Piston issue + lean issue for the experts

[mmeadows]

reviving an old post

after looking at rubber o-rings on my carb, and the gasket on my cylinder head, im going to hope my piston melted due to an air leak( cant find a 17.5 areche carb and not to mention a set of jets to try, at least not for less than $150, and i'm thinking more like $60)

i'm splitting the case and replacing every gasket on the engine

don't think ill be replacing any bearings unless they look really worn.

[mmeadows]

can these ball type bearings become spun? i thought that only happened to car bearings. my crank is still rotating just fine as far as i can tell

what makes you suggest that?

[Trafficjamz]

spun bearing

I don't think a spun bearing is the problem.

[Pete M]

Couple of questions:
Do you know what the compression was prior to your piston failure?
Have you confirmed that the head was installed with the fins pointing in the correct position?

[mmeadows]

jacknbs: did you know the guy in that video you linked is also the guy from gold rush on the discovery channel? just a funny fact ( i like the show and his scooter vids)

i also felt that the lack of scratches on the cylinder was rather unique/ not a lean issue, but im replacing all my gaskets just in case.

why do you ask about spark plug gap?

do you think i will be able to visually check the status of my bearings? i might finish cracking my case tonight depending on how Easter unfolds.

pete m: i don't know what the compression was. it was a kind of a beat up motor that i bought from elietguy50 ( great guy) so im not sure about head orientation as i have now ripped the motor apart ( but does it even fit on the wrong way? that would change what side your exhaust is on)


the piston melted on a 15 ish mile ride, with 87 octane gas

[bakaracer]

jacknbs: did you know the guy in that video you linked is also the guy from gold rush on the discovery channel? just a funny fact ( i like the show and his scooter vids)

i also felt that the lack of scratches on the cylinder was rather unique/ not a lean issue, but im replacing all my gaskets just in case.

why do you ask about spark plug gap?

do you think i will be able to visually check the status of my bearings? i might finish cracking my case tonight depending on how Easter unfolds.

pete m: unfortunitly i don't know what the compression was. it was a kind of a beat up motor that i bought from elietguy50 ( great guy) so im not sure about head orientation as i have now ripped the motor apart ( but does it even fit on the wrong way? that would change what side your exhaust is on)

right there


everyone: is there a seal that stop air from leaving pass the crank bearings or is it just the pressure fit?

right there is your issue. your using 87 octane fuel. malossi recommends 95 or higher

[jeepmaned]

mmeadows yes it will fit on all four ways. You want to keep fins flowing from fan blade off crank/flywheel, and you will see too much offset if its wrong.

[mmeadows]

i know 87 isnt ideal but is it really a guarantee for disaster? i mean ive never read anything in a honda manual about it or anything.

[bakaracer]

i know 87 isnt ideal but is it really a guarantee for disaster? i mean ive never read anything in a honda manual about it or anything.

honda is not going to tell you about octane for hopped up motors. Its against the law to modify these bikes and ride them on the street. Thats why there is no mention of it. stock unmod motors you can use 87 octane. once you up the compression or put a bbk on. you need to run 92 or higher octane to resist detonation. thats what caused the hole in the piston. even upping the timing will cause that too.

[JJ Joseph]

Regular gas, lean mixture, WOT downhill (high rpms) will really overheat your unit. The way your motor comes from the factory, it runs cool at maybe 8,000rpm max. But if you open it up on both ends and wind it up to 10,000+rpm, you can really bake it. 2-strokes need more oil and richer mixture at high rpm.

[mmeadows]

a really light pre mix plus oil pump? as i had the engine apart for this repair, i opened up my intake ports on the case and my exhaust ports on the cylinder. so i imagine conditions are going to be more intense

[mmeadows]

It has recently come to my attention that the 83-84 aero cdi is unique. is it possible this is why my piston melted?