Foreman 450 help

[Quadrider10]

Alright so I'm fixing this thing for a friend, he told me that it would sputter and backfire and gas was leaking from carb. So I get there fix the leaking problem it was the float and also fixed the backfire and sputter problem. Everything seemed in good shape. But when I start it with choke on, it runs awesome! But as soon as I turn off the choke, it just dies out I never took the entire carb off and cleaned it cause I didn't have tone or room so maybe that'd it. Without the airfilter on it runs almost the same just higher rev and little longer time before it dies. Any ideas what it could be? I cleaned the main and pilot jet when I took the bowl off and for the most part it was clean. Again, it runs awesome with the choke on full

 

[sicivicdude]

Running great with the choke on just screams a lean condition.

The pilot system on a 4 stroke carburetor isn't the same as on a 2 stroke. The pilot fuel system on a 2 stroke is made so that the "air screw" balances the vacuum. On a 4 stroke it has a pilot fuel screw meaning that the screw directly meters the fuel going into the carburetor throat.

The pilot fuel screw on a keihin carburetor is located directly under the carburetor throat on the engine side of the slide. It's buried down inside of a small hole. Under the screw is a spring, washer, and o-ring you'll need to get out before you can blast it with carburetor cleaner.

Also, the pilot system has several other outlets directly under the carburetor butterfly (not the slide!) that will need to be blasted cleaned backwards. Use the little red tube aimed down these holes to clean them out.

Also, pull the carburetor slide and vacuum diaphragm and go over that diaphragm with a fine toothed comb looking for any cracks or splits. ANY damage will cause the slide to behave improperly.

 

[Quadrider10]

Running great with the choke on just screams a lean condition.

The pilot system on a 4 stroke carburetor isn't the same as on a 2 stroke. The pilot fuel system on a 2 stroke is made so that the "air screw" balances the vacuum. On a 4 stroke it has a pilot fuel screw meaning that the screw directly meters the fuel going into the carburetor throat.

The pilot fuel screw on a keihin carburetor is located directly under the carburetor throat on the engine side of the slide. It's buried down inside of a small hole. Under the screw is a spring, washer, and o-ring you'll need to get out before you can blast it with carburetor cleaner.

Also, the pilot system has several other outlets directly under the carburetor butterfly (not the slide!) that will need to be blasted cleaned backwards. Use the little red tube aimed down these holes to clean them out.

Also, pull the carburetor slide and vacuum diaphragm and go over that diaphragm with a fine toothed comb looking for any cracks or splits. ANY damage will cause the slide to behave improperly.

Alright will do. The guy said he brought it to someone who did a "tune up" everything in the carb looks stock. So the lean condition tells me that it's just logged like u said rite? Like I said I only took the bowl off and the slide and diaphram. There r no mods to it other then a plow.

 

[Quadrider10]

alright im going back over tomorrow to take the carb out and bring it home...

 

[Quadrider10]

alright carb is clean... honestly i couldn't tell y it was doing it. no big pieces of dirt came out, nor was it clogged anywhere, ?! so im gonna bring it back and try it see how it goes.

 

[Quadrider10]

cleaned entire carb and same problem... any ideas?

 

[Braaaptor]

Id say you've still got a clogged pilot jet. I clean carbs with an ultrasonic cleaner AND aerosol spray, but Ive run into a couple pilot jets which simply cannot be cleaned. The passage in there is so small that it can gum up so badly that no amount of cleaner will dislodge the blockage.

I cleaned a carb on a CRF 100 recently, and the pilot jet was so bad that even heat from a propane torch wouldn't melt away the gunk. I threw the jet away, put in a new one, and the problem was solved.

Assuming your carb doesn't have problems, next thing to check is the intake boot between the carb and head. Also check the O ring that seals the boot to the head. An airleak downstream of the carb will make a 4-stroke engine run lean and idle erratically.

Still no luck? Be sure all your vacuum lines are hooked up correctly. Check the intake valve lash. An intake valve set too tightly will affect running, especially at idle.

 

[Quadrider10]

Id say you've still got a clogged pilot jet. I clean carbs with an ultrasonic cleaner AND aerosol spray, but Ive run into a couple pilot jets which simply cannot be cleaned. The passage in there is so small that it can gum up so badly that no amount of cleaner will dislodge the blockage.

I cleaned a carb on a CRF 100 recently, and the pilot jet was so bad that even heat from a propane torch wouldn't melt away the gunk. I threw the jet away, put in a new one, and the problem was solved.

Assuming your carb doesn't have problems, next thing to check is the intake boot between the carb and head. Also check the O ring that seals the boot to the head. An airleak downstream of the carb will make a 4-stroke engine run lean and idle erratically.

Still no luck? Be sure all your vacuum lines are hooked up correctly. Check the intake valve lash. An intake valve set too tightly will affect running, especially at idle.

carb must still be dirty. i used a small peice of wire to go in and out of the hole. and hot water.

owell ill leave it up to the other guy hes taking it to the dealer...

 

[Braaaptor]

Ok, well if he gets frustrated with the dealer, let me know. I clean carbs all day long, and can do it for you (or him) if needed.

 

[Quadrider10]

Ok, well if he gets frustrated with the dealer, let me know. I clean carbs all day long, and can do it for you (or him) if needed.

same here, except that one. if i had more time and such, i could probs do it... but thanks man will do!