What went wrong?

[skinak]

the only reason i kept going up in sizes is because it kept doing super high reving and after 5-6 passes my plugs were still clean, they had not started browning til I put the 370 in.

[sheerider11]

That's a lean condition. People have been saying that from the start.

[skinak]

No kidding... I understand that I was running lean that would be why I jetted up. When I put the 370 in then the plug was turning brown. Nothing else changed except for the head and jetting

[skinak]

Should I have been able to change heads and not have to jet up? Provided my squish was correct?

[WINDYCITYJOHN400]

Should I have been able to change heads and not have to jet up? Provided my squish was correct?

 

Yes, your head change should not have required that big of a jet change. So your obviously having a hard time understanding that something lead to an air leak. (Your not lean in the classic jetting sense....your bringing air into the motor in a way that doesn't come thru the carbs.) You can't re-jet to deal with an air leak.

You might have a squish that is now too tight...it could have lead to detonation on your first riding attempt and that could have caused an air leak. So let's drop the jetting questions and get on to figuring out what your real issue is. For starters, you should start figuring out how to do a squish check and compression check when you make changes like that.. (Since you didn't do those when you put the shaved head on)

Your going to have to figure out where the air leaked in from even if you get new pistons a rebuild the motor.

Now the piston could have broken from too much sidewall clearance combined with the added power. (beefing up power on a tired motor) Or the piston could have been tilting and/or hitting the head, then putting a side load on the bottom skirt....

 

Long story short....your issue isn't the jetting. So having those big jets didn't cause the problem. But you have some work ahead of you to find the cause.

[Starwriter]

So....... You're the guy with the stock carbs bored out so big you can see daylight on each side of the slide....... Were these carbs on the motor when it blew? If so, there's your problem. At this point, you might as well split the cases to get all the piston chunks out of the bottom. As long as it's apart, you might as well put a crank in it. Then, take those stock carbs and smash them with a hammer so nobody attempts to use them.

[skinak]

So....... You're the guy with the stock carbs bored out so big you can see daylight on each side of the slide....... Were these carbs on the motor when it blew? If so, there's your problem. At this point, you might as well split the cases to get all the piston chunks out of the bottom. As long as it's apart, you might as well put a crank in it. Then, take those stock carbs and smash them with a hammer so nobody attempts to use them.

 

Those carbs were pulled as soon as I started having problems and needing to choke them to run the motor.

 

As far as squish and compression yes I need to search the forums and figure that out. Am I needing to get static compression or kicking compression with a gauge? I kinda thought that this would blow sooner or later just didn't know the skirts would break off instead of blowing the top.

[erickson483]

Compression test is kicking with WOT about 10 times til the pressure stops going up.

[skinak]

Compression test is kicking with WOT about 10 times til the pressure stops going up.

 

 

ok thanks, wasn't sure I also read about a compression test that has to do with port timing and duration of the piston.