[racer69dude]

Fireman 454 It sounds like you might be the guy with the answers I need. I would also accept input from anybody else that has some GOOD info. I have a basicly stock NSR50r that I raced in the F1 class this year. For next year I want to convert it to a 4 stroke. Can anyone give me a run down on the issue that I will face getting this done. Also for discussion, what are the pros and cons of doing the XR conversion vs replaceing the 50cc 2 stroke with a bigger (65 or 80cc) motor? Thanks for any help you can give me.

 

[fireman_343]

Ok, first would be to sell off all your 2 stroke stuff to help fund your new motor swap project. Then figure out how many cc's you want/need for the class(s) you will race in. I'm limited to 140cc's so I went with the Tak 124cc kit and love it! If u want a cheap kit, BBR is a good one, or just a Tak 115 kit or Powroll 110 piston with inner-rotor kit and aftermarket cam... Yeah baby!!! To unleash all the power in these motors, you will need a super head with larger valves and ports, but they are not cheap!



Next you need a motor, then a bracket kit (wink, wink) to fit the XR/CRF100 motor in the NSR frame.

Then get the electrical/wiring harness for the 4 stroke (if it didn't come with the motor) It will be very straight forward to hook up. Also grab a extra long clutch cable and the clutch cable holder (it should come with the motor).



A stock carb will work, but if u can go with a bigger carb I would! The XR200 carb is a good cheap carb that people use with nice results! A different 24mm carb can be used as well depending on how crazy u go with your motor (I use a PE28mm carb). The intake can be made (see link below) or buy a offset NSF intake to point the carb straight back!



Cut off all tabs on the inside of your frame where all the 2 stroke electrical stuff was bolted to. This is the only stuff that needs cut



After u have the bracket kit (wink, wink), motor installed and electrical hooked up, you are almost done.



Next would be an exhaust. Either find a stock NSF exhaust or buy an aftermarket one from a guy with the initials BW in Texas. He has made some really good exhausts for both the NSR and NSF.

Or you can build your own exhaust, I've done that before and it worked great!



After all that, then it's time to have fun and enjoy the dark side!!! Mahahaha!!



More info on how I transformed my NSR50 into a NSF124 can be found here; Brian's NSR-120RR

NSR50 to NSF-125cc





I say the CRF/XR swap is the best because it is all bold on, and no need for welding new mounts braces etc!! Plus, if u really wanted to go back to a 2 smoke, you can... The only thing u cut off are the small mounts for electrical stuff, that can be zip-tied on if swap'n back over.

Let me know if u have anymore questions... I love to help out others looking to swap over!!

 

[coax]

Darn it! Will I be the only 2-stroke NSR guy out there? Those NSFs are killer. At least you're staying in F1 (we need to keep that class populated). It's hard to believe it became the smallest class this year. Fireman is who you need to talk to about the conversion.

 

[hammer_213]

I have stock can for ya . I left my motor alone . Advanced the timing and tuned it for vp race.fuel and got just about 9 HP . And its very compeditive in f1 and didn't cost me a dollar .



Do it bobby b . You will not be disappointed

 

[z50 chopper]

and if you do go for this conversion and need to sell your nsr50 engine and electronics and wiring harness let me know. I want to see if I could fit it in z50 or maybe a zb50 if I get one

 

[racer69dude]

Thanks for all the info Firewman 343. It is nice to have a good source of someone who has acually done the conversion to help get through the problems and challenges.



Kevin, I'll probebly stay in F1 next season and race my other bike in F2/3 and F4/5. After I do the conversion I won't have any money for higher class upgrades.



