1986 80cc Yamaha Moto4 Badger Resurrection

Yamaha Badger 80 Moto4So a little background on this little atv. My father bought a couple of these moto4 Yamaha Badgers when I was around 9 or 10 if I remember right (around 1993 or 1994). The two atvs were almost identical except the other one had red fenders instead of black. I remember both machines running decent but this black fender atv always was the slower one and as the years went by, this one was always harder to start and keep idling okay. Eventually the only way we could get it started was to push or pull start it as it just never would fire up cold with the electric start. In the course of riding over the years, the front air filter housing became broken, the seat was recovered by my mother who sewed a new one. These machines were well loved in my childhood but over the years, they were neglected and mostly forgotten.

Fast forward to today. After charging the battery, which miraculously seems to still hold a charge after sitting all winter, I put some gas in it and with the help of some pliers turned the petcock to the reserve setting and turned it over. By some miracle, it eventually started with full choke but only with full throttle held down and this is on a warm summer day. Even then it barely stays running. It will not idle and even when it does run it dies shortly after either from too much fuel or too little (my first thought is float needle valve setting).  I also noticed the intake boot is not connected to the air filter Yamaha Badger Fuel Petcockhousing I’m guessing it will need a carb clean and hopefully the cylinder is still okay with who knows how much unfiltered air going through there. The only way to move the petcock valve is with a firm twist with pliers so that will be replaced with a new oem petcock. With how it ran in the past, it might be due for a new top end rebuild but I was not able to test compression yet. For now, some new carburetor parts are on the way and a fresh oem fuel petcock.

Step 2: Rebuilding the carburetor

In a past blog post, I wrote about how to clean a carb so it will work again, because of the age and severe conditions of this carburetor (lot of unfiltered air and possibly gas flowing through it) I opted to rebuild the whole carburetor with a rebuild kit that included 2 new jets, idle screw, idle mixture screw, new gaskets, float needle valve, jet needle and adjustment clip and tension spring.  Once the parts arrived I went to opening up the carburetor and seeing the damage and get to cleaning.

YFM 80 Carb Float Bowl
Lots of dirt and sand in the bottom of the float bowl

There was lots of debris and sediment in the bottom of the float bowl so that was worrisome. I figured if I got it all back together and there was low compression or it still had issues that I could always redo the top end fairly cheap. Below are pictures of the carb rebuild process which consisted of thoroughly cleaning all the carburetor parts and then putting the new rebuild part in.


Once I had everything in place, I still had to fix the issue of the intake. After brainstorming a bit and not being able to get the intake boot connected to the intake/filter housing, I opted to go with a cheap pod filter for now until I can figure out a better method.

Pod Filter yamaha Badger
This filter wouldn’t fit because of the choke lever
Correct Pod Filter for Yamaha Badger 80cc
Correct Pod Filter with angled boot





Tire Slime in Yamaha Badger Dry Rot Tires
Tire Slime has it’s limits

I ordered a low profile one thinking it would be best to have it short so it wouldn’t touch anything but after it arrived, I realized it was directly in the way of the choke lever. I ended up going with one that had a boot at a 90 angle which seems to work great although I think water crossings could pose an issue unless I put a prefilter on it. My eventual plan is to find route it into the original air filter housing with a longer 35mm hose but for now this setup seems to work fine. The last issue was the tires being dry rotted and cracked and one not holding air at all. I decided to test the limits of slime before trying to buy new tires and I was able to break that limit with a large crack right in the tread of one tire. I ordered some new tires (Kenda K530 18×7-7) which are an inch bigger than the stock size but they still fit the bill. (it helps that there is not suspension on this machine) I had replaced the rears with the same tire as well not long ago so now all 4 tires match although they are slightly different sizes from stock but that’s all I could find close enough to the stock tire sizes which were 17×7-7 stock front and 18×8-7 rear stock size replaced with these Kenda Pathfinder K530 18×7-7 all around. Once I got the carburetor back on and the pod filter installed, it only took minor adjustments of the idle mixture and idle speed screws and she was purring like a kitten. I also drained the old oil which was last changed who knows when and topped it off with some fresh 10w-30 oil. Overall I spent less than $100 and she runs as good as she did 20 years ago!

New tires, air filter, and freshly rebuilt carburetor, and she runs like a champ!

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