Can someone tell or more helpful show me where the adj screws are for a 2001 Big Bear 4x4 fuel/air mixture on the carburetor? Is there a starting point I should work from? I think this needs to be tweaked because I get a lot of carbon on the spark plug and the engine seems to choke out and backfire slightly when I give it gas at low RPMS.

Appreciate any help I can get.

 

Sounds like too lean, if the motor pops on throttle opening. You can verify by pulling on the choke, just before opening the throttle. It should get better.
The fuel mixture screw, is on the underside of the carb, just forward of the float bowl. Screwing out, is richer

 

Pull your sparkplug and check the color white means to lean , black means to rich ; color should be a brownish tan !

On the carb adjustment turn the mixture screw clockwise counting the number turn's , untill you feel a light seat ( not to tight or you will damage the seat ) ; then turn the screw counter clockwise 2 1/2 turn's is the starting point of the adjustment on your carb !

After you get the carb mixture set pickup a can of Sea Foam from your local parts store Auto Zone , Advance or O'Reillys Parts Store ; i get it from O'Reillys for $5.99 + tax it's a great fuel treatment the best i've found !

One 16 oz. can will treat up to 25 gallons of gas or diesel fuel safe for 2 or 4 stroke engines , it will clean the fuel system and your combustion chamber of built up carbon deposit's and has a drying agent to help keep moristure from forming inside the fuel tank ; and keep's your fuel fresh longer i mix mine in a gas jug and use it every other tank full ! ...........

 

Thanks guys for the help I will give it a try. This is the diagram I am referencing to identify the right screw. Can you confirm the one I am looking at. Maybe I am complicating things. I will get out the am and look at the bike as well.



http://www.yamahaaccy.com/parts.aspx

I have noticed the muffler just off the head gets glowing red when I start with the choke on. I have heard this is a sign of too lean?

 

Those links to parts finders dont work, Im sure it has something to do with the cookies it sets on your computer, which dont make the link.
Its number 7, the screw with the spring.
Im not sure if this pic will work or not.
Reading the color on spark plugs isnt that meaningfull or easy. Modern gasoline, manditory additives, and not knowing what jet you were using (pilot, needle or main), plus the correct way to read a plug is by looking way down inside, and observing the location of the smoke ring. You can read more about it here. http://www.dragstuff.com/techa...ading-spark-plugs.html or <a target=_blank class=ftalternatingbarlinklarge href="http://www.strappe.com/plugs.html
">http://www.strappe.com/plugs.html
</a>
Id just worry about the symptoms , and jet accordingly.
If the head pipe gets red, either its running lean, or youve let it idle too long, with out cooling air flowing past it.
As long as youre working on the carb, replace, or completely clean the pilot jet. Which means removing, and cleaning with a carb cleaner(sometimes for hours) and reinstalling. Its easier to just replace it if you suspect its plugged.

 

I have a 1990 Big Bear. When using yesterday the plug fowled and wouldn't start back up. Upon investigation I found a fair amount of gas in the air filter box. I am assuming I have a stuck float. How do I fix this?"???? The left hand brake cable is also frozen tight. ( I have put penertrating oil down the cable housing)
Thanks in advance!!!

 

Fit a new brake cable, it isn't worth the hassle of trying to free it. Aftermarket cables are cheap. Float needles get dirt stuck in them, I try turning the tap off, running until the carb is dry and then opening the tap again, the resultant rush of fuel may flush the dirt out. If that doesn't work, remove the float bowl and float, check the needle for grit stuck in the rubber, and the tiny plunger, that touches the float, can spring up and down, if it doesn't spring, fit a new one. Blow the seat and jets out with compressed air and re-assemble. If fuel got into the sump (a rise in oil level and thin oil), change the oil.

 

looking for the gap size for the sparkplug on the 2002 bigbear 400

 

I have the book for the 2002 Yamaha 400FAR (water cooled, whatever that is) and gap is 0.024" to 0.028" The 350 Bruin is also covered and has same plug gap.