Jrortiz Posted April 5, 2020 Report Share Posted April 5, 2020 what should my timing be? I have a 4mil crank 65 pistons shaved stock head and stock carbs. I run 93 gas. Quote Link to comment Share on other sites More sharing options...
Stingray Posted April 5, 2020 Report Share Posted April 5, 2020 How far is your cut. The problem is it might ping with too much advance. I would try 4 deg if it pings back it off. If you can't tell if it is pinging do a wide open pull and a plug chop if you see aluminum spots on the very base of the plug then you have detonation and need the back off the timing. Quote Link to comment Share on other sites More sharing options...
Stingray Posted April 5, 2020 Report Share Posted April 5, 2020 Your displacement is 384.92\2= 192.46\dome cc stock is 27 = 7.12 compression 20 cc domes would give you 9.623 knowing the CCs of your head would help calculate your compression ratio and the safe advance with the fuel you want to run. If you calculate off the exhaust port closing your stroke becomes 29mm from port close to head due to your longer stroke. This gives you a displacement of 192.46\2= 96.23\27= 3.56 to 1 by the Japanese calculation. Ktm runs 13 .2 to 1 with a recommended fuel of 93 octane (250 xc) standard compression not Japanese . Quote Link to comment Share on other sites More sharing options...
ClaudeMachining Posted April 5, 2020 Report Share Posted April 5, 2020 Your displacement is 384.92\2= 192.46\dome cc stock is 27 = 7.12 compression 20 cc domes would give you 9.623 knowing the CCs of your head would help calculate your compression ratio and the safe advance with the fuel you want to run. If you calculate off the exhaust port closing your stroke becomes 29mm from port close to head due to your longer stroke. This gives you a displacement of 192.46\2= 96.23\27= 3.56 to 1 by the Japanese calculation. Ktm runs 13 .2 to 1 with a recommended fuel of 93 octane (250 xc) standard compression not Japanese .You dont take gaskett into account...This is the vest way:https://youtu.be/ajCE1HRWaAEEnvoyé de mon SM-G965W en utilisant Tapatalk Quote Link to comment Share on other sites More sharing options...
Jrortiz Posted April 5, 2020 Author Report Share Posted April 5, 2020 11 hours ago, Stingray said: How far is your cut. The problem is it might ping with too much advance. I would try 4 deg if it pings back it off. If you can't tell if it is pinging do a wide open pull and a plug chop if you see aluminum spots on the very base of the plug then you have detonation and need the back off the timing. Yeah I recently had detonation I believe. Put a hole in the left piston. I had an open road so decided to open bike up and I heard pinging and then it died. I thought it was because I was running to lean or not getting enough fuel but as I look Into it more it looks like it has something to do with the timing. Quote Link to comment Share on other sites More sharing options...
hoppedupandcutdown Posted April 5, 2020 Report Share Posted April 5, 2020 59 minutes ago, Jrortiz said: Yeah I recently had detonation I believe. Put a hole in the left piston. I had an open road so decided to open bike up and I heard pinging and then it died. I thought it was because I was running to lean or not getting enough fuel but as I look Into it more it looks like it has something to do with the timing. Did you do a leak down test before you pulled it apart? Sounds more like an air leak on the left side. Quote Link to comment Share on other sites More sharing options...
Jrortiz Posted April 5, 2020 Author Report Share Posted April 5, 2020 22 minutes ago, hoppedupandcutdown said: Did you do a leak down test before you pulled it apart? Sounds more like an air leak on the left side. This might sound dumb but how do I do that? It’s hard to find a decent 2stroke mechanic in my area. Quote Link to comment Share on other sites More sharing options...
hoppedupandcutdown Posted April 5, 2020 Report Share Posted April 5, 2020 Basically seal off the exhaust and intake with some plumbing and a low pressure gauge and air valve. Pressurize to 6 psi and if it doesn't hold, start spraying soapy water. Ebay has them from several good people, or look at the pics and head off the the hardware store and make one if you're handy. 1 Quote Link to comment Share on other sites More sharing options...
Jrortiz Posted April 5, 2020 Author Report Share Posted April 5, 2020 2 minutes ago, hoppedupandcutdown said: Basically seal off the exhaust and intake with some plumbing and a low pressure gauge and air valve. Pressurize to 6 psi and if it doesn't hold, start spraying soapy water. Ebay has them from several good people, or look at the pics and head off the the hardware store and make one if your handy. Thanks. I recently paid someone to redo the whole motor Into a stroker and I got about 2 rides in And this happened Quote Link to comment Share on other sites More sharing options...
SKEETER Posted April 6, 2020 Report Share Posted April 6, 2020 +12* is where da powa is Quote Link to comment Share on other sites More sharing options...
Stingray Posted April 6, 2020 Report Share Posted April 6, 2020 13 hours ago, Jrortiz said: Yeah I recently had detonation I believe. Put a hole in the left piston. I had an open road so decided to open bike up and I heard pinging and then it died. I thought it was because I was running to lean or not getting enough fuel but as I look Into it more it looks like it has something to do with the timing. I agree with others. Sounds like an air leak another quick test is to spray starting fluid at all the gasket surfaces while it idles if the rpm changes you have a leak. This is not a replacement for a preasure test but a quick test if something feels off. 1 Quote Link to comment Share on other sites More sharing options...
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