Recent Posts
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SUZUKI BANDIT 250 & 400 / Re: Greg's Bandit 400 Fuel Injection Project...
« Last post by greg737 on January 20, 2020, 08:48:34 PM »Hey Greg I hope you are good, any chance of setting up an online photo album of the build? All the pictures in the topic have expired sand all the visual reference is unfotunately gone!
Yeah, I'm still around, still have the FI GSF400, still riding it, the bike never fails to please me as it's such an different experience from my other motorcycles (the VFR800 and the EX250).
Recently my Photobucket account went down, not because I failed to pay for the account, I got billed in December 2019 and paid, have the credit card statement to prove it, so it's not because of money. Instead Photobucket is claiming that they had a "server problem" and my account was "one of the affected accounts" and they say it will be back up as soon as possible.
We'll see what happens. The GSF400 still runs great, but smokes a bit on start-up after sitting for a while (like a week or month). Long term I'm thinking about a refresh of the engine, things like pistons and the valves and maybe the valve guides.
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SUZUKI BANDIT 250 & 400 / Re: Greg's Bandit 400 Fuel Injection Project...
« Last post by nsc on January 19, 2020, 03:34:31 PM »Hey Greg I hope you are good, any chance of setting up an online photo album of the build? All the pictures in the topic have expired sand all the visual reference is unfotunately gone!
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SUZUKI BANDIT 250 & 400 / My 92 suzuki gsf250 transparent clutch cover
« Last post by chamarang on December 31, 2019, 01:59:50 PM »Transparent clutch cover
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SUZUKI BANDIT 600 thru 1200 - AIR/OIL COOLED TECHNICAL / Re: Longer travel suspension for Bandit 1200
« Last post by GETFURIOUS on December 30, 2019, 01:39:17 AM »THE HAYABUSA SHOCK WILL RAISE THE REAREND ABOUT 2 INCHES.....
THAT IS THE ONLY PART THAT I KNOW ABOUT....
THAT IS THE ONLY PART THAT I KNOW ABOUT....
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by yuckhil on December 11, 2019, 08:18:06 AM »Thanks for all this info, and the picture. I am still trying to process the possibilities, and post an intelligent response. Yes, I did have to set the throttle stop further in, and I also had to turn the pilot screws out more than the recommended 1.5 turns. Sorry, I have been living with this problem so long, I forgot some of the details. Yes, luckily regular unleaded 91 octane fuel is widely available here. I never use ethanol blends or premium fuel.
This week, all o-rings looked in good condition, esp. the ones at the emulsion tubes, which were very squashed when I first rebuilt the carbs 6 years ago. I have not removed the pilots screws in ages. What damage would I look for - the tip? Since I have had to turn them out almost one extra turn (2-2.5 turns each), does that imply that mechanism is likely working ok, and the problem starts before the slow operation mixture reaches the pilot screws?
I will try to inspect and clean out the pilot air passages as you suggested. Thanks again very much for your assistance.
This week, all o-rings looked in good condition, esp. the ones at the emulsion tubes, which were very squashed when I first rebuilt the carbs 6 years ago. I have not removed the pilots screws in ages. What damage would I look for - the tip? Since I have had to turn them out almost one extra turn (2-2.5 turns each), does that imply that mechanism is likely working ok, and the problem starts before the slow operation mixture reaches the pilot screws?
I will try to inspect and clean out the pilot air passages as you suggested. Thanks again very much for your assistance.
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by greg737 on December 08, 2019, 02:48:46 PM »You should definitely get some lengths of copper wire (because it's really soft and won't hurt the carb) and try your best to clean out the "Slow System". Poke around through all of the orifices in the system: the Pilot System Air Jet, the Pilot Fuel Jet, the Pilot Jet Needle hole, the Main Bore Bypass Ports. Poke around with the copper wire, then shoot some carburetor cleaner through the passages. Then do some more poking, then more carb cleaner.
Then replace all the rubber parts: gaskets and O-rings.
After looking more closely at your pictures I have to say it appears that your brass parts are in really good condition. Just a bit dirty from time. So just a good cleaning should be all you need for those parts.
I'm guessing that the gasoline you've been using in the bike doesn't have any ethanol added?
Then replace all the rubber parts: gaskets and O-rings.
After looking more closely at your pictures I have to say it appears that your brass parts are in really good condition. Just a bit dirty from time. So just a good cleaning should be all you need for those parts.
