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The original plan was to try and put clip-ons on the new-to-me 250 narrow-case with as little work as possible. Just take the steering crown off gently and... oops!

While I was trying to get the top triple tree off the lower steering head races opened up and bearings went all over the garage floor.

Well the grease didn't look so good, and the dust caps were a little battered so maybe taking the whole thing apart wasn't such a bad thing after all.

OK, there's nothing magic about this. I took the fender off, the speedo and brake cables, took off the headlight and took off the front tire. Last night with the help of a friend I got the forks out and the triple tree and steering crown removed. I had to use a brass drift to tap one of the for tubes out as the steering crown was pinching one fork tube rather tightly even with the pinch bolt removed.

As everything came apart the lower steering race dropped out of the head stock. It's been so long since I did this before that I don't remember if the lower race is supposed to stay in the frame. It's not even close to an interference fit.

I think that's a blessing that it came out. I am thinking to assemble the lower race, bearings and cap all just above the triple tree and then just slide the steering column back up through the head stock which will bring the whole lower bearing assembly into place. In this way I think gravity and an awkward location can't conspire to bring cuss words out of me.

But at this point my plan is a little vague. I could put the top races in and then the steering crown. However, I am concerned that the one fork tube is going to put up a fight going back in to the top triple tree.

I could try and wedge something into the slot that intersects the for tube so as to wide the opening.

I might take some emery cloth and try to massage the steering crown opening to be a little more receptive.

My main concern is to get everything back together without another bearing spill. I suspect the nut that holds the steering column in the headstock and the triple tree/steering crown against the bearing races is going to save me from a re-assembly steering head bearing fiasco at either end of the headstock, right?

If my logic is flawed let me know.

If you think the lower steering head race should be secured in the frame let me know.

Subsequent to this is going to be the task of re-terminating the control cable with new ferules for the new control levers on the clip-ons.

Someday I will learn to just leave well-enough alone.
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These forks are not the stock Ducati 31.5mm forks. These might be some kind of Ceriani 32mm forks.

Clearly part of my plan to just slide off the top steering crown to install clip-ons was doomed from the start owing to the extremely tight pinch the steering crown had on the fork tubes even with the pinch bolts removed.

Now I don't want to reassemble the bearings until I know I can slide the tubes back into place during reassembly.

The tubes slide easily through the lower triple tree. But test fitting the steering crown to the fork tubes finds both tubes quickly binding up in the steering crown.

I tried punding some flat blade screwdrivers into the slots on the steering crown leading to the fork holes. I still can't get the tubes to slide in. It gets a little better, but I am afraid that I might break the steering crown if I keep driving the screwdriver wedge in deeper.

Should I take the steering crown to a machinist? I am not sure what operation they can do to take a little material out of the holes. A steering crown I imagine is a hard thing to jig up.

Any advice?

Actually Jim, it should be an easy task to any skilled machinist. There are a few options, but if I had to guess, I would think it would be easiest to mount it to a bridgeport, or other milling machine, and bore the holes oversize with an end mill. You will hear some people call this "plunge milling"...This isn't exactly how an end mill is intended to be used, but it should work just fine... There are probably 20 other ways to accomplish the same thing. Regardless of how the machine shop chooses to do it, it really should not cost that much. I would just take it to any local qualified machine shop in your area, it would be an easy task to them i'm sure.

Joe

Thanks Joe.

Does a machinist adjust the cutting bit so that it cuts a 32mm dia hole? I just can't picture the operation in my head (not that I need to.)

Jim,
Here is the technique I use. I suspect it is somewhat unorthodox, from a mechanic's perspective, but it has worked for me on several bikes.

I have secured the lower triple tree to the downtube, using a a ratcheting tie down strap. I run the strap under the steering tensioner rings and up over the top frame tube, where it is welded to the downtube. Using a rubber mallet, I can gently encourge the top triple tree to slide up, off the bike.

For re-assembly, I install the fork tubes in the lower triple tree, so that the tubes extend 6 inches above the triple tree. Then, I grease-up the lower race, install the 42 bearings and slide the assembly up in the bottom of the downtube. WHile I hold it there firmly, as not to let the bearings drop/roll out, I ask my wife to ratchet down the strap to secure the forks in place. Then I can put the ears, clip on's in place.

Now, for the top triple tree, I slide it down to get it as close as I can to the fork tubes. Then lossen one of the fork tubes, but do not let it slide up or down. I usually put a line above the lower triple tree on the fork tube with a sharpie, in case it does move, I have a reference to get it back into position. Then, you can push the bottom of the fork tube aorund to help get the alignment with the opening in the top triple tree. I repeat this to the other fork and get the top triple tree about 1/8 - 1/4 inch down the fork tubes. Then tighten the lower triple tree and I use a rubber mallet to gently encourge the triple tree down so that it is mostly at it's final position. Using the fork nuts, usually secure/move the top triple tree to it's final position.

