Topic: Looking for protocol on front fork setup for CB750K2

[MCRider]

By that I mean the details for the process. Essentially, I know that 1. with the springs removed 2. with the top and lower triples loosened 3. raise the front wheel to full compression. 4. at that point everything will be aligned as well as its going to be.

So the question is in what order do we start tightening everything up, and why, if you have a reason.

I've spent an hour with Hondamans book, and an hour searching the forum. I know this info is out there. I remember reading it here.

My problem is the front wheel is hopping pretty bad at 45mph. Too bad to go any faster.

We've pulled the front wheel and it is perfectly true (I built it    ). The tire was installed and balanced by a shop. I've checked the bead and direction, both are fine. It wasn't balanced quite as well as I would have liked, but not off enough to cause the bounce I have, I think. Anyway, it's perfect now.

Clues?

[scottly]

Loose spokes? Binding forks, uneven oil levels, etc won't induce bouncing. Remember Sconny boy's honeymoon trip?

[MCRider]

Loose spokes? Binding forks, uneven oil levels, etc won't induce bouncing. Remember Sconny boy's honeymoon trip?

No, I don't. Enlighten me.

[lucky]

When a wheel gets trued there is more than just getting it straight.
You also have to tighten spokes one each side of the wheel in a alternating fashion.

For instance one outside spoke and one inside spoke
THEN move to the opposite side of the wheel. Repeat.

Take the wheel and measure from the outside  the hub to the outside edge of the rim.
Now measure 180º across. from outside edge of hub to outside of rim. They have to be the same on both sides of the wheel.. With in .008 thousandths.

So you need a precision way to do that. Almost no one has calipers that large.
So this is what you do. You put the wheel in a truing fixture and clamp on a steel bar that rubs against the very outside edge of the wheel outside edge. Now spin the wheel. You want the wheel to touch that metal bar all the way around when you spin the wheel.

How it gets off is that many people make the mistake of starting to tighten spokes in one place and continuing on around the rim INSTEAD of working on the same spot on the opposite side of the wheel so the hub will stay centered.

The hub must be concentrically located in the center of the rim.

If the rim is steel take a combination wrench and tap it on the spoke.
It should ring not thud.

You do not have to tighten the spokes that much, just a half turn past touching.

[MCRider]

Thanks for the tips, the wheel is fine.

Any comments about my question?

[scottly]

Loose spokes? Binding forks, uneven oil levels, etc won't induce bouncing. Remember Sconny boy's honeymoon trip?

No, I don't. Enlighten me.

It is actually Skonnie Boy. He also made several posts about the "imbalance" problem on this forum, and some time after his honeymoon log, he posted the whole problem was due to loose spokes.
Here's a link to his log:
http://forums.sohc4.net/index.php?topic=90912.0

[lucky]

There is a contradiction.

Quote:

"We've pulled the front wheel and it is perfectly true (I built it    ). The tire was installed and balanced by a shop. I've checked the bead and direction, both are fine. It wasn't balanced quite as well as I would have liked, but not off enough to cause the bounce I have, I think. Anyway, it's perfect now."

I do not see a question. No question marks.

[scottly]

Here is a link where Skonnie shares the cause of his bounce:
http://forums.sohc4.net/index.php?topic=109298.0

[MCRider]

There is a contradiction.

Quote:

"We've pulled the front wheel and it is perfectly true (I built it    ). The tire was installed and balanced by a shop. I've checked the bead and direction, both are fine. It wasn't balanced quite as well as I would have liked, but not off enough to cause the bounce I have, I think. Anyway, it's perfect now."

I do not see a question. No question marks.

Lucky: Oonce again, I must ask you to try and keep up.   

The question is clearly stated: "So the question is in what order do we start tightening everything up, and why, if you have a reason."  Worded in this manner it does not require a question mark.

My comments about the wheel were to indicate that i had addressed the wheel and its fine.

[scottly]

Sorry, Ron, back to your original question. When I fit my fork brace, I snugged all the bolts with the forks extended, wheel off the ground, and the caps removed from the top of the fork tubes. I then lifted the front wheel by hand, checking for binding throughout the travel. (no need to remove the springs, as they are free to rise up out of the tubes)

[MCRider]

Here is a link where Skonnie shares the cause of his bounce:
http://forums.sohc4.net/index.php?topic=109298.0

Scottly, Thanks for the links. I'll double check, but I built the wheel with all new parts, SS spokes and Excel Rim, spoke tension is appropriate.

I've set up several front ends over the years and they always performed fine right away. This one doesn't. Its either individually or a combination of tube alignment, internal bits are binding, the fork brace had it in a bind, etc.

I think I just read from Old Scrambler or someone similar, that with a from scratch fork one should pump them liberally to get some air out that may be trapped. never heard of that, but couldn't hurt. I'll be doing that next.

[MCRider]

Sorry, Ron, back to your original question. When I fit my fork brace, I snugged all the bolts with the forks extended, wheel off the ground, and the caps removed from the top of the fork tubes. I then lifted the front wheel by hand, checking for binding throughout the travel. (no need to remove the springs, as they are free to rise up out of the tubes)

Thanks, I'll try that. I may try it with the wheel all the way up, tighten the brace, and let it down slowly to feel for a bind.

