polaris scrambler 500 carburetor

scrambler50099 · #1 (**permalink**) 06-08-2011, 06:47 AM

Hi everyone just looking for some help on a 98 scrambler 500 i am working on.
I am new to the atv forums so hi everyone.

So i have a 98 scram 500 that i got from a friend because he couldnt fix it. It sat for about 5 months. I got it turning over and i can get it to start, but it immediatly floods when you turn the gas on.

I can shut the gas off and it will start if i hold the throttle open and it will idle all by itslef, but as soon as you turn the gas control on it floods.

So i have read about the float height adjustment i am going to check that after work.

Fuel seems to be coming up through the bowl and out the 2 holes in the front of the carb. Even if it is just sitting there its weeping out? What are some conditions that would cause this? There is a 155 main jet in here and he has a K&N. Not sure if the 155 is correct.

Also when i pulled out the Block that holds the jet sprayer in the O ring that sits underneath it was loose.

Would the choke plunger cause this problem? Just wondering what exact things can cause this kind of flooding. Needle doesnt look bad but i can see like a ring mark thats in the rubber.

**Bruce!** · #2 (**permalink**) 06-08-2011, 01:32 PM

Welcome to the board!

tt425 · #3 (**permalink**) 06-08-2011, 01:40 PM

I would say the needle is bad provided you removed all jets and cleaned them real good. Look at the needle and look for wear(make sure it has a sharp point). Did you remove the part the float needle sits inside? That "o" ring might be bad.

scrambler50099 · #4 (**permalink**) 06-08-2011, 01:55 PM

Great thanks guys. I didn't have time to pull that im going there right now. I think i read the bowl flooding is due to 3 things. That needle, The o-ring you were saying and float height.

Im going to check those three things and try it a few times. The needle could be bad. My friend claims its new carb kit and it does look unbent however it almost looks like i see a ring around it.

scrambler50099 · #5 (**permalink**) 06-09-2011, 07:28 AM

Ok so round 2 of flooding.

I pulled out the Brass part with the Oring that we were discussing and replaced that o-ring. I also put the Fuel screw back to stock setting 2.5 out?

I did a little adjusting of the float level and when i hooked the carb back up and turned the gas on it started right away almost normal. No choke, no gas.

As soon as it starts its like if you dont have the throttle open it floods immediatly, Its almost like the Bowl is dumping is load of gas all at once.

Has a 155 main jet, the pilot jet is a 40. Thought stock was 45? I cant imagine that the jetting could be that far off.

Also the chocke cable has a little wiggle in it where it goes into the carb.

And i also wonder if its possible that the fuel hoses are backwards from the pump. Which side of the carb does the Prime hose go to vs the regualr one. I think the Pump has a P on it for prime.

Also i have heard mixed things about putting a TMX 42 on here. Just dont want to spend months adjusting this carb if i can drop $300 at AAEN and call it a day. I know it may not be a HP diff per say, but if i can just strap it on and go i may do that.

I keep reading people rebuild these bst40 carbs and they still have the same issues?? its strange. I know the BST is bettter suited for a 4stroke but the float adjustment seems to be really picky.

Anyone know the stock carb setting for this carb BST40.