Oddemann Posted September 20, 2019 Report Share Posted September 20, 2019 (edited) Hello, I have a Beta Rev 80 which is surging/cutting out at high throttle/WOT. It is stalling for amoment, then picks up before stalls again.. I have cleaned carburettor and nozzles, i have checked float level, tried changing needle positions, changed gasoline and ensured fuel supply is ok. Changed spark plug. Checked air filter. I have no idea what can be the problem. I have not checked ignition timing, i dont even know how the ignition works. Any tips wold be appreciated, i still suspect the carburettor float or similar. Regards Oddemann Edited September 20, 2019 by Oddemann Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 21, 2019 Report Share Posted September 21, 2019 Did you change out the vent lines, or pinch the vent for the gas cap? Quote Link to comment Share on other sites More sharing options...
Oddemann Posted September 21, 2019 Author Report Share Posted September 21, 2019 6 hours ago, lineaway said: Did you change out the vent lines, or pinch the vent for the gas cap? The vent lines and gas cap is ok. I did also ran it without the vent lines. Is there a way i can verify the function of the float bowl ? Quote Link to comment Share on other sites More sharing options...
section swept Posted September 21, 2019 Report Share Posted September 21, 2019 Carb off and clean, tube attached to fuel inlet, gently blow using mouth into tube. Hold carb upside down, repeat blowing action....you should feel resistance to your air pressure. Float bowl off, repeat using a finger to gently lift float up....I’m guessing the float is attached to the carb and not sited in the bowl.... and lower the float allowing air in and stopping as you move the float. If the float is bowl sited then make sure any guide posts allow the float to move up and down smoothly. You will need to find actual height setting specs from the manufacturers manual. If the crankshaft oil seals are worn then this will allow a loss of crankcase compression and mixture which will affect engine performance and this is where I would be looking. If you can pull the crankshaft in and out by much then you may have worn main bearings which will load the oil seals more causing fairly rapid lip scoring. This will allow both air in and out while the engine is running. As a final few points to check as you seem to have covered most everything else, poor compression, badly worn cylinder bore, partial seizing...oil mix ratio+cooling issues. All can create similar symptoms to yours as described? 1 Quote Link to comment Share on other sites More sharing options...
section swept Posted September 22, 2019 Report Share Posted September 22, 2019 You may also have an ignition coil that is breaking down under load eg cant produce sufficient energy at high revs to keep plug sparking. Quote Link to comment Share on other sites More sharing options...
Oddemann Posted September 23, 2019 Author Report Share Posted September 23, 2019 I have concluded that carb and fuel is ok. Also compression is ok. I suspect the stator is malfunctioning and will order a new one. Then report back :-) Quote Link to comment Share on other sites More sharing options...
section swept Posted September 23, 2019 Report Share Posted September 23, 2019 3 hours ago, Oddemann said: I have concluded that carb and fuel is ok. Also compression is ok. I suspect the stator is malfunctioning and will order a new one. Then report back ? Hope you are right with that choice? Quote Link to comment Share on other sites More sharing options...
Oddemann Posted September 25, 2019 Author Report Share Posted September 25, 2019 Changed the stator today, and now it runs properly, and i am quite happy with that! And this seems like a common problem on beta. Regards Oddemann Quote Link to comment Share on other sites More sharing options...
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