I'm guessing that the gasoline you've been using in the bike doesn't have any ethanol added?
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by greg737 on December 08, 2019, 02:37:55 PM »Of course it's also true that anything else that might reduce the amount of vacuum pull on the carb's "Slow System" will cause the Pilot Jet to move less fuel.
A perfect example is the "cracking the throttle" thing. I can easily imagine how this problem would begin and then get worse.
Imagine that the "Slow System" begins to get clogged up, so the rider finds that it's now necessary to "crack the throttle" to get the bike to start. This gets the bike started but it really takes the Pilot Jet system out of use, because the rider is using the Main Jet to get the bike started.
And if the Pilot Jet system is partly or completely clogged the rider will probably have to open up the "Throttle Stop Screw" (the long, flexible finger-adjustable thing that most riders think of as the "idle adjuster") a bit more than normal to open up the throttle plates because he's idling the bike mainly (or completely) on the Main Jet system. This abnormally opened-up setting of the throttle plate stop screw would also have the effect of reducing the amount of vacuum pull exerted on the "Slow System".
A perfect example is the "cracking the throttle" thing. I can easily imagine how this problem would begin and then get worse.
Imagine that the "Slow System" begins to get clogged up, so the rider finds that it's now necessary to "crack the throttle" to get the bike to start. This gets the bike started but it really takes the Pilot Jet system out of use, because the rider is using the Main Jet to get the bike started.
And if the Pilot Jet system is partly or completely clogged the rider will probably have to open up the "Throttle Stop Screw" (the long, flexible finger-adjustable thing that most riders think of as the "idle adjuster") a bit more than normal to open up the throttle plates because he's idling the bike mainly (or completely) on the Main Jet system. This abnormally opened-up setting of the throttle plate stop screw would also have the effect of reducing the amount of vacuum pull exerted on the "Slow System".
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by greg737 on December 08, 2019, 02:15:32 PM »
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by greg737 on December 08, 2019, 11:50:01 AM »Good post, great pictures.
The truth of the situation is that all of the soft brass parts of a carb are considered (by the manufacturer) to be "consumable parts". It's a mindset that you have to embrace (and I realize doing this isn't easy, mostly because we want to believe our eyes and our eyes tell us "hey, this part looks fine!").
"Back in the day" of carbs, during a service or rebuild on a set of carbs that were no longer working well, it was just normal procedure to get the appropriate rebuild kit and replace all of those parts (the brass parts, springs, and anything made out of rubber such as gaskets and O-rings).
I'm not saying that any of your carb's brass parts are worn out, in those pictures your Main Jets and Emulsion Tubes look pretty good to me and they could all be within-spec and good-to-go. It's very possible that your Main Jets and Emulsion Tubes are not the real source of your problem.
So, because of this, I have to ask: What did you find when you disassembled the Pilot Jet system from your carbs?
The Pilot Jet system on these Mikuni BST ("Slingshot") carbs can be a problem. The Pilot Needle Jet Screw itself is tiny, and the fuel supply passageway through the body casting of the carb that feeds the Pilot Needle Jet Screw is the longest and most narrow passageway there is in the entire carb.
And... to make things even worse (and more prone to problems of a long-term, age-related nature) the BST Pilot Jet system has a very, very small rubber O-ring on the base of the Pilot Needle Jet Screw that is absolutely vital to proper operation. This tiny rubber O-ring has to provide an air-tight seal at the base of the Pilot Needle Jet Screw (where it screws into the carb body). If the base of the Pilot Needle Jet is not sealed air-tight it will not be able to make use of the vacuum pull that the carbs generate during cranking and low-RPM operation. This vacuum pull is critical because it (the vacuum effect) draws fuel up into and through the passageway from the carb bowl and through the Pilot Jet orifice. If there's no vacuum pull (or not enough vacuum pull) the Pilot Jet system won't move any fuel to the engine.
This would explain why you have to "crack the throttle" when starting the bike.
Obviously, I recognize that I'm now offering up my second theory of why your Bandit is so hard to start. But I'm just trying to help.
When you try to start the engine in colder-than-normal conditions the fuel delivery requirements are different. And if the Pilot Jet system isn't functioning due to either being clogged up or unable to pull fuel out of the Float Bowl, you will have to deliver the necessary amount of fuel by "cracking the throttle". But on a cold day your normal "crack" probably won't be enough to start the engine right up. So you probably end up "cracking" it too much which causes a flooded condition in one or more (or all) of the cylinders.
