Re: Carbon Caked on PIston Crown


Manjo wrote:
FB wrote:
Manjo wrote:

2. The crankcase breather tube used to run into the air intake stream
to the carbs, where the crankcase gases would be burnt away. Now the
tube runs to a filter element mounted on the bike frame. I'm wondering
if excessive crankcase pressure is "pushing" oil into the combustion
chamber as the piston moves downward?

Try making a road draft tube instead of running the crankcase breather
to one of those little filters. A road draft tube goes vertically down
behind the engine and the end is cut at a 45 degree angle with the long
side of the tube forward. This creates turbulence which sucks vapors
out of the crankcase.

3. There's just too much piston "rock" allowing oil to creep around
the rings at high speeds.

That sounds good. Piston rock is one of the reasons why Ducati Corse
engines are only good for 30 hours of operation.

Are any of these a possible cause of the carbon build-up?

You might try leaning up the idle mixture a bit. Then the engine will
burn oil vapors as fuel instead of allowing them to cake on the piston
tops.

FB,

Thanks for the tips and ideas. The draft tube and leaning the idle mix
will be done shortly.

On piston rock: is there a Ducati fix for the piston rock? If not,
should I look at a rebore and new pistons/rings, or perhaps
new/different pistons?

TIA for your reply.

Manjo

FB,

I have the crankcase breather hose running directly downward tied to
the frame. Before this, I ran the bike to test the pressure at the
tube alone and at the crankcase filter. At the tube, the pressure was
obvious, but seemed to lessen as rpms increased to 3000. With the
breather tube attached to the filter, I could hardly feel any pressure.

I took the bike on the road and ran it at 25 to 80 miles per hour over
50 miles. The engine ran smoother and seemed to have more power. I'm
taking the bike on a longer ride today. I'll then check the piston
crowns for carbon build-up. I'm hoping the filter has been restricting
the flow of air OUT of the crankcase allowing pressure to build too
high and therefore forcing oil up and around the piston rings on each
down stoke.

I've also leaned out the idle mix by half (2 turns out versus 4).

Thanks,

Manjo

.

Relevant Pages

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