Hammer, Let me get some things lined up and I'll give you a call about your stock can.



z50 chopper, I have a second NSR50 that I upgraded to a 63cc (thanks J reid) to race in other classes so I don't know if I will keep the 50cc as a spare or not. If I need some funds to get the 4 strock conversion done I might be selling it. I'll let you know

 

[Branyers]

z50 chopper, I have a second NSR50 that I upgraded to a 63cc (thanks J reid) to race in other classes so I don't know if I will keep the 50cc as a spare or not. If I need some funds to get the 4 strock conversion done I might be selling it. I'll let you know

Just curious, are you running the stock pipe on your 63cc motor? I'm looking at a 72cc kit and I'm wondering if the stock pipe is cut out for it.

 

[racer69dude]

Fireman, Is the XR and the CRF 100 the same motor? is there anything different in the conversion between the two motors?

 

[racer69dude]

Just curious, are you running the stock pipe on your 63cc motor? I'm looking at a 72cc kit and I'm wondering if the stock pipe is cut out for it.

No, not stock, it is a Jemco pipe from BW in texas. I don't think you will get the gains you would expect from a 72cc upgrade if you put the stock exhaust back on.

 

[fireman_343]

The motors are the same as far as getting them to fit in the NSR.. I don't think Honda has changed a thing with that motor besides ditching the points ign!

Even a XR 80 bottom end is the same!

 

[storminnorman07]

Ok, first would be to sell off all your 2 stroke stuff to help fund your new motor swap project. Then figure out how many cc's you want/need for the class(s) you will race in. I'm limited to 140cc's so I went with the Tak 124cc kit and love it! If u want a cheap kit, BBR is a good one, or just a Tak 115 kit or Powroll 110 piston with inner-rotor kit and aftermarket cam... Yeah baby!!! To unleash all the power in these motors, you will need a super head with larger valves and ports, but they are not cheap!



Next you need a motor, then a bracket kit (wink, wink) to fit the XR/CRF100 motor in the NSR frame.

Then get the electrical/wiring harness for the 4 stroke (if it didn't come with the motor) It will be very straight forward to hook up. Also grab a extra long clutch cable and the clutch cable holder (it should come with the motor).



A stock carb will work, but if u can go with a bigger carb I would! The XR200 carb is a good cheap carb that people use with nice results! A different 24mm carb can be used as well depending on how crazy u go with your motor (I use a PE28mm carb). The intake can be made (see link below) or buy a offset NSF intake to point the carb straight back!



Cut off all tabs on the inside of your frame where all the 2 stroke electrical stuff was bolted to. This is the only stuff that needs cut



After u have the bracket kit (wink, wink), motor installed and electrical hooked up, you are almost done.



Next would be an exhaust. Either find a stock NSF exhaust or buy an aftermarket one from a guy with the initials BW in Texas. He has made some really good exhausts for both the NSR and NSF.

Or you can build your own exhaust, I've done that before and it worked great!



After all that, then it's time to have fun and enjoy the dark side!!! Mahahaha!!



More info on how I transformed my NSR50 into a NSF124 can be found here; Brian's NSR-120RR

NSR50 to NSF-125cc





I say the CRF/XR swap is the best because it is all bold on, and no need for welding new mounts braces etc!! Plus, if u really wanted to go back to a 2 smoke, you can... The only thing u cut off are the small mounts for electrical stuff, that can be zip-tied on if swap'n back over.

Let me know if u have anymore questions... I love to help out others looking to swap over!!

very interestimg build. the 10,3hp what was all done to the bike at time time?

 

[Manimal]

I have a few questions....



What sprocket combo is used on the 4t conversion and or NSF?



Will the XR100 shifter still work with the conversion or is the NSF linkage set-up a must? If other, what is used?



Have any of you upgraded the XR CDI? If so, what is recommended?



Lastly, what carb settings are used for the 24, 28 and or the XR200 carb?



