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BamaRaised

Running Rich. Driving me nuts. Please Help!

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I have a 2003 Kodiak 450 i recently acquired with a carburetor full of jelly which was causing it to bog down outside of idle. I partially rebuilt the carb by adding a new needle valve/seat and replacing o-rings with a thorough cleaning. It runs very well outside of idle, the idle itself is a little choppy but it doesn't cut off or anything like that. No bogging on acceleration and throttle response is good. The old plug was fouled up and black as soot (dry) so i replaced it with a new one. Within 15 minutes of riding the brand new plug looked just like the old one. I have cleaned the plug multiple times in order to test it after I took the carb off to adjust a few things, and I can't seem to improve it no matter what i do. I'll list a few noteworthy things below. Any help would be greatly appreciated as I am at my wits end.

Mikuni BSR33 Carburetor
- Starts right up cold with no choke applied.
- Is a little harder to start when hot, but will run.
- Adjusted float to service manual specifications (13mm)
- Fuel mixture screw can be screwed all the way in, and the 4 wheeler won't shut off.
- I have noticed a minimal difference from 0 turns all the way out to 2.5 full turns of the fuel mixture screw.
- All jets are stock including the pilot jet (17.5)
- Needle valve and o ring have been tested and are not leaking
- Exhaust fumes are strong at idle but not black
- Air Filter is brand new

Other thoughts
-I have read that this may point the pilot jet being too large, but is it normal to have to downsize from factory OEM?
-Could the float height need more adjustment? Which would throw it out of the range that the service manual says.
-Judging by the old plug this was a pre-existing issue prior to the carb getting gummed up. I'm guessing it was just run rich by the previous owner since you wouldn't know it outside of the somewhat choppy idle without looking at the plug.
-Another thing i noticed was on startup it runs at a slightly high rpm for around 30-45 seconds (around 2200) before settling down to the normal 1500 rpm area.

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It is the pilot. I would wager at some pointy in its' past, someone reamed out (destroyed) the pilot instead of spending the five dollars to replace it. I'd confirm the float height when you put in a new pilot.

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Posted (edited)
12 hours ago, William1 said:

It is the pilot. I would wager at some pointy in its' past, someone reamed out (destroyed) the pilot instead of spending the five dollars to replace it. I'd confirm the float height when you put in a new pilot.

I believe you are right. I have tried virtually everything else carb related. I have confirmed that the float height is set correctly. I've probably had the carb off 8-10 different times by now trying to solve the issue. I kept telling myself that i shouldn't need to downsize a factory jet, but someone was in the carb before and i suppose they could have enlarged the jet while trying to clean it.

 

Would you suggest that I just order another factory size 17.5 jet? Or maybe order a smaller one as well just incase? Do you know of any situation where you would need to downsize from a factory pilot on a stock 4wheeler? Thank you for the response.

 

Edited by BamaRaised

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4 hours ago, BamaRaised said:

I believe you are right. I have tried virtually everything else carb related. I have confirmed that the float height is set correctly. I've probably had the carb off 8-10 different times by now trying to solve the issue. I kept telling myself that i shouldn't need to downsize a factory jet, but someone was in the carb before and i suppose they could have enlarged the jet while trying to clean it.

 

Would you suggest that I just order another factory size 17.5 jet? Or maybe order a smaller one as well just incase? Do you know of any situation where you would need to downsize from a factory pilot on a stock 4wheeler? Thank you for the response.

 

I'd order a factory OEM size jet, stay OEM as well, do not save a buck with aftermarket.

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On 5/12/2019 at 5:49 AM, William1 said:

I'd order a factory OEM size jet, stay OEM as well, do not save a buck with aftermarket.

I installed the new pilot jet today, cleaned up the plug, and it fired right up with no choke again. So I went ahead and rode it for a bit, got it hot, shut it off, then tried to restart. It would only run with the choke applied while hot.  Checked the plug as well, and it was black as soot like before. I have tinkered with a few carbs in the past, but his the weirdest thing i have ever come across. Now i am starting to second guess my float height which i adjusted according to the not so good service manual directions. Could that possibly be the issue here? Or if you have any other ideas i'm all ears. Much appreciated.

