GSF 400 Bandit not starting. Does spark

[Squishy]

Its been a while, I must say thanks a lot for your elaborate responses! REALLY!

I started to take apart the carbs, after being reluctant for a while. I really dont want to do anything wrong, when I finally did two screws wouldnt budge at all! (far left and far right on the slides that keep the four carbs together)
Of course the screws were not in good condition after a couple of tries.
 
I ordered an impact screwdriver and I dremeled a flathead out of the screw, a few hits and it was finally loose. Now I can start cleaning, although now I'm doubting whether I needed to unscrew the carbs from each other at all. But I wanted to replace the bad screws anyway, because it looks horrible.

Anyway I will continue cleaning now and let you know, thx again!

You do need to separate the four carbs from eachother to clean them (or to do pretty much anything else).

Just remove everything inside of the carbs.
Top half (in this order): Cables, vacuum cap, small o-ring underneath(!), diaphragm, needle&co, needle jet (optional, if it's really bad).
Bottom:  Bowl, float (just pull), main jet, starter jet (press really hard with a good screwdriver or you will strip it), pilot jet&co.
Choke mechanism is optional if it works OK.

Now blast the carb body (and passageways) with brake-cleaner and water, and/or pressurized air.
Blast jets with pressurized air or pinch them with a small needle.

[greg737]

And keep the rubber diaphragms away from any cleaning chemicals you're using on the carbs.  Nothing stronger than soap and water for the diaphragms.

[jayb]

I took apart two carbs, at least what I was able to do. One of these two had a o-ring missing under the vaccuum cap. So the guys at the dealer didn't do a very good job last time.

1. I think I cleaned most of the canals pretty good with copperwire, degreaser and brakecleaner. I couldn't clean this part below very well, is it possible to take off? If not whats the best way to clean?


2. Also I wasn't able to remove the part below indicated with the red arrow. Should I just poke it with the copperwire?



3. Most of the rubbers looked OK, except for the fuel seals. These were in very bad shape and they must have leaked fuel so I will replace these at least or go for the full rebuild kit.

[Squishy]

Yeah the rubber o-rings can stick to the vacuum cap and then fall off when you're not looking.. you will never know they were there if you didn't know before hand.

Yes poke them with a copper wire/sewing needle or use compressed air.

What are those 7 big rubbers in the last pic? I don't recognize them.

[jayb]

Ok thanks! The big rubbers are the fuel seals, where the gas goes from the fuel tank into the carbs they are in between the carbs. They look quite bad :)

[ventYl]

I personally would avoid using any kind of mechanical aid including copper wire (althrought it can be safe being carefull). Passage marked as [1] is "choke jet". Completely irrelevant if your engine will run on four while on choke.

Passage not marked with label is "main air" passage. I assume that this is pressed into carb body and is not removable.

The limestone at carb connectors looks like the bike was sitting in really wet garage for several years.

[Squishy]

Didn't see the picture with the red arrow.

Yes, that's the main air jet or main bleed jet and cannot be removed. This jet is not your problem because it only affects the main circuit and shouldn't prevent you from starting. It is important to have it clean in the end though or your engine will run way too rich on WOT - use a compressor to clean it.

The one next to it is more important for your situation (pilot air jet). You can remove that one.

[jayb]

Ok guys I did the full rebuild with the Litetek seals, I made a very big mistake turning the nut on without the butterfly in it. That made it bend and it took me a lot of time to bend it back and get it all working nice and smooth again.

I just installed the carbs and it started very easily without choke. About 5 seconds then it died.. before it died it went up in RPM now it wont start anymore. What could be the problem?

- Float needle?
- Pilot screw adjustment (it's set to 2 turns out) <-- 1 turn is 180 degrees right?
- fuel tap leaking in the "ON" position without vacuum ?

[Squishy]

Ok guys I did the full rebuild with the Litetek seals, I made a very big mistake turning the nut on without the butterfly in it. That made it bend and it took me a lot of time to bend it back and get it all working nice and smooth again.

I just installed the carbs and it started very easily without choke. About 5 seconds then it died.. before it died it went up in RPM now it wont start anymore. What could be the problem?

- Float needle?
- Pilot screw adjustment (it's set to 2 turns out) <-- 1 turn is 180 degrees right?
- fuel tap leaking in the "ON" position without vacuum ?

1 turn is 360 degrees.

[jayb]

thanks Squishy!  Ok I think it must be the float needle valve and it overflows the engine, because if the bikes sits for a while it will start and run for 1-2 seconds.

Does anyone know where I can get the float needle part? If I search on 13250-10000 I get no results (from the service manual)

I also found these

[Squishy]

thanks Squishy!  Ok I think it must be the float needle valve and it overflows the engine, because if the bikes sits for a while it will start and run for 1-2 seconds.

Does anyone know where I can get the float needle part? If I search on 13250-10000 I get no results (from the service manual)

I also found these

What makes you think it's the needles?
If the engine is off (and petcock in ON/RES) there is no fuel going to your carbs so the float needles have no effect on this situation. That is if your tank petcock is functioning properly.. but that is very easy to check.
Too much fuel in the bowls would explain why it starts without choke, though.

So.. here's what I'd do, assuming everything is cleaned in the carbs now.

