need help, white smoke

[anthony.sansom]

Hi guys

I bought a thumpstar dirt bike with a 250cc atomic engine (ZONGSHEN) pretty cheap
For my wife’s brother as a present, just sorting it out before I give it to him

the compression on the bike seems started within a few kicks with a new spark plug and fuel, starts 1st kick every time after

But blows allot of white smoke and gets worse when rev the bike, it also drips oil from the exhaust, I assume it’s the rings

The bike was lying on its side when I picked it up so it could also be that oil has got through the engine and up into the cam, bike had not been started for a long time.

Also engine is a little bit rately I think the cam chain may need adjusting or something

I also noticed when I drained the oil out it had a little bit of a silver colour to it, not a good sign, the was no big metal shavings in it could just be that the cam chain has been lose for a while and shaving metal of.

Ride and runs fin, only gave it a 30sec ride until I find out what the go is with it so I don’t damage anything further

Any advice thoughts and input would be greatly appreciated as I won’t to keep this as a cheap project

cheers

 

[Cactus Jack]

White smoke that gets worse as you rev it is usually caused by bad rings for sure ...

Elstars usually has the parts for Zongshens ... and they'd know how to adjust the cam chain ... I could tell you how if I saw some pics of the motor showing the adjusters ... If it has a cam chain then it's most likely got a bow type tensioner like most vertical Honda XL/XR's have ... Some vertical chinese engines have pushrods ...

At any rate you should check and re-adjust the rocker to valve stem clearances first as they can be the source of rattling sounds ...

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

Your oil colour sounds normal ... just change it , re-set the cam chain tensioner if it's a manual one , then take the bike for a ride ...

Make it lug from low revs in a taller gear to see if that helps to diminish the smoke blowing ... The load forces the rings out hard against the bore and could possibly help the ring seal if it's due to the bike sitting around unused for a long time ... If the ring end gaps are out of spec only a re-hone and new rings will help ...

It's also possible that it could be a head gasket leak from an oil gallery if someone has pulled the head off before and slapped it back together roughly (wishful thinking LOL) ...

 

[Cactus Jack]

Another rare possibility could be that the previous owner was stupid and was putting 2 stroke fuel into it ...

Now that'd REALLY put a smile on ya' dial if you changed the fuel and the James Bond smoke cloud from the exhaust stopped instantly ...

 

[FMX_22]

Another rare possibility could be that the previous owner was stupid and was putting 2 stroke fuel into it ...

Now that'd REALLY put a smile on ya' dial if you changed the fuel and the James Bond smoke cloud from the exhaust stopped instantly ...

Whats wrong with putting 2stroke fuel I a 4stroke races have being putting a cap full of 2stroke oil in the fuel for ageaz ??????

 

[Carlts]

Whats wrong with putting 2stroke fuel I a 4stroke races have being putting a cap full of 2stroke oil in the fuel for ageaz ??????

Please tell me thats sarcasm.....

 

[sean01]

lol, while that may be true its only a cap full not a proper premix of 40:1 or wat ever....they usually go like 100:1..

besides that tho the only thing that should be used in 4 stroke fuel is lead additive to extend the life of the valves and valve seats.

to the OP... another thing to try since you say the bike was found laying on its side is taking the exhaust off and degreasing the inside of the pipe.. its possible that oil has leaked past the valve seals and then into the exhaust header.. then once heated it starts to burn and gives your white smoke...

as cactus said tho... smoke under constant throttle is rings (or oil in exhaust), smoke between revs (rolling the throttle on and off) is valve seals/guides).

id be doing an oil change, then start and warm the bike for a few minutes and then hold the throttle at about half throttle for a little bit, with the occasional on off of the throttle.. if its in the pipe it should start to clear.. if it doesnt then rings are gone

 

[FMX_22]

Please tell me thats sarcasm.....

Nope no sarcasm there lol

 

[Cactus Jack]

Oil in the fuel of a 4 stroke can cause detonation ...

QUOTE [Oil. Another area that's often overlooked is detonation on one or two bores in lieu of all or most cylinders. It really takes a trained ear to determine this by the frequency of the knock and its sound. Then again, there's something particular to those bores only that is causing a problem. An often overlooked area is oil migration into the bore as a cause of detonation. If you're searching for the culprit, carefully examine the spark plugs under a magnifying glass. Oil originating at the valve guide area is a major contributor to single-cylinder detonation. Retarding of the timing may lessen this but will drastically diminish power output in all the normal combustion bores. Oil burning is a common cause of high RPM detonation. Oil has a very low Octane rating which detonates at high RPM.]

Detonation Explained

 

[anthony.sansom]

Thanks for the replies guys

Would like to keep this a cheap project as it is a present, im going to tackle changing the rings my self, is this a hard job, never done it before tho I am pretty handy careful and patient,

I would also like to adjust the cam chain and re-adjust the rocker to valve stem clearances as well tho doing these two things without doing it before may be a big task, is there any where I can get a complete guide on how to do all this and know what clearances ect are, and what tools I would need, I hate starting something and not having all tools on hand, would also like to replace any bolt I undo

Cheers again guys