Oversized Pistons???

[ElstarB2Rider]

hi guys
im just wondering i own a bike with a zongshen 250cc pushrod engine and it blows heaps of smoke! what i want to know is will getting new standard sized rings fix it or because the bore/cylinder might be worn do i have to go to an over sized piston and if this is the case do they make oversized pistons & rings??
also does anyone know the cylinder wear service limit for the 250, and ring end gap?
cheers

 

[sean01]

only the person that pulls it apart and inspects will know what it needs.
as for piston size availability... iv never seen an oversized piston for a china engine you may be lucky enough to find a piston on akunar's site.

there is no guide line in writing as to the wear limit and ring gap for any china engines that i have seen.
the engine is probably based off the xr250 engine
i would expect .003/.004 bore wear is extreme. but you would wana measure a new piston to get the clearance...
almost always guaranteed that the piston will have collapsed skirts.
anyways here is the xr250 specs

 

[Cactus Jack]

Elstar products should be able to help ...

Engine Components : Elstar Products, Factory-tuned Racing Motorbikes ATV (Quad Bikes), aftersale support, spare parts and accessories. An agent for Apollo motorbikes, Orion, Elstar Motorbikes Shineray. High-quality parts by FastAce, Motul, RK, Ariete

IF the bore's not out of spec or scored , you could give the cylinder a light hone and fit a new piston and rings or maybe just new rings ... IF not , you might be able to go up 1 mm ... You have to know the pin size , pin height , skirt length and bore clean up size ...

Maybe the rings have just worn and the oil is escaping thru excessive end gaps ???? ... It can also leak thru bad guide seals ... but that usually shows up as a white puff on start up or when you first hit the throttle and it goes away as the revs increase ... a bad inlet valve seal can cause grey smoke when you chop the throttle on deceleration ... If it gets worse as the engine revs up (white smoke) ... it's definitely the rings ...

As an El Cheapo option you can buy thicker "No Smoke" oil such as STP or Wynn's ... LOL ...

 

[dacoffee]

can you get a sleeve for them like diesel engines? no smoke is as good as getting a no smoking sticker put on side, hey funny if that worked. check see if there is a lip ontop of cylinder if there is get new cylinder if not take it to engine rebuilder and get them to check size, they do it every day.....

or you can check compression, i think its check it then do it with oil and if its higher with oil then rings are worn...that might be a better starting point, you can use any engine oil or 2 stroke oil. need to wait like 5 minutes but not wait 30 minutes is too long.
hope that helps

 

[headsmess]

wet sleeve or dry sleeve?

not really enough meat in the suckers to justify sleeving...

that no smoke solution sounds like a winner

or try no oil no oil = no smoke

 

[Cactus Jack]

Wynn's Supreme Stop Smoke - 325ml - Supercheap Auto

STP Smoke Treatment - 428ml - Supercheap Auto

Nulon Stop Smoke - 500ml - Supercheap Auto

 

[corey58]

not trying to be a smart arse, but i been told and read a few times now, the oil companys that spend and make billions from there oil products, if there were such additives to make the oil better then there competior and sell more, they would be already be added? such as Stop Leak,Stop Smoke, extra anti wear so on?

 

[headsmess]

as one person said to me...if you could put bearings in a bottle, there wouldnt be such things as ballbearings etc... in relation to these "lubrication enhancers"

um, about the additives...they may stop the smoke(slightly) but at the loss of lubricative qualities...

i think its cactus being the smart ass

is this gunna be one of these threads again?

cactus answered it in his first post with the link to elstar...so now its time for silly buggers

 

[Cactus Jack]

I threw the stop smoke oil in as a last resort alternative ... I don't listen to hearsay ... ie what a mates lesbian sisters girlfriends brothers poofta mate says ...

I've actually used all that stuff including Nulon Teflon treatment ... and it works ... IF it doesn't work ... then perhaps those expert oil companies can explain how the companies selling the products can survive in the market place for over 20 plus years ?????? ... IF something is no good , word of mouth will ensure that it doesn't sell and dies a quick death ... and the sellers disappear very , very quickly ...

 

[thump*140]

sorry but i have to agree with cactus on this one... have tried a couple of "stop smoke" fixers in my time, with a couple of them having success... Roil (spelling???) is another one, and few old cocky mates swear by it.... Having worked for SEVERAL multinational oil companies, they are no different than any other business in the world. Their main aim, is to make money first, provide a service second... so naturally, why would they introduce a product that reduces the need to purchase their product?? if your engine burns oil, why would they make a product to go into your engine, that negates the need for you to spend further money on their product??
So, companies that CANT take on the hyooooooge multinational oil companies, use technology (something multinational oil companies are reknowned for) to conjure something that works both with your engine, and the oil that is in it... ultimately reducing you engines oil consumption.... thus cutting the profits of the company that provides that very engine oil..... happily as an offshoot to all this, you end up with an engine that doesnt smoke so much anymore, is better lubricated, and consequently has a longer life...
win for us really...