2005 Suzuki JR50 mods???

[superdave144]

Calling all mini-dads...

My four year old has a 2005 JR50. He is getting pretty good and we're thinking of going racing soon. I've got a couple of questions though:

First, I'm looking for ways to make the bike run cleaner and faster. I have heard that you can get a second gear out of the bike but I'm not sure the effort is worth the performance gain on the track. Also, I've seen an FMF pipe/silencer for this bike, but will it still be legal for the oil injection class if I bolt it on?

Secondly, my son is really tall for his age (Pastrana-esque). What can I do to improve the ergonomics for him (seat, handlebars, suspension etc.)? I cringe when I see him crunched over and bottoming out the suspension.

I used to race intermediate cross country but I'm new to the minis. Also, I'm not the most seasoned technician. If anyone has any ideas at all for me drop me an email. Input is appreciated.

 

[motocross3]

I don't know if yours is the same as my brothers buy on his theres a restrictor on the exhast pipe at head mount and one where the carb mounts to the manifold. removing these really help, i removed them from him and its keeping him occupied for now. and if hes tall and ready for a faster bike you might want to consider moving up to a PW 80

 

[superdave144]

I removed the restrictor in the exhaust pipe but I didn't find one where the carb mounts to the cylinder.

I wouldn't mind putting him on a bigger bike except for the fact that we wanna start and the next step up in bikes is a Cobra and the finances aren't really available for that yet.

 

[Tomsti]

If you're going racing figure out what class and better get their rule book prior to making mods. It would suck to do a bunch of work only to find out you can no longer run the class you wanted.

 

[Jasle]

actually tomsti is right. the only places that allow the jr to race typically don't allow mods. beside all the money in the world won't make the jr competative with the 50cc racers you will encounter. take a peek at www.cobramotorcycle.com and www.poliniusa.com that is what you will see in the 50cc race class.
if you still have not gone out and bought a proper racer the AMA legal things you can do are: add bar risers to help ergo's, add decent footpegs, jet properly.

the hidden gear is actually 1st, second is the gear that is accessible. you can re gear with sprockets to make it useable but NOT legal in most racing classes anyways. every place in the country is basically 1 speed allowed.

for class3 racing, which is what the jr fits in. The Cobra P3OI is the best bike avail. for class 1(4-6 50cc) the Cobra CX50jr aka CM pretty much rules the roost. Polini has the X1 which is very competative but most kids like the ergos of the cobra best. When you hit the class 2(7-8 50cc) the Cobra CX50Sr and Polini X3 are the ticket.

if you have specific questions to texas please let me know. Most racing here is AMA and you will not be allowed to mod the JR. We race all over the state mostly traveling to Houston and Dallas every weekend. My son rides for Factory Polini but I know more than most about the Cobra's also. If you want to give me a call I'll give you honest opinions of the bikes. There are a few more brands avail but i personally don't feel they are worth the time if you want to race. the KTM is a good learner bike...but once you start racing you find its limits quite fast.

 

[superdave144]

Thanks for the info Jason,

You mentioned jetting, are there any specific jetting specs for the JRs that make them run significantly better?
I would really like to step to a Cobra or Polini (especially since Dan is 4 and already 45 inches tall) but I just don't think I can put that kind of $$$ into a mini right now (I know, I'm probably in the wrong sport). Ergonomically either the Cobra or Polini would be perfect, I'm just not sure what he would do with that much motor. When my nephew made the jump from the PW to the Polini X1 a few years back he lost his enthusiam for racing. In hindsight he probably should have stayed on the smaller bike another 6 months (He was big too).
Anyway, I think I'll try to get a hold of some bar risers; I might even buy the FMF pipe. I'll check to be sure, but if he is racing the oil injected Cobras I would think an aftermarket pipe would be allowed. Hopefully by Christmas I'll be able to put him on a Polini (I really like the X1 back in the day).

