Referring on qldman36 and jcslocum reply to Paul about start sprag cluth spring fix (http://ducatipaso.org/modules.php?name=Forums&file=viewtopic&t=173&postdays=0&postorder=asc&start=45), I had the same problems and finally tried to apply this mod. Here are some pics that may be helpful to anyone who would like to try it:

the sprag bearing:


the sprag bearing removed, you can see the spring!


The loosen spring:


I don't know if it works, but I'll tell you as soon as I will manage to re-assembly everything!

LC

The original article about this is here: http://www-ccrma.stanford.edu/~peer/Duc/duc-spragSpring.html

I add some (I hope useful) tips:

Before removing the sprag bearing, you can note an arrow indicating how it must be reassembled:


Be careful because the spring ends are different! One is smaller:


When reassembling, you can align the flywheel using these references:


LC

Some other helpful info:

Chances are the sprag clutch spring has weakened or come apart. A replacement spring from an oil seal (part # CR 19778) for around $6- works perfectly.

The part # CR 19778 is for an oil seal (CR is for Chicago Rawhide - the maunfacturer). The seal (probably a grease seal) has a spring around the inside of the rubber lip. That spring is a perfect replacement for the starter sprag spring in the starter sprag assembly. Throw the seal away and keep the spring... that's all you need.

Jon, is the seal similar to this?



(this is the one I used for the sprocket... )
What about dimensions?

LC

Luca,

Here is the detail from Chicago Rawhide:

http://tinyurl.com/bfu9l

This seal is for a 2" (50MM) shaft so the spring that is inside the seal is what you need for the starter sprag. I have yet to make this repair myself. Just going by the research that I have done in "preparation" for this one day.

Jon,good job on finding a replacement spring!
lceriani,afraid you definetly will have to source a new spring as when you shorten old one,you cut large end.Your small end has been stretched probably beyond use.Also,i hope you kept track of which way rollers go into clutch as they are NOT symetrical[sp].Only will jam[work]one way.
Carl

I noticed the rollers are not symmetrical... I tried to mantain their original position, but when I opened the part with the spring (too loose!) they "exploded" away... so I mounted them in the only way that permits to the assembly to move in the direction indicated by the arrow. I guess it's right, but I'll confirm only when I'll finish to assembly the engine cover.
I an afraid of the stretched spring, too, but at the time I had no good replacement, so I decided to keep it as it is. I need it working only for a few weeks, then I'll change the engine and I will have all the time to find and replace it.

Thanks!

LC

Appears that you may have pulled the two ends apart rather than"unscrewed",therefore the stretched end. After shortening the large end and before trying to screw ends together,back turn the small end a couple turns so that when together the spring will be"relaxed".Should be alright,but sure can't guess as to how much to cut as i don't know how loose it was on rollers.

Luca,

Thanks for going to all this effort. I haven't been brave enough to try this yet (and my bike is still being stored from my house move). Your photos make it much clearer in my mind.

Paul

does anyone have the photos mentioned above on file....they dont want to load up for me.

I am having some problems with the starting system on my 907 and on looking at the parts listings for both bikes...they appear to be very close to the same.

Excuse my ignorance, but what is the 'SPRAG'? there is no mention of it in the past list that I can see.

http://ccrma-www.stanford.edu/~peer/Duc ... pring.html

viewtopic.php?f=2&t=1401

http://www.bulldogmtnbikes.com/Spragclutch.htm

http://www.advrider.com/forums/showthread.php?t=222515

in the 907ie parts catalogue Tav.12 it`s no.24 "free wheel". When the starter turns the the bits in the "free wheel" cant.

G.

Thanks G,

Seems to be a simple fix, but fiddley to get to the spring in the first place.

A job for next weekend I think.

When i fixed the sprag on my 907 this summer i could not find the oilseal from Chicago rawhide locally so i just bought a fork seal kit for a 50mm fork from ebay.
I havent used the bike much since i installed it but so far it seems to work very well.

as mentioned in one of the texts make a mark on the starter sprag before removing it. It`s not about the position this should just make sure that you put it back in place correctly with the mark facing towards you.

All is good G,

I now have the knowledge to get me into trouble....

Shortening the spring in the first instance seems the way to go, but if replacing, the KTM option seems to be the way to go.

Thanks again.

I will take some photographs and post once I have her up and running again.