Question about predator 212 @ higher rpm’s

[ole4]

We had motorcycles coming to Myrtle Beach for bike week every year. We had to stock up on spark plugs because the bikes coming from higher altitude areas down to sea level ran so rich, they fouled plugs. Rather than rejet for the week, they just changed the plugs. It would seem that higher altitude and thinner air would make them rich, but for some reason, that does not seem true. Maybe not enough signal, or airflow to draw fuel from the bowl?

1000 feet should not be drastic, but OP stated his plug stays looking new after WOT riding.

I cant explain that but I used to go to colorado in the early 70's and I remember renting a ford elite (351 windsor with carb) and we drove up to the continental divide and drove down Pikes Peak and near the top the dam thing smoked like a diesel, had no power. However what I don't understand is if the air is less dense I would think the venturi effect and fuel signal would be less. Maybe it's the lack of oxygen plus the carb fuel mix stock is just too rich even if the fuel draw is less. Going to have to figure that one out, but for sure you drop jet sizes as you go up in altitude.

 

[MJL]

We had motorcycles coming to Myrtle Beach for bike week every year. We had to stock up on spark plugs because the bikes coming from higher altitude areas down to sea level ran so rich, they fouled plugs. Rather than rejet for the week, they just changed the plugs. It would seem that higher altitude and thinner air would make them rich, but for some reason, that does not seem true. Maybe not enough signal, or airflow to draw fuel from the bowl?

1000 feet should not be drastic, but OP stated his plug stays looking new after WOT riding.

It was the low speed cruising that fouled plugs. Engines tuned rich down low for good throttle response fouled when they never had the chance to open up, heat the plugs, and clean them up.

 

[sparkwizard]

I am beginning to suspect those guys who came from higher elevations were running with their chokes on so they would not overheat at the beach. I never really thought about it before. I just know we sold hundreds of plugs to the visitors.