Oddities

discussions specific to the 907IE
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ducinthebay
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Oddities

Post by ducinthebay »

Taking apart the 907 to put on a new front tire and discovered a few things I wanted to get your input on.
1. the pistons on the calipers are further out on the outside than the inside. It kinda suggests the rotors could stand a bit more offset. Everything is stock, and both sides match, so I guess its a design thing.
2. the front tire is not centered in the forks. Its about 2-3mm to the right. Should it be that way?
3. On the speedo cable, there is a ferrule attached to the inside cable. Should that ferrule be on the top by the speedo, or down on the bottom by the axle? Mine was on the bottom, but I always thought that they should be on the top.

Any input or insights?

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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paso750
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Re: Oddities

Post by paso750 »

Phil,

do you have the washer on the right side of the wheel?
The ferrule of the speedometer cable should be on the top. It determines how long the end of the cable is that sticks into the intrument and also prevents it to fall out if you remove the bottom end.

G.
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ducinthebay
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Re: Oddities

Post by ducinthebay »

Thanks G.
I will switch the cable around, which is where I too thought it should be.

On the front wheel alignment, I am a bit puzzled. The axle threads into the left fork leg, drawing the wheel to the left fork leg and the right leg floats in alignment (until you tighten the pinch bolts) So a washer on the right hand leg seems pointless to me. The wheel alignment is set by the speedo drive side, so I would think that the washer should be on the left side, if anything.

Wonder why they would add a washer to the right side? It wouldn't change the alignment of the front wheel. It would only affect the length of axle sticking out of the right leg. It would infer that the axle dimensions were not correct ( across the length). I wonder if its an adaptation to put an earlier Sport or Paso axle on the 907. (not that Ducati would resort to stealing from parts bins from another model :)) The 907 fork leg is narrower on the left leg to accommodate the bigger speedo drive. I am assuming that the step lengths of the two axles is different. I'll go measure a few now.

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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paso750
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Re: Oddities

Post by paso750 »

I don`t think the right fork leg floats into alignment. I guess the washer makes sure its alignment is correct.
If that washer were on the left side it would offset the whole wheel to the right.
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ducinthebay
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Re: Oddities

Post by ducinthebay »

G,
With all due respect, and there is plenty due, one leg of a motorcycle front suspension must float into alignment, and the other side is the reference. Otherwise, you will have binding of the forks. On the Paso and Sport, the left leg is the reference and the wheel is drawn to that side when the axle is tightened. Its more important that the fork legs are parallel than the location of the bottom of the right fork leg. If the right fork leg was not on the bike, and all of the rest of the parts were assembled, the front wheel would still have the same alignment. The manufacturing tolerance are such that you can not predict the overall stack of all the parts, so adjustment/float is left in the system.

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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paso750
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Re: Oddities

Post by paso750 »

I understand and agree with that but if you remove the axle I bet the gap between the fork leg and the rim is exactly the width of that washer.
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ducinthebay
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Re: Oddities

Post by ducinthebay »

paso750 wrote:... if you remove the axle I bet the gap between the fork leg and the rim is exactly the width of that washer.
Again, no truer words were typed. I took the axle out, and indeed, there was a washer on the axle, but on the left side, between the speedo drive and the fork leg. I removed the washer, reassembled, and the wheel is perfectly aligned in the fork legs. Axle protrudes about 1mm on each side of the fork legs. I have no idea what the washer is for, but its now lives in my spares bin. That would also explain the odd tire wear on the front tire that I saw.

So that is two mysteries solved. Now, about that disc offset. has anyone else noticed that the pistons are exposed at different depths from the inside to the outside? Suppose it doesn't matter that much on a 4 piston caliper. Or should I plan on putting 4 washers in-between the forks and calipers to center the calipers on the rotors? (which is what I did on the Sport when I built up that front end)

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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paso750
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Re: Oddities

Post by paso750 »

I don`t think the right fork leg floats into alignment. I guess the washer makes sure its alignment is correct.
I was wrong with this of course. I remembered the gap between the rim and fork leg narrow and this washer being a spacer between both which it isn`t. I should`ve checked on the bike before. :roll: Sorry for that.

The washer shifts the axle to the right so there`s only one reason for it I could think of which would be that the thread on the axle is too short to tightly bolt the wheel to the left fork leg hence that the end of the axle thread hits the slider tube too early. You`d have to remove the wheel, fully screw in the axle until its tight and then compare how much it protrudes on the outside. If it`s more than with the wheel in place there`s no reason for the washer. If it`s about the same the washer might make sense.

G.

on my P750
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Re: Oddities

Post by higgy »

Image



better late than never :beer:
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
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paso750
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Re: Oddities

Post by paso750 »

from which parts catalogue is that ?
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higgy
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Re: Oddities

Post by higgy »

edited from the manual
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie
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paso750
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Re: Oddities

Post by paso750 »

:lol: that`s so typically Ducati. The bearing spacer is also different in both drawings. According to the design of the brake discs I guess the picture from the wsm shows the early 907ie with 300mm discs and the picture from the parts catalogue the later 907ie with 320 brake discs.
Why one shows the washer and the other doesn`t will remain a mistery. :truck:
(but then sometimes the same pictures were used in different wsms i.e. 900SS or parts catalogues so you can`t always rely on them)
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Re: Oddities

Post by higgy »

Typical of all mid 80's-90's manuals
Honda was actually the first manufacturer to create a decent manual way back in the 70's.

Fiat and Maserati and all the Italians epitomized what not to do
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
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du907
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Re: Oddities

Post by du907 »

Hey guys.
First, the ferrule on my speedo cable has always been on the bottom. Even when I got a replacement, it was on the bottom. I know what you guys mean about it being at the top to keep it from sliding out, but the ferrule would also be acting like a bumper, only letting the cable go so far into the speedo gear, and as the cable snakes around things as it gets to the back of the speedometer, it needs some slack/play. Seems like it could work either way. Just a thought.

My front axle has a washer, on the right side between the bearing and the shoulder on the thickened part of the axle that goes through the right fork. If you screw the axle into the left fork all the way with the speedometer gear in place (no washer on that side), the speedometer gear acts as the spacer on the left side. The wheel must need the washer on the right side to get it to center, remember the shoulder on the right side of the axle, the washer can only push to that point. I went through all this after a wreck and had to rebuild the front end and get the alignment back in order.

As far as the brakes, I have found that every so often I need to take the calipers off and clean up the pistons, cylinders, and dust boots, replacing any parts that look worn. It seems that brake dust buildup, moisture and dirt in the fluid causes a film and dirt to build up causing the pistons to stick or not move freely. This could explain why some pistons are further out than others. I can usually tell they need cleaning or servicing when I'm pushing the bike around in the driveway or parking lot by the way the pads sound like they are "riding" the disc excessively or not.

Just an opinion guys.
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Re: Oddities

Post by paso750 »

The position of the wheel in the fork is only determined by whatever is on the left side of the rim. If you have no, one or three washers on the right side doesn`t make a difference regarding that. This only impacts the position of the axle.
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