Valves xs1100

[DEmily]

Hey everyone,

I had a question about valves. I have recently completed the total rebuild of my 79 xs1100. I have gotten alot of good info from everyone that has helped me get to the point of completion. However, I have a new problem. The bike has ran very little, but has ran good. After the bike setting for a week of cold weather in the garage, we got a good day and I decied to take it out of the garage and start it. I was just going to let it run a bit to keep things loose. I began to have problems keeping it running. I pulled the air filters and fired it up again. The number for carb began to pop back with gas. I assumed and intake vale might be sticking. I ran a compression check and sure enough #4 had zero. All the valves in this motor has been replaced with new ones and all lapped in well. When I removed the head I found the exhaust valve was bent? No signes of contact on the piston and timing was still where I had set it originally. Any ideas what caused this? Is it possible the engine got hot and warped that valve? I did paint the head, but removed the paint from the edge the fins. It gave it a really nice look. But have I created a problem with cooling? Any assistance would be greatly appreciated, spring is coming and I want her ready to ride.

[MartyA]

Have you put a lot of miles on the bike since the rebuild? Could it have bent right after the first startup? Did you use assembly grease when you re-assembled everything? The only other thing is something got in the valve guide? If the piston is not hit, check the cam? Did you put the correct thickness spacers in?

The cams and pistons are timed together by the cam chain, the electrical timing is bolted into the crank end, so if they all start out right and nothing comes loose the timing should not change. Unless the cam chain jumped, or the cam shafts were not aligned and installed correctly, bending a single valve seems tough to do from that perspective.

Maybe a piece of carbon got stuck in that exhaust valve seat?

I don't recall anyone talking about overheating an engine to the extent a valve warped, although I suppose you could if you let it run for an extended period parked with no air circulating across the engine.

[DEmily]

Marty,

The bike has only been drive a few times. Maybe 50 miles on it at the most. Assembly lube was used in the reassembly process with all moving parts. As for the valve shims, valve clearance was all within specs or very very close. The bike did not seem to heat up, I just thought is might be possible, as I am perplexed at how just the one valve would get bent. Obviously I will replace the valve and head gasket. I am just concerned that I do not know what caused the issue. It could happen again and then .... more money... more time. The time on the cams were precise and the chain is new. The tensioner was in place, extended and locked in. What about something being sucked through the carb? You mentioned that. When I originally started the bike the carbs flooded. I took the air filters off, reset the floots and fired it up to adjust. I can't emagine what could have gotten sucked through just setting in the driveway, but I guess that is possible.

[ratbyk]

Bent valve

Don't know if this would apply to the XS or not but on a 6 cyl. Jag engine if the cams are in and you set the head down on the bench you will bend valves. They protruded beyond the head gasket mating surface when in the wide open position.
In other words did you at any time set the head down on the bench with the valves in and the cams in. If so the valve may have been bent before you ever put the head back on the jugs.
Ken/Sooke
78E Ratbyk
83 FT500 "lilRat"

[DEmily]

Ken,

No the cams have never been in prior to the heads being installed. As I stated previously it was running good. It just suddenly acted up and I discovered the bent valve. Have yet to find anything that would lead me to a conclusion as to why it happened.

[scoobes]

while the head is off,you would be wise to check that were the valve runs down through the head is ok and the valve might have got stuck there and was bent by the cam and not the piston which part of the valve stem is bent?

[Geezer]

Re: Valves xs1100

A valve that hit's a piston won't always leave a mark. The most likely cause is the guide is a little tight and the valve stuck open when hot and whacked the piston.

Geezer

Originally posted by DEmily
Hey everyone,

I had a question about valves. I have recently completed the total rebuild of my 79 xs1100. I have gotten alot of good info from everyone that has helped me get to the point of completion. However, I have a new problem. The bike has ran very little, but has ran good. After the bike setting for a week of cold weather in the garage, we got a good day and I decied to take it out of the garage and start it. I was just going to let it run a bit to keep things loose. I began to have problems keeping it running. I pulled the air filters and fired it up again. The number for carb began to pop back with gas. I assumed and intake vale might be sticking. I ran a compression check and sure enough #4 had zero. All the valves in this motor has been replaced with new ones and all lapped in well. When I removed the head I found the exhaust valve was bent? No signes of contact on the piston and timing was still where I had set it originally. Any ideas what caused this? Is it possible the engine got hot and warped that valve? I did paint the head, but removed the paint from the edge the fins. It gave it a really nice look. But have I created a problem with cooling? Any assistance would be greatly appreciated, spring is coming and I want her ready to ride.

[MartyA]

That is what I was thinking, Geezer. He said the exhaust valve was bent, if a small piece of carbon got stuck between the valve and the seat on its way out that would leave it open and could hit the piston. The other was some small piece of grit in the valve guide, holding the valve open for a moment. When I had my head off this past summer I was careful to remove any trace of carbon. Some of the chunks were pretty big, and there was a lot of dust, also. The head has a couple of recesses in each cylinder, and it was difficult to get around the valve seats without gouging metal.

Weird, though, one valve. Were the valves matched? could one have been a few thousandths longer? Reaching here....

[ratbyk]

Bent Valve

Back in my racing days through the 60's early 70's I bent/broke screwed up a lot of valves/rocker arms/push rods. I could always trace each failure back to where the valve had fouled either the piston or the top of the block. It takes a mechanical contact with something in the combustion chamber somewhere to bend the valve.
Another possibility would be if you missed a shift and badly over reved the engine. In a situation where the valves went into a "float" situation a tappet shim may have climbed up onto the shoulder of the bucket and the valve was forced open far more than normal and tipped the piston.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[DEmily]

Thanks for all the replys. I will check the valve guides closely tonight. The bend is very slight, but appears to be about midway down the valve stem.

[DEmily]

Oh, also, the valve is moving smoothly through the guide without restriction.