SOHC.co.uk Forums > CB750

roller bearing vs. swinging arm bushes?

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Phil:
Thanks - all this information is very helpful. I was puzzled by the M3/ Adam Pop claims. It is scary at speed though! I am having a titanium swinging arm pivot machined, would increasing the i/d of a high grade bush help? Why is the bush not longer? Why not drill the centre of the pivot and put grease nipples on the ends? Can you custom produce? Sorry for all these questions...

Phil

Voxonda:
Hey Phil, no worries about the questions, always willing to share what I (think I) know. In my opinion the way to go is increase the diametre of the pivot/bearing assy, but then you have to inline drill the holes in the frame and change the swingarm. But the space behind the engine is limited. I have build a box swingarm, which is approx. 1" longer than the original and a lot stiffer. Think that is basically all you can do without going ballistic about it and replace the frame for whatever Spondon, Egli, Dresda etc. The length of the bushes is limited by the depth of the drilling in the swingarm. Making the bushes longer with this diametre brings nothing, they are long enough.
I can make the bushes by drawing. I will not drill in the pivot, because you also have to drill square to the pivot-axle and makes it a weakened area.
This is one of my bikes, almost ready for paint. Replica of a 1973 JAPAUTO Endurance racer.


Cheers, Rob

Phil:
Thanks again. I have to keep the standard swinging arm in order to comply with the CRMC rules. I think I will go for high quality bushes and keep the pivot bolt standard except replicate in titanium. Love the Japauto! I raced a 960cc Japauto in a six hour endurance race in Belgium back in the early 1970s - quite a beast then!

Voxonda:

--- Quote from: Phil on March 05, 2008, 10:57:34 AM ---Thanks again. I have to keep the standard swinging arm in order to comply with the CRMC rules. I think I will go for high quality bushes and keep the pivot bolt standard except replicate in titanium. Love the Japauto! I raced a 960cc Japauto in a six hour endurance race in Belgium back in the early 1970s - quite a beast then!

--- End quote ---

Any pic's dare I ask from the 70's???????
What you can do to further stiffen up (is that english?) the overall 'feel' of the bike is looking at both the engine mountings right front and back. I will make pictures of my 'solution'. Made the front plate in Aluminium 7075 (high tensile) and doubled the back one, meaning made a new one from two, integrating a threathbushing for the top rear engine mount, instead of the nut. Have to get some new batteries for the camera.

Cheers, Rob

Voxonda:
Found a pic but here the rear one is not ready yet. The front one wasn't polished then.

Can work with the original oiltank but then you have to space the tank outwards a bit.
works for me.

Cheers.

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