Mis firing

[93IE]

I think my luck has come to an end. Bike was starting fine cold, but after a warm up, it mis fires and backfires through the air box.I did a compression test and it has 95 to 100 psig in both cylinders. To top this off, when it backfired, I guess the sprague for the starter came apart. It will not engage at all now. As much trouble as I've had with this bike, I'm tempted to pull the motor down for a valve job with guides. I suppose I will check the clearances first tomorrow.
Does anyone know if Ducati offers the sprague?

Preston

[Tamburinifan]

Sprag is no problem, same on many others & avaliable as spare part fr Ducati.

[93IE]

I called Ducati Austin today, and they can have the sprag in 5 days, $160.00. I checked the valves and found the vertical exhaust way to tight. I sanded down the opener shim to get .004" on the opener. Depressing the closer, I had a total of .008". I think that would give me .004 on the closer. I probably need to change the shim on the closer. The horizontal was good on intake and exhaust. That was probably causing the misfire when the motor was warmed up, I hope, as the vert exhaust was not closing all the way.

Preston

[du907]

Try this site. www.mad-ducati.com under tech stuff. It has some good information with pictures to help with the sprag clutch change. I have done it myself.
Points of interest:
You will need someway to keep the engine from turning to get the flywheel nut off. It is extremely tight. If you tighten the flywheel nut to tight on re-assembly it can crack the rotor, you must torque it. Be careful to notice the spacers, washers, and bearings and the way there are located on the shaft so that you put everything back together the same. Make sure the clutch is put back in the flywheel flush and even all the way around. You can use a soft piece of metal such as a copper penny and place it in the starter gears to lock the engine so that you can torque the flywheel nut. Now is a good time to check the bearing in the alternator housing that the end of the crank shaft goes in to. Check that it is smooth, the bearing basket is tight, and it is pressed in evenly in the housing. Mine went bad at 50.000 miles. Replacement OEM bearing has a plastic bearing cage/spacer. Get one with a metal cage/spacer.

du907

[samandkimberly]

RE the sprag clutch - try the trick of pulling the one you have apart and tightening the little springs in it:

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


Works well. The same basic process works for fork seals too,

[93IE]

This sprag basically detonated. It tore up the cage that holds the cylinders in. It sored the inside of the piece that it fits in, but I cleaned it up with a hone. I had already done the seal spring trick on it, but when I went to start it yesterday after it had been warmed up, it backfired while trying to start and that was the end of the starter. Like I said earlier, I hope the exhaust valve that was too tight is the cause of the back fire. . I checked compression earlierwhile the motor was cold and it had 95 to 100 psig compression. That should be good, I would think. After the engine warmed up, I think the tight valve caused the problem. I should have a new sprag in 1 week. I keep you posted on the progress.

Preston