Fouling spark plug

My rhino is fouling out the spark plug in 5 mins. I put a new plug in, started it using the choke, let it idle for about 1 min. Then I revved it some. Pulled the plug out and its black and sooty. I've got black smoke coming out of the exhaust, which tells me i'm running rich. The plug is not wet from oil or fuel, just sooty and black.
Leading up to this, it ran great for two trail rides, then on the third one, about a month ago, it started not wanting to idle when it was cold. Once it warmed up, everything was normal. Got it home, put it in the garage. Went to start it a couple days later, and it wouldn't start. Pull the old plug out, and its black and sooty. Put a new plug in it, and it fires right up. I haven't riden it since. Went out today, started it, and its got black smoke coming from the exhaust. Within 3 mins, the plug is black and sooty.
Any ideas? I fouled both the NGK iridium and the stock replacement. Running 93 octane fuel with no ethanol. Fuel tank and pick-up are clean, carb. bowl is clean. The jets look clean also.
Does anyone have the steps for tuning the carb? And what is the knob on the right upper side of the carb. for? I messed with it the first time it wouldn't run, and believe this might have to do with why its running rich. Sorry for the long post.

#1 it sounds like the needle and or slide is stuck open, That would bring the main jet into play at idle. #2 unless your running high compresion piston you wont burn the 93 octane completely, a stock piston dosent produce enough heat to burn it properly. #3 the knob sounds like the idle control screw.

thanks for the reply mike. is the slide the part at the front of the carb that opens n closes based on engine load? i know when the engine was rebuilt n bored out a higher comp. piston was installed but my buddy cant find the paperwork for it. it seems to be idling slightly higher than when i first got it can this cause the main jet to come in too early? thanks

So Mike are saying don't run 93 in a stock motor? That's what I run in mine now should I change up? And to what?

Chief1979 wrote:

thanks for the reply mike. is the slide the part at the front of the carb that opens n closes based on engine load? i know when the engine was rebuilt n bored out a higher comp. piston was installed but my buddy cant find the paperwork for it. it seems to be idling slightly higher than when i first got it can this cause the main jet to come in too early? thanks

The slide is controled by the Diaphram,the butterfly is controled by the throttle.

lambfam660 wrote:

So Mike are saying don't run 93 in a stock motor? That's what I run in mine now should I change up? And to what?

Runing High Octane Fuel only work's to your advantage if you are runing a high compression piston and or your wanting to run more timing. It takes alot more heat to completely burn high octane fuel. To get technical about it, the higher the number the less likely it is to pre ignite or knock as some know it. All engines come with a recomendation of what octane to run, If you go any higher your just wasting money. The number has nothing to do with the quality of the fuel or the power it will give you. Hope I made sence.

good point mike very good info lots of people waste lots of money thinking higher octane = more power even in a stock motor

mike is dead on on this. its like saying well if im supposed to run 5w-30 oil and I run 20w-30 that's got to be better right? WRONG...its just not ment to run it. The real place high octane gas comes into play is anything high compression (not just pistons but turbo and super charged motors) so (like mike said) it wont pre detonate and destroy your motor.

may want to pull your carb an give it a good cleaning , then see what its doing if it was running good before , don't change the set-up just clean it an put back where it was set at before

I always ran higher octane in small engines lawnmower, motorcycle, quad, rhino, boat, jet ski, hell even my generator, I thought it was easier on the motor what a waste on my part. So what should I run in a stock 660?

lambfam660 wrote:

I always ran higher octane in small engines lawnmower, motorcycle, quad, rhino, boat, jet ski, hell even my generator, I thought it was easier on the motor what a waste on my part. So what should I run in a stock 660?

X2
it has more cleaners, and depending on what state you're in, it's not supposed to have any ethanol in it. i've run it in everything i have since new. too many problems with regular gas these days.

lambfam660 wrote:

I always ran higher octane in small engines lawnmower, motorcycle, quad, rhino, boat, jet ski, hell even my generator, I thought it was easier on the motor what a waste on my part. So what should I run in a stock 660?

