I put a new after market carb on and fixed the intake,same results.
Has the bike sat for a while? With gas in the bowls? Gas varnishing will cause a load of trouble. Also this is an old bike, when was last carb overhaul? If I had to venture a guess it sounds like a needle jet issue. Check air filter first and for any obstruction in the intake end to carb throat to be sure good clean air is getting in. Check the manifold (between back of carb and where it enter engine to be sure of no vacuum leaks. Spray some carb cleaner around the joints pipe or tubes leading to engine chamber, an increase in rpm is a sure vacuum leak. If all ok, clean carb throughout with brushing and cleaner not just a chem soak it will help a lot but not adaquatly clean jets and seats. Double check float level, even a mm off will effect some, finally knowing now all is good assuming you either used a carb rebuild kit after cleaning or at least replace any warn gaskets and o rings, go to needle jet measure for wear with specs and inspect for any dirt damage etc your issue sounds like either an over rich or over lean needle jet depending on the sputtering you describe is lean and running out of fuel at top end (floats and other jets also effects this) or is it bogging out too rich and if you back off it picks up speed then could be warn needle jet (also emulsion tube that the needle jet slides into). It’s a lot but really the only way. Best way to narrow it down is a plug chop and read the deposits on the plugs. The masters of this can dial in as good or better than a Dina-tune. I am not skilled at this but there are several internet posts about it. Good luck
SOURCE: honda 1300c backfire through carb at wide open
If you have used Dyno jet kit I have had a kit come through with smaller main jets than the stock ones causing it to run way to lean.
SOURCE: Motor spits and sputters
If it is old enough to have points then I would check them and make shure they are clean and gapped at .020. if that is noth the problem then it sounds like a fuel issue. Either a weak pump or a dirty carb.
SOURCE: kawasaki prairie 360 atv spits & sbuters at
its your choke. when the choke is to the left it will sputter around. try moving the choke completely to the right. mine does the same thing u just have to run the choke on the right side. i dont know if its supposed to be on the left or right but if u push it ALL the way to the right it should be fine. my kawasaki 360 prairie is pushin 55 mph so i think i have it set up right.- Kyle
SOURCE: have a 04 yamaha big bear 400. hard to start wont
I have an 01, and it started doing this. I don't remember the circumstances. It's just dirty in the carb I think.
1) Check for water in the gas.
2) Turn off the petcock and drain the carb. turn it back on.
3) Try it.
4) Start it with the choke on and put your hand over the air filter hole. Will cause some back flow.
5) Try again.
Worked for me. Might be dirtier on yours, or have mud in it or something.
SOURCE: 2004 v twin 16 hp 500hours on it runs but spits
You should take one of the heads off and look at the valves. You may have deposits building up no the valves.
120 pounds compression sounds pretty good for a six year old engine with 500 hours on it. It probably started life at 9 to 1 and now is around 8 to 1.
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