I presssed the starter, and heard a whirling, rattling sound which I figured was a broken starter sprag clutch spring. I figured I would shorten the spring, as has been recommended here. But I found that the sprag in my bike does not have the coil spring running in a channel around the outside of the sprag -instead the outsides of the sprag cams are solid, and there are zig-zag holding springs running around the sides of the cams, on the front and back of the clutch, as can be seen in the photo below. Anyway, I'm off to see suppliers and see if I can find a replacement sprag clutch. I'll start with the local KTM people, to see if I can save on the price of a Ducati one. I can't actually see anything wrong with the unit, and the zig-zag springs look ok, but I'm pretty sure I need to replace it

Skins,

You can fit it and test it to see if it's working by hand once you have it out of the bike. I might have one laying about to send to you if needed.

That's really kind of you Jon, I really appreciate the offer - but I've ascertained that I can get a KTM unit here quite easily at an affordable price.

But can you explain the testing proceedure in a few words for me, please?

Many thanks,
Erskine

Dunno if its a trick of light ( or whatever) but that roller ( I know its not really a roller but what else do you call it ?) closest to the camera , just right of centre looks to be worn to me ,on the right hand edge , more so than the others I can see .Which KTM part do you use?( bound to need one some day !)

The KTM part number is 5844002600

Well, with the sprag clutch in the flywheel, and the starting gear behind the flywheel also removed, and with the sprag clutch and flywheel sitting on the starting gear and held in my hand, the flywheel rotates freely and easily without noise in one direction, but not the other. I guess that's not where the problem lies, then.

So I'll put it all together, press the starter again, and try to get a better reading on the noise.

The only trouble is, having had the sprag clutch in and out of the flywheel a few times without thinking too much about it, I'm not sure which way it should go in. I can probably figure it out, but which way should the flywheel rotate freely in respect to the starting gear? At this stage I'm guessing it's anticlockwise.

That sprag clutch looks quite worn to me as well, not only on the single part.
You cannot test it properly by hand, since the acting forces during a real start are much greater than what you can accomplish by hand. I've seen perfect working sprags fail after a head rebuild and new piston rings, where suddenly the bike had full compression again.

Thank you, Michiel

That reinforces my feeling that although the unit tests OK when held in the hand, it probably does need replacing.

I can't imagine anything else that would make the kind of noise I heard.

At $NZ140 (EU79) I think it makes sense to put a KTM unit in, and see if that solves the problem.

Thanks again,
Erskine

I would have thought that the transmission from starter to the crank ,being a train of gears and this clutch that if the starter turns but the crank doesn't it would have to be either the sprag clutch, or teeth missing of gears, which would be bloody obvious.
Thanks for the KTM part #

CORRECTION: That KTM clutch seems to be the wrong unit for the 750, although I believe it will suit a 906. It's too big for the 750.

Apparently the original 750 starter clutches are no longer available from Italy. I'm trying Gowanloch in Australia to see if they can help.

It says in the interchangeability list that it is a replacement for the 906.
I found this. It says that 860GTS/MHR & belt driven 500-750 use the same one.

367 NZD
http://www.roadandrace.com.au/parts/par ... earing.htm

273 NZD
http://bevelrubber.com.au/cart/index.ph ... qepc06n1d4

G.

Many thanks, G!

That's very encouraging.

I checked my spare. I bought it from a guy who put it up for sale in the forum longer time ago.
He got it here:
http://shop.bevelheaven.com/detail.aspx?ID=67 (214 NZD)
The number on it is SKF 445419.
Strangely I can´t find anything on the internet about it. Maybe a bearing shop can.

Thanks G!

Gosh, that rotation business is confusing when you see it written down!

Hi, gents. A couple of years ago I replaced the sprag clutch with one of a mini '69 (small car). It'll cost you a lot less and it's 99,9% the same. Only the outer diameter (small lip on the casing) needs milling for 0,5mm in diameter. Since this will not move once installed I used a conventional drill. It's in there for over 6000 miles. Not once a 'rattle'.
Still enjoying the paso the most. Just changed to new tires (bridgestone) with a santa monica front sprocket. This one is 12mm offset. Works perfectly! Never had this amount of grip Modern bikes can't keep up while cornering..
Léon