Running problems with 92 GSXR750
Had my 92 GSXR 750 for a couple months now. Love it to death, despite riding like an overweight tank!
Anyway, it's got some running issues, and am hoping someone can help me out here. I'm a BMW dealer tech(cars, not bikes) by trade, but I'm NOT a bike mechanic. My last 2 bikes were brand new, so I never did any service myself. Before I give up on this, and take it into 5th Gear or EMS, I'd like to have a crack at it myself.
That out of the way, here's what she's doing;
1) Starts and idles very well. Throttle blips easily, revs up nicely.
2) Once riding, you MUST take off with a fistful of RPM, or she will bog, misfire, and barely move through an intersection. I'm talking like 8-9k rpm for a smoothish take off.
3) While cruising around, anything under 6k rpm, and she spits, pops, and misfires badly. Slow speed parking lot riding requires a LOT of clutch and throttle manipulation to get it right.
4) during takeoff, if you get it wrong, and she spits her way to 6k, she smooths out, and launches hard at 6k. Not very confidence inspiring.
5) Pulls strongly from 6k to about 10k, and then sputters off again. Not much for high end pull.
6) If you rev her up standing still, she pukes a HUGE cloud of black at about 8k rpm.
7) Ran out of fuel at 150km!
Alright, this is what she's got done, that I know about;
1) 1100 jets, or so I'm told. Can't figure out why someone would do that to a 750, so I'm skeptical that the PO knows what he is talking about. Is this a common thing "upgrade"?
2) Full Yoshi system
3) Different front sprocket. Apparently the original owner wanted to keep up with his friends on big bikes, during long distance road trips.
4) PO installed a brand new set of genuine Suzuki plugs before I bought it.
So, knowing all that, I'm leaning towards a couple things;
1) Rich running and over fueling from the 1100 jets.
2) Fouled plugs from the excess fuel.
3) Bad coils or wires. Now, being a relative noob to this bike, I'm not even sure how the ignition system works. Is it coil on plug, or remote coil, with plug wire going from coil to plug? any of these items common failures on these bikes?
So, before I go and spend money on different jets, tearing my carbs apart, swapping sprockets, and spending an assload on new coils, any opinions on this? She's a great old bike, but barely rideable in town. I'dlike to fix that before she throws me off!
oldskool suzuki rules
sorry man but the carbs gotta come apart. more than likely you'll need to get some dyno tuning done to get the main jets (top end) right, also sounds like your needle position (midrange) is wrong or the emulsion tubes (midrange) are knakered or perhaps its time to renew the float valve O-rings (flooding?).
hanging out at timmies
ignition is dis,1-4, 2-3 . coils are an issue with these bikes. your running
problem sounds like you're too lean on the pilot (idle) circuit and too rich
on the main circuit. replace the main jets with the stock size plus 1.
clean out your pilot circuits and check your float level. set your idle speed at about 1200-1300 rpm then screw in the pilot screw(1 at a time) untill the
cylinder starts to to lean misfire then wind it out till the rpm peaks then back in 1/4 -1/2 turn. do this to each carb. also i would bet the po has put in
a advanced ignition trigger cam, take it out and replace it with a stock one.
these engines dont like too much timing , they dont ping like a car, they
vibrate,overheat, get really cranky and make you really frustrated.
( i know this from personal experience)
Thanks guys, thats what I was suspecting all along anyway. I could do the work myself, but frankly, I don't want to! I've spoken with the nice folks at Essential Motorcycle Service, and will be setting up a time to have them sort it out. Will be having a valve adjustment, and a new jet kit installed, along with new rubber. Should hopefully sort this baby out nicely.
oldskool suzuki rules
a propperly set up jet kit will do ya well!