Just doing my homework for when I eventually start the conversion

 

[z50 chopper]

z50 chopper, I have a second NSR50 that I upgraded to a 63cc (thanks J reid) to race in other classes so I don't know if I will keep the 50cc as a spare or not. If I need some funds to get the 4 stock conversion done I might be selling it. I'll let you know

ok cool, I wait eagerly

 

[fireman_343]

storminnorman07, thanks! For that motor build I installed the BBR120cc big bore kit, Kitaco valve springs, lightened flywheel, 68/69 grind WebCam, BBR Rev Box, Kitaco HD cam chain, custom 1.25" short exhaust with 140cc pitbike exhaust can, 24mm round slide carb (ran a 112-114 main and 35-40 pilot jet). You can see the dyno video when it was on, two pulles and both were 10.3hp. I'll see if I can find the paper and scan a pic of it for everyone.



Manimal, the sprocket combo I run now is a 40 rear with 13/14 front on tight short tracks, for longer tracks, I use a 38 rear with either a 15 or 16 front. Again, that is with my torque monster of a motor I run now, with a stock XR100, the one guy in our club runs stock NSR gearing. I believe a stock NSF came with a 28 or 30 tooth rear sprocket!!



The stock NSR shifter will work on the XR motor conversion! I have a XR shifter that I shortened and welded together for a spare, but have not had to use it due to my frame sliders protecting everything.



I have a BBR rev box, but I'm not sure if it is working right because my bike won't rev past 10.5k rpm on the dyno, so I'm looking at getting something else for next season!! It's a secret!! Haha



Carb settings for the 24mm carb are stated above.. The PE28mm carb for me here in Ohio are a 104-108 main with a 35 pilot jet! If I could find a smaller pilot jet I would run it because I feel it's too rich. But, it does very well for where I have it tuned now, and that's with running Cam2 race fuel only! With the high compression motor I'm running, I have too run race fuel!! With the BBR kit, I ran a 50/50 mix of race and pump fuel only to help keep the motor cool!

I'll post some links to carb settings for the 200X carb when I get home tomorrow.



Hope that helps ya out!! Anymore questions?? I love talking about this stuff!! Come on, come all to the dark side!!!! You will love it!!!

 

[Manimal]

storminnorman07, thanks! For that motor build I installed the BBR120cc big bore kit, Kitaco valve springs, lightened flywheel, 68/69 grind WebCam, BBR Rev Box, Kitaco HD cam chain, custom 1.25" short exhaust with 140cc pitbike exhaust can, 24mm round slide carb (ran a 112-114 main and 35-40 pilot jet). You can see the dyno video when it was on, two pulles and both were 10.3hp. I'll see if I can find the paper and scan a pic of it for everyone.



Manimal, the sprocket combo I run now is a 40 rear with 13/14 front on tight short tracks, for longer tracks, I use a 38 rear with either a 15 or 16 front. Again, that is with my torque monster of a motor I run now, with a stock XR100, the one guy in our club runs stock NSR gearing. I believe a stock NSF came with a 28 or 30 tooth rear sprocket!!



The stock NSR shifter will work on the XR motor conversion! I have a XR shifter that I shortened and welded together for a spare, but have not had to use it due to my frame sliders protecting everything.



I have a BBR rev box, but I'm not sure if it is working right because my bike won't rev past 10.5k rpm on the dyno, so I'm looking at getting something else for next season!! It's a secret!! Haha



Carb settings for the 24mm carb are stated above.. The PE28mm carb for me here in Ohio are a 104-108 main with a 35 pilot jet! If I could find a smaller pilot jet I would run it because I feel it's too rich. But, it does very well for where I have it tuned now, and that's with running Cam2 race fuel only! With the high compression motor I'm running, I have too run race fuel!! With the BBR kit, I ran a 50/50 mix of race and pump fuel only to help keep the motor cool!

I'll post some links to carb settings for the 200X carb when I get home tomorrow.



Hope that helps ya out!! Anymore questions?? I love talking about this stuff!! Come on, come all to the dark side!!!! You will love it!!!

Vey useful info, Brian. I appreciate you sharing =)



With the BBR120 kit, being that my riding is mostly street (get the most hp's on a small budget) and some track, using the Kitaco valve springs and doing the Web cam necessary, or do the two combined compliment each other? Or would you just recommend the Kitaco valve springs and / or is there more that is involved? Or what would you recommend for the BBR120 set-up (and carb)?



