2001 yz426f about to blow!

Let me start off by saying this post isn't related to one of my bikes (thank god). A buddy "Friend 2" of mine had recently picked up a 426 from another friend "Friend 1" after the motor began seizing up. Friend 2 is having his work cut out for him. I wanted to get this up to get some feedback from people who have had/dealt with this before. I am always interested in learning more about bikes if I can, and I've always believed it's easier to learn from others mistakes. I'm no mechanic so I won't be tinkering with the bike at all but I would like to get him pointed in the right direction if I can help. The bike was purchased used by "friend 1" and had some issues to start with (Idle was turned all the way off so the throttle had to be held open) but it was an easy fix. After finding out what it was I assumed it was set up that way because of some try hard that raced the thing to death. It ran fine for a while but then the real trouble began.


This is how it happened:

Friend 1 was riding very rocky trails for a few hours when on the way back to the truck the bike shut off in 3rd under power.

The kickstarter was locked up at this point.

My friend let the bike sit for around 20 minutes then it kicked and started again

He went to put it in gear, it died, and kickstart locked. end of his riding that day.

A few days afterward the same thing happened with starting but the kickstart became permalocked.


This was the point where my other buddy bought the bike with the intention of fixing it. (a little naive if you ask me)

He decided to take it to a local shop (that is notorious for doing low quality work) to see what the problem was.

They told him the rod bearing was shot.

They replaced the rod, the bearing, and gaskets for the top end as far as I know. (supposedly upgraded to a 448cc now too)

After the work was done he went to throw oil back in and said it was leaking (but apparently an o-ring fixed it)

So now the bike runs again.


Friend 1 and Friend 2 decided to go out for a ride yesterday and that's why I'm here lol.

Friend 1 said that the bike runs like a hot turd now. It is making a popping sound from the exhaust, and the entire head pipe is glowing red. I told Friend 1 that it was most likely a jetting issue but he doesn't think Friend 2 messed with the carb durring the rebuild. I'm just looking to get a little insight from some people with real experience. I would like to give a little better description of its current state but unfortunately I haven't seen the bike since it became permalocked. I appreciate the input and hope everyone else having this issue can get a little info from this post to help them out as well. 



A cc upgrade will ask for a carburator jetting ajustment also

A cc upgrade will ask for a carburator jetting ajustment also


Not necessarily.

 my pipe glows red when I give it heaps apparently it is normal due to the thin wall steal header, as for the popping under deceleration is also normal for a 426, I would however like all have said, clean the carb and try changing the fuel, if that does not work it may need a re jet to fix 

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