Skirt collapse?

[wbks]

if a two stroke has a skirt colapse in one cylender but is stil running: besides a screwed piston and likely barrel sleeve, is there likely any damage done to the gearbox or anything? I'm about to go look at a 250 2S but i cant really afford to do a new engine only top end rebuild so any advice or help would help

[racefactory]

well, where did the skirt debris go? Fuck with the crank a bit and out the exhaust port possibly?

How can it damage the gearbox?

[wbks]

About the crank... That must be a little trouble to replace if it is damaged, huh? btw says i must spread some around before giving rep to you again. ill get around to it

[FJRider]

Lots and lots and of very small... and some, not as small, bits of metal (aluminium ???), ready and able to flow out the sump plug. All that gritty soft powdery metal, flowing around the bits that get oiled, with the oil ...how could that possibly damage the gearbox... yeah right... :doh:

[Ixion]

'Tis a two stroke. No sump. No oil. No connection at all between the crankcase and the gearbox. But if the piston has totally collapsed there may be little bits of alloy (and little bits of broken ring, which is worse) through the crank and mains. And they can mess up the crank seals. But also, "collapsed piston skirt" is a bit vague. Often if the piston lets go big time, it tends to take the little end and maybe the conrod with it. And often as not the big end too. But, other times, just a chunk breaks off, tootles away down the exhaust port, and no real harm at all. No way to know until the barrel's off.

Gearbox will be fine. Crank is the question. It is an iron sleeve barrel? Not a chrome jobby?

EDIT: DOn't forget that the ringa-dinga-ding forum is the obligatory place to post huge pictures of fucked pistons. We're getting quite a nice collection. Two smokers. It's what they do, is why we luvs them so :love:

[wbks]

Eelracing said its 'nikosil' i think. I would like to hope it is just gone out the port. He said it was still running just gutless on one cylinder. Can you get a full damage report of the crank without splitting the casings (which i'll assume is a job only for experienced bike mechanics)? Cause I'm pretty sure he's got the barrel off to tell it had colapsed but then he should know if it has a scarred barrel or not. Not sure. May go and take a look as he said I can take the engine apart if I want. I can do top end rebuilds fine but anything more complicated and im fucked.

[Ixion]

Nikasil is chrome. If that's damaged you're fucked. But if it's still running even vaguely on that cylinder, then odds are it's only a holed piston (combustion eats away the top of the piston, so the gas escapes away out the exhaust port. No broken bits to damage the crank or bottom end. ) Have a look in the ringa-dings-ding forum we have a nice assortment of fucked pistons . Mostly, just fit a new piston and rings and away you go. Experienced two smokers cna do it by the road side, and carry a spare piston with them.

It's when the bloody power valvees break up and fall into the bore that the barrel gets rooted.

[wbks]

Ok so I can take the barrel off and take a look at it, asses that it is fine and see that the piston is well rooted. But how do I know for sure that the rest of the bike is going to be fine? Because if it just needs rings, piston and thats it then this is a bargain. But if I do get it and it turns out to be fucked then I will be stuck with an unridable bike that i will only loose money on selling. Worst case scenario though, if the crank is screwed, does that mean both need replacing and how much is that?

[Ixion]

New piston, $100 - $200 usually. New chrome barrel ? Don't ask. New crank (so long as it's not a Honda), maybe $1K+. Rest is unlikely to be affected by the collpase, though of course, since it's not running, you won't know if the box,clutch,electrics etc are any good

But, of course, if the piston looks like this (http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=108934&d=1225126917), then that's another matter. Now that *is* a collapsed skirt.

[racefactory]

Lots and lots and of very small... and some, not as small, bits of metal (aluminium ???), ready and able to flow out the sump plug. All that gritty soft powdery metal, flowing around the bits that get oiled, with the oil ...how could that possibly damage the gearbox... yeah right... :doh:

2 stroke dude...

doh!!

[FJRider]

I stand corrected... but I shudder at the thought of any "loose" metal floating around where it ought not to be.

[wbks]

barrel...450ish? it had better be because thats what the seller just said. It only has 10800 ks on it and he says was running fine untill he tore it down so it should be fine otherwise. Not sure I should risk it if its going to be 1k+ if the crank turns out to be screwed. I've got an idea. Do you think it is a good idea to convince the owner to let me get someone to completely check it out? What do you think?

