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Author Topic: '2000 1200 S Carb Pilot Screw Settings  (Read 813 times)

Offline Vidrazor

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'2000 1200 S Carb Pilot Screw Settings
« on: March 05, 2017, 06:00:53 PM »
I've had my carbs rebuilt, everything stock, and while they appeared to be fine, my mechanic could not find a starting reference for setting the pilot screws. He defaulted to 2-1/4 turns in. The bike was running a bit rough, so he set them to 2-1/2 turns in. A fellow rider mentioned he felt the exhaust smelled rich after that.

However it turned out that one of the coils is failing and is getting replaced. I was still thinking about the screw settings, and I'm wondering if anyone here may know what they should be set at so he can set it correctly if there is an optimum setting implied by Suzuki for these carbs.

Thanks for any info on this.
« Last Edit: March 05, 2017, 06:43:42 PM by Vidrazor »

Offline China Greg

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #1 on: March 05, 2017, 07:23:26 PM »
The Haynes manual calls for 3-1/2 turns out... exactly where my modified B12 likes it. The factory Suzuki manula just says, "PRE SET".

Big question: How much work has been done on this bike, previously? Any "performance" mods?

One thing I learned the hard way:
MY B12 HATES A DIRTY AIR FILTER. Even SLIGHTLY dirty... I was riding across Colorado and the bike ran worse and worse...I CHECKED the air filter and thought all was fine...looked decent,,,  wasn't until I finally took a chance and put a fresh one in there that it suddenly ran tip-top.

Also-
MY BIKE WILL NOT TOLERATE AN AFTERMARKET AIR FILTER. This could just be my jetting set-up...I don't know, but no way will it take one of those crappy EBay "Emgo" filters. Suzuki ONLY for mine, whether I like it or not. It runs like Ca Ca without an OEM.

If that bike has been sitting for ANY length of time, I will GUARANTEE that your bank of carbs needs to come off for a complete douching. Most likely are the pilot jets are clogged, which are very small and seem to jam-up pretty easily when any sort of dirt is present. That would DEFINETLY cause your symptoms.
Check for ANY signs of rust inside your tank using a flashlight, (avoid using a match). If you see ANY signs of sediment you absolutely will have to deal with that... as it will never go away, and you will be pulling those carbs out for cleaning continually. If it's rusty in bottom, it's usually along the bottom seam...sometimes hard to see. If necessary drain the fuel into a clean bucket and look for flakes of rust or signs of grit. If a tank is rusty, it CAN be cleaned nicely by using Muriatic acid (from a pool store). This should be done carefully,,, as it can get messy... but it WILL clean a slightly rusty tank.

If you take the carbs apart (& I highly recommend it, as this is where 80% of all performance problems start: DIRT), take the flat black vacuum caps off the top of the carbs carefully, on a table... and as you do look to see if the little tiny black O-rings are still in their little cut-outs on the top of the carb bodies. Those are easy to loose, and if someone disassembled your carbs before, it's very possible one (or more) of those popped-out. This would cause a vacuum leak... maybe cause your symptoms.
When you put the big vacuum caps back on, take a tiny...TINY amount of RTV sealer and smear the O-rings JUST SLIGHTLY... don't clog the hole...and they should stay in place next time. Reassemble carefully, don't knock them loose when screwing the tops back on.

But if you make sure the tank is pristine, and the carbs well sprayed-out with carb cleaner, including all the tiny orifices...hosed-out with an air gun.. Fresh OEM air filter... Chances are excellent that your Bandito will run like a Sexually Abused Orangutang.

