Introduction: Suzuki JR50 Gear Mod
The Suzuki JR50 has a hidden lower gear but you have to grind away to find it. Recently I purchased an used 2002 Suzuki JR50 from my buddy since his kids outgrew it many years ago. This will be my girls first bike and we have gone through it to make sure it's ready for their first adventure. I did the first test rides in the yard to get the jetting close but I'm a big man on a very little bike (the girls enjoyed it). One thing I noticed was that this bike is pretty fast so before our camping trip I made sure the throttle stop was in good shape. The camping trip came and I had some seasoned kid riders do a little shake down. Still too fast for my girls so I had the throttle stop almost all the way in crippling the bike to barely run. I opened the throttle a little more to keep it running and the girls had a great time but it was still faster than I felt comfortable with. So I did some research and found that there is a hidden gear inside this motorcycle a low gear. Many talked about it and even explained how to get this gear to work but the forums had no pictures or step by step instructions. I am going to do this mod and document it here since this site should work for many many years.
For this you will need:
Clutch cover gasket
Step 1: Remove the Right / Clutch Cover
I like to remove stuff that might get in my way like the carb, fuel tank, kickstarter, drain oil and plastics. I do this so that I don't have fuel leaking everywhere plus it's easy and will only add 5- 10 minutes to the whole project. There is also a small round cover that will need to be removed to re assemble it.
I have highlighted the bolts that need to be removed there are two hidden bolts near the top. Also there is a large 17mm bolt near the kickstarter take that out too. The bolts in the round cover are all the same length, the rest are different lengths. You can do something to try and keep them in order but there is an easier way. When you assemble it, all the bolts should stick up about the same height.
There is a spring on the shift shaft (blue arrow) that need to be removed along with the plate. Now you can see the part that needs grinding.
Part of the clutch will fall out so be careful remember the bearing side goes towards the engine.
Step 2: Grinding Time
Now grab the shifter at the top you have neutral and down is a gear but if you try to shift up from neutral something is stopping you. That's the part you want to grind. Cover the area with whatever you can to try and stop the metal shavings. Now you want to match the other side of this part. Get a grinder (I only had an air grinder with a rather large bit) and take your time. Stop and try to shift it up into the new gear if it will not go grind some more until it does. Again take your time.
Vacuum out the shavings remove the paper towels and wipe off any metal shaving you can see. You can also lean the bike over and spray out any shavings you missed. I did all this but I'm sure I didn't get them all.
You can see the it now shifts into the new gear wohoooo!
Step 3: Assemble
Time to put it back together. Attach the plate and spring and try shifting it into all gears it should work but if not you may need to grind a little more. Clean the gasket surface and install the new gasket. This is a dry gasket and should not need any extra sealer. Make sure both dowel pins are in the center case and not stuck in the cover. That part of the clutch that kept falling out had a notch in it and it needs to be aligned with piece in the cover that keeps flopping around which is why you removed the round cover. Gently install the cover it may need a light tap but nothing more. If you are looking for a dead blow something is wrong.Tighten it up don't forget the large kickstarter bolt.
Testing time, I did something wrong the kickstarter blows through the stroke. What I needed to do is once it's installed put the kickstarter on and crank it down half way or while looking at the kickstarter lock bolt. Once the notch opens up then put the bolt in basically creating tension on the kickstarter spring. I've read that the first gear is incredibly low going only 3-5 mph, that's bull. It goes 10-15 in the new gear and feels like a correct gear ratio for the next gear it is not an extreme low gear. It is low enough to crank the throttle stop down a little and still keep it running while being slow which is what I wanted.
Step 4: Test
I am putting the oil I drained back into it for testing since it was near new. I will drain that after a few minutes to try and get any remaining metal shaving out.