turbowrenchhead Posted May 19, 2014 Report Share Posted May 19, 2014 If you look at my other post about higher exhaust port effecting cranking compression you'll see that I'm scratching for answers. If you crank over an engine with a 1/2' ratchet on the crank gear nut and spin it over by hand will you get a good psi reading? Does the kick start spin the crank several times faster then doing it manually with a ratchet? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted May 19, 2014 Report Share Posted May 19, 2014 That could be an issue. However, if you put the socket on an impact and a bit of lube in the cylinder, it should be pretty close. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted May 19, 2014 Report Share Posted May 19, 2014 I would think. The slower you go the more chance you give for blow by. Kicking happens much faster so it compresses. No chance for it to escape. Maybe I'm wrong. But I wouldn't try it by hand. Just dosent seem right. 1 Quote Link to comment Share on other sites More sharing options...
BUILDER Posted May 19, 2014 Report Share Posted May 19, 2014 That could be an issue. However, if you put the socket on an impact and a bit of lube in the cylinder, it should be pretty close. LOL You put a socket on a impact and try and crank it over to do a compression test you are going to break the end of the crank off! To answer the question no you will not come even close to getting a good reading turning it over by hand Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 19, 2014 Author Report Share Posted May 19, 2014 I didn't want to put an impact to crank nut. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 19, 2014 Author Report Share Posted May 19, 2014 When I get my clutch gasket I'll get the motor together and install it in the bike and re test cranking compression Quote Link to comment Share on other sites More sharing options...
m671054 Posted May 19, 2014 Report Share Posted May 19, 2014 Cranking speed greatly impacts cranking compression readings Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 19, 2014 Author Report Share Posted May 19, 2014 I sure hope so. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted May 19, 2014 Report Share Posted May 19, 2014 Honestly on the bench is not the way t get a cranking compression reading but it is exactly what you want t do an accurate measurement of compression ratio and or squish clearance. Bring the piston up to TDC and use a plastic medicine syringe from a pharmacy to add oil to fill up the combustion chamber till it fills right up to the first sparkplug thread on the head or dome. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 19, 2014 Author Report Share Posted May 19, 2014 How do I get a compression ratio from the measurement? Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 19, 2014 Author Report Share Posted May 19, 2014 Sqish is .045 Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 21, 2014 Author Report Share Posted May 21, 2014 I did the liquid test. I can get 14cc's of oil into the chamber when the piston is at TDC. I have no idea how to convert that into a compression ratio. I looked online and they want a dome cc height and I have no idea what it is. Lil help here please. Quote Link to comment Share on other sites More sharing options...
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