Topic: front end collapsed

[Jonm99]

Hi guys,

So I was trying to align the front forks (cb750 k7) and had a bit of an issue in the process.... Loosened up all the bolts on the front end (tube caps, caliper, fender, lower tree) with the last nut loosened being the steering stem (didn't touch the upper tree bolts). I must of loosened the stem bolt too much as it popped off and the front end collapsed on me (springs compressed, steering stem slipped out of the upper tree, but forks still locked to upper tree). I proceeded to lift the front end back up with a jack until I had the steering stem back through the top tree, put the steering nut back on, then tightened everything from top to bottom.

So two questions:
1. How do I know that I lifted the front end "enough" before tightening the steering stem? I don't see any clearance under the top triple, it "looks" alright, but it would be great to have a sanity check on this. How can I be sure?
2. At some point I accidently pulled the font brake lever when the caliper was loose, and of course there was no resistance. After I buttoned everything back up, it feels like it was, very good. But do I need to nevertheless bleed the brake now?

Thank you!

[bryanj]

Did any ball bearings fall out or do you have tapers fitted
Does it turn left to right and back with no sticky bits
If you pull and push on the front wheel spindle with wheel in air can you fell any play

Answers SHOULD be self expanatory

[Shtonecb500]

Do you have the jam nut on under the top triple, removing the top stem nut shouldn't cause the stem to slide out of the neck? Not having the trop triple installed on the bike wouldn't even cause that, because the jam nut should be installed before the triple goes on.

The lower stem only goes in one way, if everything is seated your jam nut should be tight and it all snug. I usually install my triple first, test it with the side to side test, I want to make sure there isnt any really drag on the triple side to side, if there is then i adjust it, then i slip in the forks, do the same thing until i like it. I perform this side to side test with everything installed as well with the bike jacked up. The way you do that is loosen the top triple bolts, the stem top nut only and jack the bike up, perform the side to side test and use a flat head screw driver and hammer to tighten or loosen the jam nut under the triple...most likely will have to turn the handle bars to the side to gain access to it...make sure nut to damage ur tank...or just remove the tank.

Im not understanding what you're saying about the brake.....you had a soft lever but the caliper was loose but now its installed and you have a firm lever?

Sounds like your brake is fine then? Install the brake, jack the bike up so the front wheel is not touching and roll the wheel, hit the brake, is there any drag? anything sticking? or does the wheel return back to free roll once you let go of the lever?

I really wanna know if you have the stem jack nut installed or not?

[Jonm99]

Tapered bearings...
No sticky bits, feels fine really
Not sure about the back and forth play. Will jack it up again, test, and report back.

Definitely have a jam nut in place and it was adjusted fine before, don't see why that would need to be adjusted again?The reason why the front end collapsed when I loosened the stem nut is because I had also loosened the lower triple bolts (+ everything south of that pretty much), so there was nothing to keep the weight of the bike from collapsing the forks (bike was not on side kick or center stand, just balanced on its wheels). So essentially, the part of the tube under the bottom triple was completely compressed for a few minutes until I was able to lift the front end back up. Where I am concerned is that maybe the way I reassembled the front (by manually jacking up the bike to "meet" the top triple), that maybe I did not jack up enough and the result would be front forks that are not fully retracted in the resting position (i.e maybe a bit compressed even with no load on them). How can I be sure that is not the case?

Re the brake, correct, went soft after I loosened the caliper bolts , than back to normal after retightening. Was wondering whether or not the fact that I squeezed the lever when the piston had no resistance would introduce air into the system (hence the question about bleeding). That said, it works well, just wanted to be sure.

In the meantime, it looks like I have bigger (unrelated) problems, will make a new post for that!

Thanks guys,
J

[RAFster122s]

Is the factory manual for servicing the bearings giving instructions to rotate the front wheel back and forth while tightening? I seem to remember a few years back HondaMan explaining the way to tension the front fork triple tree bearings this way…

[jgger]

If you had the caps on the forks and the springs in the tubes then you did not compress or collapse the forks. They simply moved in the lower mount while the upper that was still attached to to the forks slid up when the top nut was removed.

I'm still having a hard time trying to figure what you were trying to accomplish.  It sounds like cutting a tree branch and sitting on the wrong side. ( Not trying to bad on you ) .

