Sweet GP246F
New member
Does anyone have a 135 main jet for a 1974 - 1975 GP246F? The original Yamaha part number is 849-141432700. I have the head milled .015, cylinder bored .020, .002" thick head gasket, and ported/polished. Does anyone know if taking off a total of .081" for compression will require 110 octane? I am at .063 now, and have .018 to go by replacing the base gasket with my .002" gasket material. 
vmaxdad8657
New member
The Dennis Kirk catalog has main jets for the Keihin carb
from a size 90 right up to a size 200.
They list for $5.99 each
I knew the GP246F came with a #140 main jet, and they recommended dropping down to a #135 main jet, but if you have some modifications,
you might want to experiment with a few diffent sizes.
Do you still have the oil injection connected?
I have a stock 1975 GP-246F that has the oil injection disconnected,
and we're running premix through a tillotson carb.
It does a solid 70 mph on the jack stand.
However, we want to restore it totally to original, with the original carb , brackets, and cables, so that the oil injection is once again functional.
Let me know if you want to sell off the parts that were connected to the carb that connects to the oil injection cable.
from a size 90 right up to a size 200.
They list for $5.99 each
I knew the GP246F came with a #140 main jet, and they recommended dropping down to a #135 main jet, but if you have some modifications,
you might want to experiment with a few diffent sizes.
Do you still have the oil injection connected?
I have a stock 1975 GP-246F that has the oil injection disconnected,
and we're running premix through a tillotson carb.
It does a solid 70 mph on the jack stand.
However, we want to restore it totally to original, with the original carb , brackets, and cables, so that the oil injection is once again functional.
Let me know if you want to sell off the parts that were connected to the carb that connects to the oil injection cable.
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vmaxdad8657
New member
Some GP-246F's came with a Mikuni BN38-34SH
If it's a Mikuni carb,
Go to E-Bay.
They have a bunch of jets for the Mikuni carb.
Type in "mikuni snowmobile carb"
M N Vintage Snowmobile has them listed for $2.15 each
If it's a Mikuni carb,
Go to E-Bay.
They have a bunch of jets for the Mikuni carb.
Type in "mikuni snowmobile carb"
M N Vintage Snowmobile has them listed for $2.15 each