Vento dont like cold weather.
 

Since my Tao Tao daily driver got destoyed,I have been riding my 2003 Vento that I usually ride in the summer. The problem is that it absolutly will not start if the temps fall below 28 degrees. Above 28 degrees it starts and runs fine. The Vento has 15000 miles on it with the original cylinder and piston. I have checked the carb and enrichener and all is proper with them. With the amount of miles I am thinking it is time for a new top end. Could that be the reason it wont start when its below 28 degrees? Low compression? Thanks.

Sounds plausible..as the engine when cold needs more compression and hotter spark to ignite a frigid air/fuel mixture..whereas a warmer charge of air/fuel ignites much faster. Have you done a compression check?..;)

Today I rounded up a compression tester. It confirms that the compression is indeed on the low side. That's ok because now I have a good reason to get the BBK and pipe I have wanted to do. It is sort of interesting how much temp changes can affect how an engine will run. My take is that as temps decrease,metal contracts,thus increasing clearances between the piston rings and cylinder walls. In my case once that happens when the temps are a certain point my compression goes away through the increased clearances causing a not enough compression to run. I may not be right but it is the only thing I can think of right now.

I think you are correct. I have found that when the temp drops below 30 degrees..I cannot press out wristpins from pistons to do a rebuild or BBK for a customer. I have to turn the heat on in the shop and then they slip right out. When replacing crank bearings I heat the cases and freeze the bearings and the glide right in. Trying them both at room temp..they will not fit in. Also a note on 2T engines and cold weather. Pull your oil line at 70 degrees and the oil runs like water..pull it at 30 or below and the oil barely drips out..it's almost like honey. Which means you could also get dry starts and runs if the pump cannot move the oil. I never have this problem with synthetic 2T oil and in fact it flows like water even at 10 degrees or so outside..which is why I use it in my Scoots and Snowmobile.:tup:

When is the last time you adjusted the valves?
If they are properly adjusted and you still have low compression, then it probably is time for that new top end.