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1998 yamaha big bear

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No. Not if it's meant to have, and been running ok on the 8.You should adjust/setup the carby.

Are you sure though this black plug is new ? Are you sure you don't have an ignition problem ? Why did you change the carby ?

Aftermarket carbies are never setup for any particular model, market, fuel or altitude range.. That are all generic tune that will work after a fashion for almost any bike they will fit on. It's generally best to repair/clean your old carby.

It's just slightly possible the new carb has a problem, or perhaps only needs some adjustments. Have you tried adjusting the idle mixture and speed ? How is the bike running ? How was the bike running before you changed the carby ?

Quite likely, if the new carb looks like an exact copy of the old carb, you can probably swap all the old jets over into the new carby, including the slide and needle, and the long brass tube the slide needle fits down into.. That will probably cure the problem... if it is a carb problem..

Apart from that you need to start re-tuning that new carb..

I generally opt for cleaning the old original carb and putting that back on when ever I hear these stories....

Edited by Mech
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New carb is flooding ,black plugs, you need to dial in the fuel air mixture if you can, I v had some trouble dialing in aftermarkets . also if the air filter is not stock aftermarkets can be rather dense and cause some degree of flooding.

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Gw's right.. check the air filter..  If foam elements have too much oil they restrict the air flow, and paper ones can swell and block in humid weather if they aren't being used.

Otherwise.. It's almost certainly the carby.

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  • 5 weeks later...

Too much fuel. In my experience thats what causes the carbon buildup. Never had the issue on an atv engine, but on cars, intake leaks from the intake, valves, and headgasket can also give you inconsistent fuel delivery. Just to give something more than carb(even though that's the most likely culprit)


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