[mikey007]

So I heard something funny today when I was riding my indy 400. It sounded like a cracked exhaust and it turned out to be a hairline crack in the y-pipe where it splits and goes to the cylinders. I noticed (maybe) some loss of power today, could this be why? Can I drive it like that for now until I get a new one or can I possibly weld this one? Thanks!

 

[ridgerunner]

if you can weld, you can weld that. it isn't easy because it's pretty thing, but i would not recommend running it the way it is. i bought my sled last spring with a blown engine because of a split y-pipe. also, the pipe was the same on the 400/500 funi twins. you can probably find a replacement one for pretty cheap on ebay.

 

[mikey007]

if you can weld, you can weld that. it isn't easy because it's pretty thing, but i would not recommend running it the way it is. i bought my sled last spring with a blown engine because of a split y-pipe. also, the pipe was the same on the 400/500 funi twins. you can probably find a replacement one for pretty cheap on ebay.

Sounds good. Why does a cracked y-pipe blow a motor?

 

[ridgerunner]

mine was more than cracked... it was split right in half so it was alittle worse. on a 2 stroke as the piston goes down air/fuel are pulled in from the carb, if the exhaust has an opening in it, it will pull more air from that space as well. creates a lean condition and the engine goes pop. same thing as a cracked carb boot.

 

[mikey007]

mine was more than cracked... it was split right in half so it was alittle worse. on a 2 stroke as the piston goes down air/fuel are pulled in from the carb, if the exhaust has an opening in it, it will pull more air from that space as well. creates a lean condition and the engine goes pop. same thing as a cracked carb boot.

Okay, I wouldn't have wrecked anything driving the 5-6km home from where I found the crack, would I? It was running fine when I parked it other than maybe a little loss of power most likely due to the crack.

 

[ridgerunner]

i wouldn't worry about it too much... small crack won't do to much, but its the potential to get bigger is why i wouldn't let it go the season as it sets.

 

[RJ Gleason]

i wouldn't worry about it too much... small crack won't do to much, but its the potential to get bigger is why i wouldn't let it go the season as it sets.

A small crack will get bigger and it can reduce back pressure too much too.
You should also find out why it cracked. Usually due to excessive vibration that is often caused by clutch being out of balance (worn or broken parts inside it).

 

[mikey007]

A small crack will get bigger and it can reduce back pressure too much too.
You should also find out why it cracked. Usually due to excessive vibration that is often caused by clutch being out of balance (worn or broken parts inside it).

Well, I think I know why it cracked. It is a combination of it not being bolted down and the ball it sits on is missing.

 

[MDR122987]

you are going to want to be careful if you have it welded because i just had my hairline crack welded and it caused it to come in more so now the holes on the y pipe dont line up to be bolted back on it is only like 1/8th of an inch off but still makes it so the bolts dont go in straight... also to anyone who can answer if i just egg out the holes a little on my manifold so that the holes line up and i can get it bolted back on will i be fine to ride it?

thanks!

 

[RJ Gleason]

^^^^^^^^^
Yes you can.

 

[jamesu9165]

Well, I think I know why it cracked. It is a combination of it not being bolted down and the ball it sits on is missing.

i'm always loosing that damn ball and then finding it in the bottom of the belly pan.. think i might glue it in