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2003 Yamaha Warrior 350 Overheat and Gas/Air Mix Problems

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2003 Yamaha Warrior 350 Overheat and Gas/Air Mix Problems.

My Warrior seems to be overheating on me. I live in Metropolitan Arizona, and I expect to have some issues with heat ,but not this bad. After about 30-40 minutes of riding it wants to die on me, the only thing to do to keep it from dieing is keep it revved up at idle and between gears.

Tell me what you think about that issue.

The next issue is that my Gas/Air mixture might be off. I don't know which screw is the mixture screw, I know which one is the idle screw. And I do know thats it all the way in 2.5 turns out on the mixture.

It needs a new throttle cable and will come eventually. I'm just trying to fix these two issues for now.

And last issue, but I think its more so related to the gas/air mixture.

I takes FOREVER to start my quad. At least 10 minutes. I know its not getting enough air (or too much gas) because I had to take three of the screws out of the air filter cabin to get more air into the carburetor. When the air filter cabin lid is screwed down with all 5 screws it takes forever to start Full choke, about 10-15 minutes, and 50-75 cranks (tallying an almost dead battery), but when its propped open with a tire plug tool, it doesn't take AS long. Full choke, about 3 minutes and 25-35 cranks later!

From my understanding a finely tuned ATV should only take a minimum of 2-10 cranks to start on full choke. Could there be some other issues with my carburetor besides the gas/air mixture being off? Like like the float or the jets? Please, any help will be greatly appreciated.

Nathan L. Mesa, AZ

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Take the carb completely apart and clean it well. The fuel screw is located on the bottom of the carb in front of the float bowl. I'm not sure, but I think the idle screw is on the left side of the carb, but I could be mistaken. How long has it been since you cleaned your air filter?

Edited by DirtDemon

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I got the quad early august of this year. I haven't done any thing to it, besides replace the running switch (I've heard it called a dead man switch) on the handlebar, not the PB Switch but the one above it. I've have taken the carb off and taken it apart somewhat but didn't notice anything wrong with it. I handed it over to my wifes dad who works on primarily transmissions for vehicles. He also works on Artic Cats (don't buy them he says!!!) as well as all the other ATC/ATV/UTV brands. He said the jet wasn't clogged, but I get the feeling he didn't really look at it. Other than that, put a new battery on it, took it out to Butcher Jones, took it up a hill, rolled it, it was still running till a couple hours before we packed up and were getting ready to leave. That's when the problems happened. Actually we were having problems with it the night before on the way in to Butcher Jones. Every 15 minutes or so, it would over heat and completely die. Couldn't start it up until it was semi-cool. Eventually got it into the first cove of Saguaro Lake. Had it parked most of the night, but decided to attempt a hill, that's when I rolled it. I caught from rolling a second time, and started it came back down the hill and parked it, because I was all banged up. Later the next day, we rode the he!! out of it. Then randomly someone got on it to take it for a spin, and that's when it would start and idle but as soon as you put any throttle on it, it sounded like it was misfiring HARD CORE!!! Let off the throttle, it idles fine and starts all day. Took it to my wife's dad he noticed that the running switch was broke, snipped the wire, uncrossed them, started up and ran just fine. Not a single problem after that. It doesnt have the over heat issue as bad now, now it takes about 30-40 minutes of riding before it wants to die. I'm so flustered, I don't know where to begin.

To answer your question, no, I haven't cleaned the air filter. I will do that tomorrow, and see if it changes the performance. I'll use gas to clean it and wait for it to air out before I attempt to start it. I will let you know more tomorrow.

Nathan L. Mesa, AZ

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sounds lean to me. you should have only 2 screws on the carb: one for idle and the other for mixture. pull your spark plug and see what color it is, let us know. white is too lean, black is too rich. that will tell you where to start.

If it is lean it WILL run hot.

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I snapped a picture of the spark plug, its not even 2 weeks old about 2-3 hours max on it. Here it is... Photo0160.jpg

And another better quality picture


For only a few hours on it, it sure does look like it has darkened quite a bit.

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That plug looks pretty normal, if you chop the one side of the threads off the plug and take a look at the lower part of the insulator, it will give you a better idea of your air/fuel situation. You could still be running too lean on the pilot, or the needle clip may need to be dropped a notch. If you spend alot of time at low to mid throttle, and the pilot and needle are set too lean, that could be causing the overheating. Take the carb apart again and make sure that the jets are completely clear. Poke a small wire or something through them, soak them with carb cleaner and then blow compressed air through them. Also make sure the floats are adjusted properly. Also, improper ignition timing, dirty, gummed up cooling fins, improper valve adjustment and low grade or dirty motor oil can cause overheating in an air cooled motor. You also may want to install an external oil cooler.

