Modern Vespa

Hi all

Had my LX50 for just over a year now and I've loved riding it. Unfortunately it was stolen recently but I have managed to recover it. However, it's not in a good way. Aside from the missing badges and cut ignition loom, once I'd got it running again, the engine performance was way down.

I did a compression test and it was about 50 psi and not holding. Local dealership said I should be getting at least 100 - 150. So I bought a cylinder/piston kit and changed them out. It went together OK, and it ran afterwards. But I took it for a spin down the road and it died on me.

Did another compression test and it was down to about 50 again and not holding. On dismantling the new cylinder/piston, there are score marks down the piston. The cylinder looks OK though.

So the question is, what did I do wrong? I'm sure the rings were fitted correctly, and I oiled all the parts before I installed them. Could it be that it's not getting any oil? I'm sure the oil pump belt is intact as I noticed this when checking the drive belt. Can you tell if the oil pump is not working?

Could I get away with just changing out the piston again, and if so, any hints/tips to stop this happening again would be really helpful.

Thanks in advance

Can you post pics of the most recent seize marks on the piston and cylinder? We need to see what kind of seize it is, where the seize is (intake or exhaust side) and if you installed everything correctly. If its not that bad, you could probably get away with a light hone and new rings and just go easy on it.

As far as the pump is concerned, did you verify there is 2T oil in the tank? When you do get the scooter running again, run premix fuel though it and disconnect the oil line that goes into the carb (out from the pump). It wont pump a lot of oil but if you leave it disconnected for a while, you'll eventuallly see a puddle and can determine that the pump is in fact working.

Once everything is working as it should, you can drain the premix and go back to the oil pump.

You can get a good machine shop to rebore the cylinder, a couple of thousands...and get a overbored piston and rings, if you have a steel cylinder.....if you can not feel the score marks with your fingernail, you can just hone the cylinder, replace the rings, and this time, make sure your oil hose is working, without any bubbles of air, and connected to the carb right...I would use a premix the first couple of tanks of gas, make sure the premix gas is in the carb, before you start it back up.....Check the belt, and the cable that goes to the oil pump. Make sure the cable moves when you turn the throttle. The two arrows should match up with each other where the cable connects to the pump. There is an adjustment there, and if you put in a 70cc cylinder, you should move it to put more oil in the gas. Bleed that oil line!....If the oil line is hard and old, replace it, and make sure all the air is out of it, and use clamps.....And use good synthetic injection 2 stroke oil, it's so much better, none of that dino crap.... Make sure the oil jug says injection, and not pre-mix on it....

If bore is plated not iron new piston should be fine.