Air/fuel screw setting

[chevymanrick]

Put a 42 pilot in my carb and it started perfect, I took the fuel mixture screw out to replace it with a flat head type screw so I could adjust it, I'm having a hard time finding the "sweet spot" I got it running but it is somewhat of a pain to start in the morning had to be choked then I can get it going easy buy the more the screw is turned in it backfires and run terrible. So I think I'm close to being there but should I try turning it out alittle bit more?

[CJM]

Even with a 42 pilot I still needed choke sometimes and was lean.

If it was backfiring its to lean, turn out more. Turn it out more than 3x go tot he next larger pilot and turn the screw in further.

In is lean, out is richer.

[chevymanrick]

Ok thanks man, I was gettin a little nervous last night I turned it out about 2 turns and couldn't get it to start, I'm at about 2 1/4 ill try alittle further and if that doesn't work ill go up one size on the pilot

[ggodfreyX]

Make sure the quad is warm before you start tuning the carb and wait at least 30 seconds after each adjustment to see how it responds.

[chevymanrick]

Yea that was my initial problem I broke the oring for the fuel screw so when I replaced it it was cold and I had a pretty hard time starting the sob lol, but I'm pretty close now maybe about a half turn out and I should be good

[russellsroost31]

i think the stock setting for the a/f screw is like 2 1/4 out or somthin like that.

[chevymanrick]

Yea that's what I read in the stickys, I had it turned about 2 turns out and had a hard time keeping it running, last night I turned it about a half a turn out more and it starred up perfectly and runs like a champ now. Thanks guys

[GAZ-V-21]

where is the screw to richen i just put on a slip on and k&n filter i made a thread but just seen this one should i richen a little?

[CJM]

Depends. If your backfiring when you let off the gas and or downshifting quickly from high speed then yea it needs to be richened up.

[russellsroost31]

u cant just richen the mixture anyway u got to swap out the jets if u want it to run at its best

[chevymanrick]

Hey cjm my exhaust still had a slight cough to it, especially when its cold it'll idle fine a few seconds cough, idle fine and so on, its jetted with a 42 pilot and 158 main, replaced exhaust crush rings, any ideas as to what I can try to figure out what is causing this?

[ggodfreyX]

My 400 idled funny like that right after I changed the pilot jet. I discovered that I did not have the rubber boot from the airbox attached to the carb all the way and I had an air leak. I sprayed both carb boots with WD 40 and the engine responded. I put both of them on correctly and it cleared up.

[chevymanrick]

Originally posted by ggodfreyX
My 400 idled funny like that right after I changed the pilot jet. I discovered that I did not have the rubber boot from the airbox attached to the carb all the way and I had an air leak. I sprayed both carb boots with WD 40 and the engine responded. I put both of them on correctly and it cleared up.

Alrite ill spray some Willy dee around how did the engine respond? Clear up for a second?

[CJM]

Carb cleaner would be abetter choice to find the leak, it idles up its a leak.

To check for an exhaust leak start the quad up and let it idle a min or so till its running decent. Then take your hand (might want to use a heavy work glove) and put it over the end of the exhaust and seal it. You seal it you should be ok to see where its coming from. Incense is also a good idea, you can see the smoke from it and the air from the leak will move the smoke.

[ggodfreyX]

Originally posted by chevymanrick
Alrite ill spray some Willy dee around how did the engine respond? Clear up for a second?

When I sprayed the carb boots the idle increased slightly and then returned to normal. You can use almost anything flammable. I have even used starting fluid. When I reattached the carb boots and started it up my idle issue was gone. I did have to readjust the fuel screw since I had been messing with it while trying to figure out what was going on.