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Thank you DirtDemon, this should get me headed in the right direction. If none of that fixes it when I get the money, I will pm you if it doesn't work. Should be like a month or so.

Could the magnet on the flywheel be a possibility?

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You say it is over heating. How do you know? If it is just dieing after a time it may be some other issue. It may be a coil getting hot and not working. Also check that the fuel line is not routed near the cyclinder or head. Does the engine oil smell burnt at all? Try running the bike on reserve instead of on and see if that makes a difference. Pull the fuel line off the cacb and check fuel flow as well. Just some other stuff to check. Another thought,next time it dies on you, pull the plug and see if there is spark. If not , it is electrical. If there is, is the plug dry or wet? Have you ever tried using the choke when it dies to see if it helps at all?

Edited by handyhiker

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Ok so here's an update. I went out and tore the stator/flywheel cover off my Warrior. Timing is correct. the compression is great, and it gets fuel (probably too much because I can pull the spark plug out and its wet) but it doesn't get spark, it only gets spark when it gets a little warmer (I don't know what gets warmer to cause it to start like that, but it literally takes me a whole battery to get it to start) But being now that its December and its a high of 60 degrees here in AZ. It won't start at all. No matter what I do.

I was in at my local Yamaha Power-sports dealer a while back, and the pro said "when its a Yamaha with electrical problems its 9 times out of 10 a stator issue". Which leads me back to the first part of this post. I sanded the points of the stator with 120grit wet/dry sand paper to see if it would help, including the inside of the flywheel where the stator points float nearby, I sanded the discharge point and the strip on the outside of the flywheel that touches the discharge point. (keep in mind it was a light sanding, I didn't get into it, put a lot of pressure or time into it, just enough to freshen the surface of all the points. Still nothing, it just turns over and over with no ignition. I think I need a new stator, my carburetor's air/fuel mixture screw is frozen so I cant tweak that at all. I snapped a float arm off inside the bowl area of the carb. I JB Welded it back on because its pot aluminum and is not TIG friendly.

I did some plasma cutting/welding on it over the weekend to put some nerf bars on it, I disconnected the positive side of my battery, can someone tell me if I might have possibly screwed the CDI in the process of welding/plasma cutting.

About the carburetor, I plan on spending a little money on my quad, and getting a +7mm crankshaft and a 1mm over piston. Instead of spending $300 on a stock carburetor, I was going to spend a little bit more and get an Edelbrock carb (rated at 24.3hp) for $400-450. Is it worth the investment considering I want to turn my Warrior 350 into a 396ish cc motor? Any and all help will be greatly appreciated!

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You say it is over heating. How do you know? I DON'T KNOW, If it is just dieing after a time it may be some other issue. It may be a coil getting hot and not working. Also check that the fuel line is not routed near the cylinder or head. ITS NOT Does the engine oil smell burnt at all? FRESH ENGINE OIL THE PREVIOUS OWNER PUT IN, SO I CAN'T TELL. Try running the bike on reserve instead of on and see if that makes a difference. IT DOESN'T Pull the fuel line off the carb and check fuel flow as well. FUEL FLOW IS FINE. Just some other stuff to check. Another thought,next time it dies on you, pull the plug and see if there is spark. I WOULD IF I COULD GET IT TO RUN. If not , it is electrical. If there is, is the plug dry or wet? Have you ever tried using the choke when it dies to see if it helps at all? NO, BECAUSE IT WON'T RUN NOW BECAUSE OF SOME ISSUE, OTHERWISE I WOULD CHECK AND SEE IF USING THE CHOKE HELPS WHILE ITS RUNNING BUT TRYING TO DIE

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So, it's not runing at all right now? Are you even getting spark?

Here are some textbook answers to overheating on a Warrior:


Firing incorrect:

Spark plug dirty, broken, or maladjusted

Spark plug incorrect

IC igniter trouble

Fuel/air mixture incorrect:

Main jet clogged or wrong size

Fuel level in carburetor float bowl too low

Carburetor holder loose

Air cleaner poorly sealed, or missing

Air cleaner duct poorly sealed

Air cleaner clogged

Compression high:

Carbon built up in combustion chamber

Engine load faulty:

Clutch slipping

Engine oiHevel too high

Engine oil viscosity too high

Drive train trouble

Brake dragging

Lubrication inadequate:

Engine oil level too low

Engine oil poor quality or incorrect

Coolant incorrect:

Coolant level too low

Coolant deteriorated

Cooling system component incorrect:

Radiator clogged

Thermostat trouble

Radiator cap trouble

Thermostatic fan switch trouble

Fan relay trouble

Fan motor broken

Fan blade damaged

Water pump not turning

Water pump impeller damaged

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Also is there a way to test the CDI/Stator/Rectifier/Ignition Coil, or is it just, if you buy a new one and it doesn't work your kinda boned type thing?

