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Discussion Starter · #1 ·
I have been experiencing excessive oil blowback on a new to me 998 that had 2mm overbore HC Pistal pistons installed, along with blueprinting.

The problem first reared its ugly head when I did a quick run up a local mountain. On the way home, oil started to burn on the exhaust which had originated from the rubber tube that drops down to the bottom of the engine from the oil breather. I took the bike in and they could not find any other source. They tried to assimilate the issue but could not and concluded that perhaps with the engine being relatively fresh, that the rings hadn't bedded in properly yet.

Yesterday I did another mountain run and the problem mainfested itself what one of my riding partners described as "a huge puff of white smoke" upon decompression going into tight corners. There was also a disturbing film of oil on the fairings (mostly the left side).

Help! Any similar experiences or suggestions?
 

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Make sure your oil is filled to the lower limit. You can suck it out of the fill hole with a large syringe and piece of hose if need be. Take a peek inside your air box, it might be a little oily in there if so, look at the breather, or replace it.

t_bare
 

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Maybe it's time to change over to a Corse or aftermarket breather. I have a 999 with a 102mm bore kit, Pistals, valve, port work...nothing major, had the crank balanced, everything in the lower end was gone over with a fine toothed comb. I'm running an STM breather which has a CF valve in it, much different then OEM. It gets a little misty on the top of the breather, nothing serious, no oil build up around the seal.
Your engine must be a brute and wicked fun ride!
 

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Might be wise to get a leakdown and compression check done.
Could just be a broken ring in there.
.
 

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yeah before you mask the symptoms with different breathers etc you need to really diagnose the problem. it could just be a bit of extra blowby from the way the engine was built or it could be something more serious. I'd do davy's suggestion and start with a compression and leakdown test which will tell you if the rings are sealing well or not. if that's all fine then by all means address the symptoms (fit a corse breather or whatever).
 

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Discussion Starter · #7 ·
The puff of smoke is not related to the breather, the breather dumps the oil on the box floor, it doesnt get into the engine.
I read an interesting article that claimed that it's been reported that on a very small percentage of 998s, the crankcase pressure can build up to a point that the oil on the wrong side of the breather can get sucked into the intake (http://www.ducati-upnorth.com/tech/breather.php). Seeing as the puffs occurred during not so smooth downshifting and that the engine was recently blueprinted by a reputable mechanic, I'm holding out hope that this is the case with mine (not to mention that this would be the cheapest issue to remedy!) It's going in on the weekend for a compression and leakdown test. Hopefully I'll have reasonably good news next week. Will keep everyone posted...
 

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Discussion Starter · #9 ·
Got the bike back on Friday. They did a leakdown test and it showed what they deemed as okay values (10%). They're still somewhat dubious on this matter, thinking that it's still pretty high for a supposedly fairly fresh engine. They then checked the aftermarket breather (don't know what make) and found that it was flawed. Replaced it with a new one and sent me on my way.

Yesterday I took her for my first long ride (400 miles in 5 1/4 hours) and found no obvious evidence of oil leakage. Was too sore to hunch over the bike to remove the fairings last night but will do so today to see what I can find. Fingers crossed!
 
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