the P750 sprocket

Silly me.....I just remembered that all the newer Ducs do not use the old retainer system but instead use a flatter sprocket and use a huge nut on the shaft to hold it in place.....now, if I can just get my hands on a 520 to check it out.

as Terry and I are discussing this topic offline here a short summary of our current thoughts:

a sprocket like this would be nice, but according to Antti this could be from an early 750 Sport or similar and is quite rare. In fact I didnt find it listed ie at AFAM or JT sprockets. (if someone has some info about this let us know!)


I personally don`t like the before mentioned option 1 as I don`t trust the center bolt only.
Option 2 has by far too much offset and overhang of the drive shaft. Material could be removed from the sprockets back and the inner sprocket/adapter flanks but this would be approx. 4mm max. (still 7,5+mm offset). Downside this would need to be done with every new sprocket.

As Terry has a 748 sprocket the idea was then to reverse it. Depending on if the inner sprocket/adapter was recessed or flat the gained offset would be around 4,5-6mm which should be fine in most cases. (To compensate the overhang one could have a small prolongation of the drive shaft fabricated)



A recessed sprocket/adapter would be an original Paso sprocket with the teeth removed, a flat one an original Paso sprocket with the sidewalls removed or an 748 sprocket w/o teeth.
The advantage of this solution would be that one would need only one or two parts made by a machine shop once. Then when replacing the sprocket one would only have to have the threads drilled through of the new sprocket.

Currently Terry is leaning towards option 4, I towards option 3 as my setup is different.

Seeing that newer bikes like the 749 have a flat round retainer clip this will be the next thing we`ll check. Thinking that a bigger surface area between the 2 sprockets is better the next step would be to check if this retainer clip is flat and has the identical width as the one of the Paso. If so it would only require 2 holes drilled through it. But it looks like the outer part of this clip is sheet metal and too soft to use it instead of the original one.



Any thoughts on this matter are highly appreciated.

G.

PS: if I would have thought about this when rebuilding the engine I`d had tried to swap the drive shaft with a longer one from another Duc, it might have made things easier.

I love this kind of reply. Now show us where in Germany, Italy etc you can get those south korean/japanese Shinko tires and that sizes ??? In the US it may not be a problem finding some.

G.

I don't know if it's of any help, but the AFAM Japan website (www.afam.co.jp/E/index2.htm) says they can make offset front sprockets: "We welcome any inquiries or orders on "made-to-order" for unlisted items and models. The delivery date is about 2months, The price is from Yen18,000. Please consult your nearest AFAM Dealer or us for quotation and technical information".

GT-UK

"
Hope you got a chance to get a close look at my set up without any of this BS..... Very inexpensive tires, no sprocket spacers, sticky enough to drag hard parts. 1,000 miles now with no regrets, very happy with these tires, only unknown is how they will do in the wet and I hope not to find out on the way home...LOL"

Mike, sorry to be dense, but could you remind me which shinkos you've fitted. i asume they are 130/70 and 180/60. is hat correct. and what's the link to a photo. thanks very much. best, randy.

@GT-UK 18.000Y are 125GBP. There`s one company here in Germany which makes offset sprockets which cost €90. That`s quite a bit less but still expensive considering that it`s something that`ll need replacement sooner or later. Guess it depends on how much or how little one rides to make this investment worthwile.

@randtcastell 006 Podium front and 747 rear. Pics are on the first page of this thread.

G.

I agree, the cost of a 1 off sprocket is expensive. But if a group of, say, 20 or 30 got together, maybe the price would come down significantly.

GT-UK

Another way is to make a welded up sprocket. Take two sprockets, machine the teeth off of one, and machine the core out of the other and weld them together. If you have a good machinist, put a little lip on the two parts so that they nest and don't get welded out of round.

Cheers,