Burning oil?

[klebs01]

On my street bike, a 99 monster 750,  I have been going through oil at what seems like a quart every 1000 miles or so.  I have the big bore kit with high comp pistons and the service guy at the shop said that it was common to go through oil with high comp pistons.  Is this much oil loss that normal with a high comp setup?  The part that worries me the most is that the base gasket was replaced over the winter and I don't think the ring were replaced.

[Jeff]

No.  It shouldn't be burning oil.  High compression or not, it should not consume/burn oil. 

[Super Dave]

Were they Weisco Pistons?  Sometimes they just burn oil.  An easy break in will sometime cause the oil to move past the rings and get burned too, and sometimes an easy break in won't get enough heat into everything to make a great seal. 

If the kit was new with 1000 miles, I probably wouldn't have replaced the rings with a base gasket job either.  But I might have looked at the rings, pistons, and cyilnders to see if anything was going on regardless of a customer telling me about the oil loss.

[klebs01]

The motor has about 13,000 miles on it and the bike was also in for its 12,000 mile service when the base gasket work was done.

[Ducmarc]

you may hve exhaust guides worn (common on air cooled ducatis)also aftermarket pistons (especially JE) seem to shink from the heat I only get a season out of them. then they rock and use oil it's possible they chipped an oil ring putting the cylinder on. you have to be carful they are brittle.oil contol has always been an issure on air cooled V twins   i'd bet on th guides

[123user]

On a street bike the pistons should get pretty hot, and not rock in the bore too much, unless your not letting it warm up.  Typically, a forged piston is insensitive to large clearances (within reason) The large expansion coefficient is due to the material and forging process... they just wobble around until they heat up enough to fill the bore. 
As a note: Big Block Chevy blower pistons take 0.007"-.009" of clearance.

  Are you seeing smoke?  If not, I'd bet its the exhaust guides... Ducati has had this problem since desmo was invented.  At 12,000 miles they're extra-wobbly.

The easiest thing to do is pull exhaust cam cap on the front (horizontal for the purist) cylinder, spin the motor over until you can feel lash in the opener rocker, and wiggle the valve around.  Some front to back movement is normal, a lot isn't as good.  If it wobbles side to side a lot... you need new guides.

[Jason748]

Nate, it's time for some MBP head work & parts...

[Thingy]

I just had to have the valve guides replaced in my 748.  (The bike was smoking and I thought I needed new rings.)  When I pulled the head and turned the cam to extend the valve, one of the exhaust valves wobbled back and forth.  I sent the heads off to get new valve guides and it was not cheap...

[resurection]

leakdown test will show rings smoke at start up guides