ATV Carb Help, please!

[BRTreedogs]

Yup! This is what I've concluded also - too lean mixture, either from too much air or too little fuel. I'm not sure how to identify which one it is. When I get home tomorrow night, I'll install the new boots and O-rings, as well as rig a direct-feed bottle for fuel to the carb. I'll report back. I appreciate all the input.

Spray starting fluid around the boot.

 

[TheCougar]

Spray starting fluid around the boot.

I have done that, and around all the carb connections, and around the gasket connections... basically every place that an air leak might happen. No luck so far. Keep the suggestions coming! I'll install the new boots in case there is a leak that I haven't found. I'll report back tomorrow night.

 

[Wrench]

Grab a propane torch don't light it, but flow fuel through it. Go around the carb boot....then in the intake. If it changes idle on the boot....voila. if it changes in the intake, pull the carb, drop the bowl (those are NOT #2 philips. A #3 will work). You have a plugged pilot jet. Pull it, clean it and rock on.

 

[WV Mountaineer]

Not the same machine but, my ‘98 Suzuki 500 quad master had the same issues after rebuilding the carb. It was my petcock valve. Replaced it and it runs like a champ.

 

[TheCougar]

If it has a petcock it may be gummed as well and taken apart, replaced.

It’s 100% not the petcock. Fuel flows freely on normal and reserve. Cleaned and checked it again and it’s good.

 

[BRTreedogs]

It’s 100% not the petcock. Fuel flows freely on normal and reserve. Cleaned and checked it again and it’s good.

Any luck with the boots?

 

[WV Mountaineer]

It’s 100% not the petcock. Fuel flows freely on normal and reserve. Cleaned and checked it again and it’s good.

A guy above talked about fuel lines. I rebuilt the carb I was talking about because the fuel line was degrading and clogging it up. Might want to give that a go.

 

[TheCougar]

there’s a part in both carb rebuild kits that I haven’t identified nor seen during my carb teardowns. That’s the only thing I haven’t replaced yet. Both intake boots are replaced, fuel lines and filters cleaned and checked, all the jets have been replaced, new spark plug, new air filter, etc. I’be for two carbs that act up and the OEM carb is on its second rebuild kit. I’m running out of ideas at this point. I’ll tinker with it today and report back. This is the part I can’t identify. It’s hard to see, but there is a very fine mesh filter on it. Looking at the carb diagram, it may be a part hidden inside the carb beneath one of the jets.

 

[cnelk]

If my memory serves me correctly on these Mikuni carbs, that's the intake screen below the seat or the seat itself

 

[cnelk]

Watch this video - especially between the 05:00 - 06:00 minute marks. Its the same carb

 

[TheCougar]

Watch this video - especially between the 05:00 - 06:00 minute marks. Its the same carb

Yup, that definitely helped. I overlooked that. It wasn’t blocked, but I replaced it anyway.

 

[TheCougar]

Okay, so update: the quad is running back to normal now. Today I rebuilt the OEM carb… again, but this time. I swapped jets and put the larger ported jet on the main since I was bogging down at full throttle. That appears to have fixed it. I still need to tweak the fuel/air screw a little, but she runs great at full tilt now. There is still some hunting at idle, but it runs and I’m headed in the right direction. Thanks to everyone who gave advice!

 

[TheCougar]

Are there any approved techniques for adjusting your idle screw and your fuel/air mixture screw? Where should your idle screw be when adjusting your fuel/air screw? Right now it idles perfectly when warm and choke off. When cold and choke on, the rpm is too low and I need to feed it throttle to keep it from dying until it warms up a bit. Once warm, if I put the choke on, the motor dies.

 

[505Wapiti]

Pretty detailed process here…

Basic Carburetor Tuning Guide

www.atv-forum.com

 

[Marble]

I would put a new oil and filter in just in case too much fuel went to the cylinder and made it way into the oil. Happened on mine a couple times.

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[TheCougar]

I would put a new oil and filter in just in case too much fuel went to the cylinder and made it way into the oil. Happened on mine a couple times.

Sent from my SM-G986U using Tapatalk

Done!