450 has me at the end of my witts

A bad crank bearing wouldn't keep it from starting tho...thats my only reoccuring thought.

Try this: with the seat off and the air cleaner off, spray some starting fluid in the airbox and kick it and see if it fires. If it does and runs for a second or two, its gotta be the carb (even as unlikely as that seems now) if it does run, do you know somebody you can borrow a carb from?

Why wouldnt the bad crank bearing keep it from starting?

And I will try the starting fluid idea.

But if it is the carb.. I have no way to obtain another one. The reason I belive its not the carb is the fact that I should be able to get it to run somewhere. That and It cut out at at almost WOT but then will not start. Also I had it running a few times, it seems like it wants to run and the head pipe gets warm but it seems like it just doesnt wanna keep it up.

Mine died much like yours with no warning. It then started 2 or 3 times and died again. At this point I kicked and kicked and it fired, but died quickly. I checked EVERYTHING over and all looked fine, except it wouldn't stay running.

I noticed that it was getting harder to kick over so I started the tear down. Head was fine, valves in spec, piston top looked great. When I pulled the cylinder is when I noticed the connecting rod bearing was very stiff and it was binding up when turning over the motor.

A bad crank bearing wouldn't keep it from starting tho...thats my only reoccuring thought.

Mine would not run, or start correctly with the spent bearing. :applause:

So if yours is still turning over freely and you can't feel any tightness in the crank assembly, then it's probably not what's ailing it.

Alright I took the motor apart and praised Jesus at the fact that the crank bearing was indeed beautiful.

My piston however is mighty ****ed up. Doesnt look like I got dirt in the motor looks like the aluminum melted off and stuck to the bore on the intake side of the piston and is highly polished in a quarter sized spot on the exaust side.

My friend who is very proficient with motors thinks the bike was beat on before it was warmed up too often.

I will try and get you guys some pictures tomarrow.

A few questions though

Is the bore coated with nikasil?

and if so how can I get the aluminum thats stuck to the cylender off without hurting the coating.

Also you wouldnt happen to know how big you can go and still race legaly, I belive its 2mm?

Thanks guys

Good deal on the lower end being intact :applause:

how can I get the aluminum thats stuck to the cylender off without hurting the coating

I've used straight muriatic acid in the past. It's nasty stuff, but it will eat the aluminum away and not hurt the nicasil.

Melted aluminum jets are in there :ride: 2mm big bore 470 :applause: go for it! you can get bigger 488 or 501 or 524 :p OH here is something else to look at cam chain tensioner they like to fail too

Sounds like you ran it low on oil.......or sustained high RPMs

Alright I took the motor apart and praised Jesus at the fact that the crank bearing was indeed beautiful.

My piston however is mighty ****ed up. Doesnt look like I got dirt in the motor looks like the aluminum melted off and stuck to the bore on the intake side of the piston and is highly polished in a quarter sized spot on the exaust side.

My friend who is very proficient with motors thinks the bike was beat on before it was warmed up too often.

I will try and get you guys some pictures tomarrow.

A few questions though

Is the bore coated with nikasil?

and if so how can I get the aluminum thats stuck to the cylender off without hurting the coating.

Also you wouldnt happen to know how big you can go and still race legaly, I belive its 2mm?

Thanks guys

It is a Nikasil bore. And that stuff is really really hard. I wouldnt be surprised if you were able to pick the crap off it iwth a razor knife and clean it up with a hone and run it. The hone wont get the nikasil. The stuff is just way too damn hard. But it'll clean the aluminum transfer off and let you inspect it to see if you damaged it beyond a "simple clean up and run" would warrant.

It should have still started. You still had compression. Was the metal from the piston? Did it detonate? I'd make sure that carb. and boot are perfect before it all goes back together.

I've used straight muriatic acid in the past. It's nasty stuff, but it will eat the aluminum away and not hurt the nicasil.

Yep that is the stuff. :applause:

Was the piston scored on 4 couners from being cold seized? Do 4 strokes do that also?

It should have still started. You still had compression. Was the metal from the piston? Did it detonate? I'd make sure that carb. and boot are perfect before it all goes back together.

From what he described I'd bet what felt like compression was the piston siezing in the bore but there really wasnt enough compression to allow it to run.

The piston was polished on in one quarter sized spot on the exaust side. and on the cylender. And on the intake side the piston melted and even with muriatic acid couldnt get the bore into shape.. still was rough and had one hole in it. Not cool bores ****ed so Im gettin the thing resleved sometime this week. Let you guys in on the details as I get them. Also if you could tell me your opinions on the 13:1 piston let me know

thanks guys

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