Not sure what this technique does to the front alignment, but the bikes do seemt o go pretty straight, so it seems to work.
Tony

Will the fork tubes slide into the top triple clamp by itself- leaving the lower clamp out of the test? If the the tube will slide into each clamp individually, but not as an assembly, then the holes in the clamps aren't aligned or the tubes are bent(not likely this high up on the tube).
I've modified many triple clamps to use larger fork tubes, and spent my working life in machine shops and tool and die shops- boring these things isn't as easy as some think it is. It's easy to make the hole bigger, but to keep it aligned with the stem and the fork tubes can be a real pain- the bottoms of the clamps are sometimes just a rough cast finish, so you can't just bolt it down to a milling table and bore it out- there won't be flat parallel faces to allow it to be put in a vise, the gap makes it hard to sweep in with an indicator, etc. Plus, the low grade aluminum usually used is real gummy and doesn't want to cut cleanly- a good sharp high speed steel cutter works better than carbide. I built fixtures that held both clamps together so they were both bored in the same setup- that kept the tubes aligned, but the fixture needed to be aligned to the stem.
If the hole is too small, not an alignment problem, I'd find a shop with a Sunnen style honing machine and do a series of gradual cut/test cycles to get a nice fit. When I machined them with a milling machine and a boring bar, I made a small shim to fill up the pinch bolt gap, so the pinch bolt could be tightened down when the hole was bored- seemed to help eliminate some chatter, and the shim eliminated the interrupted cut.
If a machinist says 'sure, $20.00', I'd be skeptical- he may not understand how accurate this needs to be.

These forks were assembled when I took them apart, though it took a hammer and a brass drift to get them apart.

The lower tripple tree is fine, the tubes slide through when no pinch bolts are in place.

It's the uppers that bind.

I have to agree that the tubes are unlikely to be bent, especially in the range from the lower triple tree on up.

It's likely they took a small pounding to get them assembled and that's what I am tring to avoid on my watch. It would be nice to put the bearings/races and triple trees together, then to just slide the fork tubes in to position without stress (both to me and without beating on the fork tubes) and clamp them up.

Clearly the openings are a few thousandths too small or a little out of round.

I will start checking with machinists on Monday.

I think a machinst is overkill, especially if he's going to take a cut on a milling machine. Honing, as mentioned above, is the appropriate choice.

Rick made an important point - can you slide the fork tube into the upper tree without the lower tree intalled? Remove the fork tube from the lower tree and then try sliding it into the upper tree with nothing else assembled. If it goes, then it's an alignment problem.

If it doesn't fit without the lower tree, then it's only a matter of a few thousandths to get it to go. If it were me, I would use a piece of emory cloth to hone the parts until they fit. Heating the upper tree with a heat gun may help, too. A liberal application of grease will hold the bearings in as you are assembling.

Jim...

I actually took the time to read your post and its apparent others did not

"These are not the stock ducati 31.5mm forks"

It isn't that your forks are "bent" or "misaligned" they simply are 32mm forks, no big deal...

So listen to whomever you wish, but trying to hold an upper triple clamp on a sunnen hone is a joke, and the thought that mounting it onto a bridgeport is such an impossible task, or "overkill" is also ridiculous.

Furthermore, any "machinists" on here who think a bridgeport milling machine is a "difficult to use contraption" of sorts, or thinks this job would cost MORE than $20 (and anyone who charged that small of an amount is some kind of moron who shouldn't be trusted with your parts) obviously has not been building bikes anywhere near as long as I have. Ask Bob, or Eldert, or Nigel... A milling machine is possibly one of the most versitle tools, ever invented, and most machinists use it for countless operations on a day to day basis. There is more than one way to "skin a cat" as they say, If you take your clamp to any COMPETENT machinist in your town, I personally guarantee you that they will know exactly how to do it in a precise, professional way, and it will not take long or cost a lot, and they will definitely not be using a sunnen hone to do it. Also to set the record straight, at the risk of wasting your own time, you could post a pic of the triple clamps...Because some people seem to have the misconception that they are some sort of mis-shapen, jagged, irregular pieces of metal that are impossible to hold straight, or secure to the bed of a bridgeport. This notion is also ridiculous, if I had one laying around at the moment I would take a good pic myself to post. One last point also...ANY time you want to overbore/drill/oversize a hole you need to find the center of that hole first, and the last time I checked duke triples are not welded together, nor cast in one piece, so the notion that both clamps need to be done together in one operation is also completely false.

BOTTOM LINE, you can let people blow this all out of proportion, and make it sound like the most complicated thing ever, and perhaps it is to someone with no real experience in a machine shop. BUT
A machinist would have to be a complete amateur to mess this up, trust me....
If for some reason, you have any problem finding one in your town, you can send the parts to me if you like, along with good measurements of your forks, I'm sure I have a set of 32mm Ceriani's (possibly identical to the ones you have) and I will be sure to do the job properly and precisely without building any kind of crazy jigs or anything, and I won't even charge you aside from shipping it back to you, because quite simply, this is an easy job, if you have the equipment and know how to use it...

Joe

Jim

If you ever find a machine shop that says "Sure we can do that...$20" and then says "Oh, you want that done accurately ???, well that costs extra $$$" Run, run very fast...