Side Cover - HK2012 - VRS - 6904 Bearing. - Which one is better for New Gen Whizzers ?

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Nov 14, 2018
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Howzit Everyone.
Some say the HK2012 is the best and only way to go and if you trust and use the 6904 it will fail.
I disagree - That's a MYTH
When you think about it the HK2012 needle bearing is always in contact with the crankshaft creating alot of FRICTION. Now you need to put in a shim to take up the crank end play the HK2012 created by the HK2012 bearing cup always making contact with the crankshaft gear.
Whats going on? ( FRICTION ) The worst thing for a motor.
I know the idea was to use a good quality HK2012 bearing and your sure that the crankshaft has been hardened. The HK2012 is still gonna wear down the crank over many miles and time and become SLOPPY that's not good. It will get side (forward) to side (rear) movement messing with the valve lash and everything else.( It only took 7,000 miles for a HK2012 to RUIN one of my cranks .Yea the HK2012 wore down the crank end so much and became so SLOPPY. Something had to be done. Yes I use oil with ZINC.
I know the argument. Then why did the Vintage Whizzer use a needle bearing?
Bearings have improved over the years ALOT . But back in the 1940s the needle bearing was Whizzers best idea. So Whizzer designed all their motors with a needle bearing. So, ya always used a needle bearing.
Today is the modern world, Bearings have improved ALOT.
All modern Scooters and modern Motorcycles use OPEN or SHIELDED bearings on both sides of the crankshaft. I WONDER WHY?
So modern Whizzer had the right idea with the 6904 bearing. But the 6904 was installed with the EARLY NE crank that was designed to be used with the HK2012. The result was bearing FAILURE. Whizzer soon corrected this by designing the LATER NER crank. There is a small ledge on the crank to take up the HUGE amount of crank end play. But who knows what's in your bike? Poor quality control during assembly parts got all mixed up.
I know, Someone designed a fix for that 6904 and early NE crank HUGE end play problem. Their solution was to remove the 6904 and machine a holder for the HK2012. Sure it worked great, good idea. If your in love with the HK2012 now your back to ALOT of FRICTION.
Then someone BASHED the 6904 and told all it was a FAILURE and a bad Design.
No, The 6904 is a good design and a great improvement.
Let me show you how to use the 6904 with the early NE crank.
I made a spacer. I went down to ACE and bought an oil imp. bronze bushing 20mmI.D.x24mmO.D.x12mm I came home and cut a piece of the bushing off 3.5mm long. Slipped it on the crank installed the 6904 - PERFECT - Took up any crank end play.
Now over 20,000 miles later, No problems, NO FRICTION and the crank is never SLOPPY.
If your still worried about the 6904. just upgrade the 6904 bearing to a NACHI or another quality bearing I replaced all bearings with NACHI bearings
Almost all metric motorcycles use NACHI and ya see how long they last, FOREVER
Another reason for 6904 bearing FAILURE
If the 6904 bearing is the SHIELDED 6904 just pop off the shields on both sides and make it an OPEN 6904.
I know the SHIELDED bearing is greased inside. But shouldn't be used in a crankcase when oiled by the splash method.
What will happen is. A small amount of oil will sneak past the shields and dilute the grease. Now there is not enough grease and not enough oil to lube and cool the 6904 and yes bearing FAILURE ( Thank's Mr. Joe Lin another example of poor quality control )
For proper lubrication Just pop the shields off both sides. Get that oil moving The end of the crank has an oil passage and ya want to use it.
I've never long term tested the later NER crank. So I;m not sure if Whizzer got the crank end play right. But I measured it and all looks good
I hope this info can help someone
Here's some pictures
ALOHA Wrench
 

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