JR50 mods - polishing a turd?

[TEEEE]

I’m looking at adding some power to my son’s JR 50. He really needs a new bike and I’ve been looking at KTM’s and other 50’s with REAL suspension and power...but I’m broke. I’ve already raised the bike 1” with the fork spacers and the rear suspension relocate. I’ve done the 2nd gear mod. I still have stock sprockets.

So I’m thinking of doing two things and wanted to see if others have had any experience with this:

1. Add a pipe. FMF makes a Fatty for this. Does it really add much power? They make a silencer to go along with it...any better performance than stock?

2. Switch to premix. I’m hoping to get it to run a little cleaner. Jetting will help too, but can I just premix and run with the oil tank dry, or will that burn anything up? As for jetting, looks like there are essentially two plot jets. Is this some type of restriction? Can I get rid of the first one?

Thanks in advance for any pointers. Am I just polishing a turd, or is there something to be gained there? If anyone has something like a KTM Senior Adventure for sale in the neighborhood of a grand, let me know!

-T

 

[TimberPig]

I'm not very familiar with JR 50's, but I would anticipate the FMF pipe and silencer would uncork quite a bit of power. From what I know, the stock exhaust looks pretty choked up.

On the oil injection, I think you're going to need to disconnect and plug some lines, so as not to suck air in through the injection system and lean the air/fuel mix out. Simply emptying the oil tank will let air pass through. You can leave it intact, just disconnect the line from the oil tank to the pump, and plug the pump inlet and tank outlet off so that air is not going to be sucked in.

Beyond that, I'm not familiar enough with the bike to say for sure.

 

[XRIowa]

I have a JR 50 and was wonering about the FMF pipe. Did you get it and if so could you shed some light on how it worked???

 

[theroyz71]

Yes, you are trying to polish a turd. We have one in green. It's a great yard bike and that's it. Of course, my son is trying to qualify for Loretta Lynn's on his Yamaha PW50 and it isn't much better.

 

[TEEEE]

Well, the turd is as polished as it’s going to get. I put on the FMF pipe and TCII arrestor. It did add some power, but I wouldn’t call it a huge improvement. I also switched it over to premix and took out the “subpilot” jet, or whatever that weird second pilot jet is. Overall, it is a definite improvement, although it is by no means powerful. A little jetting work will help some too. My son is not racing or anything like that and is still having fun on it, so mission accomplished. Next season we’ll upgrade to a better bike for sure though.

Still...my son almost made it up a pretty steep hill with lots of loose rocks yesterday that would never have been possible without the pipe and the 2nd gear mod. He would have made it but got cased out on a little vertical ledge.

 

[theroyz71]

Cool. I'm glad it worked for you.

When he's ready, the Mini Adventure is a much nicer bike, more power and way better suspension. If he starts racing, the Cobra P3 is even better.

 

[TEEEE]

Thanks for the advice. He’s ready now, but my bank account is not! We were looking at a Senior Adventure. He was tentative about the height but would get used to it quick and grow into it almost as quick. It is almost exactly the same weight as his JR.

 

[XRIowa]

So where is this subpilot jet?? I plugged my sons oil injector line, for the simple reason it was ultra messy..
If you really wanna beef up the JR 50 check this site out.
http://www.barsnake.com/fame/jr50/

 

[OldTimer]

Yep, that's the shineyest turd I ever saw! :cool:

 

[theroyz71]

It's a really shiny turd. The fox shock is prbably worth more than the bike.