue what even stock was and he said around 45 hp.

some of this info i took directly from my oem manual from when i actually purchased my bike new, not many 1 owners out there anymore like mine ..... it will always have a home as i will never sell it at any price, when im gone someone else already wants it !

..unless you have a suggestion for a better replacement carb. Can you verify it is a "Mikuni VM38"?

I ran the Mikuni VM38 on my 97--it's a decent carb despite it's old school reputation. Seems to me, one of the problems with it on these bikes was a lean main jet from the factory. I stepped my main up to a 410, leaned pilot to a 35 running 42:1 at 4000ft. elevation--can't remember clip position or model but I believe I swapped out to different taper. This combo ran alot better than the stock and really opened up the top end and helped eliminate the spooge.

Always wanting more power and reliability--I swapped to a Keihin 38 MM PWK Air Striker from a CR250 and it made a noticeable difference for the better--bottom to top. Just recently, I had the divider plate installed, low speed circuit modified, and carb bored by RB Designs--huge difference especially in the bottom end. This is the single best mod I have done--next to having compression corrected for altitude, squish band modified, and a RAD valve.

Someone had a very good writeup on the carb swap not too long ago--albeit on a newer WR250.

Thanks for the info..carb swap and changes might be where I am headed with this project.. I got the WR250 engine out and modified the transplant frame a bit to get the wr in there. The issue I am running into now is that while using the rear engine tab that the swing arm goes through the back of the carb when atcached, no air filter, is right up against the cross support for the rear shock.. My question now is are their super short carb mount/flange for the wr250 also what is the thinnest carb that would work with the 250.. flatside etc.?

Open to suggestion.. I dont want to have to hack this frame and build a shock support around the carb.

1st 2.285

2nd 1.706

3rd 1.333

4th 1.050

5th 0.840

14/52 std gearing

mine has an eric gorr port job, fmf and reeds and its a super strong motor,power curve is different then my 04 yz 250 but still a blast to ride .

I am plugging this into www.gearingcommander.com trying to get some sprockets ordered and it is asking for the primary reduction.. do you have this number? I have done searches but have just found the YZ250 is 3.00... I found one at http://www.thumpertalk.com/forum/showthread.php?t=948053&highlight=2002+yz250+primary+drive+ratio

that says 2.88:1 though it doesnt specify the WR year nor was that confirmed. Can you confirm a 92' WR primary reduction is 2.88:1?

The #'s I have for the WR250 are 22/62 or 2.818, my YZ250 is 21/63 or 3.00

I don't know if they changed the primary drive ratio over the years though.

I'm in the process of doing a WR tranny conversion to my '98, I think the 22/62 ratio is from the last year '97 WR.


Old posts but oh well, 3 1996 YZ sets that I count are 62/22 or 2.818.

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