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So I have a '99 XCR-800 with the Mikuni rack carbs. They have been bored 38 to 40mm.
The only change from stock is the pilot air jet being a 0.9 instead of 1.0 to richen up the low end.
Pilot jet 145
Main 450
Mixture 1.5 turns
Needle clip 3rd slot
I took her for a ride yesterday. The Kuskokwim river is frozen, very flat, and has 4 inches of light powder on it. I drove at 5500 rpm for about 1 mile with EGT temps around 1200* F. Shut down and the plugs looked good. Pistons too new for a wash check, they are still shiney. Then took it to 6000 rpm and the temps hovering around 1275-1300*F, the curved part of the plug that extends over the electrode still looked good, the plugs had been a little wet with oil (I am off adjustment), they were now noticeably drier. When I took it to 6500 rpm, the clutches are beginning to shift, there is a greater load on the motor, and I am going 60 mph. The temps on the EGT's are at 1375*-1400*, at the entry to the danger zone with my probe placement. I am guesstimating I was a little over 1/3 throttle. The plugs were now dry except for a little oil on the end of the rim, the curved portion was not grey, but you could see the beginning of a little color change, no longer that cardboard brown.
I know the oil in the gas-tank for break-in would lean the mix out, and with the oil pump needing adjustment, that would lean it even further.
This morning it is 5* F, so I will struggle with the airbox and getting the oil pump where it should be first off. Next will be turning the mixture screw in 1/4 turn from 1.5 turns out to 1.25 turns out. This will also help the low end mix richen just a little. I think these will work well off idle to about 1/4 throttle. I will compare these adjustments to yesterdays.
Depending on how plugs and EGT's read, I will then move the needle clip down 1 slot to bring the needle farther out of the needle jet. This will richen the 1/3 - 3/4 range. It was suggested to me to move 2 slots, but I want to see how it looks with just one.
The beauty of having that flat river out there is: I can make as many runs as I want, just changing one thing on the carbs to see what the effect is.
I am going to take some spare plugs with me so I can run up to the Pol dealership and show the plugs to the mechanics and service manager for their opinions. Then back down to the river for more testing.[
]
The only change from stock is the pilot air jet being a 0.9 instead of 1.0 to richen up the low end.
Pilot jet 145
Main 450
Mixture 1.5 turns
Needle clip 3rd slot
I took her for a ride yesterday. The Kuskokwim river is frozen, very flat, and has 4 inches of light powder on it. I drove at 5500 rpm for about 1 mile with EGT temps around 1200* F. Shut down and the plugs looked good. Pistons too new for a wash check, they are still shiney. Then took it to 6000 rpm and the temps hovering around 1275-1300*F, the curved part of the plug that extends over the electrode still looked good, the plugs had been a little wet with oil (I am off adjustment), they were now noticeably drier. When I took it to 6500 rpm, the clutches are beginning to shift, there is a greater load on the motor, and I am going 60 mph. The temps on the EGT's are at 1375*-1400*, at the entry to the danger zone with my probe placement. I am guesstimating I was a little over 1/3 throttle. The plugs were now dry except for a little oil on the end of the rim, the curved portion was not grey, but you could see the beginning of a little color change, no longer that cardboard brown.
I know the oil in the gas-tank for break-in would lean the mix out, and with the oil pump needing adjustment, that would lean it even further.
This morning it is 5* F, so I will struggle with the airbox and getting the oil pump where it should be first off. Next will be turning the mixture screw in 1/4 turn from 1.5 turns out to 1.25 turns out. This will also help the low end mix richen just a little. I think these will work well off idle to about 1/4 throttle. I will compare these adjustments to yesterdays.
Depending on how plugs and EGT's read, I will then move the needle clip down 1 slot to bring the needle farther out of the needle jet. This will richen the 1/3 - 3/4 range. It was suggested to me to move 2 slots, but I want to see how it looks with just one.
The beauty of having that flat river out there is: I can make as many runs as I want, just changing one thing on the carbs to see what the effect is.
I am going to take some spare plugs with me so I can run up to the Pol dealership and show the plugs to the mechanics and service manager for their opinions. Then back down to the river for more testing.[