shee rips Posted October 15, 2007 Report Share Posted October 15, 2007 i just installed a timing plate the other day, set it at +3 for now. anyway when i still had the cover off i fired it up and played with the timing a bit with the motor running. i put in earplugs and wanted to see how far i could advance it before hearing detonation. i had the plate loose enough that i could move it by hand, and i went all the way to +10 for a few seconds and revved the motor a bit. I couldnt hear anything different at all, other than it revved quicker :shrug: it has the head shaved .020, i think my compression is in the 140s maybe 150, and im on 91 octane. i am curious to know what detonation sounds like because i thought it would be good knowledge and for a few seconds it wouldnt hurt anything. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted October 15, 2007 Report Share Posted October 15, 2007 (edited) The only time I ever heard detonation in a 2 stroke, it blew up immediately afterwards. You dont want to try and hear it. If your compression is 150, your squish is under .060", then your timing can be all the way up to +6 or so on 92 octane pump gas. Edited October 15, 2007 by Snopczynski Quote Link to comment Share on other sites More sharing options...
shee rips Posted October 15, 2007 Author Report Share Posted October 15, 2007 my squish is .035 Quote Link to comment Share on other sites More sharing options...
2strokespirit Posted October 15, 2007 Report Share Posted October 15, 2007 i just installed a timing plate the other day, set it at +3 for now. anyway when i still had the cover off i fired it up and played with the timing a bit with the motor running. i put in earplugs and wanted to see how far i could advance it before hearing detonation. i had the plate loose enough that i could move it by hand, and i went all the way to +10 for a few seconds and revved the motor a bit. I couldnt hear anything different at all, other than it revved quicker :shrug: it has the head shaved .020, i think my compression is in the 140s maybe 150, and im on 91 octane. i am curious to know what detonation sounds like because i thought it would be good knowledge and for a few seconds it wouldnt hurt anything. Its much more difficult to hear detonation in a liquid cooled machine, you will not blow the motor right up if it runs freely and most motors start detonation when they work really hard, like pulling in 4,5,6 gear, not by just revving them. It sound like a piston knocking against the cylinder head or worst, like rocks in the combustion chamber, My CR500 had done it a lot on hillclimbing, never blew the motor, had the change to sort it out, unfortunatly my RZ did it and I did not hear it and blew it up in 200m straight line, because of a faulty CDI. I have found that it is very difficult to hear it on a twin cylinder liquid cooled than any other machine, but thats my opinion Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted October 15, 2007 Report Share Posted October 15, 2007 my squish is .035 I would increase squish, your running the sst which is a top end pipe. You may bang the piston off the head in high rev situations. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted October 15, 2007 Report Share Posted October 15, 2007 the best way i havee heard it described is pebbles in a coffee can, which is pretty accurate from my experience with my turbo car. i find it very hard to hear on a 2 stroke too which is why i spend the extra on good gas and such. Quote Link to comment Share on other sites More sharing options...
nitrodave Posted October 15, 2007 Report Share Posted October 15, 2007 the best way i havee heard it described is pebbles in a coffee can, which is pretty accurate from my experience with my turbo car. i find it very hard to hear on a 2 stroke too which is why i spend the extra on good gas and such. What is squish and how do you caculate it or figure it? I have a 20over stock motor +4 timing plate noss racing head with 19 domes i am buliding. Quote Link to comment Share on other sites More sharing options...
wacko2000 Posted October 16, 2007 Report Share Posted October 16, 2007 yea what is squish? Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted October 16, 2007 Report Share Posted October 16, 2007 yea what is squish? distance from the piston to the head at the side when at tdc. You check it with a piece of solder and a micrometer. Quote Link to comment Share on other sites More sharing options...
NYUK Posted October 16, 2007 Report Share Posted October 16, 2007 it sounds like this, pting, pting, pting ting ting ting ting, a boom.BOOM! Quote Link to comment Share on other sites More sharing options...
bansheefreak Posted October 16, 2007 Report Share Posted October 16, 2007 it sounds like a deisel.. then it goes boom to total silence.. Quote Link to comment Share on other sites More sharing options...
Ricehater Posted October 16, 2007 Report Share Posted October 16, 2007 Its much more difficult to hear detonation in a liquid cooled machine, you will not blow the motor right up if it runs freely and most motors start detonation when they work really hard, like pulling in 4,5,6 gear, not by just revving them. It sound like a piston knocking against the cylinder head or worst, like rocks in the combustion chamber, My CR500 had done it a lot on hillclimbing, never blew the motor, had the change to sort it out, unfortunatly my RZ did it and I did not hear it and blew it up in 200m straight line, because of a faulty CDI. I have found that it is very difficult to hear it on a twin cylinder liquid cooled than any other machine, but thats my opinion like he said ..... the engine has to be loaded ... not just reving Quote Link to comment Share on other sites More sharing options...
shee rips Posted October 16, 2007 Author Report Share Posted October 16, 2007 ok thanks i wnated to know so if i hear it one day to shut it down but im surprised i didnt hear it when i had the timing at +10 for a second. just because it wasnt under load, just revving in neutral. i put it together at +3 degrees, will probably go to 4 later once i know my compression on a guage that i trust. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted October 17, 2007 Report Share Posted October 17, 2007 it sounds like this, pting, pting, pting ting ting ting ting, a boom.BOOM! That's kind of the response I was thinking when I first saw the topic. Quote Link to comment Share on other sites More sharing options...
knelson Posted October 19, 2007 Report Share Posted October 19, 2007 Here is how I detect deto on motors that are loud.Take a 1/2 dia. or so copper tubing about 3 inches long and mash the one end closed to about 1in up. drill a 3/8 or so hole through the side that is mashed flat. Take a head nut off, bolt copper tubing down. on the other open end of copper tubing connect a hose (I use tygon, any flexible hose will work) that will run to a set of earmuffs that you drill a hole through and connect hose to. Quote Link to comment Share on other sites More sharing options...
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