Carburetion Issues Today

Discussion in '2-Stroke Engines' started by Timbone, Nov 8, 2014.

  1. Timbone

    Timbone Active Member

    Today I ran around on the motorbike for a total of about 16 miles. Had issues with the carb all day. Different results with various choke settings and throttle positions.

    First, this is a high mileage engine that still performs like new with a good standard set up and all the systems appear to be fine. NT carb, NGK sparkplugrunning on a kit CDI. Good compression and a tight little muffler.

    The engine likes to cold start with full choke, needing about 10 pushes of the primer button. About half the time, a good roll and the engine will start on the first or second attempt. When the motor begins to run with full choke, I go to about 3/4throttle and find a sweet spot that makes it jump, I roll it just a bit, let off the throttle, then push the choke to full off, give the throttle a twist and then after maybe a bit of sputtering, the engine will start cycling and I'll be zipping very quickly down the road.

    Today after the cold start, the motor didn't want to run without choke, especially at first. Eventually, things got to normal and I got to top speed at about 7/8 throttle, as that is where the sweet spot was.

    Later in the trip, the engine was bogging down, not wanting to to advance no matter where the throttle was. I made some choke adjustments and I was able to get to top speed with full choke. I had two feelings about this: 1) the engine was running lean and 2) maybe there was some gunk in there clogging the fuel flow. Those were my feelings.

    I was eventually able to get decent performance without choke but the engine was not performing 100%.

    First maintenance issue: I removed the the air filter and it was soaked with fuel mix. There was a bit of dirt in there but it looked very clean. I used a clean rag completely dry out the sponge air filter and I cleaned all the dirt I could see inside the intake and the air filter housing. Please note (if you are still reading!) that the other side of the carb was completely clean and the intake manifold was completely clean. I checked the the needle slide and it was operating perfectly to throttle inputs.

    It was well after dark, and I took the bike for a quick spin up and down the road. The engine performed perfectly! A half mile is not enough to know for sure but it sure seems to make a huge difference.

    I have two questions: 1)how does fuel get kicked into the air intake filter? and 2) how would one know if the engine is flooded?

    Thanks in advance!


  2. Djskizy

    Djskizy New Member

    Well to answer your two questions...
    1)These engines do not come with a reed valve (one way valve intake side) so the fuel on the the air filter is normal. Crank case pressure pushes the fuel back out on the exhaust stroke.
    2) The best way to know if the engine is lean or rich is the spark plug color. If its black and wet its rich if its white and dry its lean. The perfect color is a slightly wet brown/tan.
    Timbone likes this.