jon686

Member
Jan 16, 2008
3
0
I just finished my search of 13 pages related to JR50 mods. I gave it a good honest effort before I started this thread, but did not find the specifics I was looking for. My dilemma is the same as most everyone else who posted in all the similar topics. My son has been riding since he was 2 and started on the JR50 with training wheels that I bought new. Last summer we finally got off the training wheels and he wants to try some motocross at the local track. I don't want to spend the money on a new bike before I know whether or not he really enjoys it. It is obvious he is at the limits of the JR50 in stock form, especially suspension. I read and read all the posts my search returned and found lots of mention about lots of mods, but not much specific info on how to do them. I'm mechanically inclined and am certain I can perform most of them with the proper instruction. Could someone please post some links to help me perform the following mods:

"Jet" removal (the jet the threads say is not needed)

Carb tuning ( which screw does what)

Where to buy aftermarket sprockets and what size "works"

Who has instruction/sells part for the "hidden gear" mod

Oil injector block off for premix gas

I hope the replies help others in the future. Thanks in advance.
 

Jasle

Sponsoring Member
Nov 27, 2001
1,358
0
jon686 said:
"Jet" removal (the jet the threads say is not needed)

Carb tuning ( which screw does what)

Where to buy aftermarket sprockets and what size "works"

Who has instruction/sells part for the "hidden gear" mod

Oil injector block off for premix gas

I hope the replies help others in the future. Thanks in advance.

Jet removal=remove carb. take off float bowl. big jet in middle is main jet. smaller jet is pilot jet. after open you use a flat blade screw driver and turn counter clockwise and the jet unscrews.

carb tuning=big knurled nut with flat slot is idle adjuster. small screw is the air/fuel screw. search this site for sparky jetting guide not in this section.
Many articles online for 2 stroke jetting that are adequate. Basics are same for every 2 stroke motorcycle.

oil injector block off=remove oil pump. build your own blocking plate or remove drive gear from pump and reinstall. then follow tube up to carb on the side where the oil goes in and solder, braze or epoxy the nipple closed.

hidden gear= this is the first gear that is officially hidden. directions are in this section under 1st gear mod jr50 but its fairly simple. remove the right side cover. you'll see that the shift lever has an oblong slot. it goes from center to one direction. grind the slot in a mirror reflection the other way.
I seem to remember that you have to split the case to remove the shift shaft so you cannot easily replace it if someone had one for sale. It goes through one of the shift forks... You have to grind from the center back towards the rear wheel.

sprockets=sorry cannot help on this one. I seem to remember someone mentioned where they could get one in the zillion pages of info on the 1st gear mod but not sure.
 

jon686

Member
Jan 16, 2008
3
0
Thanks for the quick and concise reply. Just what I was looking for. If you other guys can help me on the sprockets/gearing I'll be golden.
 
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