Topic: CB750K - Which Swingarm Bolt Should I Use?

[Imago]

I have 2 swingarms, one from 1972 and one from 1976.

The 1976 version appears to be beefier, and will likely be used in our 1976 CB750K build, however the bolt has no grease channels and only one zerk, (which is missing) in the center of the bolt journal to apply grease.

The 1972 bolt has zerks on either end of the bolt with grease channels, and appears to be a better designed product.

2 questions:

a) can and should a 1972 bolt be used in a 1976 swingarm, i.e. can you mix and match, and
b) both bolts seem seem fairly snug in their respective journals... but should I get new bronze bushings? If so, where?

[PeWe]

I have a K2 swingarm on my CB750 K6. I use the K6 bolt therefore no grease nipple at all. I did not refill grease back in the 80's so I do not bother.
My old K6 got a needle bearing kit early 80's, overfilled the bearings with grease and mounted it. K6 swing has a grease nipple in the center of the swing for refill. Bolt is solid.

When I took it apart 2012 the bearings were OK with plenty of good grease (bike used 35.000kms since grease fill, std grease). I mounted a K2 swingarm 2013 when my K6 swing had the bolt ears for chain cover broken.  This time MoS2 grease, high load, waterproof grease, black stuff.

(I snapped the chain on Autobahn 1988, geared down 2 steps and twisted the throttle... bang... chain snapped, cut a slice from the license plate and chain cover came loose, no cracked cases with oil leak . Chain case landed in a garbage bin in France next day. I did not tighten the drive chain in time, too much slack. ) We were lucky that 2 guys on a small bike stopped by where we were parked beside Autobahn. Got lift to nearby Kassel into a bike store that sold a new chain to me just before closing time...

I found a restored K2 swingarm on eBay with new needle bearings so it went in. I have no doubts to not add more grease.
I guess it's different when the OEM bushings are used or newer bronze. They might have fresh grease pressed in on regular basis.
I do not feel that the K2 swing is weaker than K6, not yet.

[chewbacca5000]

I just did this same thing the other day.  I have a 71 swing bolt that I drilled and tapped for american zerk fittings and installed on a 76 swing and it worked out great.

Here is the info thread  http://forums.sohc4.net/index.php/topic,148191.0.html

This is a nice upgrade.  I also cut grease grooves in the collar so the grease spreads evenely.

With the Zerk fittings I know the grease is getting in there.  The Japanesee fittings don't work well with our american grease guns.

As far a buying bushings I don't see how that would help if the swing collar is wore.  I'd imaging they make the bushes to new specs.  That is why Hondaman has people send him theirs to make the bushes for each collar.

A new collar cost close to 120 add bush 20 to 40 = 140 to 160.  What Hondaman does is more of a labor of love than a profit thing.  Gonna send him my K2 swing and let him do his magic.

[Imago]

So you replaced the Japanese zerks with US ones on the ends of the '71 bolt. Sounds good to me. I could do the same.

Did you leave the zerk in the '76 swingarm, replace it or cap it?

My '76 center swingarm zerk is missing anyway so I should do something with the hole it left behind.

[chewbacca5000]

Install another Zerk there to fill the hole.  You will be super lubed!  It was very easy to do.  The swing arm bolt metal drill easily.  I put it into the vise on my drill press and it was a done deal.  Worked out great!

I left the center one alone as it did not matter to me.  If you do not own Hondamans book it will pay for itself over and over.