Carb settings

[kbhd6180]

Redid my 93 Trail Boss 250 2x4 took off the oil injection and am going with mix in the tank. Starts ok but doesn't seem to have any guts on the get go, plus it won't stay running at idle. My mix is 32:1 so I don't think it's starved for oil. Anybody got any ideas on initial carb settings. I went all the way in and came back out 2 1/2 turns then adjusted a little from there but it still has the same problem

[Spitfire79]

Getting enough fuel to the carb? Float set properly? Is it backfiring? If so, through carb or exhaust? What all did you do?

[kbhd6180]

The only thing I did to the carb was took it off and cleaned it. It is now backfiring through the exhaust. Won't start at all with a new battery and starter. The backfire happened when we tried to pull start. The only thing I did to the motor was to take off the oil injection pump and place a cover plate over where the pump was

[Spitfire79]

When cleaning the carb, I assume you took it all apart, soaked it then assembled with new gaskets, needle / seat, etc? Backfire through the exhaust indicates a rich mixture. For some reason its flooding itself, then the excess fuel ignites in the exhaust where theres enough air to dilute the gas and reach the proper mixture to allow ignition. If you have a manual, it should tell you the initial settings for the float level, air screw, etc. Generally floats are set level with the carb body when inverted. The air screw should be about 1 turn out from lightly seated for intial starting and adjusted from there.
Hope that helps

Jeff

[djtates125]

on my polaris 400 2 stroke i eliminated the oil pump and when u do so u need to rejet 2 sizes bigger than stock.

[kbhd6180]

Spitfire
I reset the carb today and it wll kind os start but won't stay running. djtates says I need to rejet carb 2 sizes larger I would think that would just put that much more fuel in the carb. Any ideas?

[Spitfire79]

When you mix oil / gas, the jet may need to be larger in oreder to account for the extra oil and same amount of fuel required. 1 - 2 jet size increase should do it. This is where you need to watch your plugs and piston wash. Its much easier to do on a sled where you can see inside the cylinder. At the very least, check your spark plug to make sure its not running too lean. It should be a nice light chocolate brown color.
That said, on 2 strokes, the main jet mainly effects the 3/4 to full throttle range. The needle jet and jet needle operate the 1/4 to 3/4 range and your pilot and air / fuel screws look after the idle to 1/4 throttle. There is overlap in these areas so theres a smooth transition through the rpm range.
Are you sure the choke is seated properly, and set properly? There should be about 1/8th inch free play in the choke lever before it starts to open the plunger. If the choke doesn't seat properly it will allow excess fuel into the carb and it will constantly flood. When it does start, does blipping the choke make it better or kill it?

[kbhd6180]

Took the carb back off and checked everythig inside. It all looked ok put it back together and put it back on with a new fuel filter. Blipping the choke only makes it worse. Right now I have fuel mix on the floor under the bike coming from the exhaust outlet. I am at a loss at this point
kbhd6180

[Spitfire79]

Have you checked the needle / seat? Maybe its allowing fuel to flow through? It's definately flooding.

[kbhd6180]

I have the carb off the bike right now. If I push the throttle the sleeve inside that controls the needle goes up, but whenyou let off the throttle it takes a long time for the spring to push it back down. I also am not sure how far open that should be