mattcfish wrote:
Does anyone here grind there keepers down (create a gap between them) to make them fit tighter on the stem? A VW rebuilder showed me this trick used to prevent valve dropping. The only issue with this is that it hinders the valve from rotating. That said, a video of the valve train of an S1000RR at high RPM shows that the whole spring rotates, not just the valve. Watch the springs start to spin toward the end of the video http://www.youtube.com/watch?v=QuWiZ5nVKzA .
I've just been re-reading my Gene Berg VW literature. He mentions putting a slight gap in the keepers.
Chuey wrote:
I've just been re-reading my Gene Berg VW literature. He mentions putting a slight gap in the keepers.
Chuey
VW's are not BMW's. Although there are certainly similarities, VW's have much more serious cooling issues because they are pushing one hell of a lot more mass. Plus, they don't turn nearly the same rpm.
Chuey wrote:
I've just been re-reading my Gene Berg VW literature. He mentions putting a slight gap in the keepers.
Chuey
VW's are not BMW's. Although there are certainly similarities, VW's have much more serious cooling issues because they are pushing one hell of a lot more mass. Plus, they don't turn nearly the same rpm.
Gene Berg built VWs that turn Airhead rpm. The issue VW folk find with keepers that contact each other is that the keeper grooves in the valve get beat up if the fit of the keepers is anything less than perfect. Rather than pick through dozens of keepers to get the right fit, it is just as effective to grind the keepers so they have a gap when installed.
I don't see that Airheads would be any different, but perhaps QC on valves, retainers, and keepers is better and we can expect the right fit every time.
Call me Mel. Some years ago- never mind how long precisely- having little or no money in my purse, and nothing particular to interest me at home, I thought I would ride about a little and see the other parts of the world.
Chuey wrote:
I've just been re-reading my Gene Berg VW literature. He mentions putting a slight gap in the keepers.
Chuey
VW's are not BMW's. Although there are certainly similarities, VW's have much more serious cooling issues because they are pushing one hell of a lot more mass. Plus, they don't turn nearly the same rpm.
Gene Berg built VWs that turn Airhead rpm. The issue VW folk find with keepers that contact each other is that the keeper grooves in the valve get beat up if the fit of the keepers is anything less than perfect. Rather than pick through dozens of keepers to get the right fit, it is just as effective to grind the keepers so they have a gap when installed.
I don't see that Airheads would be any different, but perhaps QC on valves, retainers, and keepers is better and we can expect the right fit every time.
That could be one of the reasons why aftermarket valves drop on airheads. The valves may be great quality, but if they don't match BMW keepers, there's enough play to create excelerated ware.
VW's aren't quite airheads, but they do take alot more abuse, alot more miles, and alot more heat. All the more reason to have rotating valves, but according to some... the keeper gap prevents this (although videos I've seen seem to counter this opinion).
