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Goes only 12mph

3K views 12 replies 5 participants last post by  Ejm529 
#1 ·
I have a 2003 Yamaha FX140. Originally starting missing and now only goes as fast as 12mph. Starts fine and runs fairly good. I changed spark plugs, impeller, and air filter. Any other suggestions, fuel issue?
 
#8 ·
When I went run it yesterday it ran about 22 miles per hour and it was running about 6000 to 6200 rpms. When i would put it in revervse I could rev it up to 11000 rpms. What was odd was when I first went out to run it I could only get about 5000 rpms and 12 miles per hour and then all of a sudden it gained alittle more power and I was able to get up to 22 mph. It is running on all 4 cylinders just get get that speed in fwd.
 
#9 ·
Confused...
When I went run it yesterday it ran about 22 miles per hour and it was running about 6000 to 6200 rpms. When i would put it in revervse I could rev it up to 11000 rpms. What was odd was when I first went out to run it I could only get about 5000 rpms and 12 miles per hour and then all of a sudden it gained alittle more power and I was able to get up to 22 mph. It is running on all 4 cylinders just can't get that full forward speed.
Any suggestions or ideas???
 
#10 ·
This is a weird one. These yamaha 4 strokes usually only need the plugs changed. Its usually the only thing that happens to them. But you have already changed them. If it revs to 11000 in reverse i would'nt think it is electrical. Possibly the fuel pressure is down. You should check this. Also, sometimes the valve seats get a slight bit of surface rust causing them not to seal. This would happen due to condensation.
 
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