4Strokes.com Honda Technical: XR250L Mods by Rick Ramsey

Page 1 - XR250L Introduction; Carburetor Mods and Jetting
Page 2 - Carburetion: XR250R Vs XR250L; Exhaust System Mods
Page 3 - Air Filter, Airbox and Breather Mods; Gas Tank
Page 4 - Battery, Electrical and Headlight Mods
Page 5 - Tail Light Assembly and Brake Switch Mod; Sprockets and Gearing
Page 6 - Final Drive Ratios
Page 7 - Speedometer; Suspension Setup; Tires; Handlebars
Page 8 - Clutch Lever; Skid Plate & Guards; Spark Plug; The Ultimate; Weight Reduction
Page 9 - Esthetics; Unfinished Areas; Summary

So you just bought a brand new XR250L

Have you noticed how heavy it is? Have you noticed that it doesn't have much punch? Are you afraid to ride hard trails with it because the tires won't make it? Well, all of these thoughts occurred to me too so I did something about it.


The objective was to remove as many parts as I could from my 1991 Honda XR250L and still keep it street legal. My friend Gordo wanted to convert his but with shorter suspension that he could occasionally ride on the street. We both got what we wanted. My bike weighs 23 pounds less than when I started and has DOT approved tires that can be used on the street and off-road with some confidence. Gordo's bike weighs about the same as mine and has dirt tires on it. Gordo uses his bike in the desert and in the woods. He doesn't plan to do much street riding, but he's legal in most areas and can ride on the street if he needs.


Gordo and I have "49-state" model bikes. We don't have an over-aggressive DMV in our state, and we can get by on a lot less than people in other states. If you think that some of the things we've done might not get by your DMV, then don't make the changes. There are more than enough things to do legally. If you are making a pure off-road bike, then have at it. Where I knew about the California-specific differences, I mentioned them. I'm sure that I didn't catch them all.


The following sections describe in detail how we modified our bikes. Many parts from the XR250R ('86-'94) will fit the XR250L. These parts are sometimes lighter and/or give better performance than the XR250L parts. We used standard XR250R parts whenever possible. Working only on week nights, we each took less than a month to do all the initial work. We rode on the weekends to check our work. The biggest time delay was waiting for parts to be delivered. Cost is not mentioned much, but rest assured, neither of these project bikes was cheap. Gordo had a NASA budget, while I had a Kitty Hawk budget, so sometimes I didn't spend as much on mods as Gordo did.


Carburetor Mods and Jetting

The accelerator pump carb on the XR250L looks like it has potential. Pumper carbs can be jetted to get rid of that nasty four-stroke hesitation on the bottom and give good power on top too. However, the non-pumper carb from the XR250R is ultimately a better performer because it is designed for more air/gas flow. The needle and seat on the pumper carb are designed to make the bike EPA legal (lean) and are the biggest impediment to performance.


But, if you want to stick to the stock pumper carb, there are a few things you can do. The carb is jetted too lean. If you do any of the intake or exhaust mods, then it will be way too lean. Install a 125 or 128 main and a 40 or 42 pilot as a start (sea level jetting). While you have the float bowl off, remove the pilot adjusting screw. Be careful with the spring, metal washer, and o-ring. Heat the end with the small ear on it, and the ear will fall off. Reinstall the screw before remounting the float bowl. The pilot air screw can now be adjusted throughout its range.


There are too many hoses on the California model carb. If you don't need to be EPA legal, remove the purge control valve and canister and two extraneous hoses. Consult pages 1-22, 1-27, and 5-10 in the service manual to see which hoses to remove. Seal the holes in the carb body with short lengths of hose that have been plugged with Shoe Goo or something similar. You can seal the carb body directly if you trust yourself.


Besides hoses, there are two other differences between the California and 49-state carbs: the part numbers are different for the throttle slide and carb top. I don't know the extent of the physical differences, but I would guess that the slide cut-away is different, and the carb top has a throttle limiter.

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