KX500 Transmission shaft mods.

Bottom end tips and mods
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KX500 Transmission shaft mods.

Post by Sandblaster » Thu Jun 22, 2017 2:31 am

I've noticed that on a few KX500 input shafts under 5th gear (P/N) 13129-1744 there has been some galling.
I have even seen a few that were extremely damaged with the gear welded to the shaft.
I have never had this happen to me.
I do change my oil frequently and I run the entire 1 quart (946 ml) bottle in my trans..
I think Kawasaki recommends 850ml..
Nobody I know of that runs 1 qt has ever experienced a failure at 5th gear that I am aware of.

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KX GURU RACING TRANSMISSION OIL MODS 107.jpg
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I had a guy ask me if I have come up with a way of fixing it.
Until now, no... But I think I've got it and it is very simple..
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Thu Jun 22, 2017 12:51 pm

Other manufactures simply drill some holes in the shafts... Likely before the shafts are hardened :o

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I used a double straight flute 1/16" drill bit that I purchased from Grainger.
Drill at a very slow speed is required with a lot of oil or coolant.
When you start drilling the surface metal is very hard but once you cut past the hardened surface metal it drills very easy until you start to break through into the center of the shaft which is also hardened.
I broke both my bits and now have to remove some hardened drill bits :x

After drilling I chamfered the holes with some diamond grinder bits then ran the shaft on a polish wheel.
The finish is very smooth and I believe this will help keep your trans running smooth for many years...
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Sat Jun 24, 2017 3:25 pm

So, problem solved right?
Maybe, maybe not..
I want to be able to feed the oil a bit better.
I see two ways of getting a oil shelf or at least a better flow of oil.
One, is to use a porting tool and bore a hole at an angle back into the clutch puller cavity such as this.

KX GURU RACING TRANSMISSION OIL MODS 105.jpg
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The oil should pass through the bearing and feed the oil hole.

The other way I see is to bore a small hole from the outside of the case at an angle to just miss the clutch puller upper bearing, cut through to that ledge above the bearing and then into the clutch puller cavity. The only issue, and it's not a big one is that you will have to have the hole on the outside of the case tig welded.. After this is done you could reshape the ledge above the bearing to hold a reservoir of oil.

KX GURU RACING TRANSMISSION OIL MODS 106.jpg
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And the drill bit shown is for demonstration purposes only... I would use a much smaller bit.
I couldn't find a smaller one that was handy :o
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Sat Jun 24, 2017 3:38 pm

Here is a pic of the ledge that is above the bearing..

KX GURU RACING TRANSMISSION OIL MODS 108.jpg
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Fri Jun 30, 2017 6:00 pm

A few years ago a buddy of mine wanted to try to build a wide ratio trans for a KX500. One of the trans I sent him was from a KLR650. With a minimal amount of lathe work he was able to get it to work. At the time we decided that it wasn't worth the effort for the little difference in gearing. But lately I'm thinking that it may be a back up plan. As a lot of you know several of the gears are no longer made and this issue will get worse over time. Jason Tanner sent off two complete transmissions to have all the gears undercut. That will prevent them from slipping out of gear ever again and hopefully breathe some new life into some older sets. We will let you know how that is working out. While I had the KLR650 transmission out I took a look at the shafts... Note anything familiar?
KX GURU RACING KX500 USING KLR650 TRANSMISSION 101.jpg
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KX GURU RACING KX500 USING KLR650 TRANSMISSION 105.jpg
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Fri Jun 30, 2017 6:01 pm

Yes... oiling holes... I have seen many KLR650's with 50,000 plus miles on them so I'm more convinced that drilling some holes will be a good idea...
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Fri Jun 30, 2017 6:04 pm

Oh... These holes were .093" in diameter...
The ones I drilled were .060" in diameter... Which is good because small holes are really hard to drill in hardened material..
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Sat Jul 08, 2017 12:09 am

The .093" diameter carbide straight flute bits did the trick.
I'm 4/4... 8-)
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Re: KX500 Transmission shaft mods.

Post by Sandblaster » Fri Jul 14, 2017 1:55 am

Ok, I drilled 7 holes with no issues... Although it starts taking longer and longer the more worn the bits get...
When I drilled the 8th hole I snapped a bit..

This is how I modded this case to capture oil and feed the end of the transmission shaft.

KX GURU RACING KX500 TRANSMISSION MOD 101.jpg
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I probably got a little carried away with the porting tool.
While I'm sure this will work, I won't go quite as deep on my personal cases.
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