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 Post subject: HELP! 17 inch wheel conversion. All AOK Except Speedo won't
PostPosted: Fri Jan 12, 2018 9:15 pm 
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Joined: Thu Nov 02, 2017 12:16 am
Posts: 31
Location: UK
model: 750 Sport
year: 1989
Rear wheel went on without a hitch. We used a 1992 750 ss rear wheel and a 1996 Ducati 600 SS brake hanger and rear brake. Later rear brakes were thicker and would not work. All that needed to be machined was a small spacer.

Front came togheter perfectly with one exception. Sourced 280mm brake disc adapters from Duc_Only. He advertises parts regularly on the Paso.Org site and provided some wonderful kit.

Only problem is the speedo drive for the 750 Ss is too wide. Approx 6mm so. The 750 sport drive won't work. Does anyone know of a skinnier speedo drove or another technical solution?

Ducati Paso.org ... you are my only hope


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Fri Jan 12, 2018 11:24 pm 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1633
Location: Newzealand
model: 906 Paso
year: 1990
Dunno about the sport but the Paso ( M1r forks ) needs to loose 4mm on the left side to get the wheel in the centre , and that entails machining the inside of the fork leg . The only other way would be to get some electronic or GPS based speedo , ditch the speedo drive and make a spacer . I looked at a few ways to sort it but one way or another 4mm had to go . Same deal at the back , I had to move the wheel 4mm to the left . Just because both wheels line up with a straight edge isn't the end of it , that wheel centre line must be in line with the chassis centre line . There are at least 2 speedo drives for the 17" wheel as they are diff where they meet up with the wheel . I don't think there is any diff in the overall thickness of the different 17" drives

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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Fri Jan 12, 2018 11:53 pm 
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Joined: Thu Nov 02, 2017 12:16 am
Posts: 31
Location: UK
model: 750 Sport
year: 1989
Thanks so much for the quick response. Ma try to have forks machines as a last resort. The brembo wheel was used on a bunch of Yamahas, so I may check that avenue as well.


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sat Jan 13, 2018 5:34 am 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1633
Location: Newzealand
model: 906 Paso
year: 1990
Im pickin that if the yip uses the same wheels it probly has the same drive , possibly with a different ratio , but a quick yak to the right wreaker would probly put you straight .. If you do go for the machined fork leg you may consider getting the machinist to also make a spacer to " undo" the machine work so there wont be any drama if you want to go original again later.

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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sat Jan 13, 2018 11:21 pm 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
yeah, the speedo is the issue in that conversion. You can use the original Sport speedo drive and add some shims to fill the space. I used some 5/8" washers to fill the void. Not pretty, but it will work. The speedo drive for that newer wheel won't work unless you machine the left fork leg as mentioned. That's what I ended up doing. Alignment of the fork leg in the mill is of course a good trick, and critical to keep the front forks working well and not binding. No good way of trimming down the speedo drive that i could see.

If you do go with M1R forks, make sure you get 907 forks, or 851 forks that were made for the 17" wheel, or you are right back where you are now. Of course you will need triple clamps and clip ons for those 41.7mm fork legs. (stock Sport is 40mm)

Not sure what you had going on with the rear wheel. Newer rotor, caliper and hanger should all work together.

Cheers, Phil

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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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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sun Jan 14, 2018 11:12 am 
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Joined: Thu Nov 02, 2017 12:16 am
Posts: 31
Location: UK
model: 750 Sport
year: 1989
Hi Phil,
Couldn't get the old speedo to work with the new wheel. Looking into speedo for smaller nikes to see if I can find a slimmer unit. TZr 125 uses a brembo wheel and looks to be 5mm slimmer. Fingers crossed!


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sun Jan 14, 2018 11:20 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5272
Location: southern Germany
model: 750 Paso
year: 1987
a while back I was looking into speedometer drives and checked for similar narrow ones. I only looked for parts used on Ducatis and other italian bikes. Noone had the same ratio.


