Basically, I have a Direct Bikes DB125T-E and a few weeks ago it started having problems. First of all it would struggle to pull away, you could give it full revs but it would only feel like quarter revs, then after a few seconds it would kick in and run normal again, not a problem. But a week or two after that it got to the point where it wouldn't go past 30mph, even though before it could sit at 70. Naturally I bought a new carb and then things seemed to get worse. It would be really hard to start (although tbf, it has always been difficult to start) and when it did eventually start after a painstaking amount of time, it would pour out blue/black smoke and if you give it full revs it would just bog and die, the only way it would stay running is if you give it gentle revs, let off, then rev again and so on. Yesterday I bought a 150cc kit and a new air filter box and installed them and it hasn't started yet. It turns over fine but it wont start. I've checked spark, compression and fuel and everything seems fine. I've heard a few people saying that the valves can be a common problem but tbh I feel as though something else is at fault.
So to sum things up, it has a new carb, piston/barrel, airbox, filter, spark plug, fuel and oil, but still won't start!
UPDATE: Right, I've replaced parts etc and now its starting but it cuts out if you give it full throttle and it also wont start unless its on its centre stand. What to do next?
Since you installed a new cylinder are you sure your timing is correct?
Yeah like Joey says, are you sure? You have to make sure to set them at very small gaps (0.003 to 0.005 in. are what valves are usually set to) so you can't really guess on it or you'll end up with a useless bike until it is done right.
Replace the fuel petcock, they are easy to replace. i actually got a manual fuel petcock made for lawn mowers at advancedautoparts nearby and it hasn't let me down since. I find a lot o lawnmower parts work with scooters, even the lawn mower solenoids!
Another way to check if it is the vacuum fuel pump, take a 20oz bottle drill a hole in the lid to put a fuel hose thru, seal it with something so it doesn't leak, put the fuel line onto the carb, fill the bottle somewhat turn upside down so the gas goes into the carb and try to start. If it starts and doesn't seem to have a problem revving or starting you know your only issue is the pump, but also check to make sure the vacuum lines are good no tears or breaks. If you have a vacuum leak there might not be enough to operate the fuel pump.
1985 kawasaki 750 bobber
retired (2013 Jonway 150cc scooter 11pole stator, red racing cdi, and red coil, uni filter. 102 main 45 pilot jets. Micheline City Grip 130/70/13 tires.)
I finally just went and got a manual petcock instead of the vacuum one it saves me a lot of worry. Now I only have the vacuum line to the carb decelerator and one to the pair system which ill get rid of as soon as I get a block off plate. Its gona be nice clean and simple in my engine bay less stuff to go wrong