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On my 1985 S2 Mille the sprag bearing has broken for second time this year.
The last two I have changed are different to the first one that lasted for more then 20 000 Km.
I guess I can save this sprag bearing for some time by adjusting the ignition low, but then the engine gets dull and week.
Every now and then for the 5 years I have had the bike it backfires some times when the engine is hot, it makes a pop in the aircleaner, and then the sprag bearing is gone.

On the http://www.ducatimeccanica.com/howdi/default.html there is a flywheel with this part built in but so far I have not got any answers trying to contact the seller to order one.
Does some one here know anny thing about this, or some better parts?

Regards
Harald
 

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Hi Harald, Do you still have the standard Bosch ignition system? how are you adjusting it? Vee Two in Australia sell an uprated sprague clutch bearing assembly and there is/was another Australian company called Howdi Engineering which made one also.
 

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Every now and then for the 5 years I have had the bike it backfires some times when the engine is hot, it makes a pop in the aircleaner, and then the sprag bearing is gone.
It might be worthwhile to focus on tuning the carbs so it will stop backfiring. It sounds like it might be too rich. That could be caused by a leaky float valve, incorrect float level or incorrect jets/needle position.

My Mille never backfires and it runs strong and smooth so I know it's possible.
 

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The backfire he is talking about is not when the engine is running. It is when he is starting the engine hot. When it backfires, it spins the motor over backwards, and this is what destroys the starter sprag. It sounds like an ignition system problem (timing issue). Have you checked the ignition timing and advance?

Too rich a fuel mixture doesn't cause a backfire, it is too lean a mixture that causes a backfire (popping back through the carbs).
 

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It could also be the starter is not turning the engine over quickly enough. If the engine is stalling out near the top of the compression stroke it can cause a backfire. That's not uncommon on the kickstart models if they are not kicked properly. A new battery and/or new battery cables may cause it to crank more quickly and thus avoid the backfire situation.
 

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I would concentrate on 2 things - ignition and carbs. You seem to be having a problem in 1 or both of those areas.

On the ignition side - have you replaced the pickup wires yet? If ot, you definately need to, with some good FEP wire that can handle the heat inside the engine and outside. We have it for you if need be.

On the carbies, they MUST be in a good state of tune meaning, good seals and gaskets etc, and even more importantly they must be properly syncronized. I would make sure the intake manifold insulators are not cracked and the exhaust gaskets are properly sealing too.

On the starter sprag bearing, I know this is no consulation, but, we have em on sale right now, and a 2nd is almost half price of the first. Get a pal and order a couple...
 
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