pressure release valve

[Belafonte]

I just installed a big bore kit from weedeaterman on my Makita 6421.  The new big bore cylinder has the pressure release on the side and my stock 64cc cylinder has it on the top.  Is the old valve compatible with the new side mount arrangement or do they require different units?  I forgot to check it in the new cylinder before installation so i'm not sure if it would contact the piston.   

[dougand3]

Never worked on Makita but Husky 55 side decomp valve is threaded into a chamber that is outside the cylinder. There is a small hole (~1/8") drilled in cyl wall that pressure releases thru into this chamber. There is no way the decomp valve plunger could be in the cylinder. You could measure depth of threaded chamber and compare to the depth of threads and plunger extended on valve. The chamber depth will probably much much longer.
And this assumes the thread diam and pitch are the same. Eg. Husky is 10mm x 1.0 (IIRC).