4G T drive bearing conversion

Cobra,

That's pretty good looking! The only thing that makes me nervous is grinding down the shaft by 1mm. How did you do it, with a flat file?

Also, it looks like those 20mm OD bearings fit snugly in the clutch drum. Did you have to push very hard to press them in?

Erich
 
I used a small body grinder with flap disks and finished with an assortment of files. If you are nervous then don't do it. I've been doing things like this for years and years. If you don't want to do yourself have a local machine shop do it for you. It really is worth the trouble and expense as the bearing conversion makes the bike MUCH smoother and maintenance free. We can all agree that bushings suck! :P

The 20mm bearings push in with your fingers. It's perfect. Not too small, not too big. I did a lot of research on this before attempting to undertake.
 
Great job cobrafreak! I thought about this a few times in the past and wasn't sure how to go about it. It was either a larger pulley to fit the bearings (then you lose drivetrain ratio), or needle bearings and filling in the slot with JB weld and making it smooth (problems with getting the key in). I never really thought about turning down the crank. Your approach is really the only way to go. Just wanted to point out to others that not all shafts are 15mm. In fact, most now being sold are the 5/8 shaft which actually measure .622" or 15.79mm. so a little more material may need to be removed. I'm also not sure if the center bolt hole in the crank on the 5/8 shaft models is the same size as on the 15mm shaft. If a larger bolt is used, material could be getting a bit thin to bring it down to the 13mm required.
 
BE-tech said:
Great job cobrafreak! I thought about this a few times in the past and wasn't sure how to go about it. It was either a larger pulley to fit the bearings (then you lose drivetrain ratio), or needle bearings and filling in the slot with JB weld and making it smooth (problems with getting the key in). I never really thought about turning down the crank. Your approach is really the only way to go. Just wanted to point out to others that not all shafts are 15mm. In fact, most now being sold are the 5/8 shaft which actually measure .622" or 15.79mm. so a little more material may need to be removed. I'm also not sure if the center bolt hole in the crank on the 5/8 shaft models is the same size as on the 15mm shaft. If a larger bolt is used, material could be getting a bit thin to bring it down to the 13mm required.
Click to expand...

Thanks, I appreciate it. Yes, I agree that it was the most practical way to go. I may have made a mistake with saying that my shaft was a "15mm" shaft. My shaft really is 5/8". I just said 15mm because my head was in the metric world when I wrote my thread. The majority of bearings available in the world are in metric sizes. Roughly, the bolt hole is 6mm, and the walls are roughly 3.5mm thick. If the full amount of engine torque were on the end of the shaft, i.e. the engine clutch torque, I would be worried that there would not be enough steel. But since the sole purpose of the last 3/4" of the engine shaft is to just center the clutch bell over the clutch, I believe it will be fine. I have 100 - 150 miles on my bearings and it is no different from the day I first installed it. I believe it will be good to go for the long run. I've done the bearing conversion to two bikes so far and it is wonderful. The second shaft that I ground down ended a little bit crooked so I put PC Plumbing putty on it and hand lathed it centered after 10 minutes or so with a stationary tool rest and a sharp chisel. It was perfect when I was done. PC Plumbing putty is so hard after is hardens it actually dulled the tool steel in the chisel I used to turn it down. That bike has about 150 miles on it too with no problems.
 
cobrafreak said:
The second shaft that I ground down ended a little bit crooked so I put PC Plumbing putty on it and hand lathed it centered after 10 minutes or so with a stationary tool rest and a sharp chisel. It was perfect when I was done. PC Plumbing putty is so hard after is hardens it actually dulled the tool steel in the chisel I used to turn it down. That bike has about 150 miles on it too with no problems.
Click to expand...

I have been thinking about replacing the bushing in my hoot gearbox with a bearing. I did use the JB weld on it to take the slack out of it and it seems fine so far, but could you explain the procedure you used to hand lath the shaft true? If I do it, I would like to get it right from the the start.
 
Sure. It's more akin to wood lathing than steel lathing in that you are holding on to the tool rather than the tool being fixed to a jig. Get one of those long locking jaw clamps that you can expand to grip the engine mount and have the excess of the tool stick out toward the clutch side of the engine. This will be what you will rest the base of your chisel tool on just as on a wood lathe so you can get leverage. Hopefully have prepped the shaft with acetone before you applied your epoxy putty. It needs to be very clean for good adhesion. When your PC Plumbing putty or JB weld has set, start the engine and let it idle (in a well ventilated area so you don't inhale exhaust) and use a sharp 3/4" chisel as a cutting tool. You cut from the bottom of the shaft, not the top, and your chisel bit should be upside down so the slant of the bit is facing down. Put the left edge of the chisel lightly against the clutch as it is spinning so you can get a right angle on the cut. Take a small amount off and see if the bearing can fit snug on the shaft. Keep doing till the bearing can slip all the way down to the clutch side of the shaft. It should be true when you are done and the chisel should be in need of sharpening as the epoxy resin is very hard. You can use a strip of sandpaper as the shaft is spinning to take off the last .001" or so for a perfect fit. If you mess up, just clean with Acetone and apply again and repeat till you get it right. Sharpen your chisel with an oiled stone for best results.
 
Last edited:
This thread got a little quiet. If one did attempt to use a needle bearing and filled in the key-way over the clutch bell with pc putty, couldn't that then be ground down or lathed to perfect trueness? If that would work, taking out a little on the clutch bell would seem like small potatoes on a drill press. The clutch itself sides over the key anyways. I'm just a nervous nelly when it comes to messing with that shaft.
 
Fugi93 said:
This thread got a little quiet. If one did attempt to use a needle bearing and filled in the key-way over the clutch bell with pc putty, couldn't that then be ground down or lathed to perfect trueness? If that would work, taking out a little on the clutch bell would seem like small potatoes on a drill press. The clutch itself sides over the key anyways. I'm just a nervous nelly when it comes to messing with that shaft.
Click to expand...

High strength metal resin putty is very very hard but I doubt that is hard enough to function as a bearing race for needle bearings. You would need to fill the key way with steel.
 
I DID IT !!!!!!! Yes I was scared to mess up the shaft but I did it and I am very happy with the "Cobrafreak Bearing Conversion" I used a File to do mine...the chisels were not getting me anywhere.It took a while but it was a fun little project.I have no bell ring and it is really smooth So thanks Cobra for the great mod.
 
MotoMagz said:
I DID IT !!!!!!! Yes I was scared to mess up the shaft but I did it and I am very happy with the "Cobrafreak Bearing Conversion" I used a File to do mine...the chisels were not getting me anywhere.It took a while but it was a fun little project.I have no bell ring and it is really smooth So thanks Cobra for the great mod.
Click to expand...

Very cool! I like the name you gave the procedure, lol. C.B.C. for short, Hehehe.
 
Hey Cobrafreak (or anybody), where did the $.99 bearings go? This size bearing is easy to find on VBX, but they're almost $4.00 each. I'm kind of in a parts buying moratoreum state right now.
 
You must log in or register to reply here.
Back
Top