beewee

Thank you, does seem strange to have an air leak in system on new bike. It ran sooo sweet and gave no indication of air fuel imbalance. I accept what you say about leanout, and really im just as stumped as the dealer was when this first happened.

Never run out of fuel, and both meltdowns happened at part throttle. I have been sooooo careful about fuel and oil levels, I would not try to kill a new machine, I depend on this bike too much.

My understanding is that leanout causes most damage to piston top rather than the side of piston. Jetting is factory so surely it has been tested as appropriate.

Thank you, yes I do understand what you are saying BUT because this is now a double meltdown I am going to leave it to the dealer who has said he will contact Yamaha New Zealand for any options. I am now so nervous about this bike I cannot trust it as it is.

Thank you for the great suggestion, I am VERY tempted. This is sooooo disapointing.

This is a brand new machine, if the timing is out I need a HONDA

This is a brand new scooter (4 months use)If the exhaust port needs chamfering to prevent ring bind I am amazed. 2 stroke engines have been around for over 100 years, and if yamaha havn't figured out the bugs they should not be selling them. The spark plug was fitted by dealer at first service and is therefore correct. I will not modify any part of this engine or move away from factory fitted parts. My suspicion is with the oiler system perhaps being faulty. I am a car mechanic so understand the basics of the two stroke principal. I do not have a picture of the first piston damage, but did see it. The damage extended from the top ring down past the bottom ring, and was approx half an inch across and lined up with the exhaust port. I will bet bucks that the replacment piston shows the same damage when it is removed. I have riden this scooter from new as per instructions in hand book, and love the scooter. Its just the engine that is now the letdown.

I have a 4 month old yw 100cc 2 stroke BeeWee scooter. At 1500 km it fried the piston. The damage was down the side of the piston over the rings where the exhaust port lines up. A new piston was fitted by the dealer (who is great) and off I go again. Another 1500-1600 km and Im riding along yesterday at only about 75kmh and the engine just died as though I turned off the key. Its done it again. The dealer was baffled by what caused the first melt down. After fitting the second piston (bore not damaged) he slightly opened up the auto oiler to improve lube to system. This scooter is 4 months old and has fried 2 pistons within 3400km, has anyone encountered a similar problem with these engines? As it was a new bike I have riden as per instructions for run in period (with both pistons)and this situation is now a nasty mystery. What the hell is going on with this engine? ps. I have only run Yamalube oil in the oil tank, and 91 octane gas in gas tank.