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Author Topic: '79 cb650 swap to '81 swingarm problems, and how to fix them.  (Read 1786 times)

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Offline Soos

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'79 cb650 swap to '81 swingarm problems, and how to fix them.
« on: October 29, 2007, 02:58:53 AM »
HAHAHA...... i thought it would be a drop in part.....

I removed the '79 swingarm the other night, and started measuring the differences between the  2 swingarms.

First highly noticeable difference, length, weight was another, the '81 swingarm must be of thicker tubing, it is obviously a larger diameter.
Next was the diameter of the bolt that holds the swingarm on....the '79's is a bit smaller, about 2mm in diameter.
So I was thinking that mabey the pivot tube(that slips in the swingarm) would be interchangeable so I could use the '79 bolt and tube with the '81 swingarm.
NOO....
'81's is larger diameter(2mm)....

(hahha... and SHORTER!. Measure before cutting... measure 4 times to be sure.... should have checked this when i began... 11/1/07)


For further comparison, I took the swingarm off my '81cb650c, and compared it to the '81 spare parts bought one.
Overall length, bolt diameter, pivot tube diameter, mounts for the chainguard, were all identical.
Mabey this swingarm is off a cb650c... dunno.


At this point if I were not a machinist I would have given up....
I took the swingarm to work tonight and made new bushings to accept the tube and bolt from the '79 swingarm for the '81 swingarm.
Then I took the '81 swingarm sandblasted, welded, ground, sandblasted again, phosphated, and powder coated it.
The swingarm  LOOKS NICE!
No more sharp edges, no ugly welds showing...
All that work for about a 3/4" longer swingarm......

Now that I did all that work, I figured I would swap the swingarms before bed tonight....
HAHHAA.... now I need a longer chain!
 :o


Anyone who has done similar(swingarm swaps), is it sane/safe to put a new chain on a set of gears with about 5-6000 miles on them?
Or should I pony up the dough for a new set of gears when I get a new chain?

l8r
« Last Edit: November 01, 2007, 04:15:56 AM by Soos »
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline cb650

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Re: '79 cb650 swap to '81 swingarm problems.
« Reply #1 on: October 29, 2007, 05:34:21 AM »
It is the 79 thats diff.  80/82 where the same swingarm no matter custom or not.    I did put a 79 in my 81 racebike for the couple pounds less weight.




                         Terry
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Offline Soos

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Re: '79 cb650 swap to '81 swingarm problems.
« Reply #2 on: November 01, 2007, 03:59:10 AM »
hahahaa.....

 >:(

I just got done installing my longer swingarm(looks better!) and before I finished fully installing it, i noticed side to side play...

I made the mistake of assuming the cb650 '79 pivot bolt was the same length as the '81's..


nope.

about 1/16 inch (1mm) of difference in length or more.
Back to work to make new bushings for this thing ... again.


Would anyone if they had the chance put stellite on their pivot tube?(on the pivot areas)
Or is the tube heat material, and welding on it is a bad idea?

(Hey Hondaman!!)
Anyone have any preferencesof the best bushing material to use?
Any stainless pretty much I have access to, as well as teflon bar.
Unfortunately I do not have any oil-lite(oil impregnated bronze) to use or I would.


The last ones I made of heat treated 17-4 stainless.
Fit great, but not thick enough flange to take up most of the side to side slop.
I know I need to leave some room, so the pivot tube locks in place, and the swingarm pivots freely.
I was thinking of about 0.010 to 0.015 side to side clearances(total), or is this too close?


l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: '79 cb650 swap to '81 swingarm problems.
« Reply #3 on: November 01, 2007, 04:10:37 AM »
I have a few pictures of the (so far) finished swingarm.

I could have done better, there are a few spots of porosity I opened up in the origional welds, and did not weld them all....
But I'm REALLY happy so far.

Basic black, but it's free.
And the smudged areas are from greasy hands.

l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: '79 cb650 swap to '81 swingarm problems, and how to fix them.
« Reply #4 on: November 03, 2007, 06:56:46 PM »
Well, I went ahead and broke down and bought a new chain.
Dropped the swingarm in... again, and no slop this time. Perfect fit.

Buttoned everything back up, and realized I had to take off my Yosemite Sam "BACK OFF" mudflap.(it even light up when i hit the brakes)
It rubbed when my rear swingarm encountered a good bump.
Thought that getting sucked up under the fender wouldn't be too fun.
Especially at highway speeds.
Or better yet, rub the wire insulation, and cause a hard to find electrical glitch..

Dropped the front end about 1/2 inch as well...

I LIKE this mod's looks.


A definate plus so far, can't wait to ride it at highway speed and see if it tacks better/worse at high speed.

l8r
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-=≡ Soos ≡=-
Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650
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