Issues I had were fast idle was 3500-4000rpm, F1 C28 code, running a bit rough down low and “seemed” a bit down on power.
So I balanced the throttle bodies yesterday, first chucked in a new set of plugs, (first time since I’ve owned the bike, so well past due). NGK plugs that came out looked ok, 2 and 3 and bit darker than 1 and 4. Warmed the bike up first, idle set at 1100rpm. Ambient temps 25 deg C, K&N filter cleaned and re-oiled too.) Removed the IAS solenoid and vacuum lines, hooked up my Morgan Carbtune pro.(The tip about putting the tank across the seat rails is brilliant, works well). Anyways, found 1 was out from 2 by about 20mm Hg (26 to 28), and 3+4 were both out by 30mm Hg from 2. Synchronised 1 to 2, dead easy with the adjuster screw below (bought the right angled screw driver from Morgan Carbtune as well), then balanced 3 and 4. Set 1+2 to 3+4 after that, now all running around 28 mmHg. Adjusted TPS and STPS after that.
Found that when doing the STPS, there was a discrepancy between 1+2 and 3+4 when closing the throttle valves manually through the air box. Having the multimeter hooked up, when closing the throttles on 1 or 2, the STPS read 830 ish Ohms, when doing the same for 3+4, the STPS was reading about 804 ohms. Holding 1+2 closed, I could feel some play in the lever for 3+4. There’s a Phillips head (or JIS) adjusted between 3+4 facing upwards. The same one between 1+2 is nearly impossible to get to. I adjusted 3+4 until I got 805 ohms for both 1+2 and 3+4 secondary throttles when closing manually through the air box. Put it all back together, fired it up and fast idle went to 2000rpm, dropping back to 1500rpm after about 30 seconds and then settling to 1100 rpm after about a minute. Let it run for 5 minutes, revved it to 6500-7000rpm a few items, no rough spots or spluttering. Yet to go for a ride, it’s been too wet, but it definitely idles and sounds much smoother.
