Sandking Posted November 20, 2016 Report Share Posted November 20, 2016 I had a head milled for a pump gas bike by a sponsor. The bike has t6s, k&n filter with airbox no lid, +4 timing, and stock reads, 300 main 27.5 pilot. Compression ended up at 150. The bike blew a hole through the left side piston and broke the skirt a few hundred yards from camp on the first ride. Question is 150 too high for this set up. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted November 20, 2016 Report Share Posted November 20, 2016 No my guess is airleak because your a tad rich on jetting . You guys need to start getting in th habit of leakdown before tear down , it takes away the what ifs and guessing . If it passed a leak then u move on to mechanical failure Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted November 20, 2016 Report Share Posted November 20, 2016 Post a pick of piston hole was it a clean blowtorch hole or was there deto around it Quote Link to comment Share on other sites More sharing options...
Sandking Posted November 20, 2016 Author Report Share Posted November 20, 2016 This wasn't my bike I just sent the head out for milling. I did a leak down test before tearing it apart and the intakes on both sides leaked pretty good. Quote Link to comment Share on other sites More sharing options...
Sandking Posted November 20, 2016 Author Report Share Posted November 20, 2016 Is there a way to tell the difference between a lean pop vs another type this guy's bike was put together by a yamaha mechanic and I've been fixing things since. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted November 20, 2016 Report Share Posted November 20, 2016 Yeah that's a super lean condition Quote Link to comment Share on other sites More sharing options...
Sandking Posted November 20, 2016 Author Report Share Posted November 20, 2016 Yeah that's a super lean conditionThanks, I really don't want to send the head back for 10 lbs of compression. Quote Link to comment Share on other sites More sharing options...
n2otoofast4u Posted November 20, 2016 Report Share Posted November 20, 2016 I'm just a dummy, but there had to have been some signs that shit was whack! To do that with a few hundred yards of camp, there had to have been some funny business going on. Quote Link to comment Share on other sites More sharing options...
Sandking Posted November 20, 2016 Author Report Share Posted November 20, 2016 I'm just a dummy, but there had to have been some signs that shit was whack! To do that with a few hundred yards of camp, there had to have been some funny business going on.His bike always had a deep sound to it from the first time it came out which I told him wasn't right, he originally had different mains in each carb, and one of the carb caps was sealed with silicone and a set screw due to stripped threads. He was also fouling plugs. I replaced his carbs and jetted the bike then when I put a timing plate on it I found a post on the stator came loose which was fixed and tested. Sucks but the guy who completely rebuilt the motor recently screwed it all up. And I found the crank seals were in backwards. The bikes in pieces in my garage now waiting on cylinders. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted November 20, 2016 Report Share Posted November 20, 2016 That thing must of run away, or he thought he was wfo. A bike that lean will make zero power and a whole lot of noise Quote Link to comment Share on other sites More sharing options...
Sandking Posted November 20, 2016 Author Report Share Posted November 20, 2016 That thing must of run away, or he thought he was wfo. A bike that lean will make zero power and a whole lot of noise He said it ran pretty well then he herd it pop and immediately turned it off. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted November 23, 2016 Report Share Posted November 23, 2016 They always run great rite before they pop 2 Quote Link to comment Share on other sites More sharing options...
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