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8 hours ago, BamaRaised said:

I installed the new pilot jet today, cleaned up the plug, and it fired right up with no choke again. So I went ahead and rode it for a bit, got it hot, shut it off, then tried to restart. It would only run with the choke applied while hot.  Checked the plug as well, and it was black as soot like before. I have tinkered with a few carbs in the past, but his the weirdest thing i have ever come across. Now i am starting to second guess my float height which i adjusted according to the not so good service manual directions. Could that possibly be the issue here? Or if you have any other ideas i'm all ears. Much appreciated.

Your issue is backwards. Cold engine+ choke, hot engine, no choke. Sure you do not have the choke and hot start confused? If say, the float were too high, it would still be too high (and too rich) when hot.

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13 hours ago, William1 said:

Your issue is backwards. Cold engine+ choke, hot engine, no choke. Sure you do not have the choke and hot start confused? If say, the float were too high, it would still be too high (and too rich) when hot.

Ignore what i was saying about the choke while hot. Apparently i was already so annoyed with the thing yesterday i wasn't giving it any throttle to start without the choke when it was hot. So i fired it up again today and ran it a bit to get good and hot. When i tried to restart it right after i shut it off, i was able to get it started by giving it a little throttle but, it would not idle without shutting off.  It would run for a couple of seconds after i released the throttle then cut out.

The initial start was as usual. Fired up instantly without the choke being applied. Strong exhaust fumes, not the smoothest idle ect.

 

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10 hours ago, BamaRaised said:

Ignore what i was saying about the choke while hot. Apparently i was already so annoyed with the thing yesterday i wasn't giving it any throttle to start without the choke when it was hot. So i fired it up again today and ran it a bit to get good and hot. When i tried to restart it right after i shut it off, i was able to get it started by giving it a little throttle but, it would not idle without shutting off.  It would run for a couple of seconds after i released the throttle then cut out.

The initial start was as usual. Fired up instantly without the choke being applied. Strong exhaust fumes, not the smoothest idle ect.

 

Sounds rich. So the float is correct per the manual, right pilot jet. Float needle valve works, slide is working properly?

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18 hours ago, William1 said:

Sounds rich. So the float is correct per the manual, right pilot jet. Float needle valve works, slide is working properly?

I'm positive on the needle/seat and pilot jet. Slide seems to be working properly as well, when it is pulled down it goes right back to its original position when released. I'm beginning to second guess myself on the float height. I had adjusted it 3 a couple of times prior to the pilot jet swap. The image in the service isn't as detailed as it should be in my opinion. The float has an arched top and the gasket mating surface is angled. So the float height isn't the same from front (closest to the needle) to middle (its highest point) to the back. At first i tried the way the image shows, 13MM height closest to the needle/seat. I was still running rich and the atv would just lose all power after being full throttle for a few seconds as if it was running too lean at high throttle. So after some research i saw where someone had the set same model of carb to 13MM on the back side farthest from the float, which is how i have it set right now. It still runs rich that way but runs good outside of idle at least, with no cutting out at high throttle good throttle response accel ect. I'm thinking that maybe the pilot jet and float height were an issue at the same time? The old pilot jet did look at little larger to the naked eye when i swapped it for the new one. I haven't adjusted the float height at all since i installed the new pilot jet. I'll attach a screenshot of the service manual instructions. Any input is appreciated. This thing is about to drive me nuts.

When it says top of the float, does it mean the peak of the arch (middle) of the float? 

carbfloat.png

Edited by BamaRaised

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The image is pretty clear on the float height and how to set.

Flip the carb over. Ensure the floats are gently resting on the valve pin and not depressing it. If the weight does depressing it either the spring is weak (replace needle valve) or you can hold the carb at a slight angle to reduce the force of gravity. The measure point is the top/flat seam of the float

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6 hours ago, William1 said:

The image is pretty clear on the float height and how to set.

Flip the carb over. Ensure the floats are gently resting on the valve pin and not depressing it. If the weight does depressing it either the spring is weak (replace needle valve) or you can hold the carb at a slight angle to reduce the force of gravity. The measure point is the top/flat seam of the float

 

That's the way i had it set initially before i replaced the pilot jet and it was still running rich.  I was also having the issue where the machine would just cut out after being at full throttle for a few seconds (the engine wouldn't completely shut off but it would just lose all power as if it were running out of fuel). That made me second guess the initial setting, and led to me trying other things. I am going to reset it to that height today and see if it makes a difference since i installed the new pilot. I'll let you know how it works out.

Edited by BamaRaised

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