# 2003 XR100 gear ratios

I have tried to search on this several times but I really haven't come up with anything. I am mini road racing my XR100 and have been playing with sprockets but I have a spread sheet that will calculate speeds and ratios based on the transmission. I don't really think it would do too much for me but it is a tool to help me with gearing. I have been staying with the 46 tooth rear sprocket and adjusting the fronts to best match what track I am at. I wanted to use this tool to help me decide what size rear aluminum sprocket I want to buy next time without spending \$200 on different sprocket sizes.

The last couple of tracks I ran a 16/46 sprocket with a bridgestone BT45 tire at 110/90-16 on the front and rear. I ran a 17 tooth front but it couldn't pull 5th gear well. The sprockets are both steel with a 420 chain conversion. I had a 120/70-17 rain tire on when I tried the 17 tooth front sprocket so that may have made some difference.

I just got a set of Sun rims in 2.75 front and rear and bought a set of 125 slicks last weekend to run on them. I think the rear is a 120/595-17 and the front is a 95/580-17 based on the bridgestone site. The math follows in theory...

16in = 406.4mm + 110/90 = 99mm tall = 505.4mm total

17in = 431.8mm + 95/580 = 55.1mm tall = 486.9mm total

17in = 431.8mm + 120/595 = 71.4mm tall = 503.2mm total

17in = 431.8mm + 120/70 = 84mm tall = 515.8mm total

So I couldn't pull the 17tooth front sprocket with a 46 tooth steel rear sprocket and a 120/70 tire. But I am curious of I can pull a 17/48 aluminum sprocket with a 120/595 slick that is 12.6mm shorter than the rain and has the reduced weight of the slick and the aluminum sprocket helping it out.

I have 13-17 front sprockets with a couple of chains that I swap out when I need to go shorter. I am trying to find the longest gearing that the bike will pull on a flat straight away and still have the ability to change the front for more grunt on the tighter courses and when the tracks have elevation. How much does the aluminum sprocket help out? I look at the other sites and I see a 36 rear aluminum. I wonder if the 36 can be pulled. A 13/36 is almost the same as the 17/46. I wonder if reducing that much reciprocating mass will allow the bike to run. I could try going between a 12 and 13 front sprocket and having a 36 tooth rear sprocket and see if I can race on those gearings.

Thanks for the help, I can't find the gear ratios anywhere. If anyone can offer up any information please do.

Thanks again,

Chris

I should have said that I have a 120 wiseco piston and with a hot cams cam and an ATC200x carb. It has a few more ponies than stock. I have a friend that has the super head and the inner rotor ignition but I haven't sprung for that kit yet.

Thanks for the help though,

Chris

Dont get the inner-rotor, there kick start killers.

well.. I tend to agree there too. I have raced it at Jennings Gp, Nashville and Barber during the weekends that I raced the big bike there. I am really just trying to decide which rear sprocket I want to buy by this whole topic or if I want to go ahead and get 2. Mabe the 36 and the 47 or 48 rear aluminum sprockets. That way I have a bunch of room to play.

Thanks for the responses.

Chris

## Create an account

Register a new account

• ### Similar Content

• Anyways so I got a 1985 xr200r RFVC, and I have heard that the oil really overheats and in some cases people have had their bike (Rarely) go up in flames, however I don't want to take any chances and I heard that there is a way to put on some sort of oil cooler... How do I do it??
• By Yamiha
I have a '01 XR200 and i was wondering it anyone could give me a top speed for it. Where i live its more 2 lane highways and things so i cant find a good straight to run it with a car in. Thanks
Payton

