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Yamaha Carbon Foweling Plugs

M

motorsportsandmarine

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Hi, Im working on a 2007 Yamaha 40hp that continues to carbon fowl plug #1 and #3... Plug #2 comes out perfect.:confused: I put new plugs in each time I run it and run it for 10min at various RPM's. It starts no problem and shakes alot at idle but at wide open throttle it will run perfect.

Work that has been done- Cleaned the Carbs two times, checked valve clearance, Ran stabil throgh the gas, all coils and wires are getting correct voltage and withen spec, Thermo valve is working correctly, Compression is good, synk~n~link the carbs perfectly, there is no water in the gas.

This motor looks brand new and does not have any oil or fuel leaks anywhere. When we place it in the shop tank there will be floating black carbon deposits all over. We have to clean the tank after running it two or three times.:mad:
 
Change the thermostats yet?

Did you adjust the idle needle screws all to the same number because they are all different
 
PBRMAN said:
Float valves not holding pressure or primestart valve not shutting of enrichment.
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Thank you for the response. We changed the float valves from carb two to carb three and had the same problem so i assume thats not the problem. We have placed a new primestart valve in and still the same problem.
 
justintime said:
Change the thermostats yet?

Did you adjust the idle needle screws all to the same number because they are all different
Click to expand...

The thermostat is working correcty, the spec is like 140-160 degrees and the engine warms up to 153.

I adjusted the idle needle screws all to 20 on my sink gauge as it stated in the service manual
 
You need to adjust the air/fuel mixture screw on the carbs that running rich which are #1 and #3. Good luck.
 
Vinh said:
You need to adjust the air/fuel mixture screw on the carbs that running rich which are #1 and #3. Good luck.
Click to expand...

PROBLEM SOLVED.... The throttle plates on cylinder #1 and #3 where installed backwards from the factory, put them back to normal and engine runs great... Thanks for the help everyone
 
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