Check the connections to your coils, and make sure the plug-caps are screwed-on the wires completely.. nothing loose or corroded. I've rarely seen coils go bad on these Suzuki models...unless someone futzed with them. LOOSE CAP... yes, perhaps.
« Last Edit: March 05, 2017, 07:48:01 PM by China Greg »
Black '98 B12S, JE 1216cc bore kit, port work, Yosh RS3, Ivan jetting, drag bars, modified Corbin Gunfighter, Hyperpro shock, Racetech Gold valve kit, stainless lines, Wave rotors, polished wheels, fender eliminator, bar-end mirrors, NEP throttle lock, Adaptiv TPX radar detector...140K miles

Offline China Greg

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #2 on: March 05, 2017, 07:33:35 PM »
In terms of ..trusting your mechanic... well, that's your call...  but I worked in three shops, and there have been plenty of times when I saw half-baked jobs. The fact that your guys says there's a "bad coil"... make sure you see it.. and WHY is it bad.
Just because the guy says "he cleaned them"... doesn't ALWAYS guarantee that all those pilots are free and clear. Did he pull every jet out? Did he strip the carb bodies and spray out the tiny Venturi holes in the bellmouth?

Just SAYIN'...... Like my Master Mechanico teacher warned me, "IF YOU HAVEN'T SEEN THE PROBLEM WITH YOUR OWN EYES.... YOU CAN'T BE SURE OF ANYTHING".
.
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« Last Edit: March 05, 2017, 07:48:23 PM by China Greg »
Black '98 B12S, JE 1216cc bore kit, port work, Yosh RS3, Ivan jetting, drag bars, modified Corbin Gunfighter, Hyperpro shock, Racetech Gold valve kit, stainless lines, Wave rotors, polished wheels, fender eliminator, bar-end mirrors, NEP throttle lock, Adaptiv TPX radar detector...140K miles

Offline Vidrazor

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #3 on: March 06, 2017, 12:45:58 AM »
Bike is fully stock. I can trust my mechanic. He simply couldn't find any reference data on jet screw position starting point.

"The factory Suzuki manula just says, "PRE SET".

What exactly does that mean?

Thanks for your replies.

Offline China Greg

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #4 on: March 06, 2017, 11:42:43 AM »
"PRE SET" in the manual simply means that the screws were turned to a certain number at the factory, and that Suzuki won' help you to change that. This is because they are legally bound to comply with US EPA emissions requirements, and are trying to push you away from doing any "modifications".

Again, my Haynes manual says 3-1/2 turns... which is exactly where I've been running mine for 130,000 miles.

PS.. the photo of your bike looks nice; but two things:
1) Those header pipes are TOO DARK. If you see any blue color... that means you're motor has been running too HOT. Something was wrong with the jetting... or there was blockage in the carbs. Question: are ALL four pipes the same color, up near the cylinder head? If one is different than the others... you can probably guess that's where a problem is. Generally the pipes should turn a GOLDEN color. BLUE means it's been over-heating. Again... the carb cleanliness and settings.

2) I can see at least ONE thing that has been modified on your bike: the turn signal lenses were changed from yellow to clear. if THOSE have been changed... what else might have been changed that you don't know about?
Again, I would make sure that you have a real OEM Suzuki air filter... and that it is VERY clean... GRAY is no good. It needs to be WHITE.
Black '98 B12S, JE 1216cc bore kit, port work, Yosh RS3, Ivan jetting, drag bars, modified Corbin Gunfighter, Hyperpro shock, Racetech Gold valve kit, stainless lines, Wave rotors, polished wheels, fender eliminator, bar-end mirrors, NEP throttle lock, Adaptiv TPX radar detector...140K miles

Offline Vidrazor

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #5 on: March 06, 2017, 12:10:24 PM »
Well, there's some mods, like the lines,as I said. There's also now a smoked windscreen instead of the clear one you see there.

Ultimately I don't know what kind of stuff was done, I can only go by what the guy told me. Being his bikes were all kept immaculately, I accepted his comments on face value to some degree. Always a risk when buying a used bike. Overall it seems the bike is OK.

The bike was certainly running hot when I go it. With the choke in one night when I started it in ~25 weather, the pipes were glowing by the block at 2.5-3k rpm. I'll tell my mechanic about the pilot settings.