1. Remove the float bowls again and have the carbs upside down, wiggle the floats a bit and measure the floatheight as mentioned in the manual (I think it's 14.6mm +- 1mm). This is the height from the gasket surface to the top of the floatbowl.
2. Set mixture screws to 2x out from fully in (so 2 full turns)
3. Visually check whether the 4 butterfly valves are opened slightly and roughly the same. You can do this by looking from the front of carbs at the very small holes under the butterfly. Use idle screw ("throttle stop screw") and the sync screws in between to adjust.
4. Check whether the o-ring is under all vacuum caps.
5. While vacuum cap is off, check whether the choke mechanism opens all 4 plungers and closes them fully.
6. Put everything back together. Use fingers to check whether needle slide goes up and down freely.

7. Ps. You can check whether the float needles leak by putting in fuel/water, then connecting a transparant hose to the float drain and opening it up.
Hold/attach the hose in a U-shape upwards next to the floats. Once you open the drain it should fill the hose and stop right around the top of the bowl.

8. Don't forget the vacuum hose to the tank. If you use an auxiliary fuel supply close the vacuum hose off.
Use clean fuel and set petcock to pri. Wait 20s, use choke, no throtttle and start. Don't forget to set petcock back to ON/RES.

[jayb]

Because I remember looking at them and thought they looked like they were in bad shape. I left them in the float assembly because I didnt know how to get them out. I checked them by blowing in the float assembly and see if they would block the air if I pushed the bowls up. They did, so I thought OK. Now I think that was a bad way to check that :)

Too much fuel would also explain why the engine does start after it has been sitting for a while.

Thanks Squishy again! Checking the float height is another thing I didnt do yet

[ventYl]

If needles weren't tight and were leaking you probably ended up with hydrolocked engine sooner or later.

AFAIK OEM needles cannot be purchased on their own. They are only available as float assembly and fairly costly (about 110 euro per carb). But I found one company which sells "economy carb rebuild kit for GSF400". I don't remember it's name but you should be able to find it using the name of kit with google. This kit contains O-rings, needle, jets (?) and bowl gasket (?). For something like 1/4 of price of one fuel assembly.

But I've seen fairly worn-like looking needles being tight even if I blown into the fuel reservoir to check how much pressure is needed to overcome their tightness. It requires quite a lot of pressure even in such case.

I personally would check the O-rings of float bowl assembly for perfect tightness. If they are shrunk they might also leak fuel resulting in non-even engine run because of different fuel levels in different carbs. But the behavior you are describing usually means that some passage or jet in main system is blocked in your carbs. I have experience that when not using ultrasound cleaner even strip-down cleaning process might result in something still sitting in those passages eventually blocking them up. Using compressed air or syringe with small diameter hose attached instead of needle is preferred. Syringe is better because if you are using some cleaning solution you can examine it for residues which it cleaned out of passage. Also drag of liquid is usually large enough using smaller pressures compared to air.

If you don't have compressor available you can buy cans of compressed air.

[no friction]

hi this is my first post here. I recently bought a 97 vc 400 that had the same running symptoms you described. i did a complete rebuild of the bike in these last five weeks but that running issue persisted.
for me i found the problem was a couple of things.
/i had a intermitant earth grounding / a bad side stand diode / and the clutch switch contacts needed cleaning.
runs okay now i just need to fine tune it . Have not synced the carbs yet after rebuild
Your's is a lot nicer looking condition than i got mine in im envious  the previous owner of mine  ran it into the ground until it would not run anymore.
But i have to say i was very suprised to find every engine component was still in good running spec even after it had been abused so badly. well after a lot of work it was.

Other thing i noticed was good nut and bolt quality. if you need o rings for carbs you can buy all you need for 5£ that come in a box as standard nitrile o-rings . instead of buying them for crazy prices
if you need a link or something for the rings i can get one for you. that is for the BST32ss carbs

You probably know this already but when you set your float heights hold the frame of the floats down as the o-ring or shape of the float frame pushes them up off the carb body which will give u incorrect float height.

then test your needle is closing and opening properly by covering the holes in the carb sides with fingers and blowing through the fuel intake.
Turn the carb upside down and back over whilst blowing.

did you find that vacuum tap annoying ? i spent about an hour testing mine and results were still inconclusive haha i went back into house and my face was red. dont know what girlfriend thought i had been doing in the garage lol.

good luck with it

[lknbandit400]

All these guys are smart folks and giving you some really good info - just from experience, I'll add what I've found in my efforts with my B4's over the past few months:

Good work on the carb rebuild.  Knowing how reliant on good o-rings these carbs are, it's hard for me to believe the bike won't start with a rebuild and fire to all plugs (unless compression is low - doubt it).  However, I will say with even those conditions met, this is one of the most temperamental bikes I've owned.  My first thought is that you should try to start it with full choke.  IIRC you said it ran for 5 seconds without choke.  I'd bet with an $24 USD investment of new plugs and full choke, along with your carb rebuild she will fire right up.

Another thing you could do is try to bump start it.  For some reason the first time I rebuilt my carbs on my b4 with new o-rings and all, the bike wouldn't start off the button.  I bump started it once and ever since then it will start first hit right off the button.  Don't ask me why.

Another thing - I have another b4 I recently purchased as a "non-runner."  The bike wouldn't start at all.  Had fire, and fuel.  Threw new plugs in it an rode it for an hour the next day.