Topic: Disassembling front forks - K1 750

[ZTatZAU]

^^ ^^
Thanks Stu!  Thanks John!
I'll consider using the Rustoleum Rust Dissolver spray that Stu recommended; but, since the tops of my fork tubes are only very lightly rusted, I thought I'd try that 0.003 Wire Carding Wheel I previously mentioned in another thread, at slow speed in my drill press.  It seems to be working quite well, but the still assembled fork is pretty awkward and somewhat heavy to manipulate, so I've started to disassemble the first of the two forks.

I have the large circlip out of the lower slider... (it wasn't easy!)... but I'm not sure if that's all that holds the assembly together.  Do I need to remove the bottom hex head bolt before the fork tube, oil seal etc., can be removed from the lower slider?

Thanks!  ZT

[denward17]

Yes, you need to remove that bottom bolt before the fork tube comes out.

Have you drained all the oil out?  Might want to have a container ready to catch the rest of the oil still in there.

[ZTatZAU]

Yes, you need to remove that bottom bolt before the fork tube comes out.

Have you drained all the oil out?  Might want to have a container ready to catch the rest of the oil still in there.

Thanks Denward!  I've been wondering about draining the oil.  A small amount of oil ran out of one fork as I was removing the boot from the lower fork leg. (So it's probably good that I'm replacing the fork seals!)

I'll pull the hex head bolt out of the bottom, stand the fork up in a bucket... and then take the drain screw out... then probably need to pump the fork to force the oil out.

Is that about right?

[denward17]

Yes, you got it right..

Edit: BTW, that circlip comes out easier when you have the tube pulled out, more room to work.

[ZTatZAU]

Yes, you got it right..

Edit: BTW, that circlip comes out easier when you have the tube pulled out, more room to work.

Thanks Denward!  I'll remember your tip on the second fork.
ZT

[ZTatZAU]

Yes, you got it right..

Edit: BTW, that circlip comes out easier when you have the tube pulled out, more room to work.

Thanks Denward!  I'll remember your tip on the second fork.
ZT

Hang on there Denward!  I'm all about making things easier and I admit to being less than familiar with disassembling these forks but...
as I'll soon be attacking the second fork, I've been pondering your suggestion and wondering...

How can I remove the fork tube from the slider without first removing the large circlip?  As I understand the assembly, the circlip holds the fork seal in place and the components affixed to the bottom end of the fork tube (fork pipe guide/bushing, stopper rings, damper valve, piston, and lower snap ring) cannot pass through the fork seal but rather must bring the fork seal out of the lower slide as the fork tube is removed.  EDIT:  How can all this happen without first removing the large circlip?

What am I missing here?
ZT

[Don R]

 I get the snap ring first, then I jerk the chrome tube out, it may bring the seal with it. An extremely stuck seal might require a little heat. I also tap the new seal back in with a piece of PVC pipe.

[denward17]

My mistake, I assumed the forks were like the 550 I just completed......Remove the circlip first I guess.

[ZTatZAU]

I get the snap ring first, then I jerk the chrome tube out, it may bring the seal with it. An extremely stuck seal might require a little heat. I also tap the new seal back in with a piece of PVC pipe.

My mistake, I assumed the forks were like the 550 I just completed......Remove the circlip first I guess.

OK!  I'm stuck and could use some more help!

I'm still working on the first fork... I have the bottom, hex head bolt out,,, have the circlip out of the top of the lower slider... and still can't get the fork tube and/or the fork seal to move.

I've met Don R so, I know he's got a lot more heft and brawn than I have; but so far no amount of "jerking" on the fork tube has resulted in any movement.

I've heated the top of the slider around the fork seal to where it's too hot to hold... bolted my old trusty 1x4 to the axle holder bolts,,, sprayed some Aero Kroil in and around the fork seal... stood on the 1x4 while pushing the fork tube down against the pressure of the spring... and then jerked up on the fork tube.  No movement... yet!

Suggestions appreciated!
ZT

[ZTatZAU]

...
When I did my forks I struggled to find a diagram of what I found inside; then I cam across this in an old issue of Classic Motorcycle Mechanics. Maybe it'll help.

