Topic: Which parts should rotate inside the swingarm?

[Raul CB750K1]

This is regarding my CB350 twin, but I guess it applies to any of the other SOHC'4. I just reinstalled the swingarm last week and there is something that left me thinking.

I removed the plastic bushings and installed new ones -metallic- bought at the Honda dealer. I used the "old" part number and got those, so it's simply the originals were superseded. For the axle and internal bushings I used the old ones (when I say "internal bushing" I mean the cylinder that got inside the swingarm bushing, through wich the swingarm axle crosses.

Well, putting back the bushings was harder than removing the old ones. The swingarm was painted and the painter painted the inside, but anyway, I sanded it and then used a long bolt and big washers to drive the bushings into place. Big deal.

Now comes what, for me, doesn't seem right. I expected the internal bushing to easily slide inside the swingarm bushings, and the same goes for the axle to easily slide inside the internal bushing. This internal bushing have a hole and a channel, that is suppoused to drive the grease injected in the axle. But the internal bushing was tight inside the swingarm bushings; not too hard, but it was necessary a few knocks with the rubber mallet (for both sides of the swingarm). The axle slide easy.

Then I thought: "no problem, as long as the swingarm assembly can rotate against the axle everything seems right". But the axle is a tight fit, so to tighten it it has to press against the swingarm. The only way for the swingarm to be free of the axle force is that the "internal bushings" are slightly longer than the external bushings, so the tightening force is exerted against the internal bushings -that would remain locked" while the swingarm will rotate against them. That is, axle and internal bushings would be locked and the swingarm would swing. In such a case, it would be a problem because the internal bushing was a tight feet as I said. Of course I could move the swingarm with my hands, but it was tight, it wouldn't simply fall.

My wishful thinking told me that it would just free up with the use, but I'm concerned I could have done something wrong. It could be that the outside bushings would not be perfectly aligned, but I tightened both up to the bottom, and i guess there should be some more tolerance. The old ones simply fell off, but it is no valid reference because a) the old bushings were made of plastic and probably were worn and b) one of the internal bushings was not original, and somebody had put a thickness gauge in between to compensate the difference in diameter   


Can anybody tell me if there is something wrong on what I did or, on the contrary, that's the way it should be?


Thanks in advance

Raul

[nickjtc]

Very timely. This from this morning:

http://www.sohc4.us/forums/index.php?topic=21160.0

[Raul CB750K1]

Very timely. This from this morning:

http://www.sohc4.us/forums/index.php?topic=21160.0

I have already read it, but in my case, the parts are new or like new. I have installed new seals and caps too, so I really can't understand where the problem is.

[bryanj]

Way too long since I did a 350 all i can say is the 750/500 where the bolt clamps the "sleeve" with grouves into the frame by pinching the ends and the "Bushes" fitted into the arm swivel on this, Could get better with grease

[Kamal]

There are bushings, shafts, and a bolt to hold everything together.

The bushings should be tight in the swingarm.  The shaft should be a "bearing" fit to the bushings.  Finally, the bolt squeezes the shaft against the frame.

SO, the bolt and shaft are fixed tight against the frame, and the swingarm and its bushings float and rotate on the shaft. As long as your bushings are fully seated into the swingarm, no amount of pressure holding the bolt and shaft to the frame will bind anything, as the swingarm and bushings should be just slightly narrower than the shaft itself.

First thing is first, without any grease, and on the bench, your shaft should be a good fit into each bushing, even a slight bit of play that will be taken up by the grease.  If your bushings don't have a nice smooth fit on the shaft, I would go back to square one and figure out what is binding and why.

Kamal

[Raul CB750K1]

There are bushings, shafts, and a bolt to hold everything together.

The bushings should be tight in the swingarm.  The shaft should be a "bearing" fit to the bushings.  Finally, the bolt squeezes the shaft against the frame.

SO, the bolt and shaft are fixed tight against the frame, and the swingarm and its bushings float and rotate on the shaft. As long as your bushings are fully seated into the swingarm, no amount of pressure holding the bolt and shaft to the frame will bind anything, as the swingarm and bushings should be just slightly narrower than the shaft itself.

First thing is first, without any grease, and on the bench, your shaft should be a good fit into each bushing, even a slight bit of play that will be taken up by the grease.  If your bushings don't have a nice smooth fit on the shaft, I would go back to square one and figure out what is binding and why.

Kamal

Crystal clear explanation, thank you very much.

