Fastassbanshee96 Posted October 14, 2010 Report Share Posted October 14, 2010 What exactly is detonation and how does it happen. I've always been under the impression that it's when you have too much compression and not enough octane. Is this true. Also if you are running lean can it blow a hole in your piston and if so how long does it usually take. My buddy just had a 4mil long rod built running v force 3 reeds dune ported case matched fmf fattys stock carbs cool head with 22cc domes running a 340 main and a 40 pilot. Is this jetting pretty close to what similar setups are running. I know his pilot is probably a little high but he would rather that than it be running lean. Also we live in Michigan. I'm asking all this because he just got the motor back and put in, did the break in on it and it blew up. There is not even 2 hours on the motor and he did the break in correctly. Still hasn't even gotten to give it everything it has. Maybe 3/4 throttle. Also he's running 93octane when it's setup to run 91. What do you guys think it could be and is this jetting close enough to where there shouldn't be a problem. Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted October 14, 2010 Report Share Posted October 14, 2010 Are the domes cut domes for the 4mil setup? Did you check the squish before you started it? Did you do a leak down test on it? Quote Link to comment Share on other sites More sharing options...
J-Madd Posted October 14, 2010 Report Share Posted October 14, 2010 What exactly happened to it? Locked up? Lost all compression? Quote Link to comment Share on other sites More sharing options...
Fastassbanshee96 Posted October 14, 2010 Author Report Share Posted October 14, 2010 Yes the domes are cut domes and the motor was built by a reputable builder( don't want to drop names if it's just a fluke). I would guess that the builder did the squish and I know he did the leak down test. We were riding and it after the break in and were just kind of idling next to eachother going probably 25mph when we heard a pop. We instantly shut them off and pushed it back to the truck a pulled a plug. The bottom of the plug was smashed in and you could see signs of where some thing hit it. I then took with the plug out and put my finger over the whole and turned over by hand and it feels like there is pretty much no compression in the right cylinder. Everything looked and seemed to be good on the left side. He is taking the head off tonight and is supposed to let me what he finds. I'm guessing a whole in his piston. Quote Link to comment Share on other sites More sharing options...
tripledsracing Posted October 14, 2010 Report Share Posted October 14, 2010 (edited) ouch!..sounds like a rod bearin failed.. Edited October 14, 2010 by tripledsracing Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted October 14, 2010 Report Share Posted October 14, 2010 How much timing is he running? Im running a 4mil dune port with 23cc domes and +6 timing. Im just on the edge of 93 octane. Quote Link to comment Share on other sites More sharing options...
Fastassbanshee96 Posted October 14, 2010 Author Report Share Posted October 14, 2010 He's running +3 timing right now. And as far as the crank bearing, how could that happen with a motor that has not even 2 hours on it and the crank is brand new. And it hasn't been beaten on at all. Quote Link to comment Share on other sites More sharing options...
dirtydownunder Posted October 14, 2010 Report Share Posted October 14, 2010 detonation is when the air/fuel mix ignite from heat or compression instead of firing on time with the spark plug. Quote Link to comment Share on other sites More sharing options...
tripledsracing Posted October 14, 2010 Report Share Posted October 14, 2010 He's running +3 timing right now. And as far as the crank bearing, how could that happen with a motor that has not even 2 hours on it and the crank is brand new. And it hasn't been beaten on at all. either wrist pin,wrong base gasket,plus a new rod bearing can be bad,domes cut wrong!..you got major problems if the plug hit the piston though!.. Quote Link to comment Share on other sites More sharing options...
tripledsracing Posted October 14, 2010 Report Share Posted October 14, 2010 (edited) guy on ps had same prob and his bike went lean and caused it to deto to were the plug gap closed also...but he didnt lose any compression! Edited October 14, 2010 by tripledsracing Quote Link to comment Share on other sites More sharing options...
Fastassbanshee96 Posted October 14, 2010 Author Report Share Posted October 14, 2010 detonation is when the air/fuel mix ignite from heat or compression instead of firing on time with the spark plug. Ok but for example if you are setup to run race fuel and you run regular gas then you will probably detonate early. But if you are setup to run on 91 and you run 93 then how do you detonate. I was always under the impression that it was all in the octane. Quote Link to comment Share on other sites More sharing options...
tripledsracing Posted October 14, 2010 Report Share Posted October 14, 2010 guy had same prob!.. http://www.planetsand.com/forums/ubbthreads.php/topics/1060967#Post1060967 Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted October 14, 2010 Report Share Posted October 14, 2010 octane is what keeps deto from occuring.....however say if there is a large burr on your head it can begin to heat up and actually cause pre-ignition. are you sure that it started to deto? or did it get lean on itself and break a piece of the piston off and that's what smashed the plug... Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted October 14, 2010 Report Share Posted October 14, 2010 91 octane for that setup doesnt sound right. When I had my motor done by HJR he sent me 20cc cut domes to run 110. Then I called him to figure out what size domes to go with for 93 octane. He sent me the 23cc domes and said it was going to be real close. Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted October 14, 2010 Report Share Posted October 14, 2010 Yeah, the one carb could have had a stuck float or after riding it something could have come loose to cause an air leak, pretty much anything could happen Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.