A/F & cooling issues. Please help this noob!

[brook32v]

So I bought my first ATV today. It is a 2001 Yamaha Warrior, and I love it! Anyways, this Warrior really does run great, but there are a couple things that have brought a concern already. The first thing I noticed right away is that the engine (IMO) seems to get extremely hot in comparison to my buddy's Warrior after beating around on it for a while. Overheating? No, I wouldn't go that far, but I really don't feel that it is operating under regular temps. What would cause this?

Secondly, I think the tune is off some. Although it runs fine under WOT and idles correctly (sometimes a hair higher then it should maybe), the engine will often die if I were to tap the gas quickly. This will happen often, and it will sometimes be kinda hard to start afterwards. It did backfire once when this happened. I don't know hardly anything about ATV's, so I'm somewhat thrown against a wall here. What would be the smartest way to pin point what is going on? ANY info would help greatly.

Thanks!

 

[griff]

Need more info....

How does the airbox and air filter look, stock?

Any after-market exhaust on it?

Stock carb?

Jetting could be off, if its too lean it will run hotter.


How fresh is the oil? Oil filter look OK?

 

[brook32v]

I haven't even looked at the filter & box. I assume it is stock. The exhaust is stock, except for the baffle taken out. Looks lie a stock carb. Fresh oil.

That is all I know. I just bought it yesterday.

 

[brook32v]

UPDATE:

The air filter is NASTY. I'm talking as bad as you could ever imagine. The spark plug also looks like someone crapped on it. It isn't white though, so it must not be running too lean.

I got a new filter and will pick up a new plug today and see if this will cure most of the issues. I wonder if those things were making it run a tad warmer from having to work harder?

 

[griff]

Yikes.... it would have been running rich based on what you found, which usually lets things run a little cooler.

BUT, if it was clogged up that bad, there may be other issues.

After you get that filter and plug swapped out, pick up a small bottle of STP Fuel Injection/Carb cleaner, and add about 1/4 bottle to a fresh tank of gas and go run the piss out of it.

 

[yamarider]

That stuff could definitely cause it to run less than perfect. Riding with a clogged filter is like riding with the choke pulled out. I've had experiences where running too rich has also caused the machine to run hotter than normal, so maybe some simple maintenance will take care of all of this.

 

[griff]

That stuff could definitely cause it to run less than perfect. Riding with a clogged filter is like riding with the choke pulled out. I've had experiences where running too rich has also caused the machine to run hotter than normal, so maybe some simple maintenance will take care of all of this.

I was thinking, if the filter is that plugged up, there would be a substantial lack of vacuum in the venturi... no strong vacuum signal = fuel isnt being pulled out of the jets.

That low velocity air would have little to no fuel in it, making it damn lean. That would explain the hotter running temp.

 

[brook32v]

Thanks for all your inputs, guys.

I replaced the filter, plug, sprayed some cleaner on the air side of things, and gave it a bath. It runs totally different now. It no longer wants to die. I only ran it for 20 minutes or so around the yard, so I can't confirm if it is still running on the warm side. I think everything is cured though!

This is what my Warrior looks like. She is in need of new stickers and rear tires.