Topic: K1 750 - Going Back Together Questions

[bryanj]

I have never had a thrust break unless abused, nor the felts tear unless abused

[Don R]

 I've loosened the motor mount bolts and jacked the frame slightly open.

[HondaMan]

I have never had a thrust break unless abused, nor the felts tear unless abused

+1.
And I have rebuilt a LOT of these swingarms. What usually breaks them is lack of grease for decades, which wears the outer rim thin, followed by removing the arms unevenly (pulling one side out, then the other) during disassembly. It is also possible to crack them by installing bushings wrong, i.e., not having the ends of the bushings recessed 3mm like they should be, followed by assembling the end bushings and seals and forcing it all back into the frame. If that didn't crack them, the subsequent tightening of the arm and crushing of the end bushings breaks them.

Most of the arms I have rebuilt (for these bikes) since the 1990s have the terrible cast MIMs-metal bushings that replaced the original phenolic bushings these bikes had before the F2/K7. The original ones wore out for lack of lube and the shops replaced them with the MIMs-metal type Honda made since, and they did not seat them fully: this is because the MIMs bushings are about 1mm longer than the phenolic ones, and the installer didn't take the time to measure the depth they were inserting those bushings - to the outer edge - after the install. In the case of the K0 and Old Factory K1 bike frames, the bushings are shorter by 3mm and so were their bored sites in the swingarm: if you try to install the MIMs-metal bushings into those arms they end up almost flush at the outer end. Obviously, this then requires starting over with correct parts...

During the New Factory setup the swingarms changed quite a bit. Their metal got thicker and the welds greatly improved, and the bushing holes all got bored to the same depth for a change. The hole size for the bushings was 1.0440"-1.0444" in these later arms, which became 1.0384"-1.0424" ion the F2/3 and later ones. The later ones have the same depth to the bushing-site holes as in the post-Old-Factory arrangement, so the same bushings could be used, if a 10-ton press was required to get them seated (I use a 20-ton...) or else some proper aftermarket bronze bushings could be used (which were correctly sized for K0/1 Early, K1-K6, F0/1, and then the post-1976 versions, all 3 are different by a little bit and 3 different size bronze bushings were marketed until 2002 or so).

So, there's quite a bit to get right when swapping out these bushings, and it is mighty easy to not know these things, and end up with a poor fit-up. That's why I bought a lathe and make them to fit the arm in question.

[PeWe]

About swingarm bearings.
I gave my K6 a needle bearing kit in early 80's.
Not an issue, 836cc with closer to 80whp and cruised in rain a lot during long rides to and from sunnier countries.

It got another swingarm when restored 2013. (The old had no chain guide brackets after a chain issue.)

That got also needle bearing kit.
Has now done almost 50.000 km and much more power. Ca 10 dyno visits with torture. Still working fine.

My K2 has such a kit too.

[willbird]

About swingarm bearings.
I gave my K6 a needle bearing kit in early 80's.
Not an issue, 836cc with closer to 80whp and cruised in rain a lot during long rides to and from sunnier countries.

It got another swingarm when restored 2013. (The old had no chain guide brackets after a chain issue.)

That got also needle bearing kit.
Has now done almost 50.000 km and much more power. Ca 10 dyno visits with torture. Still working fine.

My K2 has such a kit too.

I put such a set in my K2 back in 95 and put 20K on it with no issues. I was thinking about asking why they seem to not have any advocates. I think maybe using the parts usually used there is no way to grease them ?? I never really thought about that at the time. Sending a little grease in is one way to push any contamination out. Looking on Ebay one NOS option comes in a green box that looks a lot like the NOS tapered needle bearing triple tree bearing set.

Bill

Bill

[HondaMan]

About swingarm bearings.
I gave my K6 a needle bearing kit in early 80's.
Not an issue, 836cc with closer to 80whp and cruised in rain a lot during long rides to and from sunnier countries.

It got another swingarm when restored 2013. (The old had no chain guide brackets after a chain issue.)

That got also needle bearing kit.
Has now done almost 50.000 km and much more power. Ca 10 dyno visits with torture. Still working fine.

My K2 has such a kit too.

I put such a set in my K2 back in 95 and put 20K on it with no issues. I was thinking about asking why they seem to not have any advocates. I think maybe using the parts usually used there is no way to grease them ?? I never really thought about that at the time. Sending a little grease in is one way to push any contamination out. Looking on Ebay one NOS option comes in a green box that looks a lot like the NOS tapered needle bearing triple tree bearing set.

Bill

Bill

I've installed just 2 sets of those [otherwise nice] roller bearings. One said to 'use the original collar', which left the arm looser than it started out. The other supplied a collar to fit the bearings, but it was too short by about 0.2mm, so the assembly would bind when the arm was tightened up. Both were then rebuilt with custom-fitted Oilite bushings I made for them.

What brand of roller bearings kit actually fit? And, couldn't the inner collar be drilled for grease passages, then the bolt drilled, too (or just employ the early bolt, it has grease passages already) to keep lube in it and push out contaminants over time?

[PeWe]

The kit look like my first kit from early 80's that got grease when installed, no new grease after.

