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Burnt Valve

bmetcalf

Well Known and Active Forum Website User
VOC Member
After going on one cylinder and trying checking if new plugs were needed or a good carb clean would do it, I checked the mag timing. My thumb over the rear spark plug hole didn't detect compression, so I blew air in the cylinder with the valve adjusters out and it came out the exhaust pipe. I lifted the head and this is what I found. (Screwdriver added for extra drama.)

DSCN0541.jpg

The head nuts were barely more than finger-tight. Do you think that had anything to do with the valve? It was installed in 2005, I think.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
Pipe was OK, The adjuster was tight, I had adjusted them a few weeks ago. At the end of May, I rode to another Vincenteer's house in 46F weather and while riding into the wind at 70 mph, I felt a loss of power. Before then, it was running great and was a one kick starter.
 

timetraveller

Well Known and Active Forum Website User
VOC Member
Have you got lead free valve seats? I found tappets tightening up with lead free fuel over here in the UK and a tight tappet could lead to valve burn out. Have a good look at the seat and see if it shows signs of starting to 'pocket'.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Bruce, I think that was a badly made Valve, Where did you get it ?. I think I would change the other three while you are in there, From another supplier !!. All The Best Bill.
 

Bracker1

Well Known and Active Forum Website User
VOC Member
Reference MPH 449, an article by J.Bradshaw with regards to too high fuel octane with low compression engines as well as the use of oils that allow "coke" build-up in the valve area. Or could just be a soft spot in the valve. Mine looked the same, and I had Steve Hamel put some fancy ones in. Good Luck, Dan
 

mercurycrest

Well Known and Active Forum Website User
VOC Member
Bruce,
I bought some valves from Doug Hollis eons ago and they did the same for no apparent reason. My AMA Flat Track Racing friends said:"Ahah, G&S Valves!" I contacted Doug and he found out sure enough they were. G&S seemed to have fixed the problem and they are now reliable. Maybe, you got one of the old ones? Since we're "buddies", I'll give you what you originally paid for the bike, that way Loretta won't be on you about the "money pit." :cool:
Cheers, John
 
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