3C cylinder head wanted

Robin Webster

Robin Webster

Hero member
Location
Silverstone
In the never ending saga of the 3CE I am trying to get running the bike has been with GED for a while. He says the cylinder head is beyond retrieval and needs replacing. Anyone have one? Price and location please.
 
Robin Webster said:
In the never ending saga of the 3CE I am trying to get running the bike has been with GED for a while. He says the cylinder head is beyond retrieval and needs replacing. Anyone have one? Price and location please.
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What's the problem exactly?
A lot can be done to retrieve those heads.
Paul
 
To the best of my knowledge as told by Ged Shorten the exhaust valve shims are too thin to be practical. This I assume means that the valve is recessed too far into the head. I am sure the seat base could be built up by weld and re-machined to bring distances back to stock but Ged cannot find anyone to do the job.
 
Robin Webster said:
To the best of my knowledge as told by Ged Shorten the exhaust valve shims are too thin to be practical. This I assume means that the valve is recessed too far into the head. I am sure the seat base could be built up by weld and re-machined to bring distances back to stock but Ged cannot find anyone to do the job.
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it is a shame that the UK is running out of shops that can do those types of repairs

I'm very lucky as one of my best mates that lives three blocks from our place owns and operates a cylinder head shop and your issue is a repair that we do on a regular basis
By your description we would probably remove the Valve seats, machine in a new seat pocket and machine up custom seats, shrink into place using liquid Nitrogen and then recut the seat and blend in the chamber to suit
Valve guides would be replaced, new valves, springs, seals on both sides and shims back in the 2.90 - 3.10mm range

I'll send you a pm
 
Robin,

Of course the shims are too thin, same as with about 85% of those old heads still "running", just. :rolleyes:

Rebuild the valve seats with weld? Just as good as chucking the head into the bin... seat inserts need to be installed, brings the valve geometry back to as-new, maybe better. I've done dozens, Keith can do it, so can Red, amoungst others.

I have a couple of used heads in stock, but they'll be no better than yours. Good used heads are rare, first question to ask is how thick were the installed shims when it was relegated to the shelf.

piet
 
Robin Webster said:
To the best of my knowledge as told by Ged Shorten the exhaust valve shims are too thin to be practical. This I assume means that the valve is recessed too far into the head. I am sure the seat base could be built up by weld and re-machined to bring distances back to stock but Ged cannot find anyone to do the job.
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As described below, that is repairable.
As Piet writes, most bikes that have been used over the last half century will be like that. Particularly with those crap heads.
Paul
 
pf1 said:
I know you don't want to deal with the guy you bought the bike from but he has a Corsa head.
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After following this saga would the seller consider 'selling' the head for a few pints on the bar & a bit of commiseration?
 
IAG said:
@redax5 @sfcpiet Any merit in tipping the vales to increase shim thickness?
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Not much.

You might gain a bit of shim thickness, but the actual damage isn't being addressed. The valve head is by now recessed in the chamber to the point that flow as well as CR is compromised. All OK as long as you're satisfied with an engine running at around 40-50% of its true potential... :rolleyes: As Red has correctly stated, this has most probably already been done. Personally, I have very rarely come across a triple head that has been properly overhauled. Mostly half-arsed attempts like valve tipping. Then there is the insane amount of skimming done in the past, in truth, many heads are ripe for the scrap bin. It often takes a lot of effort to un-do past sins.

Restoring correct valve seat geometry brings the old clunker back to life once again, as well as offering shim thicknesses that will last you for quite some time. Actually a lot longer than the originals as modern materials are a lot more durable.

piet
 
God knows how long since Red did my head, and it hasn't needed any shim changes bar a couple of swaps after the first 1000ks. My guess is 10 years and maybe 80 to 100000ks. Bloody hell, that's an educated guess, but a very crazy number. So that's 1 x 400k weekend ride a month, by 12 months, plus 1 x 3000k multi-day ride a year for 10 years, and that comes out at 93,600k, and that's probably a conservative estimate. Forgot the COVID year, so that's not included.
 
Why don't you ask the engineering company with all the race experience who you took it to and who fucked it up beyond repair to pay for a new one?
 
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