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There are tests you can do with a multimeter, I would suggest buying a manual. If will have directions and specs for the electrical tests you need to do, and it will have other info that you will need to do motor work, like torque specs and wear limits. The first thing I would test is wiring, connections, grounds, and switches. There are a few switches that could be keeping your ignition from even being turned on if they aren't working properly.

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To test coil:

Touch one of the meter probes to the lead terminal. Touch the other probe to the ground. Replace the ignition coil if it is out of specification.

Primary Resistance: 0.18 - 0.28 Ω @ 20°C (68°F)

Here are electrical specs for you:

Ignition System DC C.D.I. Magneto

Generator System AC Magneto

Battery Capacity 12V 12AH

Battery Type GM12CZ-4A-2

Headlight Type Bulb Type

Headlight Wattage 30W/30W

Taillight 5W

Brake Light 21W

Neutral Light 3.4W

Reverse Light 3.4W

Voltage 12V

Ignition Timing (B.T.D.C.) 10° @ 1,000 rpm

Advanced Timing (B.T.D.C.) 33° @ 5,000 rpm

Advancer Type Electrical

Magneto F4T466

Pickup Coil Resistance 459 - 561 Ω @ 20°C (68°F)

Rotor Rotation Coil Resistance 0.083 - 0.101 Ω @ 20°C (68°F)

C.D.I. F8T38675

Ignition Coil 2JN

Minimum Spark Gap 6 mm (0.236 in)

Primary Winding Resistance 0.18 - 0.28 Ω @ 20°C (68°F)

Secondary Winding Resistance 6.32 - 9.48 kΩ @ 20°C (68°F)

Spark Plug Cap Resin Type

Cap Resistance 10kΩ @ 20°C (68°F)

Charging Current min. 12A or more at 3,000 rpm

Charging Current max. 17A or more at 8,000 rpm

Charging Coil Resistance 0.83 - 0.101 Ω @ 20°C (68°F)

Voltage Regulator Type Semi Conductor-Short Circuit

No Load Regulated Voltage 14.1 - 14.9 V

Rectifier Capacity 14 A

Rectifier Withstand Voltage 200 V

Battery Specific Gravity 1.280

Starter DB5DT

Out put 0.7 Kw

Armature Coil Resistance 0.011 - 0.013 Ω @ 20°C (68°F)

Brush Overall Length 12 mm (0.47 in)

Brush Overall Length min. 8.5 mm (0.33 in)

Brush Spring Pressure 650 - 950 g (22.9-33.5 oz)

Commutator Diameter min. 28 mm (1.10 in)

Commutator Diameter max. 27 mm (1.06 in)

Mica Undercut 0.6 mm (0.024 in)

Starter Relay MS5D-611

Amperage Rating 100 A

Coil Winding Resistance 3.9 - 4.7Ω

Fuse 15 A

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No luck, I found a deal on RMStator.com for the Stator, CDI, Ignition Coil Spark Plugs, Pulsar Coil Pickup, Krypton Light Bulbs, and the Flywheel Cover Gasket for $200 and for another $100 for the Voltage Regulator/Rectifier. I plan on putting some work into my quad, like getting a Stroker Crankshaft +7mm a +1mm stroker piston, an Edelbrock 24.3 rated hp Carb. So I'm going to replace all of that stock crap with higher performance parts. I did test the CDI and two of the wires were testing fine. around 460 ohms. Never tested the Voltage Rectifier, didn't feel like it. :aargh:

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Just an update, I am going to order the Banshee YFM350X Haynes Book for my Warrior 350 for electrical specs and engine stuff. I got a $50 Amazon gift card for christmas that I'm going to use for that. I am going to replace all that stuff mentioned in an earlier post about the RM Stator deal. Don't know when, probably as soon as I get an extra $300 to spend (probably tax return season). I have to take my carburetor in to work so I can mill out my frozen air/fuel mixture screw, put a helicoil in it, then get a rebuild kit for a new pilot screw. I have to order some HTS-2000 Brazing/Soldering stuff for the pot aluminum float arm I snapped off inside the bowl area of my Carburetor trying to disassemble my carburetor to soak it in some Chem-Dip to clean it, and break junk free and nylon brush it down. So as soon as I get the parts, probably mid February I will update again. Well I'm going to go out to my quad and take my carburetor off right now to see if i cant get that pilot screw/'air/fuel' mixture screw off by hell or high water. See ya then, Nathan L. Mesa, AZ

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Don't order a Banshee manual, a Banshee is nothing like a Warrior. Neither the motor or electrical systems share any similarities aside from displacement. You can find a manual for a Warrior if you look for it. Try Ebay. I hope you haven't ordered it already. I would just find a used carb on Ebay or at a salvage yard, along with a rebuild kit, that will be far easier and probably even just as cheap or cheaper than trying to repair the damage.

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