Hey guys, I have a Yamaha champ 100 for my son and it has been working ok since I bought it this summer but recently I checked the spark plug and it looks really dry almost white and it didn't idle correctly so I adjusted the two screws on the side of the carb. it idles fine now but boggs under load. May not be anything to do with the adjusting I did but I think it is. my question is what are the two screws for and how should they be adjusted? I always turned them all the way in and 1-2 turns out but this doesn't seem to work. My son is getting frustrated with the bike so I really need some help. Thanks

 

One screw is the fuel/air screw the other is the idle speed screw. It raises and lowers idle speed. You may need to go though it and make sure the jets are clean. Look for videos on youtube. Champ,Badger I think used the same style carb,possibly the smaller Moto 4. Should be some videos that could help you.

 

Anyone know what one is the air fuel screw and will it affect how it runs under load?

 

The screw inline with the carb slide is the idle screw. The other is the fuel screw. Usually 1.5 to 2.5 turns out. If it still bogs the fuel screw setting wouldn't be the cause,but a dirty,plugged up jet could very well be.They still have rebuild kits for these old models on ebay,amazon.https://www.ebay.com/itm/Yamaha-Cham...MAAOSwAO9ZQFWV

 

Clean the carb dude.

 

There is only 1 carb kit available for that machine and all youll be able to use are the gaskets and O rings your carb is getting plugged on it take it apart and clean it. Make sure you use a wire from a wire brush to get in all the holes on the jets. also there is an additional brass sleeve that is below the pilot or main jet that pushes out also and there are holes in that also to clean. Them little carbs are a B to deal with but youll get it. Once you get it cleaned and ready to go put your intake hose next to a heater and get t warm so its flexable or youll have a heck of a time getting it back on. You might need heat to get it off the carb also when dismantling it. I just rebuilt one of these machines