engine failure!!!

[JDR215]

hi, riding my bike at the track the other day, all was going really good, then the engine just stopped, bit like a fouled plug. I pulled the motor apart and it looked like something had gone through it. There were indentations all in the head, and golden, brass like specs and shavings in the motor. the piston and rings are all in good condition, (besides the score mark which is roughly 2mm wide). the score mark is also on both sides of the barrel, intake and exhaust. Does anybody know anything or heard of anything like this? My bike is a
'99' CR250, any help is gretly appreciated, so until i get my bike fixed, blast a berm 4 me!!!

[Michael Parker]

my old 125 did this twice. basically the reason for this is BAD GAS, i really dont care what anyone else has to say, trust me, when you get your bike fixed run race gas in it and i guaruntee it will not happen again.

[char393]

well there ya go, guess when you get your bike fixed, run it on race gas..next time it grenades, you can send michael parker the bill.

[kuritaro9]

since there were brass shavings, i would venture to say that the crank failed. mainly, the brass thrust washers, causing the rod to have too much side to side movement, until it finally grenaded...and the indentations in the head could be from the bike detonating.did you here any sounds like pfftt pfftt...? i know it sounds strange, but that is one of the sounds a bike on the verge of a seizure makes...

[Keetoman393]

If the brass rod bearing wore out, you would also get up and down free play with the piston which would cause it to hit the head. Take Michael Parker's guarantee!

[Michael Parker]

Originally Posted by kdxchar393

well there ya go, guess when you get your bike fixed, run it on race gas..next time it grenades, you can send michael parker the bill.

like i said, i dont care what anyone else says.
ive had a bike do this twice and after switching to race gas, it never happened again.
unless someone else has had this happen and can offer a solution more proven then mine, i dont care what you all think.

[kuritaro9]

Originally Posted by Michael Parker

like i said, i dont care what anyone else says.
ive had a bike do this twice and after switching to race gas, it never happened again.
unless someone else has had this happen and can offer a solution more proven then mine, i dont care what you all think.

you are partly right when you say race gas fixed the problem with blowing your cranks. the jetting in your bike was probably very lean, thats why the race gas tended not to blow the bike up. when you run race gas, its not unusual to go 4 or 5 sizes leaner on the jets. but with that same jetting using pump gas, you would have way too lean, and more than likely, thats why the crank blew up.

however, racegas is not the be all-end all solution to blowing up motors. a stock motor and even some modified motors wil run just fine with regular gas and some minor jetting changes. all the race gas in the world wont fix a bike that has a poorly set up carb. and sometimes, cranks just go. esp. on bike that have a lot of time on them.

now as far as not caring what anybody thinks, thats your perogitive, but its kind of a negative way to approach a public forum. i dont think people were flaming you for your suggestion, it sounded more like people were just poking a little fun at it. really not something to get bent out of shape over.

anyway, you were in fact, partly right on your solution...

[Aus_Rider_22]

Good post Kuri

Although fuel may have some impact on a bike performing poor or breaking, it won't miraculously solve the overall problem or state of the bike.

No-one tried to flame/put you down, Michael.

[JDR215]

ive also found a small piece of steel in my exaust pipe, it is roughly 2x2x6mm
in dimensions. My crank doesnt feel like it has any free play up or down, it matches the score marks in the piston, but i cant work out what it could be from, one theory i have is, it is part a spark plug, but my recent plugs are all in good condition, maybe i changed 1 and didnt notice, i dont know. it still doesnt explain the brass though, unless the crank bearing is rooted as well.
i plan on stripping it right down and having a good look, not worth putting it back together to have it fail again. And ive checked my carby, and there is nothing which would indicate bad fuel, but thanks 4 the info anyway. Still if u have any theories let me know, at least my 50 is still goin!

[kuritaro9]

if there are chunks of brass, then its more than likely the crank thrust washers that have been shelled. that is the only source of brass in that area of the motor that i can think of off hand.
is the motor seized up? you probably have some bits of aluminum from the piston in the pipe from the score marks. you may have got lucky on the cylinder. i had a few seize up, and on occasion, with some careful cleaning and inspection, i was able to remove all of the deposited alum. on the cyl. walls, only to find that the nikasil plating was still in great shape. getting it off though was the pain.i think i used muriatic acid to clean mine.

[JDR215]

it didnt seize, the rings jus got jammed in 1 side of the piston so it lost all compression, its not a piece of piston, its a magnetic steel of some type. the cylinder has a groove in it, wen i get some spare time, (and some cash) i wil strip it down and replace the bearings, and suss it out. thanks everybody for ur feedback.

[kuritaro9]

if you get a chance to look at the piston, see if you can find the ring locating pin. if it was a stock piston, its possible it could have fallen out, and allowed the rings to rotate in the grooves, catching one of the ports.
also, take a few detailed pics if you can, and post them.

[boogieonmyfinger]

Originally Posted by JDR215

ive also found a small piece of steel in my exaust pipe, it is roughly 2x2x6mm
in dimensions.

Just pour race gas on it, and it will go away. I also guarantee it. No one will dare question my authority on this. Even if you do, that doesn't make you right. I have more proof.

[boogieonmyfinger]

Originally Posted by Michael Parker

like i said, i dont care what anyone else says.
ive had a bike do this twice and after switching to race gas, it never happened again.
unless someone else has had this happen and can offer a solution more proven then mine, i dont care what you all think.

Will you take a job as my personal mechanic? I can only pay you 75 grand a year, though.:

[drajasingam]

I think a similar failure happened to my CR125 before I bought it. The head was covered in dings from shrapnel, and the crank lower end was all over the place. Somebody did a quicky rebuild on it and then sold it, then I ended up with it after another owner. To fix it properly, you'll need to do a bottom and top end rebuild. Depending on the condition of the cylinder bore, you may need to bore and sleeve it, or replace the cylinder.

[chaz24367]

I am currently rebuilding a 1994 that the same exact thing happened to.

I split the case last night and the lower connecting rod bearing (which does not have very much up & down play in it) looks like it is actually missing a few of the rollers in the bearing.