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4 Stroke Bicycle Engines & Kits 4 stroke engine kits are great if you want reliability or do not want to mix your oil and gas. Learn from each other how to get the most out of your 4 stroke bicycle engine

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  #21  
Old 03-06-2012, 01:30 PM
cobrafreak cobrafreak is offline
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Default Re: 4G T drive bearing conversion

Here is a video of me demonstrating how smooth the clutch bell is now that the bearings are installed. I took the transmission off to demonstrate. Don't laugh at my work glasses, they are only for garage use. They double as birth control, Lol!
http://www.youtube.com/watch?v=-cbs7...s2jeCQ8w_Ysc_E
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  #22  
Old 03-07-2012, 05:06 PM
Erich_870 Erich_870 is offline
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Default Re: 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
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  #23  
Old 03-07-2012, 07:18 PM
cobrafreak cobrafreak is offline
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Default Re: 4G T drive bearing conversion

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.
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  #24  
Old 03-07-2012, 07:22 PM
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hmiwb hmiwb is offline
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Default Re: 4G T drive bearing conversion

It's on my "to do" list. Thanks for sharing!
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  #25  
Old 03-09-2012, 04:44 PM
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The_Aleman The_Aleman is offline
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Default Re: 4G T drive bearing conversion

<removed out of protest to certain "staff" practices in this forum.>
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Last edited by The_Aleman; 03-14-2015 at 08:42 AM.
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  #26  
Old 03-09-2012, 05:12 PM
cobrafreak cobrafreak is offline
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Default Re: 4G T drive bearing conversion

If you have any issues contact me.
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  #27  
Old 03-11-2012, 03:13 PM
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MotoMagz MotoMagz is offline
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Default Re: 4G T drive bearing conversion

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Originally Posted by The_Aleman View Post
Got my bearings in today. I may install em tonight, if not then this weekend. Let ya fellas know how it goes!
Well how is the grinding going?My bearings should be here Monday.

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  #28  
Old 03-11-2012, 07:14 PM
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The_Aleman The_Aleman is offline
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Default Re: 4G T drive bearing conversion

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Last edited by The_Aleman; 03-14-2015 at 08:42 AM.
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  #29  
Old 03-12-2012, 07:22 PM
BE-tech BE-tech is offline
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Default Re: 4G T drive bearing conversion

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.
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  #30  
Old 03-12-2012, 10:10 PM
cobrafreak cobrafreak is offline
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Default Re: 4G T drive bearing conversion

Quote:
Originally Posted by BE-tech View Post
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.
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.
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