If I don't hear more, I'll just experiment with different sequences and see what i come up with.

[Harsh]

I think I just read from Old Scrambler or someone similar, that with a from scratch fork one should pump them liberally to get some air out that may be trapped. never heard of that, but couldn't hurt. I'll be doing that next.

Yes that is true.  With the fork cap off you need to pump the fork many many times until you don't hear/feel air being pressed out of the damper rod.  You can feel the air vibration in your hands when pumping the fork.  Yah yah yah I know that sounds silly, but it is the easiest way I can think of to describe it.

I can't say whether or not not clearing the air out of the damper rod would cause wheel hop, but it does sound some what logical.

[Brantley]

I've always gone with the bottom up on the triples. I've been told the lower does most of the heavy stuff and the top is more for alignment. Not positive, though. One other thought, since I chased a similarly phantom hop: were you at the shop when the tire was installed? I ask 'cause my problem wound up being water trapped between the bead and rim. You know how little kids always draw the sun with rays? After hitting 45-50mph on even a short ride my rim was the sun and the sidewall was the rays of whatever lube was used to install the tire. Maybe deflate and check that?

[Retro Rocket]

This isn't meant to sound harsh but instead of "thinking" the wheel is right, and i may just be, i would put a different wheel on and see what happens, or recheck spoke tension, {they may have settled once ridden} just to eliminate that completely. It could be a rebound problem as well, if for some reason the rebound damping isn't working properly then you could have these symptoms, after all, a shock without damping is just a pogo stick.... I have seen similar problems with front end bounce and it is usually front wheel/tire related...
Just saying

[MCRider]

I think I just read from Old Scrambler or someone similar, that with a from scratch fork one should pump them liberally to get some air out that may be trapped. never heard of that, but couldn't hurt. I'll be doing that next.

Yes that is true.  With the fork cap off you need to pump the fork many many times until you don't hear/feel air being pressed out of the damper rod.  You can feel the air vibration in your hands when pumping the fork.  Yah yah yah I know that sounds silly, but it is the easiest way I can think of to describe it.

I can't say whether or not not clearing the air out of the damper rod would cause wheel hop, but it does sound some what logical.

Sounds Good, will do.

[Old Scrambler]

MC...............Good to hear you are OK after the somewhat controlled laydown...............About the wheel hop............Terry has already pointed out the fork brace so check to make sure it is properly fitted.........no pressure, binding, pulling ............just sets in place and is perfectly level with the axle.  I also see that others have pointed to the tire and wheel for potential issues, and I agree they are worthy targets. 

I had a similar hop a long time ago on my early K3.......same fork internals as yours..........easy fix was a wheel weight.  Fork binding, sticksion, miss-alighnment, even a a twist or slightly bent fork seldom causes wheel-hop at 45-50 mph.

So you checked the rim to see if its true.........have you checked the outside circumference of the tire?  I once had a really out of round tire on the rear that hopped like crazy and could only be fixed by replacing it.

Regarding your original question............with the bike supported and wheel mounted but loose, I observe my top tree to make sure the tubes are balanced (in my case, just a hair above level with the tree) and lightly snug the top and bottom trees...........then I lower the bike to put weight on the wheel and make sure the bike is balanced. I use a carpenter's level as a straight-edge to make sure the tubes and axle are in-line with triple-trees.........then I tighten the bottom tree (about 20lbs) and snug the top tree to 12 lbs. Now I tighten the axle nuts and make sure the front is tight before the back nuts.  I don't have a fork brace other than my fender.

If I replaced the fork oil, I "pump" the front wheel with the caps off to make sure no air is locked into the bottoms of the forks. I don't use preload, but I do use 10w fork oil.  My forks are on the stiff side. In the mid-70s HONDA softened the forks on most of their bikes and in the late 70s added air-assist.  They rated the air-pressure at 17-20 lbs.  I have found that to be WAY too much air. I follow their directions on later models to only use about 4 lbs on my other bikes that have air-assisted forks.

I'll be going through a front-end procedure in a week or so when my new tire arrives.......last one was an IRC 100/90 and lasted about 10,000 miles. This time I'm going with a Dunlop TT100 design to match my new rear.

[MCRider]

OS: Many thanks!

As mentioned the rim is very true, spokes tight, etc. I just checked the tire (new BattleAx) and it is very true as well.

As mentioned the wheel was not balanced to my satisfaction. It is now. Chrome tape weights. I said i didn't think that would do it, but maybe it will!? That would be great.

Unfortunately, I'm going to go ahead and 1. pump the fork legs and 2. go thru an alignmnet  regime.  So if at the end it no longer bounces, we won't know which thing was the culprit and can only assume it was a combo of all.

I have air forks as well. At rest with weight on the forks, I pushed the valve in to release all air pressure. I have 220cc of ATF in each, but never pumped them, to my memory.

Thanks again, I have a plan now.