Thanks again,
David
#522

 

[Jasle]

nope the pipe is not allowed. the class is a "stock" class. the cobra OI comes stock with almost 9hp. The JR does not come with the FMF stock. Thats why you cannot compete with a bike that has 2.5Hp. Even with the pipe the bike is still WAY off in power. you need some head work and porting to get even halfway there. Then you are still suffering in the suspension area. I've even seen rip snorting 60 kits...Still don't compete!
I don't remember any jetting tips but I do remember being several sizes big on the main.
Save the $200 you'd spend on the pipe for a decent bike. Over on poliniusa a guy is selling a decent x1 for $650... just keep looking and you'll find a deal you can afford eventually. Just let him get as good as he can on the stock JR. You can drop thousands in the jr and still not be competative with the racers...

 

[superdave144]

That's a shame about the pipe, you'd think a simple bolt on performance upgrade like a pipe would be within the limits, especially with the PWs and JRs down on power like they are.

Your probably right about the JR; it's probably more trouble than it's worth trying to make it fit him better. Anyway, I may put the risers on but I'm probably not gonna mess with the pipe.

Seems like local tracks choose to inforce the rules at their disgression too. My son Dan raced his first race at Village Creek in Fort Worth this weekend in the oil injection/shaft class and lined up next to an XR 50. I wouldn't have thought that would have been allowed.

A couple of questions though, is their a Polini dealer in the DFW area with a showroom where I can look at these bikes? And if I decide to go that route and buy a Polini or Cobra, is there anything I can do to govern the bike's power a bit so that Dan doesn't get shell shocked by the hit?

Thanks again for the info,
David Dickinson
#522

 

[Jasle]

there is a new Polini dealer in DFW somewhere. i have not dealt with him yet. you'll find that most of the polini and cobra dealers are quite small and have very limited bikes on the floor. If your ever down in austin shoot me a note and your more than welcome to test ride ours.
to govern them down there are a few things you can do. first adjust the clutch hit so its not so violent. you can fasion a washer to block the exhaust port but that might not be necessary. also a piece of tubing inside the carb to block the slide from going all the way open can be used as a limiter. I used these methods to get my 3 year old on a cobra cm. worked like a charm. biggest hurdle is the noise. Had to use ear plugs. you might get away with just the soft hitting clutch. then practice rolling throttle on and using brakes while on the stand for a few minutes to get comfy with the controls. then run around the flat area for a while. I hooked a rope to the rear so I could be the brakes in case jr forgot. then after a while I stopped being the brakes and that was it. its pretty cool how the kids really do cut the throttle when they get scared. its the hitting the brakes thing you need to work on.
the clutch adjustment is easy in the X3. just adjust some screws. the X1 you need to adjust the nuts on the 3 shoe. the cobra's ahve adjustment by taking some shim out of the clutch. all 3 are realativly easy to do.

the Xr50 fits in Class4 racing. many times the bikes line up at the same time but are not in the same class. I've seen as many as 4 different classes on one gate due to low numbers in each class. this helps to save time.
For AMA racing its pretty much only the 50cc classes that are not allowed to have mods. in 65cc and above its all pretty much legal unless racing a stock class for Loretta Lynns or another national. insurance thing. no mods to 50cc bikes allowed. for a long while class 3 was an even playing ground. the ktm came out with their OI that had 5HP and it killed the pw's and the jr's. then cobra trumped them with the 9HP P3OI. Now KTM answered back but cobra dropped out. These bikes squeezing in class 3 has really ruined the entry level racing class in my perspective. You rarely see the pw's battlilng anymore.

 

[superdave144]

Scoring

Oh, by the way, they were definitely scoring the xr 50 against the PWs, JRs, and oil-injected CMs at Village. They had separate gates for the regular 4-6 and 7-9 classes. There were several PWs with the FMF silencer on them as well. FYI. I imagine they don't get away with that at the BIG amateur races.