Tweet
bent valve
Hey all,
I have been working on this 79 xs1100. Some of you might remember my previous post. I had completely rebuilt the bike from front to back. Had it running good. Only drove it a few times and bent a single exhaust valve. I took all of you insights and made sure all carbon was removed from the head, checked the valve guides and everything I could think of. Something I found and I would like everyones opinion. When I inspected the lifter caps I found some minor scratches on the sides of several. I proceeded to check the head and found the cylinders for the lifter caps had some minor scratches in them. I could not see the scratches but I could feel them with my finger nail and I ran my finger nail around the hole. I put the caps back in and took the a valve and worked each of the caps up and down in the cylinders. I noticed that three of the eight lifter caps moved up and down with resistance compared the the rest. Two of the three casps had even more resistance at the top of it's travel just before the valve would close completely. I took a piece of 1000 grit sand paper and gently scuffed the inside of the holes. I then used a dremal drill with a polishing pad and a super fine polishing compound and polished the holes down. I also polished the outside of the valve lifter caps. I then cleanded the holes and the lifters completely and lightly oiled the caps. The caps now slide up and down with ease as the rest of the caps did. One of the valve lifters I worked on was the number 4 exhaust which was the one that bent. I would assume we scratched the lifter holes while removing the valve. Could this have been enough to slow the closing of the valve down just enough to allow contact with the piston? My thought was that at an idle it probably would not but at a higher RMP it would almost be like having a floating valve. What do the experts think? Could this be what happened?
I have been working on this 79 xs1100. Some of you might remember my previous post. I had completely rebuilt the bike from front to back. Had it running good. Only drove it a few times and bent a single exhaust valve. I took all of you insights and made sure all carbon was removed from the head, checked the valve guides and everything I could think of. Something I found and I would like everyones opinion. When I inspected the lifter caps I found some minor scratches on the sides of several. I proceeded to check the head and found the cylinders for the lifter caps had some minor scratches in them. I could not see the scratches but I could feel them with my finger nail and I ran my finger nail around the hole. I put the caps back in and took the a valve and worked each of the caps up and down in the cylinders. I noticed that three of the eight lifter caps moved up and down with resistance compared the the rest. Two of the three casps had even more resistance at the top of it's travel just before the valve would close completely. I took a piece of 1000 grit sand paper and gently scuffed the inside of the holes. I then used a dremal drill with a polishing pad and a super fine polishing compound and polished the holes down. I also polished the outside of the valve lifter caps. I then cleanded the holes and the lifters completely and lightly oiled the caps. The caps now slide up and down with ease as the rest of the caps did. One of the valve lifters I worked on was the number 4 exhaust which was the one that bent. I would assume we scratched the lifter holes while removing the valve. Could this have been enough to slow the closing of the valve down just enough to allow contact with the piston? My thought was that at an idle it probably would not but at a higher RMP it would almost be like having a floating valve. What do the experts think? Could this be what happened?