Subject: 1993 YZF750R 70K KM's (bone stock)
Issue: Poor low-speed carburetion. (under 5K RPM)
Been battling an irritating carb issue that has slowly been getting worse over time.
- Very poor idle when cold;choke operation is not as effective as it used to be.
- Higher Idle when warm; (under 1000 when cold, about 15-1600 when warm.)
- 'Stumble & stutter' at low speeds; 2K - 4Kish RPM.
- Poor mileage; 170-180K per tank instead over 220-230K.
- Clears up after 5K, and seems to pull strong on up to 10K+.
I've been searching around various technical threads (on various sites), and the common issue seems to be accelerated wear on the needle jet and emulsion tubes, which causes a rich low-speed circuit.
I have not had the carbs apart yet, but plan on doing it next week. I have new emulsion tubes on order from the dealer ($45CAN ea - ouch!) that should be in on Tuesday or Wednesday.
My plan is to:
-check/clean the carbs out
-replace the emulsion tubes
-check/reset the float heights (most articles I read said to DROP the float height 1mm or 2 mm for better performance)
-then re-sync the carbs.
Sounds like a fairly simple plan, but there are always little glitches and finicky little things that come up while the carbs are apart.
Anyone else tackled this job that can offer any advice?