@The Lone Builder, can you provide a link to the entire Classic Motorcycle Mechanics article you mentioned?
Thanks!  ZT

[BenelliSEI]

This can be very frustrating. On my Sandcast project they just didn’t want to come out. At one point I was convinced my forks must be different than anyone else’s! Here’s what I did:

1. With a very long, sharp punch, I  knocked two small (tiny) holes in the seal face, from the top. The seal has a steel ring around the top and sides. Place the holes 180 degrees opposite each other.

2. Screwed two sheet metal screws in the holes. They are facing up, parallel to the fork tubes. PROTECT the tubes with a few winds of duct tape.

3. Using a small (8-10” long) carpenter’s nail puller (crow bar), get under the screw heads and slowly lever the seal out. You lever against the edge of the fork bottoms. Protect the ledge with a small strip of aluminum sheet, cut to fit. The seal is usually down below top edge of the fork leg. Once it gets level, you should be able to grab the screw(s) with a pair of pliers and just pull it the rest of the way.

This took me a while, as I didn’t want to damage any of the original parts. To punch the holes I actually bought a small alignment punch and sharpened the end to get down to the seal. Good luck!

[BenelliSEI]

I just read what Don wrote. My seals were really stuck but I never tried that. In theory, if you really warmed up the neck of the fork leg (where the seals sit), they should increase in diameter and the seal should pop out. I’d try using a propane torch and do what he suggest, before my suggestion.

[ZTatZAU]

I appreciate your reply John and you sharing your can-do attitude and method.  I am wondering...

I haven't yet removed the top filler bolt/plug at the top of the fork tube.  If the plug is removed, can you then remove the spring and shuttle valve assembly from the center of the tube?

Might this make it easier to use the tube as a slide hammer to force the fork seal up and out?
(I'm still guessing what all this looks like inside.)
ZT

[ZTatZAU]

I just read what Don wrote. My seals were really stuck but I never tried that. In theory, if you really warmed up the neck of the fork leg (where the seals sit), they should increase in diameter and the seal should pop out. I’d try using a propane torch and do what he suggest, before my suggestion.

You may have missed it in my post... but I've warmed the top of the fork leg to where it was too hot to hold with a heat gun.  I've been hesitant to use a torch out of fear I'd ruin the finish on the fork leg.

Please let me know about the question I just posted while you were typing... i.e. removing the inards first.  Is this possible?  Advisable?  Necessary? Might it help?
ZT

[ZTatZAU]

Please let me know about the question I just posted while you were typing... i.e. removing the inards first.  Is this possible?  Advisable?  Necessary? Might it help?
ZT

YEP!  Removing the top plug and the spring helped... A LOT!!!
2 or 3 upward pops and the tube came right out with the fork seal!!!
I'm still learning!
ZT

[BenelliSEI]

Sorry. That gives you the long stroke. I assumed it was out!

[ZTatZAU]

Sorry. That gives you the long stroke. I assumed it was out!

No problem John!  My posts/questions ae often quite wordy; so you may have missed that part.

With the forks now disassembled, and cleaning up nicely, I've moved on to installing my new steering stem and a set of All Balls tapered roller bearings  To that end, I was pleasantly surprised (unlike my experience with other vintage bikes) that I was able to disconnect all the connectors in the rat's nest of wires in the headlight without pulling any of the wires out of the factory made snap in connector ends.

Headlight & shell, wiring harnesses, gauges, handle bars, throttle cables, front brake line and caliper are all removed as I get ready to separate the steering stem and top bridge.  My CB750 newbie question of the day is...

Should I be able to remove the eared fork covers from between the triple trees without first loosening and separating the steering stem and top bridge?

I'd like to take some accurate measurements of the space between the triple trees to duplicate and double check the spacing after installing the All Balls roller bearing kit.

Thanks!  ZT

[BenelliSEI]

Assuming the fork are out, they should slide out but they’ve been there a long time! Loosen just the top nut and tap the top yoke free a bit. Once the fork ears are out, you can snug it up again and take your measurement.

[ZTatZAU]

Assuming the fork are out, they should slide out but they’ve been there a long time! Loosen just the top nut and tap the top yoke free a bit. Once the fork ears are out, you can snug it up again and take your measurement.

Thanks John!  I'll give that a try!
ZT

[M 750K6]

Will the distance be the same, worn out rollers vs. new tapered bearings?

[ZTatZAU]

Assuming the fork are out, they should slide out but they’ve been there a long time! Loosen just the top nut and tap the top yoke free a bit. Once the fork ears are out, you can snug it up again and take your measurement.

