Mikuni Tuning Issue

Redtail250 · 07-01-2022, 01:30 PM

Hey all! I’m back in need of Hawk wisdom. Calling jerryhawk and megadan lol. So I’m having trouble tuning my carburetor on my 2020 Hawk 250. My problem is I have an off idle bog, yes, lean bog. Once warm, at any speed in any gear in any atmospheric condition, with any load combination (just me or 2 up, luggage or not), at various altitudes in Pennsylvania, it will bog right as you take the throttle up from its rest point. After that, it will pick up and go and I mean haul ass with no bog. Doesn’t do it when the engines cold. Have chopped plug and it’s a perfect lightish hazy brown indicative of clean thorough burn. I’ve experimented with many jetting combinations to no avail and yes I’ve looked and searched through the forum for information and have my Hawk set up as per recommended jet sizes/screw settings, and still have this problem. I am using genuine mikuni jets from jetsrus. Specifications are as follows:

Main: 110
Pilot: 25
Mixture screw: 1.5 turns out from snug, to the left, counter clockwise.
Needle clip at 1st notch down from middle (1 notch richer, needle is 1 notch higher).
Valve lash: .003 on intake and .005 on exhaust
Lawn mower fuel filter installed and clean.
Single stage pod filter
eBay SS exhaust
Idle speed approximately ~1200
Mileage: 2,500 miles
Tuning altitude: ~800+ (Chambersburg PA)
Fanatically serviced/maintained/washed and detailed
No leaks, no backfires, starts immediately with full/half choke depending on ambient temperature.

07-01-2022, 01:30 PM	#1
Redtail250 Join Date: Aug 2021 Posts: 7	Mikuni Tuning Issue Hey all! I’m back in need of Hawk wisdom. Calling jerryhawk and megadan lol. So I’m having trouble tuning my carburetor on my 2020 Hawk 250. My problem is I have an off idle bog, yes, lean bog. Once warm, at any speed in any gear in any atmospheric condition, with any load combination (just me or 2 up, luggage or not), at various altitudes in Pennsylvania, it will bog right as you take the throttle up from its rest point. After that, it will pick up and go and I mean haul ass with no bog. Doesn’t do it when the engines cold. Have chopped plug and it’s a perfect lightish hazy brown indicative of clean thorough burn. I’ve experimented with many jetting combinations to no avail and yes I’ve looked and searched through the forum for information and have my Hawk set up as per recommended jet sizes/screw settings, and still have this problem. I am using genuine mikuni jets from jetsrus. Specifications are as follows: Main: 110 Pilot: 25 Mixture screw: 1.5 turns out from snug, to the left, counter clockwise. Needle clip at 1st notch down from middle (1 notch richer, needle is 1 notch higher). Valve lash: .003 on intake and .005 on exhaust Lawn mower fuel filter installed and clean. Single stage pod filter eBay SS exhaust Idle speed approximately ~1200 Mileage: 2,500 miles Tuning altitude: ~800+ (Chambersburg PA) Fanatically serviced/maintained/washed and detailed No leaks, no backfires, starts immediately with full/half choke depending on ambient temperature.
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