Oil burning problem Small Kids bike..(NGC)

[bigbikerrick]

Hello Folks, my "compadre" bought my 6 year old Godson Fernando, a little Yamaha TTr 50 trail bike for X mas. The kid has taken to it really well,its a 4 stroke forward mounted cylinder cute little bike with a 3 speed tranny and automatic clutch. A couple of days ago, it started smoking really bad,  its oil smoke, you can smell it,and see the white smoke out the exhaust.The plug is wet black with oil, but still sparks, inside of muffler opening is black,and "oily". It started all of a sudden, after running perfectly. The bike was purchased new,and only has about 20 hrs use, I did the first oil change a while back, and the oil level is fine,oil clean,no weird noises from engine, air filter is clean,but it currently runs crappy, lacking power,and idles poorly. These bikes are known for great reliability,and  can take abuse from kids. This one is almost like new,and has not been abused. It just fell outof warranty a couple months ago, so I am the one that will be getting it sorted for him.
  any ideas on where I start? Compression check? Leakdown test? What could possibly cause a sudden oil burning issue all of a sudden like that?
This little fellow, rides mostly around a little track that his dad made for him outside his house in the outskirts of Tucson, but he also wants to go out desert trail riding with me when his skills get better, etc. His dad uses a side by side mostly, so he will be my riding buddy as he gets more familiar with the bike.
  He is bummed, as he is used to riding his little bike every day, especially now that all the kids are mostly staying close to home. I am open to any suggestions where to start looking.
Thanks
Rick.

[oldbike54]

 If it is smoking that badly and running poorly and it happened suddenly , it is likely a broken piston ring or a scored cylinder wall from a wrist pin that has slipped .

 Dusty

[Muzz]

If it is smoking that badly and running poorly and it happened suddenly , it is likely a broken piston ring or a scored cylinder wall from a wrist pin that has slipped .

 Dusty

My thoughts too.

[Moparnut72]

Me three. Sounds like a ring to me. My lawnmower did the same thing a couple of months ago. I haven't looked into it yet, just replaced it for now. All wheel drive Husky so worth looking into it this winter before I junk it.
kk

[Kiwi_Roy]

I guess your Godson is going to learn how to wrench as well as ride, may be a life changing experience.

[s1120]

I guess your Godson is going to learn how to wrench as well as ride, may be a life changing experience.

This!  Back in the day you couldn't own a trail bike without haveing to do some major repairs off and on on them. Granted they were two strokes and a lot lest work to do top ends on!! 

[berniebee]

Before you take the engine apart, check the air filter box for oil. (I know you said the air filter is clean but...)
Many trail bikes start smoking after being crashed (Or even just laid down on the side.) because engine oil will flow through the engine breather into the air box, where it gets sucked into the combustion chamber.   

Also ( I didn't see it mentioned) a bad valve guide can also cause smoking.

If the smoke appears mostly on acceleration --> piston rings.
If the smoke appears mostly on the over run -->  valve guide/seals

If the smoke appeared suddenly (ie: from one ride to the next) it's probably a broken ring or oil in the air filter box.

[Sasquatch Jim]

It's broke, fix it.

[bigbikerrick]

Hi Folks I just wanted to follow up here, I finally had a chance to go to my little buddies house and look at his bike.What BernieBee wrote has stayed in my mind, so I re checked the air box,and found some oil in there from the breather. The oil was very clean,and almost invisible , unless you look really close.
  In questioning the owner, he told me the bike had "stalled"  in the middle of one of the berms on the little track he rides,and the bike layed down for a while in an almost upside down position, due to the berms wall. He had to wait for his older brother to help him lift the bike etc. This scenario happened 2 times according to him, except the second time he was able to lift the bike himself! 
  Anyway, I cleaned everything up, installed a new plug, got on the little bike myself,and ran it down the road, giving it an "Italian tune up" its now running very well.
Thanks to all for the help, I appreciate it, and am very happy not to have to tear into this little engine!
Rick.

[oldbike54]

 

 Dusty

[Muzz]

Good gnus.

[nc43bsa]

Good gnus.

Thank ewe!

[usedtobefast]

That makes way more sense than a broken internal engine parts.  Those things should take a ton of abuse and keep on going.

Plus if a kid says it fell over once, maybe twice ... figure it fell over a dozen times!!   

Glad it is all sorted out with min trouble.

[80CX100]

Rick, you gotta love it when the cheap easy fixes work 

I don't know if it was the Queen Mother or Epstein that coined the phrase, "That's just Dandy Andy" 

Would've been nice to have a photo of you doing the Italian tune up and the smile on the young lad's face as his bike didn't blow up,lol.

Glad the young lad is riding, not wrenching

Good on you

 

[lucky phil]

Hi Folks I just wanted to follow up here, I finally had a chance to go to my little buddies house and look at his bike.What BernieBee wrote has stayed in my mind, so I re checked the air box,and found some oil in there from the breather. The oil was very clean,and almost invisible , unless you look really close.
  In questioning the owner, he told me the bike had "stalled"  in the middle of one of the berms on the little track he rides,and the bike layed down for a while in an almost upside down position, due to the berms wall. He had to wait for his older brother to help him lift the bike etc. This scenario happened 2 times according to him, except the second time he was able to lift the bike himself! 
  Anyway, I cleaned everything up, installed a new plug, got on the little bike myself,and ran it down the road, giving it an "Italian tune up" its now running very well.
Thanks to all for the help, I appreciate it, and am very happy not to have to tear into this little engine!
Rick.

Excellent news. Yes it's the classic issue. When I worked in a large hardware store for a short time recently I had an irate customer bring in a new petrol engineed pressure washer complaining it had seized, he was quite irate about it. It did indeed not turn over ans with a "see I told you so" demanded his money back. I asked him to wait and went to the tool section and came back with a plug spanner and pulled the plug and pulled the start cord. Oil burped out of the cylinder and away it turned and started. How did you transport this I asked and he said in the back of his SUV. Laying on its side, obviously? Well yes was the reply. So the problem has been operator induced then and its fine now so you wont be needing any refund. I felt the need to slam dunk him due not so much being dumb but being "irate" and dumb.

Ciao

[berniebee]

Glad it worked out. I think Godson Fernando owes me a beer!     

[Sasquatch Jim]

Apparently itsnot broke.