Montjuic head repairs

AndyB_11

Full member
Location
Bedford
Morning all, I?ve just posted a wanted request for a cylinder head even though I?m expecting it to come back blank you need to ask the question.

Failing getting my grubby little fingers on a head I can work with I?m going to have to get mine repaired and there lies the problem. I?ve known about part of the problem (2 small cracks) for a few weeks but been leaving it thinking if the worst came to the worst it?s usable. Well I was wrong, it?s not really usable for the reasons listed below.

It?s got cracks running from one spark plug hole to two valve seats.
It?s already had one oversized valve seat fitted by a previous owner.
It?s got one valve seat that?s been re-cut so the seat area is about 4mm wide and the valve sits very low in the seat.
It?s got one valve that sits high in the seat by about 1.5mm.
I don?t want to heat it up to fit new guides in case the cracked segment or the seats move.

Apart from that all?s well in the World. I?ve got new guides and seals which was the reason for stripping the engine and I then concentrated on other jobs rather than looking too closely at the cylinder head  :(

I?ve emailed and left voicemail for Keith Nairn and I?ll try again but if anyone can suggest other options then I?ll be more than slightly grateful.

Apart from that I?ve just fitted new 72.5mm 10.2:1 pistons, the forks are away having emulators fitted, new front master cylinder purchased and fitted, all three brake calipers refurbished, new wheel bearing waiting to go in when the wheels come back from being painted and lockdown has been quite a useful period of time  :)

 
From what it seems, the seats can be removed, the damage ground out and welded, and new correct seats fitted and cut as per spec. I would get in touch with Piet/OCT to get an appraisal.
 
The issue with the valve seats could be that one has already been replaced with what outwardly looks to be an oversized insert. I?ve got a few doubts in my mind regarding the quality of that repair because since stripping the top end I?ve found a few other things pointing towards a bit of a cavalier attitude towards quality.

I?ll send Piet a pm asking his opinion because at least he knows what he?s looking at and I?ve put so many hours into the bike over the last few weeks that I don?t want to finish it with a rubbish cylinder head.

A further example of the previous rebuild being a bit dodgy is that when I lifted the barrels and removed the pistons they had different types of piston ring on each piston. I can only assume that the owner broke a ring and thought they?d just get a set of 72mm rings the correct thickness and use them. I?d have gone for the same type on both pistons but maybe I?m a bit too anal about it all?
 
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