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Members Birthdays
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4th November 2016
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Biker
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Join Date: Jan 2011
Posts: 6 Sportster/Buell Model: XLH Sportster/Buell Year: 1990
Reputation: 10

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Quote:
Originally Posted by aswracing
Just to add another piece of data ... back when we were using straight wound springs, we had huge, huge problems getting people to clearance rocker boxes correctly. The larger springs would hit the rocker boxes, which made the valves land sideways on the seats, which caused seat recession and leaking. I can imagine that given enough time, it would also cause a seat to fall out.
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But if we're talking about a set of stage 2 heads that was done ten years ago, man, I'd sure look at the spring to rocker box clearance. If not properly done, it could definitely have contributed to this failure, and in our experience, it was a very common mistake.
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This is an excellent point and one that I discussed with the guy who did the tear down and rebuild this last time. He looked and thought I had clearanced them sufficiently, but it would be a good idea for me to double check them and wouldn't be that hard to do. This always seemed like one of the more plausible explanations for the seat failure. Thanks for bringing it up!
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4th November 2016
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Senior Master Custom Bike Builder
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Join Date: Apr 2012
Posts: 3,643 Sportster/Buell Model: XLH 883/1250 Sportster/Buell Year: 1991
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I had a valve seat come out on an old VW I owned. Did not break the valve off, but traveled up and down with it without further damage. It happens.
Also dropped a valve on my 1971 van one time, that was a bit more involved. The valve head embedded in the #4 piston was a cool memento.
John
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4th November 2016
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Senior Custom Bike Builder
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Join Date: May 2013
Location: Wisconsin
Posts: 2,576 Sportster/Buell Model: XLH883/1250 Sportster/Buell Year: 1988 Sportster/Buell Year #2: 2001 Other Motorcycle Model: Blast Other Motorcycle Year: 2013
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Here is a picture of mine

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