Tight spot after new rings fitted

[jonathanjoy]

Hi
I’ve just fitted new rings to my 1929 flyer. I,ve noticed that there is a tight spot when I rotate the crank, as I don,t want to run it in this condition. Is this common or have I dropped a clanger !!!. What should I check / measure first ?

regards Jonathan

[dave bushell]

Have you checked the ring gap? You need about three thou per inch of diameter.ie about 0.009″ in total.
Dave

[jonathanjoy]

Thanks Dave for the prompt reply, do I make any allowance for the brass ring stop ?

jonathan

[TedParkin]

😀 😀 Speak to Roger Moss Jonathan!!!!!! 😀 😀

[jonathanjoy]

Sound advice , Ted, I’ll see if can ring Rodger tomorrow

Jonathan

[scott596]

Jonathon, the trouble is that the top edge of the old rings will have developed a radiused corner and this will match a radiused wear ridge in the bore, replacing the top ring with something with a sharp 90 degree edge will cause the piston to tighten up at the top of the stroke and could cause damage to the top groove of the piston or excessive wear to the gudgeon pin bosses, the choices are, put your old rings back in, grind a bevel on your new top ring, or turn your top ring groove to a lower position fit your new ring and then find a thin undersize spacer ring to fit the gap above the ring. Alan Noakes.

[jonathanjoy]

Solved !!! 💡

Cleanliness is next to Godliness !!
A small piece of congealed oil was trapped in the corner of the brass piston ring stop, keeping the ring slightly open and causing a tight spot when the crank was turned.

thanks for the advice it put me well on the way to the solution , although it does indicate that the bores are not perfectly cylindrical may need a rebore in the near future

Kind regards and thanks again for your contributions

[Author]

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