ET: Engine (Twin) Fogging for Mosquitos; Valve Guide Issues and Solutions

timetraveller

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When it happened on my bike there was no trace of the guide itself and the lock ring was in three pieces up with the valve springs. I have no idea how it could do that but it did.
 

ClassicBiker

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Update:
Last week I removed the remaining guides and measured their o.d.s and the i.d.s of their respective holes.
Both inlets measured 0.501 as did their respective holes. A light tap with a drift and raw hide was all it took to remove them. The rear exhaust was 0.564 and the hole was 0.563. Rather than beat it out with a drift and hammer, I used a length of threaded rod and made a puller which eased it out in a controlled manner.
The front exhaust hole was 0.568.
So I'm thinking for the inlets 0.502 for a slight interference fit, 0.564 again for the rear exhaust and seeing what the Spares Co. has for extreme oversize.
I also measure the depth of the recess in the heads that the liner spigot into and how proud the liners stood above the muffs. Looks like I'm going to be spending some time with some emery on the surface plate.
Steven
 

Robert Watson

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Before you start knocking off the height of the liner above the muff, check the depth of the recess in the head where it fits, or do I recall from a previous post that the gap was excessive?
 

ClassicBiker

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Before you start knocking off the height of the liner above the muff, check the depth of the recess in the head where it fits, or do I recall from a previous post that the gap was excessive?
Hi Robert,
No quite the opposite. The liners protrude less above the muffs than the depth of the recess in the head. I am going to spend time rubbing the heads down. Using a depth micrometer I measured the depth of the heads near the cylinder stud holes and the compared that to how far above the muff the liner protruded in the same areas. The respective measurements either matched or the recess was deeper by 0.001". Which is what I suspected as when I did a leak down test, I could hear air escaping up the front right cylinder stud of the front cylinder. Reading through "40 Years On", "Another 10 Years", and the latest "Into the Millennium" There needs to be at least a 0.002" gap between head and muff. I don't have that, which is a relief in one regards, as the air I heard leaking is not from a cracked head.
Steven
 

vibrac

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I always found that protrusion of the casting around the exhaust pipe made the flat Emery solution difficult as it restricted the pattern of movement to the edge of the board
 

ClassicBiker

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Well I had considered inverting the heads on 2x4x6 blocks placed across the cylinder stud holes and clamping down just off of the face and skimming on the mill. :eek: Then I came back to my senses. Thoughts of breaking a fin by clamping down to much or watching a head sail across the garage because it wasn't clamped tight enough entered my head. Plus the nagging doubt of are the top faces of cylinder head bolt holes really parallel to the bottom face, are they actually a single plane or were they just cleaned up to provide a clamping surface without regard to anything? The fact that after the heads are assembled on the engine and the nuts tightened then the brackets that secure the UFM to the engine sit on the nuts leads me to believe locating up down in that location would be okay. But how to secure safely and leave a clear tool path, that is what bothers me. It would be interesting to see how they were located when originally manufactured or how the new replacement heads are done.
Steven
 

oexing

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Steven,
I machined the faces around the bolt holes at the top first to get same height . Then I mounted the head upside down onto a plate with pillars with same height again. For clamping I think to remember that I put some bit of plastic or cardboard into the exhaust for setting a clamp onto that. At the intake the clamp can go onto the casting so no fins are used. Maybe you can put the whole affair onto a plate in a lathe to turn the recess and big surface in one operation for exact depth all round.

Vic
 

Bill Thomas

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Steven, I use the same grinding paste on both the liner and the head, So would work out, Both touching at the same time, We are only talking a thou, Seems to work for me. Cheers Bill.
 

ClassicBiker

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Bill, I haven't disturb the barrels, yet. I have a large thick ring of steel ground on both sides. I was considering turning a shoulder on one end, such that is would fit into the recess in the head. Then I was going to put some Prussian blue on the head and see if where the liner contacts is flat. Then doing the same for the top of the liner. Thus avoiding disturbing the barrels.
Steven
 
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