Brian Conrad's NSR-120RR

What is Brian up to now...Putting in a 2002 XR100 motor in his NSR50!

(July 2008)

   I have turned to the dark side and went with a 4 stroke motor in my NSR.  After testing out what I could do with a Kitaco and Athena big bore kits, I set my sights on a 4 stroke conversion after having a few good battles with bikes with 4 strokes in them.  Starting things off with a 2002 XR100 motor, I quickly started to do the research and calling people I know who have already done the swap.  A lot of help was given by a friend out in San Diego Ca, Brian Werner, who just did the conversion last year. I called him and we talked for what seemed like hours on the phone.  I quickly filled up 2 pieces of the yellow legal pad paper with info and parts that were needed for the conversion. With a lot of valuable information from Brian Werner, I started to think this shouldn't be too hard.  I then sold the 50cc motor, the exhaust and other parts I didn't need to fund the project and the fun began!

Brian Werner sent me the same aluminum that he used and a drawing of the brackets he made.  After a lot of templates of Brian's design, I thought I would try something different and maybe easier to make. A few plastic templates later I designed my own rear motor mounts and fit the XR100 motor in the frame. Only thing I had to cut/grind down a bit was about 1/8" of the bottom rear mount on the frame, this was done so the mounts would not bend once all the bolts were tight..  UPDATE-- I forgot to loosen the swingarm bolt, if you buy my kit, the most you will have to do is grind down a small amount to fit the brackets and motor).  Getting the right height of the motor and spacing so the front and rear sprockets line up right was a little bit of a challenge, but once I figured it out things were smooth sailing from there.  Todd Patton of TK Racing products was nice enough to provide me with a few scrap front mounts that he makes, I used them as a template to make my front mounts and added an extra hole for the front NSR frame bolt.  He helped me out with a few things and I want to thank him as well! 

Now that I got the motor in the NSR frame, I set out to figure what exhaust I was going to use.  I found a few importers that could get some sweet exhausts from Japan, but after I seen the price tag, I thought I would try something different.  My first thought was to go under the tail like the NSF100.  Then after looking at all the tight bends that were needed, I thought I would call Brian Werner up once again and take a page out of his book.  I went with the same idea he had with his exhaust.  Mount it under the motor and have a pipe stick out the right side of the motorcycle, MotoGP style!  After finding a small Pit Bike exhaust can on ebay, my next hurtle was finding someone to custom bend an exhaust header for me.  After a few calls to some friends that race with me, I found a shop that builds race car frames.  Took the NSR there and it was nothing for him to make.  He made one of the coolest looking exhausts for my NSR. Thanks Shawn!

Okay, so far the motor is in, exhaust is done, now the next step is to figure out what big bore kit to get.  After a lot of research and going back and forth with different kits and what would be best for me and the classes I want to race in, I went with a BBR 120 kit. I'll run a more aggressive race cam then the BBR's, but I think the kit is nice and will do just fine.  A huge thanks to Kent Klawon for showing me how to rebuild the top end of the motor! 

The final step is getting the motor dialed in right.  I'll be using a Keihin 24mm round slide carb for the initial tests, and if for some reason I can't get it to work, I'll go with something different. I did make my own intake but went with a Kitaco intake for a 24mm carb from CHP. You can all and order one for around $25.00. For the one I made.. I cut a stock intake close to where it bolts to the head, stuck some conduit in there and JB welded it.  That will be the piece that my rubber heater hose will fit on to.  I then waited overnight for the JB weld to set, and then cut it short enough for a small clamp to go over it.  I then cut some heater hose, attached it to the custom intake and carb and it was done! Great thing about this, is you can make it as long as you want and play around with it.  But, like I said, I've been using the Kitaco intake and keep the one I made as a spare.

I did look over a few things when putting this motor in... nothing too bad but something you'll want to know if you plan on doing this conversion!

The shifter, stock throttle cable and chain length were 3 things that need addressed! With the shifter, you can use your stock NSR shifter, but might need to bend it a little bit for it to work.  Mine was bent from crashing on it, so I'm not sure how much you really have to bend a good shifter for it to work.   When I had the 63cc motor in I used a 1/4 turn throttle with my carb.  You can use a 1/4 turn throttle with this swap, but just take it easy on the throttle since you now have a lot more torque!   Anyway, I stuck the stock throttle back on, but ran into a problem with the carb plunger not closing all the way.  So, I cut off about 1/8" off the throttle stop inside the throttle casing. That allowed the throttle to close when it was off.  Also, I had to order a new DID 420 chain and cut off a few links so it would work out. (Update.. I now run a 1/4 turn Kitaco throttle and love it!)

 I think the XR100 motor in this light frame and the NSR's suspension will do great!  I'll post what problems (if any) I'll run into once I get it on the track. I also plan on taking the bike to a Dyno and I'll post the HP numbers once that is done. More info and updates/pictures to follow!

Thanks to: Brian Werner, Todd Patton, Shawn McNealy, and Kent Klawon for all the help on this project!  Without your help and support, it wouldn't be where it is now!

Click on the pictures to enlarge them

EXHAUST PICTURES

So, the 2009 season is approaching fast and it is time to get the motor the way I want.  Well, I wanted to do the Yosh 125cc kit but thought I would put that money towards my suspension since I had a few issues with that.  So, the only motor mods that I will do for the 09 season is a new WebCam 68/69 grind, and a lighter flywheel as well as a larger oil pump.  I'll post pic's of everything as soon as can and report the changes the cam and lighter flywheel do for the bike.

I took the bike to the track to shake things down, she ran good and I now have to get use to the lighter flywheel and Webcam... I use to have a lot of engine braking, but now the bike just wants to keep going, so I have to adjust to the new mods, once I come to grips to the new motor mods, I'm sure I'll enjoy the bike and my lap times will drop!  I also could tell a difference with the front forks, they felt great and www.35motorsports.com did a great job with them.  I might have to adjust them a little here and there, but right out of the box, they feel 100% better then before!

Check out the video below!