Machining specs for new muff, liner

[TouringComet]

I have a new muff and liner, and need to provide instructions to the machine shop. What interference fit for fitting the liner to the muff? What clearance for my Kemp low expansion pistons, considering the So Cal climate, 2 - 4 thou? What is the target height for the muff, from bottom face to top (deck height?)? To minimize/eliminate lapping the cyl head, I've heard of machining the lip on the liner, the notch in the cylinder head, and/or the top surface of the muff, to provide a slight clearance between the muff and cylinder head, for the area where you would use the coarse lapping compound. How many thou?

 

[timetraveller]

Muff to liner clearance 6 thou. Deck height 3" + 30 to 50 thou. That is not critical unless you are going to be using squish bands but see note 1) below. Piston to liner clearance 2.5 to 3 thou. Base of cylinder head to top of muff 2 to 3 thou.

Note 1) When low clearance piston first became available several people had piston seizures and blamed the piston. Roy Robertson, and possibly others, found the problem. With a very low clearance it is important that the base of the muff is at 90 degrees to the axis of the liner. Many are not. Checking some of mine typically showed a run out of about 5 thou. The solution is to make two fittings, with accurate centers which are good fits into the top and bottom of the liner after it has been bored and honed. Putting the assembled muff and liner into a lathe with centers now allow the base of the muff to be checked and machined flat if it is not perpendicular to the bore. If the run out is fore and aft then it is not too important but if it across the engine then you do not need much error here to get rid of all of the 2 to 3 thou piston clearance.

Note 2) My background is astronomy, not engineering, so wait for confirmation or correction of these figures from some of the Clubs experts before cutting metal.

Good luck

 

[Bracker1]

Why not let Steve Hamel at Sterlingcycle do the necessary machine work. He is experienced with the aforementioned machining, and runs motorcycles at Bonneville which will have similair conditions as SoCal. Cheers, Dan

 

[Bill Thomas]

Norman you are too Modest,
I have one of your alternator Kits, (Super Job)
I think you had a slip of the pen!, You put clearance , Should have been
Interference?. Thanks for the tip on barrel alignment, I didn't under stand how it upset it.
One thing to remember when fitting muff to liner, Keep weight on it when cooling or it will creep out, I had one of our top men do mine once and when I got home you could get your thumb-nail under the top rim.
All the best Bill.

 

[TouringComet]

Why not let Steve Hamel at Sterlingcycle do the necessary machine work. He is experienced with the aforementioned machining, and runs motorcycles at Bonneville which will have similair conditions as SoCal. Cheers, Dan

I'm well aware of Steve H, and would love to use him all the time, in fact, we've discussed having him redo my Shadow motor. I'm in Los Angeles, so the distance (shipping, etc) is a hinderance for every job. Thanks for the info T T.

 

[Bracker1]

It is a hassle when everything is far away. I will say the crank parts I just bought from TPV arrived within a week. The machining and quality is magnificent. TPV is one of the best companies I have dealt with.

I did have some machine work done locally to my Shadow cases, and fortunately Steve H is going to rectify the damage.. It's easy to do a bad job and tough to do a good one. Live and learn. Dan

 

[Tom Gaynor]

The head seals on the top of the liner, and ideally the head will be in hard contact with the liner and "soft" contact with the muff. But it is the liner seal that is essential, and I took the top of the liner down with a file to avoid spending the rest of my life lapping. 0.002 to 0.003 clearance when the head is sitting on top of the muff is proably about right. I've had no problems at all. Note also that 28 lb.feet torque on greased head nuts is PLENTY, and if you can get off with less, good.

I have a new muff and liner, and need to provide instructions to the machine shop. What interference fit for fitting the liner to the muff? What clearance for my Kemp low expansion pistons, considering the So Cal climate, 2 - 4 thou? What is the target height for the muff, from bottom face to top (deck height?)? To minimize/eliminate lapping the cyl head, I've heard of machining the lip on the liner, the notch in the cylinder head, and/or the top surface of the muff, to provide a slight clearance between the muff and cylinder head, for the area where you would use the coarse lapping compound. How many thou?