Brand new 4mil locked up. WHY?

[CAJUN BANSHEE]

I just had my motor built by a fairly known builder in my area. He is not a major shop but he is the one to turn to around here. Here is what I have: full drag port, 4mil crank, trued and welded, dual pingle, 34mm pjs with 140 mains, 112 vp fuel @ 40:1, wicked intakes, bored 50 over, timming plate +4, lock up with r6 clutches, cool head with 20cc domes at 140lbs compression, cpi out of frames, brand new wcr trans and tons of other sht that dont matter right now. I ran 1 1\2 tanks of fuel just around my house in about a 2 week time frame and motor pulled hard but cut out bad on top end and would foul plugs like crazy. Brought the bike back to him and he found he had 180 mains in the carbs, so he replaced them with 140's and the bike ran great and the plugs were a cardboard color. Went to the dunes last Sat. and motor locked up after two drag races (third tank of gas). The motor was at an idle when it happend, thank God. Pulled motor down and found the intake piston skirt on the right cyl broke and wedged between the crank and the case. I am not edging to talk sht on this guy, just want to know what happened because he cant tell me and now a few thousand dollars later and 3 tanks of gas I am looking to caugh up another 3-4 hundred dollars again. Thanks for any replies

[So Cal Suspension]

I just had my motor built by a fairly known builder in my area. He is not a major shop but he is the one to turn to around here. Here is what I have: full drag port, 4mil crank, trued and welded, dual pingle, 34mm pjs with 140 mains, 112 vp fuel @ 40:1, wicked intakes, bored 50 over, timming plate +4, lock up with r6 clutches, cool head with 20cc domes at 140lbs compression, cpi out of frames, brand new wcr trans and tons of other sht that dont matter right now. I ran 1 1\2 tanks of fuel just around my house in about a 2 week time frame and motor pulled hard but cut out bad on top end and would foul plugs like crazy. Brought the bike back to him and he found he had 180 mains in the carbs, so he replaced them with 140's and the bike ran great and the plugs were a cardboard color. Went to the dunes last Sat. and motor locked up after two drag races (third tank of gas). The motor was at an idle when it happend, thank God. Pulled motor down and found the intake piston skirt on the right cyl broke and wedged between the crank and the case. I am not edging to talk sht on this guy, just want to know what happened because he cant tell me and now a few thousand dollars later and 3 tanks of gas I am looking to caugh up another 3-4 hundred dollars again. Thanks for any replies

 

A 180-140 drop on the mains is pretty significant. That might have had something to do with it. Sounds like it was running very lean, and grenaded.

 

You can't always rely on plug color. Different types of premix and gas will produce different colors. Plug color is a good starting point, but shouldn't be relied on 100%.

[BANSHEE HP]

110 gas is too much octane for 140psi, it will acctually make you go slower.

 

lets just say that it was jetted perfect with 140's, running around your house or up and down the road. now take that bike with the same jetting and swtich to a paddle tire and throw the bike in the sand and the load on the motor is increased alot. turning those paddles in sand is alota more work for the motor then a dirt tire on grass/gravel/dirt/asphault. when i jet a bike on the dyno and know the air fuel ratio is spot on, i always go up a few sizes in jets when the bike will be running in the dunes.

 

matt is right 180-140 is huge jump, and it was probally leaner then a popcorn fart in the sand.

[Larry's Shee]

What kind of pistons are they? Were the windows on pistons modified? Who assembled the motor? what was the squish? Where did the domes come from? Was this fresh bore?