If you are concerned about the front end then jack it up and support it loosen the top pinch bolts and tighten the top nut then start over.

[HondaMan]

When you get it all put back together and straight again: loosen the top triple tree cap nut about 2 turns, then the 2 top-of-fork bolts about 1 turn each so you can tap the top triple tree up far enough to reach in adjusting nut on the steering pivot stem. Then (if you have one?) use the rear shock adjusting wrench (it is curved with a round stud or flat proud notch on the end) to tighten that steering-tree nut. Tighten it until the steering is dragging heavily, then back it off until it turns without friction side-to-side, then re-tighten about 1/8 turn from there. Then slide the top tree back down to normal position and snug up those 2 little botls and the fancy crown nut.

Ride it about 5-10 miles and see if it stays snug without a 'clunk' feeling when you hit bumps. If it 'clunks'  then you'll need to add about another 1/8 turn of tightness to the steering-tree nut a little more.

If these are brand-new tapered bearings, then plan on doing this "snugging up" bit in about 100 miles or so. It usually takes that long to fully seat the bottom bearing up into the frame. In the old days we told the customers to "come back in a week and ignore the clunking you will feel in the meantime" to accomplish this full-seating business. If they were just passing thru and wanted the bearings installed we had to tighten them until they dragged and then warned the riders that it was going to take 50-100 miles before they would loosen up and fully seat. Either way works: one is more work than the other, but is more accurate in the end.

[Jonm99]

I'm notorious for sitting on the wrong side of the tree (the triple tree, yeah?) 😊

I had the axle caps loose (springs in place and untouched), forks definitely compressed (bottom tree was almost touching the front fender).

Anyway, I'll rejack it up, loosen the top, and readjust the jam nut for good measure. That said, it's still not clear to me how this adjustment is related to the compression of the forks? I suppose I'm missing something here, but if the forks are still a bit compressed even now (not to the naked eye), opening the top triple (just the fork nuts) would release any remaining downward pressure (i.e they would slide upwards until fully extended)... right? Why would the otherwise already adjusted jam nut get out of whack?

Thanks again!

[HondaMan]

I'm notorious for sitting on the wrong side of the tree (the triple tree, yeah?) 😊

I had the axle caps loose (springs in place and untouched), forks definitely compressed (bottom tree was almost touching the front fender).

Anyway, I'll rejack it up, loosen the top, and readjust the jam nut for good measure. That said, it's still not clear to me how this adjustment is related to the compression of the forks? I suppose I'm missing something here, but if the forks are still a bit compressed even now (not to the naked eye), opening the top triple (just the fork nuts) would release any remaining downward pressure (i.e they would slide upwards until fully extended)... right? Why would the otherwise already adjusted jam nut get out of whack?

Thanks again!

Ah, I see: I thought (for some reason) you were working with the steering head bearings(?).

The forks will sit about 1/2" compressed (or so) when the bike is sitting on the centerstand, from it's own weight on those forks.
If you wish to have the front forks fully extend, then you'll have to jack the front of the bike up a little bit. I use the front bottom crossmember bolt tunnel under the engine for this action. The top of the forks should be set flush with the top of the upper triple tree (steering head). On the forks that have a fork cap, the cap itself should fit above the upper triple tree: on the bikes with the black plastic cap that fits into the hex hole in the top of the fork, the top tree should be flush with the top end of the fork tube. Many have lost the black plastic caps: in that case, just make the top of the tube flush with the top of the triple tree.

[Jonm99]

Got it, thank you!

While I have your attention (it's not everyday one can consult with HondaMan :-)), can I ask you for your help on another, more critical, issue I am having with the bike (the dreaded white smoke)? I posted the details on a separate thread: http://forums.sohc4.net/index.php/topic,193478.msg2258802.html#msg2258802

Thanks again!
Jon

[Kelly E]

When we built the 74' CB 550 we had gone through the forks but once the bike was done we took it off the centerstand. I sat on the bike, grabbed the front brake and rocked it forward to check out the front end. It went down and never came back up. The springs checked out when we put the forks together. Once we stopped laughing we took the springs back out and they were shorter. We wanted to try out the stock springs first, I already had a set of Progressive springs so we put them in and problem solved.