Little back story, Bought a 95 xplorer 400 that ran but had some carb / oil pump issues and noticeable piston slap. It still fired right up with one pull and would run pretty good just smoked pretty bad and didn't want to idle. Found the oil pump linkage was rusted and ceased up 3/4 open, throttle cable was disconnected. I decided to disable the oil system and just mix in the tank 40:1. It cut the smoke down a little.
After that I bought a carb rebuild kit and a 1mm larger piston. Rebuilt the top end and carb. Reassembled and there is no more piston slap but the carb was over fueling the motor and smoke is just pouring out of the exhaust. Played with the carb settings, float level, pilot screw, idle screw moved the needle down everything I could think of. Finally broke down and bought a new 34mm mikuni carb. Installed it and it is still just pouring gas in the motor, and pouring smoke out of the exhaust. Pulled the reeds out of the intake the lower ones were open a tiny bit so I took them apart flipped them over reassembled with them closed and still have the same problem. I'm all out of ideas and maybe 600 bucks the way it's looking.

thanks in advance for any help with this.

 

Two carbs and still doing the same thing? Stock jetting was a 200 main,30 pilot. Most times the stock main jet was too large. I'd drop to a 190. Also go back and check compression even though you have a new top end.Problem could be there.Plus if cranks seals were't replaced and are leaking,especially the one behind the drive clutch, the crank case can't build up enough pressure to atomize air/gas/oil mixture properly. That could be your main problem.These are simple carbs and normal air screw setting should be between 1.5 to 2 turns out.

 

Yes sir 2 different carbs, one rebuilt and one new. I changed the jets in the new one with the ones I took out of the factory carb and it was a 200 main. I couldn't read the pilot jet but it should be good. I ordered a set of crank seals this morning and watched several how to videos. I will change them this weekend when they come in, probably a good idea even if they aren't the problem. I will check the compression this evening when I get home from work. Something seems to be making it pull to much fuel through the carbs, if I put my hand behind the carb while its running it sprays my hand with fuel, when I take the carb back off the inside of the intake and carb are dripping with raw fuel. The only way to get it to idle is with the Pilot screw several rounds out and the idle screw all the way in. It fills my 25X30 shop up with gas smoke pretty quick so I haven't tried running it very long. Thanks for the help with this, I haven't had a head scratcher like this in a while.

 

May or may not be seals,but if the seals are bad it can't ignite all the fuel efficiently as it can't compress the air,oil,fuel mixture into a fine mist and shoot it up the transfer ports for ignition. Fuel that it can't take will be forced out the back of the carb.If compression is low(below 100 psi) it can do the same thing.

 

Ok, thanks again, I will report back this evening with the compression findings.

 

Compression was 115, I don't have a working starter on it right now so I had to do it with the pull rope. Would think it is close to accurate still. Pulled the stator cover off and there is a little oil behind the cover. Have to gather a couple thing to tear it the rest of the way down to see the seal

 

With a new bore and hone and piston you should have a compression reading somewhere around 135 psi or so. 115 should be enough in most cases for one to crank,but again if the seals are bad,no amount of compression will help.