text: Odd Fuel Mix Problem | Motored Bikes - Motorized Bicycle Forum
  Odd Fuel Mix Problem
  Discussion in '2-Stroke Engines' started by woodyvt, Apr 28, 2009.
  I posted a problem last September and, while I can ride pretty consistently I am having a nuisance problem maybe you can "float" around your brains for me.
  My original post here: http://www.motoredbikes.com/showthread.php?t=15542
  Bike runs great, starts right up every time, never have had to choke it.
  Here is the problem: My engine is always getting too much fuel at speed and I have to constantly on/off on/off the fuel petcock to keep it running. I am sure you can imagine that on a long 10 mile run this gets very annoying.
  With a full open fuel petcock it quickly loses power so I shut the fuel flow off and it immediately picks right up and runs sweet for a pretty good distance till it starves. I open the petcock for just a couple seconds till the bowl fills and then off again.
  I have adjusted the carb float tangs to a lower position but then it seams like it starves for fuel. It's either too much or too little. I have taken this carb apart so many times I could do it blindfolded and can't see what the heck the problem is.
  I am a mechanically inclined person and I'm just not getting this. I can park it running with the fuel open and it will idle all day. It seams like when the throttle is open at speed there is so much vacume into the cylinder that it's drawing more fuel into it than it can use and by doing that it constantly fills the fuel bowl thus supplying even more unnecessary fuel.
  I have read all posts here regarding this and I am befuddled.
  I have not altered anything on the HT kit other than, because I mounted my engine slightly more upright than most people, I "leveled" the carb intake so that the fuel bowl would be level.
  Is it supposed to be "not level" (I don't know how else to say that) and tilted downward toward the rear? That just seams like a silly thought...
  woodyvt, Apr 28, 2009
  If it runs perfect at Idle what about at mid range? still flooding? If so drop the needle down some. Other wise you may have to either do the jet mod threaded here says ez jet mod. Baiscally soldering your jet closed then re drilling it out with a really small drill. I have read that most of the carbs will fit a del orto jet. I think the original is about a 72. Maybe a 68?
  I'm no expert but if it's not the float I would say jet size. The jet affects 1/2 throttle to wide open throttle. You could try playing with different sizes, by soldering and re-drilling the jet.
  Shadeslay, Apr 28, 2009
  adjust your carb float height.
  BSA, Apr 28, 2009
  get a new carb, they are cheap enough to replace.
  Skyliner70cc, Apr 28, 2009
  Well, I FINALLY got that stabilized. It took a combination of things and adjustments. 1) I moved the needle c-clip to highest position. 2) I adjusted the small tangs upwards on the fuel float shut-off. 3) I adjusted the large tangs downward on the fuel float shut-off. Also, just part of general maintenance I cleaned the spark plug. It's still getting a wee bit too much fuel but it runs pretty consistently and I no longer have to "on/off" the fuel petcock.
  Skyliner suggested a new carb. Sometimes the simpler you make something, like this carburetor, the trickier it is to find just the right sweet spot to make it work due to elevation and other factors. I think the newer improved carb that I have seen available with the fuel/air adjustment would solve the problem but (always a "but") I have so much into this money-pit the thought of spending more makes me nauseous.
  Just a note: My gas mileage has been awful compared to other peoples' experience. I have gotten better mileage with 500cc motorcycles. I am sure these adjustments will increase it a lot but still...
  woodyvt, Apr 30, 2009
  two good points noted
  woodyvt said: ↑
  I think the newer improved carb that I have seen available with the fuel/air adjustment would solve the problem
  but (always a "but") I have so much into this money-pit the thought of spending more makes me nauseous.
  point #1 -- better carbs may be a very good thing
  point #2 -- ones thinking about buying HTs need to know this
  are we truly saving money ???
  this may be ghetto but it worked for me. i noticed that i was having problems with the carb seeming to flood out often and tried many things but to no avail. finally i tried going with a longer hose which i then loosely tie wrapped to the frame which kinked it in the shape of a "7" going to the carb. the more loose the tie wrap, the less the kink. the extra hose length with slight kink prevented carb flooding. i think if you had a short hose that goes straight down from the petcock to the carb, you're going to increase the likelyhood of flooding.