89 is a good fuel for the Rhino, Even with a new CDI.

thanks I'll try it and see would it make any difference if I have a irridium plug?

Chief1979 wrote:

...... i know when the engine was rebuilt n bored out a higher comp. piston was installed but my buddy cant find the paperwork for it.........

Before you switch back to regular grade fuel, get a handle on the compression ratio that the machine is set up at. With a higher compression piston rather than stock, you may need the higher octane rating.

As far as the running extremely rich, you may have something going on with the float and/or float valve. If the float is not maintaining the proper fuel level in the float bowl, that may be causing the richness across the board. Do you see any fuel overflow coming out of the overflow hose hanging down from the carb?

Steve, I will check the overflow hose for the carb. tomorrow. If its not running out, I can assume the needle and float are operating correctly, right?
Rhino727, I was thinking about cleaning it out good too. I've worked on carbs alot, but wasn't sure if the carbs on these machines is anything like a carb. on a hotrod. The slide that is co ntrolled by the diaphragm is a little confusing to me. Is there a way to check that the slide is working correctly.
Thanks for all the replies gentlemen. I will try to find the engine set-up tomorrow. I know I've ran 93 octane in it since I got it, and my buddy always ran 93 in it.

choke sticking??

James, the choke handle on the dash moves back and forth, but it does feel sticky. I guess I need to go back to basics and make sure everything is working correctly. The rhino was running perfectly, so it would make sense that something like the choke or slide are sticking. Thanks

pull it out of the carb and put a little oil on it then see what it does

You're saying pull out the choke cable and lubricate it, right? I will also check make sure the slide is moving freely.

Pull the choke off the carb and lube it, they can stick and not close all the way.

Chief1979 wrote:

Steve, I will check the overflow hose for the carb. tomorrow. If its not running out, I can assume the needle and float are operating correctly, right?
Rhino727, I was thinking about cleaning it out good too. I've worked on carbs alot, but wasn't sure if the carbs on these machines is anything like a carb. on a hotrod. The slide that is co ntrolled by the diaphragm is a little confusing to me. Is there a way to check that the slide is working correctly.
Thanks for all the replies gentlemen. I will try to find the engine set-up tomorrow. I know I've ran 93 octane in it since I got it, and my buddy always ran 93 in it.

Look for fuel stains where the fuel would have spilled out of the overflow hose. You will have to have the engine running (fuel pump operating) to see the overflow actually happening. An easy way to check the float level is to replace the overflow hose with clear line. Then arrange the hose to loop upward above the top of the carb before going back down. While the engine is running open the drain valve on the side of the carburetor. Fuel will then flow into the clear hose and stabilize at a level even with the height of the fuel within the carb. It should end up pretty much level with the seam between the float bowl and the body of the carb, if the float is operating correctly.

Chief1979 wrote:

Is there a way to check that the slide is working correctly.

you will be able to see it move up and down when you remove all the intake items and blip the throttle (while it's running).
be very careful, however, and don't get too close to the carburetor. if it backfires, you could get burned really badly.

Will do. I'll do that after work and report back this afternoon. Thanks for the headsup fellas.

Quote :

Look for fuel stains where the fuel would have spilled out of the overflow hose. You will have to have the engine running (fuel pump operating) to see the overflow actually happening. An easy way to check the float level is to replace the overflow hose with clear line. Then arrange the hose to loop upward above the top of the carb before going back down. While the engine is running open the drain valve on the side of the carburetor. Fuel will then flow into the clear hose and stabilize at a level even with the height of the fuel within the carb. It should end up pretty much level with the seam between the float bowl and the body of the carb, if the float is operating correctly.

Ok, I'm going to verify the choke cable is operating correctly, and then I will check the float level.

08Rhino450SE wrote:

Chief1979 wrote:

Is there a way to check that the slide is working correctly.

you will be able to see it move up and down when you remove all the intake items and blip the throttle (while it's running).
be very careful, however, and don't get too close to the carburetor. if it backfires, you could get burned really badly.

Ok, I know that is working because when I was replacing the spark plug, I had the intake off cleaning the K&N filter. When I started it, I noticed that slide would move up and down when I blipped the throttle.