Call MFG supply(the link I posted,they should have the Moose carb kit for your model even if it isn't shown) Check the oil to see if it's over full or smells like gas. If so change the oil and filter. OPT

 

Do you know the correct way to set the float height for a 2003 Sportsman 500 HO? I assumed the float should be level with the bottom flange(when upside down using gravity) , but it seems to sit much lower with the new needle/seat, which would technically allow a higher fuel level in the bowl. I forgot to look at the old one before I took it apart.

Do you know exactly what carburetor is on this model? I'd like to start researching for carb adjustments etc.

 

You can slightly bend the float tang(that holds the needle) down a little to lower the fuel level in the bowl,BUT the main problem on this carb(BST40) versus the older model BST38 isn't just the diameter (38 versus 40) but the way the BST40 uses the float assembly to actually hold the needle and seat down with the pressure from the carb bowl! I had problem from day one when they first came out! Hard to keep em from dripping even just a little through the overflow tube. Some wouldn't leak until you were at an idle and would bubble a little out of the tube. Some guys have experimented with different size metric o-rings around the needle valve,but don't know if it helped any. Some of the fuel could be from not enough pressure on the needle valve or the o-ring itself,but just try the tang first to see if it stops dripping. Again this is a Mikuni BST40 carb. OPT

 

Thanks for the help.

I got a new needle and seat and the fuel leak is fixed, but it doesnt seem to run the same as it did before. It seems to be much more sensitive to the choke setting. I was just wondering if I set the float incorrectly. I bent the tab so the float was parallel to the splitline (when in an upside down position with all 3 tabs of the plastic float assy pressed against the housing).

Is this the correct proceedure?
How sensitive is the float adjustment?
Is there and idle air screw?

I didn touch anyting else ( excpect the idle stop).

Might have to take it apart again.

 

On this carb the float does sit down a little below parallel with the carb body compared to the old BST38.(The old BST38 carb float height was 14 mm from top of float to carb body by the manual,when held sideways with float touching the needle slightly) BST40 is supposed to be 14.7 mm,BUT not always accurate on this newer style float assy, plus if you've bent the float tang UP any at all,could be the problem with the way it's running! If it's not leaking ,but feels a little rich, check that you have a little free play also on the choke cable. Plus you can pull the top cap off the carb and see if the brass plunger is closing in all the way. You can adjust for slack if needed where it screws into the carb if it's not closing,plus at times the brass plunger can get a little corroded and PB Blaster can free it up. The fuel/air adjustment screw(or pilot screw as it's called) is under a round block off plug in the carb body,just in front of the carb bowl. This is factory preset,but you can carefully drill through it with a small bit,be careful and not damage the air screw when you go through the plug!Then you can use a drywall screw to pull the plug out exposing the adjustment screw. While the engine is at an idle,you can use a small screw driver or carb adjusting tool to fine tune the idle.That's what this screw mainly adjusts,the idle circuit! Usually they're preset between 2 1/2 to 3 turns out from a lightly seated position.Check the factory setting first before you attempt any further adjustment! Here is the best link I've found on working on this carb! This carb is a little different externally( it's off a KTM LC4) but is the same basic carb internally on this type float system. http://www.advrider.com/forums/showthread.php?t=347184
OPT

 

Thanks again OTP. You have been extremely helpful.

It looks like I set the float wrong. I adjusted it so it was parallel with the splitline when totally upside-down. According to the link you sent, its suppose to be set parallel when held at a slight angle, but will drop in much further if rotated all the way upside-down.

How do I know what angle to hold the carb when checking the setting?

Thanks again for your patience.

 

About at a 45 degree angle on the carb to see if the float is parallel with the carb body(just when the tab is barely compressing the float needle) If it's not,adjust the small tang to where it is parallel. Then see if it runs better. On the older carbs you can set the float level with em upside down,but not on the BST40! OPT

 

Well, I took it apart again. It turns out the float was actually set pretty darn close to correct. (I guess that makes sense since I didnt think I bent the tab that much....if at all). So I'm not really sure why it doent seem to run so hot. Maybe thats how it always ran.

The choke plunger seems to be fine, except I lubed the cable a little, and now it wont stay in the choked position. The spring in the carb seems to be enough to pull it back to the un-choked position. A little bit irritating.

I changed the oil just to be safe, even though it didnt smell like gas.

I guess I'll have to wait till the next time we get snow to give it a workout (I use it for plowing snow in the Winter)

I thought I saw a few drips from the overflow when it was running, but seems to be dry when its off. I think you said this is kind-of normal

Thanks for the help OPT. You really know your stuff.

 

To make the choke **** stay out just tighten the rubber coated nut at the pod a little more.This puts pressure on the choke shaft and you can adjust the tension. Keep us updated on how it does. OPT

 

Just fixed my buddies Polaris 500. The problem with the gas leaking out of the overflow is a needle and seat issue caused by a bad O-Ring on the seat. The seat will fall out of its orifice and drain all the fuel from your tank. Replace the O-Ring and make sure it has a tight fit.