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  340 single crank bearings ... again!!!
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   Author  Topic: 340 single crank bearings ... again!!!  (Read 213 times)
GaWajn
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340 single crank bearings ... again!!!
« on: March 12, 2019, 12:00:12 PM »
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Ok ... I have a bit of a mystery here. I am rebuilding a 1970 340 single for a friend if mine. I took a decent 1970 335 bottom end to use in this build because I only had the cylinder and head to start with from the 340. All good so far right?

Everything is going according to plans ... remove the original crank bearings STEYR NU305 C3 ... at least I think that's what they were. I will fish them out of the garbage to make 100% certain.

Get new FAG NU305 C3's ... install the inner races onto the crank using the original shims that were there with the original bearings ... lightly freeze the bearings and install in the cases. Put everything together and there is over 1/4 inch axial play!!!!!!

Take everything apart ... examine ... the original inner races had shoulders and are marked NJ305 C3! Oh boy ... this could be a $150 mistake!!!

I am headed out to work as I write this. Tomorrow morning I will post pics along with measurements. I have never done a 1970 335 bottom end before ... I am missing something for sure ... but what?
« Last Edit: March 12, 2019, 12:02:14 PM by GaWajn » Report to moderator Logged

1970 Ski Doo TNT 292 Bogie (Restored)
1974 Ski Doo Elan (Habs - custom)
GaWajn
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Re:340 single crank bearings ... again!!!
« Reply #1 on: March 13, 2019, 07:49:01 AM »
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After a little bit of research, this is what I have come up with. If anyone can confirm or contradict my findings, please chime in!



This is the page from the 1970 book. Both bearings are the same for the 335/340 and cross to NJ305 C3. The axial play is limited by the shoulders on the inner races, along with shims as needed.

Here is a pic of the inner races.



In the 1971 book, there is one bearing which crosses to Nu305 C3 and the other is a 6205 C3 with a groove ring. I believe that the groove ring is what prevents to much axial play in this setup, and why the NU305 C3 does no have a shoulder on the inner race.

Here is a pic from the 1971 book.



Here is a pic of the NU305 C3 inner race.



Are my deductions based on research from the parts manuals accurate/correct?

This being said ... the NU305 C3 inner races that I have installed on the crank are on there tight. The only way I will be able to remove them is by destroying them. If I have a  kind of distance sleeve machined and installed to act as the missing shoulder ...   Will this work? Is there any way to save the current installation or have I lost my $150 that I paid for these bearings?

Your input is appreciated as always ...
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1970 Ski Doo TNT 292 Bogie (Restored)
1974 Ski Doo Elan (Habs - custom)
olympic
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Re:340 single crank bearings ... again!!!
« Reply #2 on: March 14, 2019, 09:54:57 PM »
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Hey GaWajn you are talking about making a ring to put on the inner race so it would have shoulder correct. That should work as long as you compensate for the shim because you want it go up against the journal. The nj305 c3 the shims stop the inner race and sets the end play as you know but the ring needs to be made up so it sets the end play not your shims.
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GaWajn
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Re:340 single crank bearings ... again!!!
« Reply #3 on: March 15, 2019, 05:27:08 AM »
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Understood ... thanks ...
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1970 Ski Doo TNT 292 Bogie (Restored)
1974 Ski Doo Elan (Habs - custom)
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