Nytro Exhaust

[Nytroman]

On the last outing, my Mcx Nytro seems to have a miss when it first hits full boost. I noticed that the inside of the exhaust tip seems the have a lighter grey coating than the normal dark color. I was first running just premium pump gas, and thought it was just a poor batch. I added a gal. of 113 and still no change. Rpm's are reaching max of 9200 for a few seconds, and have looked over everything for a pinched line etc. I'm going to pull the plugs tonight, not familiar with the 4 strokes yet, should coloring represent same as a 2 stroker.
Any suggestions appreciated, don't want to melt it down

 

[firecat99]

yuppers plugs should always be a golden brown for a good burn, trucks cars everything that has plugs

 

[stephenclark]

What fuel are you running?
I am definetly not an expert on the chemistry of what is happening but I have noticed that engines running race gas always have a light brown film on the inside of the exhaust. On pump gas machines the film is pure black.

 

[turboless terry]

nytro man you are running to many rpm and it is popping against the rev limiter. you need to reclutch to get the rpm down.

 

[BigFish BC]

nytro man you are running to many rpm and it is popping against the rev limiter. you need to reclutch to get the rpm down.

yes that poping noise is the rev limiter your motor is starting to break in & will pull more rpm as you get more miles on it,9200 is max on this motor.

 

[spray25]

According to MPI there is a soft rev limiter at 8900 and a hard limiter at 9200.

 

[Nytroman]

Thanks guys, I was discussing that with a buddy last nite. I took it out again and it is getting close to that 9200rpm, was going to call service to see where the limiter is at. Pulled the tank to check the plugs, they look like they have only been in 2minutes, but found the aluminum fuel tank cap where the return line is to be leaking through a pin hole in the weld. Great for a burn down, just tigged it and need to put back together. Might be something you guys want to watch for, leaking fuel + hot turbo may not mix
appreciate the info