400sbc Posted January 28, 2011 Report Posted January 28, 2011 ok i need to know the right way to take a banshee compression test? some people told that i have to take out both spark plug, some tell to WOT it when cranking, actually i just put my meter on one side and i keep the plug in the other, and switch process for each cylinder thanks Quote
gotta_goatsfast Posted January 28, 2011 Report Posted January 28, 2011 Pulling both plugs makes it easier to kick over... but I always fear that I'll draw in dust through the other hole. I always hold the throttle open when I do a compression test though. Quote
Jereme6655 Posted January 28, 2011 Report Posted January 28, 2011 i was told by a site sponsor that you should pull both plugs and you DO need to hold the throttle wide open.....then kick until the needle on the guage stops rising.... Quote
guns4children Posted January 29, 2011 Report Posted January 29, 2011 Wow! I have been doing at all wrong I never took both plugs out and never held WOT. I feel like an dumb ass. Quote
BluBanshee98 Posted January 29, 2011 Report Posted January 29, 2011 Also adding a few drops of of MMO or some kind of to help the cylinder seal stay lubricated. Quote
Jereme6655 Posted January 29, 2011 Report Posted January 29, 2011 you don't really want to add any oil or anything into the cylinder while your checking the compression. reason being is it will throw off your actual compression test. Putting oil down the spark-plug hole is a way to find if youve got a problem with your rings sealing against the cylinder walls.......say if youve got around 95 psi and are curious if its a problem with the guage or if your compression really is that low......put about a spoonful of oil down each hole and redo a comperssion test......you'll notice that each of your compression readings will be up a decent amount higher. This worked out for me when a guy installed a piston in a dirtbike cylinder without getting the ring ends lined up with the peg that is in the ring groove. He couldn't get the bike started even after the rebuild.......when i got it i asked why it only had 90 psi when it was JUST rebuilt....so i put some oil in the cyl and kicked and got over 110psi in the jug.... pulled it apart and looked at the wall of the cylinder he scored the shit outta. Quote
BluBanshee98 Posted January 29, 2011 Report Posted January 29, 2011 you don't really want to add any oil or anything into the cylinder while your checking the compression. reason being is it will throw off your actual compression test. Putting oil down the spark-plug hole is a way to find if youve got a problem with your rings sealing against the cylinder walls.......say if youve got around 95 psi and are curious if its a problem with the guage or if your compression really is that low......put about a spoonful of oil down each hole and redo a comperssion test......you'll notice that each of your compression readings will be up a decent amount higher. This worked out for me when a guy installed a piston in a dirtbike cylinder without getting the ring ends lined up with the peg that is in the ring groove. He couldn't get the bike started even after the rebuild.......when i got it i asked why it only had 90 psi when it was JUST rebuilt....so i put some oil in the cyl and kicked and got over 110psi in the jug.... pulled it apart and looked at the wall of the cylinder he scored the shit outta. I generally do a compression test on a 2 stroke to verify if the rings are toast, after I have inspected the reeds. When the engine is supplied fuel/oil mix to run the engine, rings seal as they should when you do a compression test. A DRY cylinder will not give you an accurate reading. Quote
Jereme6655 Posted January 29, 2011 Report Posted January 29, 2011 I generally do a compression test on a 2 stroke to verify if the rings are toast, after I have inspected the reeds. When the engine is supplied fuel/oil mix to run the engine, rings seal as they should when you do a compression test. A DRY cylinder will not give you an accurate reading. ahhh....now i understand why your doing your tests with a little oil in the cylinders....your talking doing the test AFTER youve pulled the carbs and the reeds. I always do compression tests while the engine is still fully assembled while its in running condition (or WAS running condition just can't run anymore). correct.... a dry cylinder wont give you a totally accurate reading. but if the carbs are still on and functioning correctly then you will be getting a fuel/oil mix into the cylinders while your checkin the compression. Quote
tbcustomz Posted January 29, 2011 Report Posted January 29, 2011 I am getting 110 and 115 on mine right now with stock head and a cold engine at 900 feet above sea level. Does this mean I need a rebuild? Should the engine be warmed up prior to testing? I was thinking about pulling the head and checking the ring gap and looking for any scoring in the cylinder walls. Quote
Jereme6655 Posted January 29, 2011 Report Posted January 29, 2011 that is getting pretty low.....might be a good idea just to pull the head....and also it is good to look for ring-ridges. if its got some ring ridges starting then its time to rebuild! Quote
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