I hope someone can help me here. My B40 trials came to me as a non runner and I've yet to get it running.
I noticed there was a lot of hissing coming from the bottom end as I kicked it over (high crankcase pressure).
I've tested the compression and I have about a 4 to 1 ratio.
Today I have removed the cylinder and checked the rings, they are burred on the edges and the gaps in the bore measure over 3mm (should be 0.3mm or less).
The bore is really good, no scratches or scores and hardly any lip at the top of the bore.
Question is, how do I get replacement rings to fit? The only info on the piston crown is 80 then a gap and a 6, both look as though they have been done by hand with letter punches.
Is there a way of measuring the piston and bore to confirm sizes to enable me to order the correct replacement ring size.
I'm a retired engineer and have all the necessary precision measuring instruments.
Doug.
Doug
similarly Im an inspector in a machine shop.
bore size should be 79mm, over sizes normally 0.010" to 0.040" (0.25 to 1.0mm) there may be oversize to 1.5mm if you can find.
ring gaps should be 0.009 to 0.014"
ideally the bore sould be cross hatch honed finish.
the next job, to find the piston and rings for a rebore.
usual suspects are Draganfly, TMS, Burton etc
Thanks for that, I guess it's a plus 40thou by the looks of it, I will make enquries with draganfly and the others for the right rings.
Give Cox and Turner in Verwood a call. They specialise in pistons/rings and stock good quality nos.