Question about predator 212 @ higher rpm’s
- Thread starter devlinrules12
- Start date
I was just gonna say since brookbank (the new guy) says it runs great on any main or pilot, He could already be too rich for that size carb but if he's jetted even higher and is running good now then that's good, for now 
What is your guess as to why he tops out at 3800 wide open? I assume his governor in not connected.
Yeah I wondered about the gov, too. It's the topping out at 3800 but still being called "good" that has me thinking it's a richness problem. Like he's bumping into a limitation rather than coming up short of it. He said it runs good no matter the jet, which tells me he doesn't have the mixture dialed in but may just be happily over-fueled. Plus he wouldn't be saying it runs "good" if he was under-jetted. Nibbi PE24 ships with 108-115 main jets, and only one design for their too-long nibbi needle (which is undoubtedly still too far buried in the hole). He says it doesn't run better than 120 no matter how much bigger the main jet. So I'm thinking pull that needle up higher to get it out of the way at WOT and he may find better fuel flow, and might even find he can jet down toward 120 or 115 again and maybe find his sweet spot. Two cents..
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Just a thought. If the spark plug is of the wrong heat range, too hot, it may stay white and not show any deposit colors.
The engine in this case is highly modified from original, race cars/high performance cars run cooler heat range plugs than normal street cars.
Maybe your stock heat range plug is no longer correct for your engine.
If it were me, I would go to the auto parts store with the original spark plug and purchase a plug that is 2 or 3 steps cooler.
Just some food for thought. Let us know what you think.
The engine in this case is highly modified from original, race cars/high performance cars run cooler heat range plugs than normal street cars.
Maybe your stock heat range plug is no longer correct for your engine.
If it were me, I would go to the auto parts store with the original spark plug and purchase a plug that is 2 or 3 steps cooler.
Just some food for thought. Let us know what you think.
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.
1000 feet should not be drastic, but OP stated his plug stays looking new after WOT riding.
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Main jet correction chart for different altitudes and temperatures
Air density decreases with decreasing pressure and increasing temperature. If an
engine is operated at higher sea level, the weight of the aspirated air decreases,
whereas the aspirated fuel quantity remains practically the same. This results in richer
air/fuel mixture than at lower sea level.
The general rule for jetting is to drop one main jet size for every 2,000 feet of elevation increase. You can also go one clip position leaner on the needle jet. This is a good start for high-altitude adventuring, but depending on the temperature and humidity, you may need to go leaner or a touch richer.
Air density decreases with decreasing pressure and increasing temperature. If an
engine is operated at higher sea level, the weight of the aspirated air decreases,
whereas the aspirated fuel quantity remains practically the same. This results in richer
air/fuel mixture than at lower sea level.
The general rule for jetting is to drop one main jet size for every 2,000 feet of elevation increase. You can also go one clip position leaner on the needle jet. This is a good start for high-altitude adventuring, but depending on the temperature and humidity, you may need to go leaner or a touch richer.