Hello from Cali, Colombia

[reyrob]

Hello and Merry Christmas to all Vespistas!

My name is Rob and I own a 1995 Bajaj Plus 150.
This is my first scooter of this type. I previously owned a Vespa GTS300 but never a 2 stroke mania one.
I recently changed the piston and cylinder and so far I rode approx. 500 miles.
I am having a problem and maybe, someone can help me.
When I ride for ver 30 minutes at a steady speed of 60km/h, the bike shots down immediately. I put it immediately in neutral and coast until I come to a full stop.
I then kick start it and the engine starts up immediately with no problems and it will ride for another while at the same speed until it stops again. There more I let it "rest" the longer I can ride at the same speed. I feel the the problems comes from the fact that cylinder and piston are new and with the heat they expand to the point that the piston no longer can travel in the cylinder. Does it make any sense?

I'd really appreciate if you guy can help me!

Thanks a lot!

[reyrob]

Anyone?

[henri]

hi n welcome to the forum . it does sound like your heat seizing your new barrel an piston .there are many causes for seizures ,timing/carb jetting/lack of 2 stroke oil. as its your 1st 2stroke you are aware that the engine needs 2 stroke oil aswell as petrol .an as its a new barrel maybe you havent run it in properly,or the piston was supplied to big . H

[reyrob]

Dec 27, 2015 17:12:01 GMT henri said:

hi n welcome to the forum . it does sound like your heat seizing your new barrel an piston .there are many causes for seizures ,timing/carb jetting/lack of 2 stroke oil. as its your 1st 2stroke you are aware that the engine needs 2 stroke oil aswell as petrol .an as its a new barrel maybe you havent run it in properly,or the piston was supplied to big . H

Hi Henry, thanks for your reply.

I am using the correct 2 stroke oil and the size of piston is the correct one. It came in a kit with the barrel and all the bits that go with it. I was told not to run the bike faster than 50km/h and I haven't. 
I'm adding more than the recommended 2-3% n2 stroke oil to the petrol mixture to ensure all is well lubricated but if I run the bike at 50km/h for more than 30  minutes, it seizes.

What to do?

[henri]

by adding more than 2% oil to your fuel you are upsetting the carburetor settings an causing it to run lean this will make motor run hot an seize .am afraid just changing fuel to 2% mix probably wont cure your problem now .as were it has seized will have marked the barrel an piston causing a rough spot that will rub an seize again . it needs cleaning up/hone-ing an piston polishing . H

[reyrob]

Dec 29, 2015 17:17:54 GMT henri said:

by adding more than 2% oil to your fuel you are upsetting the carburetor settings an causing it to run lean this will make motor run hot an seize .am afraid just changing fuel to 2% mix probably wont cure your problem now .as were it has seized will have marked the barrel an piston causing a rough spot that will rub an seize again . it needs cleaning up/hone-ing an piston polishing . H

Oh no!!! The mechanic told me to add more oil to the mixture!!!!!

[reyrob]

It only happens when i'm riding at a constant speed. After it happens, the engine starts immediately and sounds perfect. I'm assuming that if there was a damage, it would not sound as healthy as it does, or would it? :S