[racefactory]

This all depends on what bike it is? ie. if it's a tzr250 3xv then it's like rocking horse shit to find this shit... and very expensive too.

if it's a RGV VJ22 well that's a totally different story, your drowning in spare cylinders pistons etc etc.

shouldnt worry about rings and piston they are not hard to find and not too expensive generally but like the other guy said it's the fucking crank. If you buy a brand new crank expect it to set you back nearly 1 grand. However if it's an rgv, fuck you just need to do a little searching and you'll find something.

who knows though... it may not ahve done anything? when it comes to 2 strokes... i reckon just get that thing a cylinder from wreckers get a new piston and ring and be done with it. you'll know about it if there's something wrong with the crank... That's the thing with 2 strokes you just keep replacing the shit dont you? start the bike and listen for knocking and rumbling from the bottom end.

but from some prior research... getting the crank split... new parts... labour... costs as much as getting a new crank. wreckers/second hand i say.

[wbks]

Yea well its a VJ23 if my rgv lingo is right. its just the crank im worrying about. So if I get a crank for say 1k then ive spent over 4k on it so the purpose of getting a cheap bargain is defeated.

[wbks]

eyeyeye i dont know what to do

[racefactory]

well you in luck... rgv engine parts are easy to get hold of. just call a couple places you'll find something in no time.

you'll know about it if the crank is on the way out... start it and listen for rumbling and knocking.

[wbks]

Yea but for how much say a crank?

[racefactory]

not sure but seen them on trademe so i wouldn't fret at the cost. should be able to get something for less than 500 surely? Call a wrecker tomorrow and find out.

[wbks]

Ok will do. Hopefully it is reasonably cheap. But is bying a used crank realy a good idea? Like do they last a life time for the bikes untill they are damaged through blow ups like this or are they changed every # kms as well?

[speedpro]

With the barrell off, if it looks like my avatar, it's screwed. What's left of the piston is still there. It's just hard to see.

[wbks]

Surely I could see it when i check it out though... So what do you guys think...Check it out, make sure the barrel is not screwed and if not its sweet? And is taking the barrel off on these bikes simple? Like simple as taking one off a single cylender two stroke dirt bike? Or is there more to it?

[Ixion]

Two stroke cranks last longer than top ends. But not as long as fourstrokes (I'm talking modern ones, not the older generation, some of them went more or less for ever).

If you ride a two stroke you just need to reckon on, and budget for, replacing these things regularly. Almost all two smokers will have been ridden hard, really hard. And when they go , it can be either ho-hum, 5 hundy bucks and all good, or oh shit.

I guess in round terms, a top end each year, two if you're unlucky, and a bottom end every two or three top ends. Unless you're unlucky. Luck comes into a lot with a two smoker.

They're expensive because everyone wants one. Supply and demand. No new ones, learners want them cos they go fast (which reduces the supply still more, cos the learners crash them); experienced riders want them, cos , um cos, uh shit, I dunno why two smokers are so appealing, they just are.

[wbks]

Bottom end every 2-3 top ends as in new crankshaft? Maybe I'm too poor for a two stroke. 1994 rgv250's go for say 5500 and this one is 3. But after $700 worth of rebuild and possibly $500 for a second hand crank it is just about the same price as a running one only newer. Should I just buy a running one even though it is more expensive and has more km's on it?

[Ixion]

Yes, but you could buy the running one, and a month later have the top end go. Two strokes are not known for predictability. And factored over the time, the cost is not that great. If you do say 25000km per year, a topend each year and a crank after three, thats only a bit over a thou a year. And you may be lucky, some folk get better mileages (of course, some also get less) . And you can normally do it yourself, so you have no labour costs.

But, all in all, noone should buy a high perfromance two stroke because they think it will be cheap transport. (AG100s are another matter). It's a labour of love.

(I suspect part of the reason two strokes are dear at the dealers is because a wise dealer is going to factor in a margin to cover the buyer who comes back after a month with a blown motor. I I were a dealer I'd want a lot more margin out of a two stroke than a four stroke.)

[wbks]

So if you need to replace cranks then surely its not a good idea to buy a used one that likely already has a lot of kms on it? How can i get a faster bike before i get my full:eek5: I'm half way to buying a 400 and putting 250 stickers on it. But even that must be slower and badder handling then the two stroke. And whats the 'ringa ding ding' forum you talked about?

[Ixion]

Probably not really. A used low mileage one might be OK. Or if you just needed a cheapy to get the bike going and flog it off. But trying to scrimp on parts for two strokes tends to some back and bite you on the bum. They cost to run, just something one needs to accept.