Add my story to the pile. This weekend tried my luck on one of those 1/4 mile drag strip simulators on the back of a semi truck. The first run was 11 sec 1/4 mi @ 142 mph. Not bad for a begginer. Second run the chain skipped over a sproket tooth. I stopped quickly and walked the bike off and repaired it (tightened the chain).
On the ride back home, something wasn't right. After few miles determined engine surging was very bad. Around 3-4k rpms, Higher RPMs in lower gears where engine load is minimal. Accelerating in 1st gear was like strangling a rubber chicken.
It's real bad I thinking on way back, I screwed something up. Still ridable with adapting to gear and throttle combination to stay clear of surging.
Next day I was confirmed to go on a 500 mile group ride. No time to do much more then lube the chain and keep adapting. I put some Fuel injector cleaner gas treatment thinking it's a fuel injector passing a kidney stone. During downhill section pulling in the clutch revved engine to blow it out ( a habit from driving cages that seemed to help ). No effect. Thinking the skipped chain might have damaged the speed sensor. Had all day thinking what could possibly happened from stressing the engine during that 1/4 simulator drag race. Dislodged some fuel crud and lodged in an injector. My plan was to replace the speed sensor with a spare I have laying around (Salvaged Busa I got duplicates of bunch of stuff
) More extensive was after the replaced sensor with no effect to pull the injectors off for cleaning.
After getting home spent a few hours looking into surging problem. Researched the Web and checked the Service manual looking for references to engine surging. The service manual gives minimal info beyond Dealer Mode self diagnostics. But on the web read couple articles addressing Suzuki surging. There was a real problem when Suzuki had to meet emission standards. Leaning out fuel mixtures was neccesary to conform to standards.
An article about the Suzuki Bandit series. Suzuki resolve much of the surging by fuel mapping to throttle position and engine RPMs. This method was adopted to use on other Suzuki bikes including the Busa.
A light went On, That's it I thought. The 1/4 mi simulator track I really wacked the throttle, it may have effected the Throttle position sensor. Section (4-30) in the Service Manual addresses the throttle position sensor, adjusting.
1- Set the idle speed to 1,150 rpm. 2- use the 'Dealer Mode' in the self diagonstics. 3- loosen and adjust the readout to ( -COO ).
First I had to run to Sears for a set of Security Torx bits to fit the mount screws on the sensor. Pulled the seat, hump and accessed the Self Dianostic connector. Lefted the Tank to gain access to the idle screw and Throttle position sensor.
Sure enough had an error reading in the calibration indicating ( upper dash line COO). Adjusted to ( -COO ) and gave it a test ride. Busa ran as it did before. The severe surging was gone.
There was still the normal low level surging. While I was at it, I'll try to adjust the throttle sensor to slightly on the rich mixture side. *Just a fraction beyond ( -COO ) to indicate ( _COO ). Another test ride the surging was even less.
I left it at this adjustment. The surging is very small. Reving high in 1st gear can still detect surging. But it's beyond normal riding practices.
Interesting was during the group ride. Either from adapting the engine and gear combination. Or from the Throttle sensor out of adjustment. Gas mileage was incredable. Was hard to get less the 38 mpg. Through goat trails in 2nd, 3rd gears for miles getting 38 mpg. 43mpg on busy freeways with varing speeds. This is higher then I usually get 34 mpg twisties and 40 mpg on freeways.