sl1000
03-29-2008, 01:13 AM
Hej guys,
I came across some interesting reading on the Dutch Aprilia forum.
A ducati-guy fixed his sprag clutch by shortening the spragclutch spring about half an inch. The dutch guy did the same, and his is working like a charm again.
The real good thing would be to find a new fresh spring that would fit properly I guess. any engineers with ideas on where to find the right spring?
anyway, interesting reading:
http://www.mad-ducati.com/Technical/StarterSpragClutch/SpragClutch.html
http://www.mad-ducati.com/Technical/Engine/AlternatorCover2.html
http://www-ccrma.stanford.edu/~peer/Duc/duc-spragSpring.html
and the most interesting part:
The following modification might be looked at as a tiny fix, but has saved me at least $800 -- and perhaps even more if I initially knew about the following:
One of the most annoying thing is when my Ducati refuses to start, as the starter slips and stutters. First I thought this might be a problem for bikes with lightened flywheel and/or synthetic oil, since installing the Nichols flywheel the starter-sprag has acted up three times... and it didn't matter how new the sprag was, soon enough it begun to slip -- often making it impossible to start the motor. As you might understand from reading some other entries of this web-site, I believe Jon Nichols is a brilliant mechanic (and manufacturer) who has this "urge" to make things work. So after collecting lots of info about the sprag, (I even purchased a crank-shaft seal for a Chevrolet which was rumored to contain a similar spring to the Duc-sprag's, which is essentially the weak part). Anyways, I brought my bike to Nichols' and started to badmouth his flywheel -- blaming it for making the sprags go awry. Uncharacteristically for him, instead of starting a verbal rebuttal of my accusations, Jon picked up a magnifying glass to look closer at the sprag and the spring which holds its rollers in place. He then found the opening where the spring is "screwed" together (into its loop). He cut the spring shorter and put it all back together and boomm.. just like that -- the bike started up as if having a new sprag.
But infelicitously less than six months later, my starter acted up again.. this time I decided to do it myself. When looking at the sprag-spring I realized that it could have been cut a whole lot shorter than what Jon initially did -- making it much snugger. So I did, and needless to say; now it works like a charm.. and this was almost four years ago.
If anyone has questions regarding a bad starter sprag, I'm happy to answer any question you have. The stuff you'd need in order to do a hack like this is a 30 mm wrench-socket for the flywheel, a tube of red lock-tie for the flywheel-nut -- and then, most importantly, make sure to put the sprag and the stator (amateur for the alternator) back the same way as you took it off. Note that both the sides of the stator look pretty much the same which makes it tricky to get back the right way if you forget to put a marker (or something) on it to indicate which side is which.. By the way, that Chevrolet crank-shaft seal-spring is too thick.. nice try though, eh..?
I came across some interesting reading on the Dutch Aprilia forum.
A ducati-guy fixed his sprag clutch by shortening the spragclutch spring about half an inch. The dutch guy did the same, and his is working like a charm again.
The real good thing would be to find a new fresh spring that would fit properly I guess. any engineers with ideas on where to find the right spring?
anyway, interesting reading:
http://www.mad-ducati.com/Technical/StarterSpragClutch/SpragClutch.html
http://www.mad-ducati.com/Technical/Engine/AlternatorCover2.html
http://www-ccrma.stanford.edu/~peer/Duc/duc-spragSpring.html
and the most interesting part:
The following modification might be looked at as a tiny fix, but has saved me at least $800 -- and perhaps even more if I initially knew about the following:
One of the most annoying thing is when my Ducati refuses to start, as the starter slips and stutters. First I thought this might be a problem for bikes with lightened flywheel and/or synthetic oil, since installing the Nichols flywheel the starter-sprag has acted up three times... and it didn't matter how new the sprag was, soon enough it begun to slip -- often making it impossible to start the motor. As you might understand from reading some other entries of this web-site, I believe Jon Nichols is a brilliant mechanic (and manufacturer) who has this "urge" to make things work. So after collecting lots of info about the sprag, (I even purchased a crank-shaft seal for a Chevrolet which was rumored to contain a similar spring to the Duc-sprag's, which is essentially the weak part). Anyways, I brought my bike to Nichols' and started to badmouth his flywheel -- blaming it for making the sprags go awry. Uncharacteristically for him, instead of starting a verbal rebuttal of my accusations, Jon picked up a magnifying glass to look closer at the sprag and the spring which holds its rollers in place. He then found the opening where the spring is "screwed" together (into its loop). He cut the spring shorter and put it all back together and boomm.. just like that -- the bike started up as if having a new sprag.
But infelicitously less than six months later, my starter acted up again.. this time I decided to do it myself. When looking at the sprag-spring I realized that it could have been cut a whole lot shorter than what Jon initially did -- making it much snugger. So I did, and needless to say; now it works like a charm.. and this was almost four years ago.
If anyone has questions regarding a bad starter sprag, I'm happy to answer any question you have. The stuff you'd need in order to do a hack like this is a 30 mm wrench-socket for the flywheel, a tube of red lock-tie for the flywheel-nut -- and then, most importantly, make sure to put the sprag and the stator (amateur for the alternator) back the same way as you took it off. Note that both the sides of the stator look pretty much the same which makes it tricky to get back the right way if you forget to put a marker (or something) on it to indicate which side is which.. By the way, that Chevrolet crank-shaft seal-spring is too thick.. nice try though, eh..?