High Elevation Jetting?

[307dobbs]

Hello, I just purchased a 2023 Hawk 250, per my research upgrading the stock carb is suggested. I am not finding much in the way of jetting for high elevation. I am sitting at over 5000 ft and likely will be riding at higher. I will be ordering a VM 26 clone carb. The bike is together and fires right up, but only wants to idle at half choke. I still need to check valves that is a later this week job. Does anyone have jet size suggestions?

[TominMO]

Stock carbs tend to be set up to run lean at sea level, and that is what you want for higher elevations. Lean at sea level will probably be about right for 5000 feet, because at higher elevations you lean out the carb (if it is properly set up for sea level) so it doesn't run too rich, due to less available oxygen.

Full choke is too rich for elevation, which is why it idles better at half choke. I'll bet you don't even need half choke at all, or for a very short period. Your stock carb is probably fine.

[Thumper]

Yes it should run better at 5000 feet as stock. It is odd that it still needs more fuel (choke to idle). Maybe don't spend the money and do all of that work to change the carb just yet. Try two things first:

1. adjust the airmix screw. That might be all it needs
2. elevate the idle with the slide tower position screw (a little higher)

Since you are at over 5k in elevtion, original jetting could be just fine, really!
At any rate, these two adjustments will inform you about how close it is and whether or not rejetting is necessary.

If you can get it to idle with these adjustments, then ride it for a week or so and do a plug check. You have probably heard this, but blackening means too rich (unlikely since it wants choke to run!) Whiteness if it is too lean, which is indicated by your need for choke. But as I said, a little airmix adjustment might fix that.

[TominMO]

BTW you hopefully have an NGK spark plug, not a Chinese brand such as Torch.

[bigdano711]

I went with the Nibbi PE28FL, but the stock PZ30 did really well at the same elevation. I'm in Big Piney, WY. I see you're in WY, too. It's just a pain to get to the air mixture screw on it. Plus, the Nibbi is really nice. Stock jetting on the PZ30 was pilot 40 and main 105. I've been messing with my Nibbi and it was rich on the main and seems lean on the pilot. I've got the main close at 105 but may come down to 102. I get a rich pop (I believe?) on decel from wide open, just discovered today with my new pipe. :-) The pilot is at 40 and I may try a 42. After that, needle, which is currently in the middle.