Topic: 1970 CB750 project "Dad's bike"

[ECM]

Noted that chain guard is from a K1 bike as the end is longer. Honda changed from the short guard to a longer one on the K1 model to reduce oil from slinging up on the passengers legs. So your Dad must have changed that out at some point.

Talked to my dad last night and he said he has never changed the chain guard, that is the one that came on the bike.  So maybe this was one of those evolution pieces that happened mid year?.... 

[ECM]

Pulled the collar from the swingarm today.  Odd colors?  Everything okay here? I don't feel anything abnormal with my finger. I found that my dad had put Bronze bushings in.  Not sure if I should remove these before sending the swingarm to powder coating?  (Powder coater said all bearing and races should be removed prior to Powder coating as they can really get jammed in there after the baking process never to be removed again)  If I do remove do they need to be replaced with new bronze bushings?

[Trad]

That collar is in fantastic shape. No pitting or scoring.

[CB750faces.com (Lecram)]

Yes, great story. You mentioned opinions welcome - stock or slightly custom. You will get a lot of different ideas on that one. Me, I enjoy trying to take these bikes back to OEM as they came off the showroom floor. I like the challenge more than putting on new custom parts. Plus, how can you beat that look of the early 70's. It will cost you though if you go with OEM exhaust...or take the easy route and find some aftermarket to stick on there until you can find and afford OEM. Noted that chain guard is from a K1 bike as the end is longer. Honda changed from the short guard to a longer one on the K1 model to reduce oil from slinging up on the passengers legs. So your Dad must have changed that out at some point. Maybe he did not toss it out as those are costly and hard to find if you decide to take it back to stock.  But keep in mind it is your bike and do with it what you and your son will like for sure. You mentioned Dad ordered a blue/green and orange. The CB750K0 Four was available in one of three colors: Candy Blue Green, Candy Gold, or Candy Ruby Red. The tank, side covers, air box and upper forks were of the basic color (blue/green, gold, or red). The headlight shell was also the basic color. Good luck with this neat project and keep us updated on the progress.

Honda changed the chain guard from 1021880. I own two K0s (103... and 104...) and both have the long versions. The long K0 version is slightly different from the K1 chain guard, barely visible. So this guard should be right for this bike.

[CB750faces.com (Lecram)]

Great project! It looks pretty original, but a load of work to do.

[calj737]

Definitely remove your bearings and bushings prior to powder coating. You run the risk of grease and grime leeching out during the heating process and destroying the beautiful finish of the powder coat.

Ditto on the condition of that collar!

[Stev-o]

Definitely remove your bearings and bushings prior to powder coating.

+1.  Then clean it out real good and buy a piece of all thread, 2 large fender washers and nut and put it in the swing arm. This will prevent the PC from going in there, and you'll be able to install the new bushings with no issue.

[ECM]

Definitely remove your bearings and bushings prior to powder coating.

+1.  Then clean it out real good and buy a piece of all thread, 2 large fender washers and nut and put it in the swing arm. This will prevent the PC from going in there, and you'll be able to install the new bushings with no issue.

So I will need to replace the bushings when I remove them or can they be reused?

thanks so much everyone.

[calj737]

It's advisable to replace them with new oil lite bronze bushings. Many members source them from a chap in Germany for around $20

[Stev-o]

It's advisable to replace them with new oil lite bronze bushings. Many members source them from a chap in Germany for around $20

Cal knows his stuff, I'll make it easy for you, click here...

http://www.ebay.com/itm/Honda-CB-250-360-400-500-550-750-Four-swingarm-bronze-bushing-set-bearing-new-/251851928293?vxp=mtr&hash=item3aa38b72e5

[ECM]

It's advisable to replace them with new oil lite bronze bushings. Many members source them from a chap in Germany for around $20

Cal knows his stuff, I'll make it easy for you, click here...

http://www.ebay.com/itm/Honda-CB-250-360-400-500-550-750-Four-swingarm-bronze-bushing-set-bearing-new-/251851928293?vxp=mtr&hash=item3aa38b72e5

The bushings I have don't have the lip on them.  They insert all the way into the swingarm tube.  These look like ones for a later bike.  Are they interchangeable so I can eliminate the end cap that sits under the cup washer?

[ECM]

So have steadily been trying to get the pistons un-stuck for a few weeks now.  Lots of sitting with ATF/Acetone in the bores.  Now even resulted to a bit of fire to heat things up and still can't budge them.
 
Any other options I should consider?  I am not sure if disconnecting the connecting rods from the crank and taking the jugs with pistons to a machine shop is the next step.  Not sure if they would be able to help me other than maybe taking a press to the pistons.  I would like to save the connecting rods as I really don't want to mess with the mix and match of new connecting rods/crank/case to get everything balanced and bearing tolerances figured out like I have read about.
 
Can a machine shop do anything for me?  (I called one today, but they are off on Monday's, will have to follow up tomorrow)  Anything else I should consider to get these pistons unstuck?
 
An extra piece of info, I do have another set of pistons/jugs/head I got as a packaged deal as I knew I was going to need new pistons anyway.  Not sure if that helps in figuring out options as this might turn to a destructive process to get this engine rebuilt.

[calj737]

"Resorted to a bit of fire..."  Pursue this approach. You'd be surprised at how long you may need to BBQ those pistons to get them free. Mine took 2 hours of tending the fire. Ignite, burn, refill, ignite, marshmallows, refill, etc...

When they ultimately did move, they didn't move far. I had to use a breaker bar on the crank bolt (the alternator side ONLY) and then only slipped them high enough to reach the bottom of the sleeves. I applied propane to the sleeves to get them the rest of the way loose.

You can use Kerosene, Diesel (smokes like a beetch) or SeaFoam. It won't hurt anything. Just do it all outdoors and be sure your motor is securely fastened to something so when you go to cranking on the alternator bolt, it doesn't topple.

[Davez134]

It's advisable to replace them with new oil lite bronze bushings. Many members source them from a chap in Germany for around $20

Cal knows his stuff, I'll make it easy for you, click here...

http://www.ebay.com/itm/Honda-CB-250-360-400-500-550-750-Four-swingarm-bronze-bushing-set-bearing-new-/251851928293?vxp=mtr&hash=item3aa38b72e5

The bushings I have don't have the lip on them.  They insert all the way into the swingarm tube.  These look like ones for a later bike.  Are they interchangeable so I can eliminate the end cap that sits under the cup washer?

Yes, you can use these bushings on your swingarm. I used those exact ones on my '72 after removing the "old style" ones without the lip. Then all you need is cup washer.
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