The truth of the situation is that all of the soft brass parts of a carb are considered (by the manufacturer) to be "consumable parts". It's a mindset that you have to embrace (and I realize doing this isn't easy, mostly because we want to believe our eyes and our eyes tell us "hey, this part looks fine!").
"Back in the day" of carbs, during a service or rebuild on a set of carbs that were no longer working well, it was just normal procedure to get the appropriate rebuild kit and replace all of those parts (the brass parts, springs, and anything made out of rubber such as gaskets and O-rings).
I'm not saying that any of your carb's brass parts are worn out, in those pictures your Main Jets and Emulsion Tubes look pretty good to me and they could all be within-spec and good-to-go. It's very possible that your Main Jets and Emulsion Tubes are not the real source of your problem.
So, because of this, I have to ask: What did you find when you disassembled the Pilot Jet system from your carbs?
The Pilot Jet system on these Mikuni BST ("Slingshot") carbs can be a problem. The Pilot Needle Jet Screw itself is tiny, and the fuel supply passageway through the body casting of the carb that feeds the Pilot Needle Jet Screw is the longest and most narrow passageway there is in the entire carb.
And... to make things even worse (and more prone to problems of a long-term, age-related nature) the BST Pilot Jet system has a very, very small rubber O-ring on the base of the Pilot Needle Jet Screw that is absolutely vital to proper operation. This tiny rubber O-ring has to provide an air-tight seal at the base of the Pilot Needle Jet Screw (where it screws into the carb body). If the base of the Pilot Needle Jet is not sealed air-tight it will not be able to make use of the vacuum pull that the carbs generate during cranking and low-RPM operation. This vacuum pull is critical because it (the vacuum effect) draws fuel up into and through the passageway from the carb bowl and through the Pilot Jet orifice. If there's no vacuum pull (or not enough vacuum pull) the Pilot Jet system won't move any fuel to the engine.
This would explain why you have to "crack the throttle" when starting the bike.
Obviously, I recognize that I'm now offering up my second theory of why your Bandit is so hard to start. But I'm just trying to help.
When you try to start the engine in colder-than-normal conditions the fuel delivery requirements are different. And if the Pilot Jet system isn't functioning due to either being clogged up or unable to pull fuel out of the Float Bowl, you will have to deliver the necessary amount of fuel by "cracking the throttle". But on a cold day your normal "crack" probably won't be enough to start the engine right up. So you probably end up "cracking" it too much which causes a flooded condition in one or more (or all) of the cylinders.
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SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by yuckhil on December 08, 2019, 01:44:09 AM »I removed the jets and slide assemblies. Lots of blackish fuel residue on the white plastic slide holders. Some fuel residue even on the air inlets before the butterfly valves. This bike is my daily commute vehicle, I ride mostly at low throttle 5,000 rpm.
Jet needles look like new. Needle jets look good except for a little corrosion at the entrance of #1 (LHS). I poked the back of a 2.6 mm drill bit through each one, and I see no significant wear. A 3.2 mm bit goes smoothly in each one, and stops 8 mm from the end.
Main jets #1 and #3 (clock-wise from top RHS) have a visible mark. I scraped it with a toothpick, and it seems just a discolouration, not really a worn groove. Is this what you described?
How would I clean out the pilot air passages - just flush the 2 air jets below the throttle body with carb cleaner spray and then compressed air, or any other ports as well?
Let me know if I can post any more information or pictures to help diagnose the problem. Please let me know if you have any other ideas, thanks!
Jet needles look like new. Needle jets look good except for a little corrosion at the entrance of #1 (LHS). I poked the back of a 2.6 mm drill bit through each one, and I see no significant wear. A 3.2 mm bit goes smoothly in each one, and stops 8 mm from the end.
Main jets #1 and #3 (clock-wise from top RHS) have a visible mark. I scraped it with a toothpick, and it seems just a discolouration, not really a worn groove. Is this what you described?
How would I clean out the pilot air passages - just flush the 2 air jets below the throttle body with carb cleaner spray and then compressed air, or any other ports as well?
Let me know if I can post any more information or pictures to help diagnose the problem. Please let me know if you have any other ideas, thanks!