• I decided to compile a list of common modifications for the XR200 in hopes of eliminating some of the common questions asked on this forum. These modifications are intended to improve the overall performance of the bike, without sacrificing reliability. Feel free to suggest amendments or things to edit.
The XR200 is an excellent offroad machine; however, it was for the most part obsolete about 20 years ago. The bike can still be accredited to having probably the best reliability of any full size bike out there. When properly setup and modified, the "little XR" can run with the modern big bikes, especially in the tight and nasty technical terrain.
INTAKE: Remove the airbox snorkel on top of the airbox. It just takes a little prying and it's out. For \$20-\$40, you can get an aftermarket filter (UNI, TwinAir, No Toil), that will help increase airflow. Rejet one size up on the main and pilot.
Here are the stock jetting specs to give you a basline:
Stock jetting
XR200 (not XR200R)
main 102
pilot 35
Needle position 3rd groove
Pilot screw initial setting 1 3/4 turns out
XR200R (81-83 only)
Main 138
Pilot none
Needle position 3rd grove
Pilot screw initial setting 2 1/2 turns out
XR200R (86 and later)
Main 112 (86) 110 (87 and later)
pilot 38 35(98 and later CA only)
Needle position 3rd groove
Pilot screw initial setting 1 1/8 turns out
When these things are done, the bike will breath much better. This is the single greatest modification for a bike ridden at high altitude.
Overall cost w/out filter: about \$10 for jets; \$20-\$40 for the aftermarket filter
ENGINE: The greatest improvement to the XR200R engine is a big bore kit. Here are the 2 most common kits: http://www.powroll.com/P_HONDA_XR200.htm
Other options include porting and polishing the head, high compression pistons, hotter cams, etc. The more you do, the more reliability is reduced, but it is a trade off for power. Another option is an ’83 -’85 ATC200X cylinder head. It has a .5mm smaller bore, so it would need to be bored to 65.5mm, however, it has much larger cooling fins. For motors that are constantly being run in extreme temperatures, this is an option to consider.
Overall cost: Varies by modification, expect to drop \$200-\$1000
EXHAUST: There are several aftermarket exhausts on the market. These range from silencers to full systems. Prices range from \$80-\$500. Most aftermarket exhausts will give about the same improvement. The engine will rev quicker, which can be nice, but mostly they all just make the bike louder. For mild improvement to the stock system: grind the weld off of the inside of the header and remove the small cap held on by 2 8mm bolts at the exhaust tip.
Overall cost: 0-\$500
SUSPENSION: This is a major weakness with '92-'02 XR200s. The first option for the forks is to give the springs more preload by adding a larger spacer on top of the springs. The second, most common option is to swap out the entire suspension. '84-'91 XR200 forks and rear shocks will bolt right up, and ‘81-’83 XR200R forks will with the corresponding triple clamps. '84-'89 CR125/250 front ends will bolt up to any XR200R with the addition of a spacer. This particular swap is more complicated, but also adds a disc brake and improves the bike tremendously when used in combination with an '84-'91 XR200 rear shock. See this thread for more info on CR front ends: http://www.thumpertalk.com/forum/sho...1&parentpage=2 These parts frequently show up on Ebay and can be obtained very cheap. Also, a visit to racetech.com or similar suspension tuning company couldn't hurt with any setup. Emulators and progressive springs will get conventional forks nice and plush. Currently, XR250 rear shocks are in question as to what years will work; therefore, I do not recommend them at this point. Many people have them on their 200, however there is not a definitive answer for the years yet. Be sure to research before you buy.
Overall cost: Generally less than \$100; for Racetech tuning, expect to drop \$200+.
WHEELS: An 18" rear wheel from an '86-'89 XR250 will bolt right up. This can help because the 17" wheel spins too much sometimes, and tends to work its own spokes loose. There is also a much greater tire selection with the 18" rear wheel.
Overall cost: Generally less than \$100
LIGHTING/DUAL SPORT: Lights can easily be added to the 200 by tying into a pink wire that just comes up under the tank, then loops right back down to the stator. This wire has no purpose, and was left behind in the wiring harness, because the non-American XR200s had lights, and Honda didn't pay to change the wiring harness or the stator. I have personally tested it up to 75 watts, but I wouldn't recommend going much higher. From there it is simply a matter of wiring it the way you want it. In any application you will need a 12v voltage regulator. I would be happy to assist with any questions on the wiring you may have, since I have redone mine several times to change things. Also, please visit this thread for some diagrams (about halfway down the page): http://www.thumpertalk.com/forum/sho...d.php?t=431097 Each wiring job is different, so it is difficult to write a generalized way to do it. For dual sporting, there are kits from Baja Designs and similar companies, or you can be creative and pull parts together yourself, and in result save lots of money. The first time I had lights on my bike, it only cost me \$6. A speedometer cable can be attached to the speedometer port on the front brake hub, as long as you can find a way to mount the speedometer. TrailTech computers are the easy alternative to the manual speedometer.
Overall cost: Dependent upon creativity. Baja Designs kit runs around \$450