Date: Fri, 22 Aug 1997 14:59:02 GMT
From: (Erik W. Miller)
Subject: Re: '84 saab 900T- vexing turbo problems

A fair number of years ago, a friend had a turbo'd bike (Kawasaki 750 Turbo). He being an Aircraft Mechanic and extremely anal, his habit was to completely disassemble the motorcycles that he bought (it was used) and go through them in minute detail. When he got to the turbo, he took that apart too, though we tried to convince him otherwise. He found that the bronze (?) bearing had worn out of book spec, and had what looked like small pits in the surface of the bearing. Not happy with this at all, he looked into the alternatives: New part from Kawi--outrageously expensive (part alone was $800) Rebuild turbo--less expensive, but still too much for his taste, and the only people who would do it were an outfit that rebuilt Kenworth turbos in Arizona. So, he made a new bearing from new material. In doing this, he found out two things: took the turbo apart after a couple of weeks and foung that the new bushing looked exactly like the old one had, and he also found out that for that application, the machining was down to four digits (.0001) which is extremely difficult to do without special equipment. So why tell this story? It is entirely possible that you have recieved a turbo with a bad rebuild--the spec's are extremely exacting (even for the big ones on trucks) and it is quite concievable that Q.C. isn't what it should be at organizations that rebuild the units. Another common source of the cloud you speak of is that oil gets burnt into the area where the shaft is supposed to seal and the resulting carbon buildup allows more oil to seep past the seal area. This was common on a turbocharged bike that Yamaha built and the fix was to disassemble the turbo periodically and scrape the carbon out. Probably not the problem with a new turbocharger though. You didn't mention that option of last resort though--have you tried getting a new unit from the dealer? ewm >Try another turbo vendor (TurboCity, CA). But first have second turbo >bench tested. Oil flowing past >seals- diagnosis (TurboCity's)- bearing wear/poor components/ sloppy >rebuild (?). I understand a >possible bad rebuild, but bearing wear in 5 minutes. How can this be >with oil brand new, flowing per spec >and verified clean ? THIRD turbo installed last week. SAME PROBLEM. > >Any ideas on what this engine is doing to these turbos ? How can the >oil supply over-pressure to blow past >the seals ? If that's what's happening. Any ideas and/or suggestions >are greatly appreciated !!

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