Wages of sin no doubt...

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Onder

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Head a full overhaul. Implanted on bike. Started second kick. Rode a few miles. Never started again for two days. Looked at ignition of course it wasn't that. Did a differential compression test. Bingo. Hung intake I thought. Pulled head. Tiny piece of metal on seat ate into seat and valve.
These things are sent to try us.
 

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Good catch. Looks like the seat made the donation, but can it be reground? I would think a new valve may help avoid too deep of a seating. Replacing a valve seat is expensive and anxiety inspiring.

What is your plan?

I hesitate to ask, but if you didn't do the work, have you spoken with the shop that did do the work?

Best.
 
Both the seat and the valve have lost material. The valve is a brand new Kibblewhite. The seats are original.
The work was done a long time ago the head sat on my shelf.
Im in the UK, anybody have a shop that can do the job before I die of old age?
 
Seager Engineering get good reports. And / or Norman White is a good option.
 
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Head a full overhaul. Implanted on bike. Started second kick. Rode a few miles. Never started again for two days. Looked at ignition of course it wasn't that. Did a differential compression test. Bingo. Hung intake I thought. Pulled head. Tiny piece of metal on seat ate into seat and valve.
These things are sent to try us.
Worth a try...

It's hard to tell how deep he seat damage is. The seats don't seem very deep so it might be able to be recut. If you don't have a seat cutter, I would try lapping it in with the now bad valve. If the seat cleans up, I would get a new valve, lap it and move on. If it doesn't work, you're only out a little time.
 
The pit in the seat is deeper than can be lapped out. I gave it a quick lapping and it extends almost the full width of the seat. Replacing the valve is easy. Wish I still had my set of cutters. It does make me wonder what caused it.
 
When I was racing my 500cc Triton, it backfired once then lost performance. I thought it was a simple tuning error, so I did not pull the head off the motor. I raced the bike for a few more meetings before I pulled the motor apart. I had fitted cast iron valve guides. A small triangular piece of metal had come away from the end of the guide of one of the inlet valves and passed through the motor. It put a dent in one of the exhaust valves' seat.
In recent times, I have read Paul Dunstall's tuning notes - he mentioned this can happen.
 
The pit in the seat is deeper than can be lapped out. I gave it a quick lapping and it extends almost the full width of the seat. Replacing the valve is easy. Wish I still had my set of cutters. It does make me wonder what caused it.
It has to be something very hard to dent both the valve and seat and to even slightly bulge the seat. In the first picture, it looks like something sitting on the seat rather then a pit - is that just an illusion?
 
It has to be something very hard to dent both the valve and seat
Since I read this post last night I openly wondered where such a hard piece could have come from. Nothing in the carb is that hard, was there something in the air filter housing that might have gotten sucked in? My best guess would be that the piece came from the valve seat, can't say.

A question for the welders amongst us: Could the crater in the seat be welded up and re-cut without damaging the head? I ask because replacing the seat is expensive and if the work isn't done with the diligence of a neurosurgeon the head becomes a candidate for a lamp or the bin.

So, Onder any leanings for the cure?

Best.
 
Seager Engineering get good reports. And / or Norman White is a good option.
Seager Engineering is a good choice, but be aware that it is unlikely to be a quick turnaround as they have recently moved premises which has backed up their workload. I had to wait 5 months for some cylinder head work to be completed. Now that the move has taken place the turnaround times might come down?

When I spoke to Norman White last year, he told me he had stopped taking on any work as he was retiring. Is he still doing some work?
 
I was wondering if that might work for this too, since it is more focused.
I've never seen laser welding done
But I'm a welder and anything that involves heat also involves expansion (even more so on something circular) then contraction which is very often smaller than when it started out
Also distortion ,so I doubt the valve seat would remain circular
So unless laser welding involves no heat I can't imagine it working
This is just an opinion
 
Laser does involve heat but so focused and of short duration it could work, the problem is likely to be getting the new metal to be valve seat material.

This is from the welders Norman uses on Norton heads


1. No pre-heating of the part is required

2. Heat distortion is virtually zero, large areas can be built up without any concern of the part moving, the ability to weld without distortion saves time, and money spent on attempting to recover the part that has distorted therefore no extra machining cost or even the chance of having to scrap the part are involved.

3. The heat effected zone is very small which means the part being welded would not rise above 30°C and the structure of the base material remains the same. This allows any hardening treatment done to the part prior to welding will remain the same.

4. Parts can be welded either before or after hardening with the hardness value of the material being matched or coated with a harder wearing coating.
 
I was not thinking of adding extra metal, just ‘pooling’ the damaged area and then re cutting the seat.

Maybe worth sending some pictures to, and having a chat with, these boys:

 
Fold your tent if you wish. It was simply a question… so if you know the answer please don’t fold your tent…
 
Ok, here’s another daft idea…

Would an oversized valve be enough to seat on the outer, un damaged part of the seat, then re cut to suit?
 
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