Just bought a sportsman 500 efi. I have put 50 miles on it, the fist 20 of those miles at low speed as suggested in the manual for break in. I ran the break in period primarily in low gear at or below 15 mph. I removed the spark plug at 50 miles and found it to be dry fouled (black carbon). The dealer says it is most likely a result of the low speed operation, but in low gear I feel like the rpms should have been sufficient to get a clean burn. Anyone experienced the same problem? Also used stabil fuel stabilizer after the first 20 miles and a friend suggested he had a Honda that would always foul plugs with fuel stabilizer. Anything to that? Thanks for any imput.

 

I don't know for sure, but when breaking in the machine. Don't rew the motor to hard. Haven't you done that all the time by running it in low gear?

Low gear is for towing and going really slow, not to be used at 15 mph, not in break in time anyway.

Shouldn't you be in high gear and run the machine in normal rpms??? Does the manual say you sould run in low gear?

 

The manual says to avoid high speed during break in. It also says that at speeds below 10 mph to use low gear. It suggests varying the speed during break in, which I did. At any speed over 10, I shifted to high gear. I don't think I over reved the motor. In fact, the dealer suggested the problem may be from operating at too low of an rpm range. I don't know...
I think I have properly complied with the limited information in the manual for break in. The thing is, I live in the Rocky Mountains, and most of my riding will be up and down steep terrain at moderate to low speed, often in low range. I was also told by the dealer to burn regular unleaded, not premium at this altitude. He says the higher octane in premium is slower to burn at altitude. The contridicts what I have always be told about running premium in small engines. I am going to put in a new plug before my next outing and try some running at 15 - 30 mph in high gear. I will pull the plug then and see what happens.

 

I have 87 hrs. and 1200+ miles on my 500 efi. Still have the original plug in and don't anticipate chang ing in at least 5000 miles. Why are you using fuel stabalizer?

 

gjbldr it is now a proven fact that normal stress 1/2 to 3/4 throttle in short bursts is the best thing for a new engine... if you think about it when you buy a lawnmoer you run the thing at normal operating range, do the same with your atv... do not baby the machine when new you will have carbon deposits and lose ring seal