Thanks John!  I'll give that a try!ZT

Fork covers are off, measurements taken, and the steering stem and top bridge have been removed.

I put the old steering stem in the freezer overnight (-10°F) to shrink (contract) everything down as much as possible.  I'm now looking for some item I may have lying around the shop, that I can heat up in the oven which can then, quickly and efficiently, transfer its heat to the old bearing race on the bottom of the stem, to expand it, without warming up the stem like a heat gun would likely do.  Any suggestions?

Will the distance be the same, worn out rollers vs. new tapered bearings?

I hope so! Or at least pretty close, if possible.  I'd like to minimize any extra open space between the top bridge and fork covers.  I'm still working through the 26 page tapered roller bearings thread for the best way to accomplish the conversion on my K1 750.

==============
And then there's this... I'm having great difficulty removing the fork lock from the old steering stem.  I've read all the fork lock threads I could find here and I'm fairly certain I do have the correct key, but I can't get the key to turn.

I've soaked the mechanism with Kroil and wiggled and wiggled the key with no luck.  All I can see of the key code on the front of the lock, is the letter T... (same as the code on my original ignition key)... but the rest of the numbers on the lock are worn away and unreadable.  Can anyone confirm my recollection that ma 1971 K1 750s (mfg 12/70) used the same key for ignition and fork lock.

ZT  (SOHC Apprentice)

[denward17]

I just went through this (installed All Balls tapered bearings) on my 550.

What I did to get the old races out:
1-Soaked with PBblaster top and bottom.
2-Forgot to use heat gun on bottom race, and had a hard time getting it out (cut off a piece of rebar to use as a drift with a 3lb hammer), and it shattered coming out.
3-Used heat gun on top of stem and the top race came out easy.  I think the heat melted the old grease that was stuck around the race that helped.

Mean while, the new races were in the freezer for a couple of hours, heated up the stem with a heat gun and the top race almost fell into place, used a brass punch to finish.  Bottom race was a little bit tighter and had to use a smaller punch to get it home.

On the steering stem, I used PBblaster and heat gun to beat the old race off with a smaller drift.  Then inserted it into the freezer overnight.  Next morning installed the smallest washer, seal and the bearing.  Then put it together.

Make sure you look at your bearings/races real good, as they are different sizes for top and bottom.

Good Luck..

[ZTatZAU]

I just went through this (installed All Balls tapered bearings) on my 550.

What I did to get the old races out:
1-Soaked with PBblaster top and bottom.
2-Forgot to use heat gun on bottom race, and had a hard time getting it out (cut off a piece of rebar to use as a drift with a 3lb hammer), and it shattered coming out.
3-Used heat gun on top of stem and the top race came out easy.  I think the heat melted the old grease that was stuck around the race that helped.

Mean while, the new races were in the freezer for a couple of hours, heated up the stem with a heat gun and the top race almost fell into place, used a brass punch to finish.  Bottom race was a little bit tighter and had to use a smaller punch to get it home.

On the steering stem, I used PBblaster and heat gun to beat the old race off with a smaller drift.  Then inserted it into the freezer overnight.  Next morning installed the smallest washer, seal and the bearing.  Then put it together.

Make sure you look at your bearings/races real good, as they are different sizes for top and bottom.

Good Luck..

Thanks Denward!  That's pretty much what I'm planning, except for... "On the steering stem, I used PBblaster and heat gun to beat the old race off with a smaller drift."...

On the old steering stem, I'd like to cool the stem and heat the old bottom race to minimize any beating required to remove the race.  Once removed, I'd like the old race and bottom seal to be in good shape so as to accurately measure the original bottom bearing stack height as described in All Balls' instructions.

Cooling the steering stem is no problem but heating the old bottom race on the steering stem, without warming everything up again, is more of a challenge.  I'm thinking about heating something up, like a heavy 1-3/8" hex nut, in the oven and then slipping the nut down over the steering stem to rest on the old race to transfer its heat to the race.  Hoping the race will then come off the stem much easier.

But, what do I know?
ZT

[denward17]

That might work, dunno.

You will destroy the stem washer and seal, but that race is pretty thick, don't think you will damage it because you don't have a lot of room for a big drift/punch.

I clamped mine down (upside down of course), in a bench vise with wood all around the stem and wood on the bottom as not to damage the threads on top of stem.

[BenelliSEI]

The race is not that tight on the stem. Just whack it.