Topic: Please Help Switching swing arms

[livetoskate]

I am having a problem.
First I have a 1978 cb750 k and a 1976 cb750k whole parts bike.
I have a transmission problem with my 78 so I pulled the engine and am planning on doing the work on it,but that is a big project for the lttile time I have right now.So I pulled the engine out of my 76 and put it in my 78 frame so I would have some wheels for the time being.
I want to use my 78 real wheel.

The  Problem:
1)The 78 runs 630 sprocket and chain and my 76 has a 530.

2)The final drive flange on the 78 is much thicker than the final drive flange on the 76.There for it holds the spocket out about 3/4 of an inch or so farther away from the wheel.So I can't just swap out the sprockets on the final drive flange,because then the rear sprocket and the engine sprocket are not at all in line.So I tried to swap the whole 76 final drive flange and sprocket into my 78 wheel and now my problem is that the whole wheel/final drive flange assembly is to thin for my 78 swing arm,because of the different thickness in the two final drive flanges.If I put it into my 76 swing arm it seems to fit  fine.

3) The swing arm  wider on the 78 than the 76 (aprox. 1 inch) So I thought since it fits in the 76 swing arm that maybe I could just swap the 76 swing arm onto my 78 frame.
I am just worried that it might not work with my shocks because of the 76 swing arm being thinner.
   Please if anyone has any idea or advice  let me know,I know it is possible because I have heard of people doing it before.

Thanks alot

[mystic_1]

So I tried to swap the whole 76 final drive flange and sprocket into my 78 wheel and now my problem is that the whole wheel/final drive flange assembly is to thin for my 78 swing arm,because of the different thickness in the two final drive flanges.

Couldn't you add some axle spacers to take up this extra space?  If you center the wheel in on the axle (centerline of tire on centerline of bike) is the sprocket aligned properly?  If so, this is the way I would go.

The shock mount issue would definitely be a problem for swapping the swingarms.

mystic_1

[754]

The most you would have to do using the stock 78 arm isadd a spacer.

[livetoskate]

I tried with the spacers I had have between the two bikes and none of them work.
What would you recommend Go to a machine shop and have them make one to the size I need?
I will check if the sprockets are aligned when I center up the wheel with the bike.
Thanks let me know if you have  any  other ideas or tips.

[mystic_1]

You'll definately need custom spacers.  Get the wheel centered and make sure the sprocket lines up.  If it does, you're golden, just measure the gap on each side (if any) and have custom spacers made up.  You may even be able to find suitable pre-made axle spacers online somewhere.

If the sprocket is not aligned properly when the wheel is centered then you'd have more issues to deal with.

BTW, not that this helps your issue but if you go to the Cycle Exchange website under Honda and scroll down to look at their offset rear sprocket setups, they have some interesting data on the differences between these drive flanges. 

Good luck to you!

mystic_1

[gerhed]

You'll definately need custom spacers.  Get the wheel centered and make sure the sprocket lines up.  If it does, you're golden, just measure the gap on each side (if any) and have custom spacers made up.  You may even be able to find suitable pre-made axle spacers online somewhere.

If the sprocket is not aligned properly when the wheel is centered then you'd have more issues to deal with.

BTW, not that this helps your issue but if you go to the Cycle Exchange website under Honda and scroll down to look at their offset rear sprocket setups, they have some interesting data on the differences between these drive flanges. 

Good luck to you!



mystic_1

I use washers as spacers religeosly (sp?)!

[754]

The difference is not an inch.. more like 1/4 or 3/8 inch. You may be able to cut a spacer down. Its not a real big deal, just take the time to do it right. If you are patient you could cut down you 76 spacer, but that involves a square and ability to work carefully.


As a machinist, I just cringe, when I see a stack of washers .. I mean its not so bad to mock up or measure but I have seen pretty quick dragbikes with that kind of (work) on them..