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Crankcase pressure/clutch cover leak?

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  • Crankcase pressure/clutch cover leak?

    Hi guys,

    This morning I'm checking my oil level before going to work, since my bike seems to have a slow leak somewhere on the bottom of the clutch cover, near the stand, and it turns out I'm a bit low. So I pull the filler cap, add a half quart, check it again, looks good, so I start it up to warm up while I'm getting my gear on.

    So I get my jacket on, and straddle the bike to put on my helmet and gloves, and all of the sudden my right pants leg is getting blown away from the bike. I'm thinking to myself "crap - I must have blown the mid-pipe or something, because that's definitely exhaust", but when I look down, it's actually that I forgot to put the filler cap back on!
    I swear the pulses coming out of the filler cap were strong!!!
    The flow coming out the cap pushed on my hands 6" away from the hole about has hard as your exhaust would 12" from the can. That is way more crank-case pressure than I would expect, but I only know car motors, not bike motors, so I don't know if that's the way it's supposed to be or not...

    So is it normal for your crank-case to be really pressurized like that? What does *your* bike do when you start it with the oil filler cap off?

    I just want to make sure I didn't lose a ring or something! :-)
    My bike still seems to be running perfectly smooth and strong, so I don't think it's a major issue, but I wanted to check...

    As an aside, if the crank-case is that pressurized, it doesn't surprise me at all that gaskets would leak - that's alot to hold back! It also makes sense now why the 1k Gixxer this year added those windows between the bottoms of the cylinder bores to allow cross flow of the crank-case air...

    Also - the way I noticed that my bike was leaking a bit was that after a hard braking stop, I would smell oil-smoke and sometimes even see it (!) coming from under the fairings. So I cleaned it off, and took a look to see where it might be coming from, and it looks like it's coming from the back bottom of the clutch cover right above the stand. I checked the bolts there, and they were all really really loose, so I tightened them up hoping that would fix the problem. Looks like it didn't. Is this a common problem/leak-area on TLs? If so, do I just need a clutch cover gasket or is there something more involved? I know I know - "take it apart and look", but I wanted to pre-order the gaskets from Ron Ayers before I pull it apart, so that I don't have that much down-time. Here in Mass we've only got a few weeks of riding time left, and I want to make the most of them! :-)



  • #2
    I always put the filler cap back on before starting

    Never tried it, but is sounds like the bike will be fine

    Keep those bolts snug bro
    May 2003
    August 2004