Cylinder head rebuild?

[excess11]

The valve guides on my 78'E are shot. I can only go about 100 miles before I start fouling pluggs. The bike will not start again until the pluggs are cleaned once fouled. The bike is a 78' but has a 81' head on it. The original head was replaced because the timing chain jumped and bent all the exhaust valves. I found the 81' head on ebay for $60.00 and was suppose to be a good head. Well the valve guides are not so good!! I would like to get my head rebuilt because I dont want to chance another used head. I have heard of some mail order rebuild companys out there has anyone used one of these or can you recommend someone to me. I do not know of anyone local that does machine work on motorcycle heads.

[prometheus578]

"You left out a lot of details."

don't get offended if I question your knowlege, as I don't know just where you stand, etc.
Why do you think it's the valve guides?
Do you know the difference between fuel fouled and oil fouled?
I can assume the engine is still together(from your comment about the "hundred miles", so if it's together, how did you check the condition of the valve guides? One usually has the head apart, opens a valve a little and measures the side to side play.
Does the bike smoke? You didn't mention that. If it's oil fouling the plugs, the engine should smoke about as much as I do(I need to quit)
Might be old, brittle valve stem seals...
Be that as it may... any machine shop that does automotive work can do the head from a motorcycle. A head's a head.

[TomB]

I agree with Prom, check it's not poor fueling first.

Unless you are burning a lot of oil.

The guides on these engines don't generally suffer from wear, old style rocker actuated valves used to suffer because of the side forces exerted on the valve stem, but the XS's use buckets which push down in line with the valve.

If you are going to take off the head you'll be taking the exhaust headers and carbs out/off. When you do you can get a pretty good look at the valves to see if the stems seem oily.

The valve stem seals can fail coz of the age of our bikes but these can be done with the head still on the bike.

[John]

TomB

How do you disssemble the valve springs and such with the head still on the engine? I had to buy and modify a valve spring compressor to do the job. Do you stuff a rag in through the spark plug hole and then set the engine so that cylinder is at TDC, or do you use air pressure to hold the valves closed? I've done that on a car engine, but the springs are right there on top of the head, not recessed like the bike engine.

[excess11]

Valve guides

I am fairly sure its the valve stem seals. (This is what I meant in original post.Not valve guides) The bike does not produce smoke on acceleration,but when the throttle is closed after acceleration. If I am coming down a large hill and roll off the throttle the person behind me will be lucky if they can see where they are going. Large cloud of blue grey smoke. It clears up once back under throttle. When I had the head off the first time I checked the cylinders and they looked great. They still had the cross hatching marks and no ridge at all.

[skids]

Re: Valve guides

You are probably right about those seals.

Originally posted by excess11
I am fairly sure its the valve stem seals. (snip) ,but when the throttle is closed after acceleration. (snip)

[TomB]

John

Do you stuff a rag in through the spark plug hole and then set the engine so that cylinder is at TDC

Yep.

I havn't done an XS engine yet but have done others.

I have used a very simple hand tool made from a file handle fitted onto a piece of tube that fits down the bucket hole with cut outs in the sides. It also involves a lot of grunting and swearing and the help of a very understanding wife with a magnetic screwdriver

Mathh has come up with a really good but simple way of compressing the valve springs here

I recently help a mate work on a VR6 VW engine which uses hydraulic buckets, the valve guide seals were a bitch to get off (much grunting and swearing again ) I imagine the XS seals could be the same, or is that just me being pessimistic about a job which I've got coming up soon myself ('78 XS11 80K miles and burning a little oil)

[prometheus578]

Yes, John... compressed air is one way.
The other... get the piston moving upward on the compression stroke, and feed into the spark plug hole some rope... like the rope used to pull start lawn mowers. Yes, the rope holds the valves closed after the upward moving piston compresses it.
I think I once ground away the sides of a spark plug socket and using my son's body weight on the socket(with an extension), the valve spring collapsed so I could remove the retainers through the ground away portion.