Bandit Alley

MODEL SPECIFIC => SUZUKI BANDIT 600 thru 1200 - AIR/OIL COOLED TECHNICAL => Topic started by: wanted9867 on March 28, 2017, 03:54:44 PM

Title: 2002 bandit woes
Post by: wanted9867 on March 28, 2017, 03:54:44 PM
Hey guys. Back on New Years I became the owner of a 2002 bandit 1200 with 32,000 miles on her.
Hadn't been ridden in some time, just ran occasionally. Had sat under a cover for a year or more.
1,400$-couldn't pass it up.
3 months later, new tires, new brakes, new oil, cleaned carbs and rebuilt, valve job, new new New everything.
Bike had a straight exhaust on it from the previous owner. No jet work so it was running quite lean.
I put 110 main jets (up from 100) and 20 pilots (up from 15), shimmed the needle one shim.
Pilots are set roughly 3.5 turns out or so.
Stock air box, stock air filter. No high flow anything just the open exhaust.
Bike runs pretty well. Good throttle response, feels strong but I feel like sometimes there should be more power available.
I get an off idle studder when I'm cruising. If I accelerate quick through first bang into second and hang at 3-3,500 rpm to cruise, I get a rythmic studder and a loss of power (but only for the .5 seconds that it's sputtering)
If I slowly roll up on the throttle and increase speed, or if I'm really gassing it she runs strong and smooth. Only when I hang the rpm to cruise do I get the sputter. Usually 3-3500 rpm but the throttle position is 97% closed so I believe I'm on or very near to being on my idle circuit at that time. Because of that I fiddled with my mix screws but that didn't seem to fix it much. Varying grades of fuel from 87 to 90 to 93 change the sputter some but don't eliminate it. Not really an issue as the bike seems strong but this problem is a bit annoying if I'm in traffic and I need to hold a slower speed. She likes to cruise at 60-70 and pulls hard past 130-40 but she hates the low speed maneuvering. If I continue to hold her at 3-3500 cruising in traffic I will get surges where she jumps forward and then hangs for a moment, not aggressively but enough to feel. Absolutely not a smooth power delivery like I feel when I'm increasing throttle.
Are my jets wrong? She runs fine otherwise and my plugs don't look bone white or sooty.  Spraying around my carb boots reveals no vacuum leaks, so I'm not sure if it's a lean issue or a rich issue or what.
Could it be my coils are weak? I know they're usually a go/nogo part but maybe?
Any ideas guys? I have a few more questions for the experts if anyone is here. I have taken my bike to two shops and both have tried playing me for a stupid kid and have both ripped me off charging me to even look at it but offering no solutions but "bringing it back to stock because my jet work is the cause of all the problems".
Any input?
Thanks so much   
Title: Re: 2002 bandit woes
Post by: wanted9867 on March 29, 2017, 04:25:12 PM
Today the bike caught the studder at 3,000 rpm as I shifted into 2nd to cruise. Instead of the studder clearing it lasted a split second longer so I yanked the gas to see what would happen. Instead of clearing and accelerating as normal the studder remained and seemed almost like I hard miss. As I let off the gas the studder remained but the rpms dropped then she shut off.
I cruised to a stop and waited a second, cranked and she came back to life as normal.

Could my float height be the cause of this? Am I having intermittent fuel starvation due to my floats being too high or low?
Title: Re: 2002 bandit woes
Post by: asskickinpeanuts on March 29, 2017, 09:21:56 PM
Almost sounds like an FJ1200 I had.  Given hard gas, it would stutter.  After a few minutes it would shut off.  started happening kind of sudden.  The cause?  Pinched fuel hose. 
Title: Re: 2002 bandit woes
Post by: Vidrazor on March 30, 2017, 11:27:26 PM
Interesting. My bike has that jerking stutter at lows rpms. Typically in slow speed traffic I feel it the most. I also notice a slight power surge between 3.5-4k. Once in higher gears and revs everything smooths out. Throttle response has been perfect and as expected, since I got the bike, when it was in worse shape.

When I first got the bike it was really bad. Idle also varied between 900-1500(!), along with low level backfire. I had the carbs rebuilt and it smooth the idle and stutter out, but didn't eliminate it. My mech found a bad coil, replaced it, made the stutter smoother but still there. He pulled out and readjusted things in the carbs, and now the idle is constant, and the stutter is at an absolute minimum, but still there. Still have the power surge between 3.5-4k. Still has occasional low-lever backfire, especially when starting the bike from cold. Pilots are set 3.5 turns out, which is what the fellow China Greg here said was listed in his Haynes manual. I just ordered the Haynes manual, but I don't see this 3.5 turn listing he said is in his. All I see it "Pre-Set" for U.S. models, so I'm not sure where he got this info from and if this is a correct setting. My mech thinks it's way too much. We'll see.

So here's my hunch on this. My bike for some reason does not have a throttle position sensor. My mech checks his charts, and strangely for my 2000 year model the charts do not list one, but it does for 1999 and 2001 models. The cable that hooks up to a TPS is on my bike. I have a feeling my bike needs a TPS, even though it's not listed in the specs. Granted, this is all speculation on my part, but I think that's what's causing the problem.

So, A) does your bike have a TPS and B) do you know if it's working/adjusted correctly? Just throwing that out there.
Title: Re: 2002 bandit woes
Post by: asskickinpeanuts on April 02, 2017, 04:45:54 PM
Yes, my 2001 has a TPS.
Title: Re: 2002 bandit woes
Post by: wanted9867 on April 10, 2017, 03:25:03 PM
I do have a TPS but it is unplugged. According to what I've read it serves no purpose so I unplugged it and the bike, other than this studder seems just fine. My idle is butter smooth but does need to be cranked up at times to start, and as she warms I can slow the idle back down. Isles perfect. Studder is incessant and you describe it perfectly. Lately it's been between 3.5 and 4K rpm. I just gas it hard and she runs fine.
My thoughts are since you're in a higher gear usually, the rpms are up but the throttle is only barely cracked. Once you wring the throttle open onto the main jet circuit she picks right up. I thought it may be improper jetting on the Low circuit. My jets are 20's up from 15. Bike ran super hot when I got it and has an open exhaust, so the jets are all larger but I'm having the exact symptoms as you- just zero lean sneeze.

I have no idea how to adjust my TPS. I tried once and it didn't seem to read right on my ohmeter
Title: Re: 2002 bandit woes
Post by: Vidrazor on April 10, 2017, 11:22:10 PM
The TPS modifies the timing at low RPMs. This is why I think it's the cause of the problem. It may not be tho. My 2000 uses a different set of carbs and not make use of the TPS. I though this was rather odd.

My mech got the idle to be smooth as well, but I still have a mild stutter. Other than the TPS, I believe it can only be either the CDI or something in the block, possibly the timing chain. The only other thing is that it is inherent in the design of the engine and most people just don't seem to notice it. Annoys the crap out of me.