I greased everything before installing. As I said, the shaft were a slightly tight fit inside the bushings. Once knocked down into place, there was no way to rotate them with the hand, but obviously, once they are pressed against the frame by the bolt, the turning force provided by the swingarm will make it turn no matter how hard they are. As the bushings are new and original Honda -so I assume no fabrication mistake- and even when the shafts where used, in a worst case scenario they could be worn but in that case it would even increase the play inside the bushings. But it seemed too tight for me. I bought the bolt and shaft on eBay. Probably it comes from a CL350 -because I've been buying parts of these bikes as I know they are pretty similar-, but if my memory serves me the part number was the same for the shafts. Also, I installed modern grease zerks -posted about it a while ago- and after installing everything I pumped a shot of grease to the point that it went out past the seals...


Don't know, I could probably dismantle everything but I don't think there could be something wrong inside. I mean, the way the parts fits inside is a one-way. Even if I disassemble the swingarm, there is no way to install things the wrong way. Shafts are of different lenght, but as I say, if you reverse them there would be no way to install the set.

Actually, when I noticed how tight were the shafts I removed them, cleaned the grease and lubed with WD40 thinking that maybe the grease was too thick, but it didn't make a big difference.


Raul

[Kamal]

I looked over the microfiche online for both the CB and CL 350.  Very straightforward.

The only thing I could think was that maybe there was some old, dried oil on the shafts (collars) or bushes?  So, I thought to clean them through with some acetone before applying the grease.  Any chance this may be the cause?

Also, maybe the new bushing design (steel) was of slightly different dimension, and matched to the new shafts (collars) that were supplied at that time (how ever long ago that was).

In the end, I'm curious to know how much drag is put on the swingarm motion once everything is bolted down tight. It may simply be good enough for regular street use.  Are you gonna race this bike?

Kamal

[Raul CB750K1]

I carefully sanded the shafts before the first installation. The ones I used are not the ones in the picture above, but they also had some light rush and I sanded them to get rid of it. Obviously I blowed them with compressed air to eliminate all the particles.

The difference in the bushings inside diameter is the only possible explanation I can think of. Regarding about the swingarm movement, it's something like this: with the swingarm installed, it remains in place by itself, without installing the rear shocks. I can move it up or down and it will stay in the point where I leave it. Once the shocks and the rear wheel were in place, by placing my weight over the rear part of the frame the swingarm moves up and down, though I can't feel what is the bushing resistance because the strenght to compress the shocks is much higher than the bushing's resistance.

My gut feelings tell me that once the bike is reassembled, my body weight and the road bumps will make the swingarm swing. The concern would be that the swingarm gets stuck somewhere so the shocks are unable to put it where it should be, but I don't feel it will be that way. Probably the shafts will free up with the use, but obviously I don't plan to disassemble it just to check it. With the modern grease zerks, pumping a little grease every now and then is easy and convenient so there is no reason why the inside of the swingarm should remain dry.


Raul

[Kamal]

with the swingarm installed, it remains in place by itself, without installing the rear shocks. I can move it up or down and it will stay in the point where I leave it.

As long as you can move it up or down fairly easy, like with one hand, without having to brace yourself and really apply force, you should be fine. 

In the end, its a slight performance issue, and not a safety issue; keep in mind, all bushings wear, and if they are a little too tight now, they will wear to the perfect clearance before long, and then will move on to wear so much as to need to be replaced yet again.

[Raul CB750K1]

with the swingarm installed, it remains in place by itself, without installing the rear shocks. I can move it up or down and it will stay in the point where I leave it.

As long as you can move it up or down fairly easy, like with one hand, without having to brace yourself and really apply force, you should be fine. 

In the end, its a slight performance issue, and not a safety issue; keep in mind, all bushings wear, and if they are a little too tight now, they will wear to the perfect clearance before long, and then will move on to wear so much as to need to be replaced yet again.

That's what I thought, it would be a matter of time for them to wear, but couldn't help to wonder why was it such a tight fit.

[bryanj]

Raul, I suspect that paint residue has closed up the "new" bushes slightly and/or the swing arm holes are slightly oval plus add to that Hondas QC has probably slipped a bit over the years and you get a tight fittment like yours.

If you want to race or drive like a "nutter" it might be worth removing and polishing the inside of the bush(s) if not and you are more "normal" which i suspect, what with kids, wife AND a 750 leave it alone and grease well every 1,000 miles or 6 monthly even if you dont ride as grease goes hard.

[Raul CB750K1]

Thanks for the tip Bryan. I plan to use the bike as a leisure vehicle, so I guess I will leave it alone and grease every now and then. Thanks Kamal for your help too.



Raul