Thanks again for your replies.

Offline China Greg

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #6 on: March 06, 2017, 12:19:59 PM »
THERE'S NO WAY those pipes should be "glowing"!
If that was the case... either you left the choke on faaaar too long (say, 20 minutes plus) or there was something DEFINITELY wrong with your fueling. You run an air-cooled bike that hot for long and you could crack the head.
Black '98 B12S, JE 1216cc bore kit, port work, Yosh RS3, Ivan jetting, drag bars, modified Corbin Gunfighter, Hyperpro shock, Racetech Gold valve kit, stainless lines, Wave rotors, polished wheels, fender eliminator, bar-end mirrors, NEP throttle lock, Adaptiv TPX radar detector...140K miles

Offline ventYl

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #7 on: March 06, 2017, 02:40:40 PM »
Just a little detail about "PRE SET".

Some manuals add "set by very special equipment" and that's true. Carbs are different because there are manufacturing tolerances and pilot jets are working under the worst conditions of all carburetors mechanisms so it has to be set most precisely.

Basically you need to set each carb on it's own. I've never seen such OEM equipment but theoreticaly it can be "replaced" by pyrometer in exhaust right near cylinder head. That's the only place where you can measure just one single carb. Neither pyrometers with exhaust pipes of same geometry than stock nor this "special equipment" is part of workshop standard equipment so it is basically impossible to do same kind of setting. And it is not necessary unless you are going to fiddle with intake or exhaust.
Bandit 400 1991 - stock except of swap from GK75B to GK75A

Offline China Greg

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #8 on: March 06, 2017, 03:24:52 PM »
yeah..., I think that level of tuning would be appropriate for someone desperate to get the last ounce of power out -- i.e., serious competition.

For the many bikes I've worked on and adjusted the pilot screws, I can't ever remember seeing a bank that had individual screws different, one-to-the-other, on a bank of carbs. If there WAS any difference, it couldn't have amounted to more than a 1/4 turn.

If the rest of your bike, carbs and ignition, are within factory parameters, there's no need to worry about individual adjustment.. other than possibly a Lean-Drop test...and a good Synch.
Black '98 B12S, JE 1216cc bore kit, port work, Yosh RS3, Ivan jetting, drag bars, modified Corbin Gunfighter, Hyperpro shock, Racetech Gold valve kit, stainless lines, Wave rotors, polished wheels, fender eliminator, bar-end mirrors, NEP throttle lock, Adaptiv TPX radar detector...140K miles

Offline ventYl

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #9 on: March 07, 2017, 05:14:23 AM »
I expect that with aging the differences may get larger. I bought pyrometers and while B4 has these ports on stock headers I am encouraged to try to hook them up. Just to see what I am able to read and how it reacts to adjustment. I don't have an ambition to squeeze the last horse power hidden somewhere in the engine by this. Just to fulfill my curiosity.
Bandit 400 1991 - stock except of swap from GK75B to GK75A

Offline Vidrazor

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #10 on: March 07, 2017, 03:32:39 PM »
"THERE'S NO WAY those pipes should be "glowing"! If that was the case... either you left the choke on faaaar too long (say, 20 minutes plus) or there was something DEFINITELY wrong with your fueling."

I had to run the choke for a several minutes because the bike was running rough at the time, especially in that temperature. It was running at 25-3k. There was certainly something wrong, which is why I had the carbs rebuilt and system checked out for inconsistency in running that it has. However it appears to be fine, temperature-wise, with normal use. I've also brought the bike up to around 140 and the engine has not shown any issues.

Offline Vidrazor

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Re: '2000 1200 S Carb Pilot Screw Settings
« Reply #11 on: March 08, 2017, 11:27:25 PM »
BTW, would you mind taking a snapshot with your phone of the Haynes page showing the pilot jet settings? My mechanic feels it's way too rich a setting. That setting is for a stock setup, right? Thanks.

 

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