Darmah Rear Sprocket

If you need technical information or help with your BOSCH ignition squarecase Ducati 900SS - Darmah engine - post your FAQs, comments & questions here.
sevicke
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Post by sevicke »

look at those pics what a state of affairs you should buy a harley instead of gearing the poor ol darmah so highly, next yourll be going on about the big ends been weak, had to modify the spocket carrier, dont you think they would have noticed the chain rubbing in the factory. Are you planning a run at bonneville ?

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BevHevSteve
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Post by BevHevSteve »

exactly - I think 2.44 is PERFECT on a darmah [16:39]
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wdietz186
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Post by wdietz186 »

Maybe you guys like to pootle around at low speeds and higher revs but in open areas the 16/36 works just fine for empty backroads and highway work.You can always downshift you know!

sevicke
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Post by sevicke »

some guys just dont get it she wont go any quicker geared like that, maybe at bonniville you could get a bit more, shes a combi not a harley.

David Frith
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Post by David Frith »

I ended up removing the spacer from behind the 36 tootth rear spocked and machined a chamfer on the edge of the spocket carrier, this worked fine
I had no problems with the clearance of the 16 tooth front spocket.
But I have since put the 15 tooth back on.

Dave
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lomax
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Post by lomax »

ups.....lots of different statements

Sorry for driving this worn sprockets - I must have been crazy 13 years ago and didn't recognize it after bringing it back in operation this year. :oops:

The idea for high gearing was to preserve the old engine from high revs - especially on german highways, where you drive faster as on US highways. There is no intention to get it faster knowing it would not work that way anyway.

I will use a 15/36 gearing now, because I already got a new 36 rear sprocket and the 15 front sprocket is still in good condition. The worn 16er sprocket has to be replaced anyway.

Next time I might try another gearing like 16/39 (which is not much different to 15/36).
Btw - what was the original gearing of the Darmah ?

Joe
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Cheers from Germany
(Ducati 900 SD, Suzuki GSX-R 1000 K6, Suzuki GSX 1200 Inazuma)

sevicke
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Post by sevicke »

the point is power is a combination of torque and velocity, with higher revs
youll require less torque to produced the same power, labouring the thing at high speed demanding high torque to produce the same power. Is purely
loading up the motor for no gain. Considering the reputation these things have for doing big ends. I prefer letting the thing rev a bit more freely their
designed to spin and do so nicely. Me I have a nice new big end that cost a pretty penny. Then fifth gear went split in two, lucky it sat on the kick starter shaft and did no damage. Another victim of high torque. A few more dollars new gears Thats three rebuilds so far,I dont know if these are the greatest motors in the world have my doubts. But there dam cool.

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Craig in France
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Post by Craig in France »

lomax wrote: <snip>
Btw - what was the original gearing of the Darmah ?

Joe
Hi Joe,

From the owner's handbook for each model:
SD: 15:38

SSD: 15:36.

HTH

Craig

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lomax
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Post by lomax »

Mercy beaucoup Craig :-D

lomax
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BEVEL DAVE
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Post by BEVEL DAVE »

I have always run either 16-38 or 16-36 on my road bikes.
A good desmo engine will pull 16-36 easily on the open road & pull to well up into the rev range with no hassles.
Anything I use around town or general riding gets a 38t rear.

My old race bike spun easily up over 9000rpm in top with 16-36 gearing at Phillip Island & Eastern Creek.

Dave.

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Post by Aussiess »

So how didi you find that 16-36 gearing for those tracks??
Did you have any other eng mods that would assist/ Imola cams, stroking, bore etc?
Am interested as I am looking at gearing for these venues for my NCR rep track bike.
Was thinking 16-37 as I had 16-38 and it was just not quite right for gear selections for me, but I was being a pussy and running engine in too and didnt want to blow too many $$ worth of engine work on first day out!!!
Regards,
Grant
79 900SS , 82 MHR and 78 NCR Replica

BEVEL DAVE
Diana
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Post by BEVEL DAVE »

Std. stroke, 88mm bore, 12:1 comp. & round case Imola cams with 42.5mm Malossi carbs & hi-rise twin pipes. The heads were a pair of Gowie specials also.
That gearing was ok for Eastern Creek but still short for Phillip Island but it was still good for acceleration out of Honda, Siberia & MG. Clicked top gear coming onto the straight & just held it on till 9000rpm.
Not good for crankshaft life but fun!!!

Dave.

Den
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Post by Den »

Sorry to get off the topic of how fast we all used to be, but:

You may want to use a straight edge to check your sprocket alignment
before simply turning around your countershaft sprocket.

I had a problem with my chain clearance and checked the alignment of my sprockets.
http://img.photobucket.com/albums/v85/d ... /setup.jpg

Notice that the wide boss is on the INSIDE and there is still a 5mm gap.
http://img.photobucket.com/albums/v85/d ... ap/gap.jpg

I used a 5mm thick washer behind the WIDE boss to obtain proper sprocket alignment.
http://img.photobucket.com/albums/v85/d ... p/shim.jpg

The sprockets involved are 15/34


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