Author Topic: Calling Carb/jetting Gurus need that last little bit of help (Read 3950 times)

rider123 · « **on:** November 10, 2005, 01:36:15 PM »

Hello I have a brand new 2005 Bandit 1200S and I've been having some low speed/throttle problems. I took it back to the dealer and they drilled the plugs for me and slightly tuned it. I say "slightly" because I'm still having a few bugs that are almost worked out. I was still having a bit of a stumble at low rpm (almost gone) and it felt a little mushy, not bad but still slightly there. I turned it out a half a turn and it cleaned it up almost entirely however occasionally I have this little glitch that seems to come on when warmed up. Intermittantly when I "blip" the throttle I get sort of a die off of the engine. I'll blip the throttle and instead of it reving to 2000-2500 or whatever it will misfire and only rev 100 -200 rpm and then the idle will drop to 1000 rpm then climb up fairly fast to the 1250 I have it set to. The weird thing is that it only happens occasionally. I'm not 100% sure but it seems to happen more when I sit for a while at idle, say a traffic light. Out of say 5 or 6 "blips" on the throttle one will be a "bad" one. As I said it's much more noticable at full hot so I'm thinking I may have backed out the mixture screws a little too much. What do you guys think?

For example I'll set at a light, blip the throttle X number of times and then one will be "bad"(feels like a misfire). Theorettically it may still be lean, as you "blip" it it normally goes to 2000-2500 rpm then the throttle is shut off then quickly "blipped" again. THis I'm assuming would simulate quick low speed on again off again low throttle inputs. If it was slightly lean shutting the throttle down at 2500 rpm there would be alot of vaccuum and only a pilot jet to supply fuel.

Also what is the standard turns out on the mixture screws stock? I'm guess ing around 2.5-3.0 on a 2G Bandit with the 15 size pilot. Is this correct? Would it be advisable to reset the mixture screws on all the carbs and start from there? Any help would be much appreciated.

For fun I think I'll turn the mixture screws in 1/4 turn just to see what happens. I tried using the best idle speed adjustment method but turning the screws from where the dealer set them. 1 turn either way didn't seem to affect the idle in any way that I can determine without a hand held Tach.

Any theories out there?

Edit: oops sorry every other throttle position after 1700 rpm works perfectly so I know it's just the slow speed circuit (pilot jets) Fuel octane used: 89

rider123 · « **Reply #1 on:** November 10, 2005, 04:05:18 PM »

No one...Oh oh.

PaulVS · « **Reply #2 on:** November 10, 2005, 04:22:34 PM »

Before doing anything else, I'd turn the A/F screws 3 1/2 turns out and shim the needles with 2 washers each.

Go with 87 octane also.

rider123 · « **Reply #3 on:** November 10, 2005, 04:25:22 PM »

ok I will. I don't think it needs any shimming however once on the mains it has lots of power with no hesitation. But I think you are right about the A/F screws. Since the dealer didn't tell me what he did, and I forgot to ask(took his word it was fixed). I think the best thing is on Saturday it's going to be warm and sunny. I'll reset all the mixture screws to 3 turns out which is stock and start from there. Have you found that 3.5 turns out helped you out on a stock bike?

PaulVS · « **Reply #4 on:** November 10, 2005, 04:27:54 PM »

Quote from: "rider123"

ok I will. I don't think it needs any shimming however once on the mains it has lots of power with no hesitation. But I think you are right about the A/F screws. Since the dealer didn't tell me what he did, and I forgot to ask. I think the best thing is on Saturday it's going to be warm and sunny. I'll reset all the mixture screws to 3 turns out which is stock and start from there. Have you found that 3.5 turns out helped you out on a stock bike?

Yep... 3.5 with stock stuff. Mine is jetted so my a/f screws are at 4 turns out. Shimming is only about a 20 minute job once you get the tank off.

Red01 · « **Reply #5 on:** November 10, 2005, 07:15:27 PM »

I already replied to this in the shorter thread you posted on this elsewhere.

FWIW - I'm at 3.5 turns out with a slip-on and Stage II Holeshot kit... but then my jets, needles and air filters are different from stock.

rider123 · « **Reply #6 on:** November 11, 2005, 12:06:01 AM »

Thanks before driving home from work I set the two outer carbs at 3.0 out which is stock according to Haynes. There was a noticeble improvement in driveability I'm looking forward to getting the inner carbs at 3.0 tomorrow and go from there. Which begs the question, what is "stock" to the EPA?

Thanks for your replies

Red01 · « **Reply #7 on:** November 11, 2005, 12:50:24 AM »

They don't care about how many turns, they care about exhaust emissions.

rider123 · « **Reply #8 on:** November 11, 2005, 02:36:03 PM »

Thanks alot guys for all your help. I almost have it sorted. It seems that the 3.0 turns in the Haynes manual is almost spot on. It's just slightly lean now but its really cold so I'm hoping if it warms up in the spring it will be fine. The idle is just slightly erratic now which means it just need the fast idle method to clean the last little bit up and smooth the idle.