Topic: Swing arm questions??

[750]

Hey guys,
I don't know if I'm posting this in the right place so if it needs to be moved feel free but I feel as though it belongs here.  My cafe build has begun!! In order to upgrade breaking on the cheep and because it looks cool, I am using wheels, breaks and a rear swing arm from an 82 GPZ 750 R1 that I got for $75.00 and bolting up to a 77 CB750K frame and forks.  Luckily (or maybe not so luckily)  I am a machinist so for the most part this is pretty easy stuff.  A bracket here or a spacer there and everything pretty much bolts up.  The front wheel is easy, just center it between the forks, build a few brackets for the newer breaks and I'm on my way.  The rear wheel is where I'm searching for answers.  I have the swing arm mounted and centered in the frame (had to make two .093" spacers, one for each side and drill the swing arm hole to .625" to make it bolt up)  and everything works and looks great.  The drive line isn't much of a chore as I can either add a spacer behind the sprocket or remove material from the sprocket hub.  Where I'm having trouble is figuring out a good reference to center the wheel off of.  Can I center the wheel by using the center of the neck and center of the frame back bone to construct a straight line to the back of the bike and center my rear wheel off of that line??  Or is there a better way?  For that matter, after reading my processes, is there a better way to do any of what I'm doing (besides of course using different parts)?  Thanks for any info you are willing to share. 
Tom

[754]

I have done quite a few. Remember not every bike has a wheel centered in the frame.

 I usually use a pce of 1/4 x 3/4 bar to line up wheels. Honda though uses a floating sprocket, make it trickier.  Put the back wheel you want to use, in swingarm, then hold straight rod against the sprocket (Machinist clamps may help), has to reach front sprocket. Now steer the rear wheel till the rod and front cog are prrallel.. this means rear wheel is in plane. now looking at the rod to front cog, you can measure how much rear cog has to move.

 Use a stock rear wheel to find  center of tire to frame, use that point to center new wheel.. you can use a bob off rear fender brace or a square on a CB 750.

[750]

I have done quite a few. Remember not every bike has a wheel centered in the frame.

 I usually use a pce of 1/4 x 3/4 bar to line up wheels. Honda though uses a floating sprocket, make it trickier.  Put the back wheel you want to use, in swingarm, then hold straight rod against the sprocket (Machinist clamps may help), has to reach front sprocket. Now steer the rear wheel till the rod and front cog are prrallel.. this means rear wheel is in plane. now looking at the rod to front cog, you can measure how much rear cog has to move.

 Use a stock rear wheel to find  center of tire to frame, use that point to center new wheel.. you can use a bob off rear fender brace or a square on a CB 750.

Thanks So much for the information/ reply, but I don't quite know how using the stock wheel will work unless I put the stock sing arm back on which isn't possible (without making some thin bushings) as I drilled the frame for the current swing arm. However, I will remember this for the future.  I could put the stock wheel in the new swing arm but I don't know how that will help me find center of my frame.  I think I must be missunderstanding what you're telling me or maybe I didn't write my story clear enough. Sorry if it's confusing.  I do have another 77 CB750 but I'm leery of using it as a reference as I don't know it's history and don't know how consistant frames were back then.  I really wish I had used the plumb bob before I drilled the frame but now I have to get creative. Thanks again for the reply.

[HavocTurbo]

I have found...

Sometimes you have to shim both the front and rear sprockets to get them to line up.

Some people scoff at that notion.... some don't.

Either way you MUST line up the sprockets in order for any arm wheel combo to be safely useable.

[750]

I have found...

Sometimes you have to shim both the front and rear sprockets to get them to line up.

Some people scoff at that notion.... some don't.

Either way you MUST line up the sprockets in order for any arm wheel combo to be safely useable.

Absolutely.  I totally agree.  Though, it's not the sprockets I'm concerned with.  I can make that happen in my sleep.  My worry is making the front and back wheel run on the same plane.  That said.  I think I have it figured out.  Please chime in if I'm wrong, but once I have the front end on and solid I will remove tires from both wheels and run straight edges (one from each side understanding I may have to shim them out to meet the width of the rear wheel) from the front wheel to the back wheel. and center the rear wheel on the strait edges.  I know this is a loos explanation but I think I'm making sense.  Please tell me if there's something I'm missing.
Thanks
Tom

[Hannibal Smith]

Yep, that does work.

But, as 754 has stated, some bikes run parallel but not in line from the factory, but if your model runs in line, then that system works.

You just run 2 blocks to accommodate the wider rear, then run straight edges back, triple check everything, and you will be close enough. Getting yours wheels aligned in the vertical (straight up and down) is more important anyway.

[754]

Sorry I was a bit of a hurry, what I posted at the end, should have been at the beginning.. that said I meant if you had the wheel on before you started you could have made a reference point.

 I would not worry about tires off during aligning, go off the wider and try to get that parallel to the front.

  I have to say at this point I have found over time that a set if 4 inch inside calipers (dividers) is the biggest help in figuring wheel spacers..  if you get under 1/2 inch use drill bits out of a up to 1/2 inch drill index..

I at one point wrote at some length a post on tips for setting up wheel spacers, it never seemed to get any response and appears to be lost in the sands of time..

[750]

Thank You all for your help.  I wouldn't even be attempting to build a cafe without this forum.  It's not that I couldn't do it but I don't know that it would be as enjoyable if there weren't people like you to bounce questions off of.  
Thanks again
Tom

[HavocTurbo]

Thanks aren't really necessary...

Just remember, don't #$%* it up Tom or we'll all kill you.


hah j/k. 


Remember to post pics!!!!