here is the cause of my misfire

[ram33]

short story of my bike is as follows:
brought as non runner - told it wont start
got it home and tried with battery to hear dreaded sprag clunk
stripped engine bottom and replaced sprag spring and cleaned carbs
bike started but splutter/ slight misfire
idle screws were seized  so got replacement carbs to find misfire still there (and vac cap poping off)
check valve gaps and all ok, after head scratch, take closer look around head and see valve guide has lost a chunk.
remove head to find bit in piston top and in cyl head, bores untouched but valve has slight bend and doesnt seal.
now fitted replacement head

[Sin_Tiger]

  that's really odd. I can only think it's been a cack handed job at some time in the past. Had the head been off before? What sort of mileage has it had?

Well done spotting that, it wouldn't have been top of my list for things to check 

[ram33]

head didnt look like it had been off in past. done about 52k miles
it seems to much of a coincidence that the bike had faulty sprag and valve at same time?
maybe the valve guide had seized to the stem and broke when i 1st tried to start it or maybe this caused the engine to jam for a second and break the sprag

[Sin_Tiger]

I wondered if it had been sat for a long time but unlikely with that sort of UK mileage and I don't see the signs of rust like I would expect.

At least you can still get the bits individually so the head is sortable.

[ram33]

I wondered if it had been sat for a long time but unlikely with that sort of UK mileage and I don't see the signs of rust like I would expect.

At least you can still get the bits individually so the head is sortable.

when i got it i was told it had been stood a couple of years.
can you get the valve guides?

[Mustang]

I wondered if it had been sat for a long time but unlikely with that sort of UK mileage and I don't see the signs of rust like I would expect.

At least you can still get the bits individually so the head is sortable.

when i got it i was told it had been stood a couple of years.
can you get the valve guides?

nope triumph uses a special process with liquid nitrogen to permanently bond the guides and valve seats to the head   , they will gladly sell you a new head though

[ram33]

I wondered if it had been sat for a long time but unlikely with that sort of UK mileage and I don't see the signs of rust like I would expect.

At least you can still get the bits individually so the head is sortable.

when i got it i was told it had been stood a couple of years.
can you get the valve guides?

nope triumph uses a special process with liquid nitrogen to permanently bond the guides and valve seats to the head   , they will gladly sell you a new head though

thats what i thought
we use liquid nitrogen at work to fit bearings (heat part and shrink bearing) so i can put them in ok, if i could get one

[Sin_Tiger]

You learn something from the Master everyday 

I came across something similar years ago, got a specialist engineering shop to machine out a bush in a diesel head, make a copy with same material and interference fit it back, was still running fine several thousand hours later.

Depends if you have the right contacts 

[ram33]

im a machinist by trade so i could prob make one if reqd but the rst of the guide looks ok, i think a new valve and it would be fine. got another head fitted now though

[Sin_Tiger]

You'll know a lot more about it than I do then