Many sellers.
I have a new kit like this for my slow going CB750 build. Another "bitsa" bike. From CCC.
https://www.ebay.com/itm/401002104209?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=oURKvVbeSKm&sssrc=4429486&ssuid=XgCEg0CPSya&var=&widget_ver=artemis&media=COPY

I have had thoughts to grease again. 10 seasons, ca 50.000km so far.
But can be tricky with shocks on.
Maybe at next rear wheel removal. Shocks off, support under swing arm, shaft out. More new grease.... I think I used MOS2 grease last time.

Now when I think about it, I have to inspect at next tire replacement


Take out the "steel pipes" inside swingarm on each side took time.

A hand hacksaw blade thru it, mount the hacksaw when blade is inside swingarm. Saw parallel to swingarm.
Stop in time before cut marks in swingarm.
Now possible to fold it inwards with a hammer and screwdrivers.
Finally punch it out from other side with a fat durable screwdriver or similar.

[HondaMan]

I once saw an amazing swingarm arrangement someone custom-built on a 750. I didn't get to see the parts for it, nor how the mods to the frame or arm were done, but it had 2 tapered roller bearings, one on each side of the frame, such that the nut could be tightened until the arm would not 'drop' on its own weight, then loosened until it would, and then a thin locknut went against that big nut to hold it right there. I was puzzled by how the collar could be arranged inside the swingarm to be large enough to hold the arm snugly (maybe it had bushings inside it, but a press-fit collar?). And, how was it assembled.

 I've long mused that if I got to do a full custom buildup of one of these frames (maybe for me?) that I would like to attempt that. I even bought a "can't be titled" scrap 750 frame to experiment with, but it's been under a tarp now almost 10 years, waiting...

IMHO that could be the ultimate SOHC4 swingarm setup. I think the inspiration was from an old Harley flat-tracker (maybe the 750?) that had a normal straight bearing on one side and a tapered one on the other. That one could be tightened to ft-lbs of torque (which isn't what tapered rollers usually get in real life) to make sure the arm didn't wiggle: I think that arm's tubing was not big enough to not flex on its own, but the SOHC 750K0-6 box-section arm would do nicely.

IMHO.

[newday777]

The kit look like my first kit from early 80's that got grease when installed, no new grease after.

Many sellers.
I have a new kit like this for my slow going CB750 build. Another "bitsa" bike. From CCC.
https://www.ebay.com/itm/401002104209?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=oURKvVbeSKm&sssrc=4429486&ssuid=XgCEg0CPSya&var=&widget_ver=artemis&media=COPY

I have had thoughts to grease again. 10 seasons, ca 50.000km so far.
But can be tricky with shocks on.
Maybe at next rear wheel removal. Shocks off, support under swing arm, shaft out. More new grease.... I think I used MOS2 grease last time.

Now when I think about it, I have to inspect at next tire replacement

Per
Does this kit usage not allow using grease zerks in center or ends of the swingarm?

[seanbarney41]

I have Dunstall boxed swingarm on my Gold cafe bike, installed with tapered roller bearing kit also from Dunstall.  I have the bearing numbers recorded somewhere.  It would be simple to make the spacers/washers required and this swingarm pivots effortlessly.  I believe the dimensions of the pivot are identical to a stock swingarm.

I also have a needle bearing kit from Bikemaster made in Japan.  It fit too loosely as Hondaman says so I aborted it's installation and went with bronze bushings

[bryanj]

Mark, if using tapers i would try and do it like Goldwing and use stepped threaded pins in each side with threads in the frame

[PeWe]

The kit look like my first kit from early 80's that got grease when installed, no new grease after.

Many sellers.
I have a new kit like this for my slow going CB750 build. Another "bitsa" bike. From CCC.
https://www.ebay.com/itm/401002104209?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=oURKvVbeSKm&sssrc=4429486&ssuid=XgCEg0CPSya&var=&widget_ver=artemis&media=COPY

I have had thoughts to grease again. 10 seasons, ca 50.000km so far.
But can be tricky with shocks on.
Maybe at next rear wheel removal. Shocks off, support under swing arm, shaft out. More new grease.... I think I used MOS2 grease last time.

Now when I think about it, I have to inspect at next tire replacement

Per
Does this kit usage not allow using grease zerks in center or ends of the swingarm?

Nothing for refilling grease.
A hollow shaft/pipe with no holes for grease that fits inside the needle bearings included in the kit.
The long CB750 bolt that clamps it together fits inside.

To refill grease, swingarm need to be off the bike, the inner pipe to removed to refill.
Possible to push it in a bit and grease, then from other side.

My K6 first set was still greasy inside after 7-9 years use. The grease has nowhere to go if not leaking outside.
I'll check the K6 just for sure at next wheel off.
If I used sticky black MoS2 grease as my K2 got.

[ZTatZAU]

SWINGARM UPDATE!

Thanks again to all who replied.  I received a new set of OEM Honda OEM felt seals, plastic thrust bearings, and dust cap washers.  It was a tight fit but with a little finesse, it all went together just fine.

The problem was indeed the aftermarket, replacement felt seals which were easily twice as thick as the OEM Honda felt seals.
ZT