Sorry if I sound ignorant, I just don't know much about the 4t motors.

 

[fireman_343]

Here are some links to jetting for the 200X carb..

BBR 120cc / Exhaust / ATC200X carb. What is your average jetting ? - ThumperTalk

Jetting help - XR100 w/BBR120kit and 200x carb - ThumperTalk

LOTS of info on the BBR120 kit posted by Gman!

ATT: BBR 120 kit Owners - ThumperTalk

More info on mods for the 100 motor.. what're the "best" 100 performance mods? - ThumperTalk



As far as the Kitaco valve springs, it wasn't necessary, I had them and they were stiffer springs then the stock or BBR valve springs, so I thought it would be better for the bike. The BBR kit is VERY good for a person on a budget. I'd say at least an aftermarket cam and 24mm carb is needed to get the most out of that kit, the BBR cam is a stock cam (friend and I dialed it in and it had the same spec's as a stock cam).

A rev-box would help you out on the street as well, because the bike won't rev past 10K rpm with the stock CDI on. Gearing for the street would be hard I think.. I don't know how fast you need to go, but I would assume a very small rear sprocket like a 28 or something would be needed! Figure out your final drive ratio and what works best for you... I don't have a clue about street riding mini's! Sorry!



Search around the thumpertalk forum... lots of good info on there about the motor and different kits that people use and different carb setups as well.

 

[Manimal]

Thanks for the links. Once again, great info =)



One of the links takes me to the Engines Only website, who are incidently local to me. CRF/XR100



I had just learned there are two options with the BBR kit, stage 1 and stage 2. The stage 2 offers the springs and aftermarket cam. Definately a direction I will probably go with.



I also see that they offer two types of exhaust, a standard side mount and an under style exhaust (Outlaw Low). The low is what I initially had planned to go with and glad this exhaust already exists. Hopefully there won't be much mods needed to fit the NSR chassis.



As for the gearing (sprocket combo), as long as I have a baseline of what's used on the track for a particular set-up (basic or slightly altered [stage 2] BBR120 w/ 24mm carb, exhaust, and rev box), will give me an idea of what street gearing I will need for the area and elevations I ride, +/- a tooth or two (rear).



Oh, and glad to know that the NSR shifter works with the XR motor. Using it, will it be standard or GP shifting?



Just curious is all. FYI, my current shifter linkage style on the NSR is GP, so I can adapt to either.

 

[fireman_343]

The exhaust might be the hardest part of the whole swap, unless u are good with mod'n things, it will be diffacult to find a direct bolt on exhaust. Like I said, The Jemco exhaust would be everyones best bet for a somewhat cheap but great exhaust with the least about of modified parts needed.



If BBR says they have a aftermarket cam, I'm sure it's the same cam I had... It's a stock cam man!! Get a WebCam, or something similar!



If you are close to Frank Nye of EO... Then I'd go down there an talk to that guy! He has a lot of info on these motors and is known to build fast reliable XR motors! Only thing is, his prices are a little on the high side, but I've heard nothing but great things about his work!! He would be the first place I go to if I were u!

 

[Jeff Lebowski]

I have a second NSR50 that I upgraded to a 63cc (thanks J reid)

Glad to hear you're getting use out of my old jug. If you want to make it even faster send that thing down to Billy and let him work his magic on those ports. Even though I went to a 65cc top end, I swear the port work he did made the biggest difference. If I exit corners perfectly my bike can hang with Fireman's Takegawa monster.



Long live two-strokes!

 

[fireman_343]

Yeah, well...u have a inner-rotor kit and I don't! That won't happen next year when I install one!! But, like u did me, I won't tell ya I put it on!! Hahaha

I still have a few tricks up my sleeve!! First thing I to get rid of that tiny stock NSF exhaust that isn't letting my monster breathe