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sun Jan 14, 2018 1:04 pm 
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Joined: Thu Nov 02, 2017 12:16 am
Posts: 31
Location: UK
model: 750 Sport
year: 1989
Thanks! This is really helpful


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Sun Jan 14, 2018 3:26 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5272
Location: southern Germany
model: 750 Paso
year: 1987
according to an online tire size calculator if you go from a 130/60-16 front tire to a 120/70-17 the instrument will indicate -6% in speed and with a 130/70-17 it's -8% so at 100km/h it would show 92km/h. Here in Germany that wouldn't be legal. An instrument is allowed to show 7-10% more but zero less than actual speed. Don't know how rules are in the UK.


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Mon Jan 15, 2018 4:26 am 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
1989750Sport wrote:
Hi Phil,
Couldn't get the old speedo to work with the new wheel. Looking into speedo for smaller nikes to see if I can find a slimmer unit. TZr 125 uses a brembo wheel and looks to be 5mm slimmer. Fingers crossed!

Yeah, it doesn't fit right up. I had to re-bend the tab on drive, and modify the plate on the wheel a bit. Like I said, it ain't pretty, but it is functional.

Phil

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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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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Mon Jan 15, 2018 9:53 am 
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paso grand pooh-bah
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Joined: Thu Nov 03, 2011 10:13 am
Posts: 622
Location: Scotland
model: 907 I.E.
year: 1994
paso750 wrote:
according to an online tire size calculator if you go from a 130/60-16 front tire to a 120/70-17 the instrument will indicate -6% in speed and with a 130/70-17 it's -8% so at 100km/h it would show 92km/h. Here in Germany that wouldn't be legal. An instrument is allowed to show 7-10% more but zero less than actual speed. Don't know how rules are in the UK.

In the UK they can read up to 10% fast but 0% slow. Most speedos read around 5 - 10% fast. -6% on my 907 would bring it almost down to reading the correct speed. :D

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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Mon Jan 15, 2018 10:04 pm 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
In the U.S.A., there is no speedo check. So running without a functioning one is almost feasible. If there is a speedo on the dash, then you are good, basically. i have never heard of anyone ever being checked that they have a functioning, much less accurate speedo.

Get any speedo drive that will work, then find one of those digital speed radars on the edge of town and ride past it till you know where some key speeds are, and put a sticky on the glass.

Phil

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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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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Tue Jan 16, 2018 9:19 am 
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paso grand pooh-bah
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Joined: Thu Nov 03, 2011 10:13 am
Posts: 622
Location: Scotland
model: 907 I.E.
year: 1994
For information. In the UK a speedometer, working or not, is not part of the annual MoT test. So like the in USA, they are never checked.

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2017 Supersport 939
2015 Scrambler Classic
1982 Pantah 500SL


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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Tue Jan 16, 2018 8:15 pm 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1633
Location: Newzealand
model: 906 Paso
year: 1990
In NZ it seems that as long as the needle moves ..... and aint obviously wrong no one give one. Somewhere in the rule book it sez that you must have a working speedo and more important a working odometer . In NZ diesel vehicles pay a separate road user charge based on distance travelled so you can see why the enforcers want an accurate odo . Electric speedos are a boon here as it so simple to interrupt the signal from the drive unit .More than one peep I know does this . One has it wired so that it only works when the air con is on

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 Post subject: Re: HELP! 17 inch wheel conversion. All AOK Except Speedo w
PostPosted: Thu Jan 25, 2018 9:24 pm 
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Joined: Wed Oct 27, 2010 5:52 pm
Posts: 364
Location: Essex UK
model: 907 I.E.
year: 1992
I put showa’s on my 907 with a later 3spoke wheel w 25mm spindle. I took 2mm off the outside edge of the new type speedo drive to centre the wheel w no problems. Also the gearing was +50% reading fast. I put a mechanical km converter at the drive that almost corrects it.


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