GSF 400 Bandit not starting. Does spark

[jayb]

Hi! I bought a Bandit GSF 400 (1992 / 22500km) for my girlfriend a while ago. The bike looks in mint condition, but the owner had left it standing for two years. Now it won't start.

I first tried putting new gas and starting with a car battery, also drained the carbs. Unfortunately the fuel tap doesn't have a PRIME option. I checked for a spark and cleaned the plugs, they looked like they were in good condition. After a lot of starting it showed some life at one point running for about 2-3 secs!

I tried a lot more times without luck, so I thought it must be a fuel issue. I checked the following:
- Gastank = clean
- Vaccuumpump = working
- Carbs = were not dirty and from what I could see it looked fine
- The correct sparkplugwire on the correct cilinders
- Spark = YES (doesnt look blue though)

So now it doesn't seem likely anymore that it's a fuel issue.

Could it be the CDI, even though it sparks? If so how would I check this..? Maybe starting from the car battery fried something by accident..

[greg737]

I first tried putting new gas and starting with a car battery, also drained the carbs. Unfortunately the fuel tap doesn't have a PRIME option.

Are you sure it doesn't have a PRIME setting?  I think Suzuki didn't print the word "PRIME" on the fuel petcock but there's no doubt that it has that function...

[jayb]

OK I will double check! thanks

I remember trying turning the tap in all directions but it would only point to RES and ON

[greg737]

I remember trying turning the tap in all directions but it would only point to RES and ON

That's why I put in the pictures of the Owner's Manual pages, to show you that the "blocking screw" has to be removed before you can rotate the petcock switch to the PRIME position (which, as mentioned, is unmarked).  The arrow on the petcock switch has to point upward (vertical) to select PRIME.

Good luck.

[Gouraami]

I hope it starts, otherwise you are going to get to know your carbs very very well    possibly better than you know your girlfriend   

Edit - Also check the simple things, like are the spark plug leads in the correct order.
I doubt you blew the cdi, the person who had my bandit before me used to connect it to the car battery all the time while trying to get it started

[Squishy]

If it has really been sitting for 2 years, big chance the carbs have been clogged up.
Did you also check the bottom (carb bowl)? That's where the damage will be. Did the bike come with fuel still in the bowls?

[greg737]

I doubt you blew the cdi, the person who had my bandit before me used to connect it to the car battery all the time while trying to get it started

B4 connected to a car battery - no problem.

B4 connected to the battery of a running car - this seems to cause problems.

(While working on my project B4 I connect it to a car battery all the time)

[jayb]

If it has really been sitting for 2 years, big chance the carbs have been clogged up.
Did you also check the bottom (carb bowl)? That's where the damage will be. Did the bike come with fuel still in the bowls?

Yep  still had fuel in the bowls, I opened up the carbs but it all looked very clean. Also after draining they would fill up again. I checked the line from the bowl to the jet(?) by blowing in them, I could blow air through all four of them, some needed more pressure though.

[Squishy]

If it has really been sitting for 2 years, big chance the carbs have been clogged up.
Did you also check the bottom (carb bowl)? That's where the damage will be. Did the bike come with fuel still in the bowls?

Yep  still had fuel in the bowls, I opened up the carbs but it all looked very clean. Also after draining they would fill up again. I checked the line from the bowl to the jet(?) by blowing in them, I could blow air through all four of them, some needed more pressure though.

Did you also check the small one next to the main jet? That one is going to give you trouble when starting. Might be under a rubber cap.

[jayb]

Ok I just had a new try with a fresh battery, it started to run instantly for about 2-3 seconds again! Now thats pointing me towards the carb again and I can almost rule out the CDI

Also I did now manage to get it on PRI, thanks Greg!

I now took out the carbs again to give it a better look, thanks for the tip Squishy I will look at that

[Squishy]

Also whether the choke mechanism works properly... not only the cable etc. but if you have the carbs open anyway, check whether the tubes/piston thingy doesn't get stuck.
Btw be careful of the little o-ring on these carbs, under the top vacuum cover of the carb! When you get the cover off they will stick and fall the ground and you will never see them again.

[greg737]

The reality of your situation is this: You probably should rebuild these carbs.

Even if you can overcome the starting problem (getting the fuel flowing again after years of sitting in storage) I'm betting there are other issues just waiting for their turn on stage.

There's a reason why this Bandit was parked a few years ago.  Probably because over time it had become harder and harder to run.  Eventually, when it became really difficult to deal with it got pushed to the back of a garage and forgotten.

The Mikuni carbs on the B4 are good but they require attention.  Your carbs are 24 years old now.   You should replace all the old rubber parts.  Here's the guy who can provide you with all the rubber bits: http://www.litetek.co/Carb_Kit_Suzuki_GSF400.html

While replacing all the rubber bits with high quality Viton is a great move, there might be another issue. 

Some of the brass parts of carbs wear with age.  In the B4 carbs the most common worn brass part is the emulsion tubes.  The emulsion tubes can become eroded into an oblong shape on their inside rather than perfectly round because the needles drag against them as they move up and down.

The larger gap around the needle caused by eroded emulsion tubes causes too much fuel to flow into the air/fuel mixture, no matter how you try to tune them otherwise.  This condition causes a B4 to turn into a hard-to-start, poor-idling, over-rich pig.  Which, as mentioned earlier, often causes it to be abandoned in the back of a garage.

[Squishy]

Hm I don't know..
My 400 is 25 years old, almost 85000KM and still all the stock rubbers, needles, and tubes.

But yeah I do recommend opening the carbs up and giving everything a good clean. You can then also check the state of the o-rings and the wear on needles/emulsion tube and whether they need replacing.
Personally I think it's quite a relaxing task on a winter day. 

[ventYl]

Most probably things like diaphragms and choke rubber parts will be OK. O-rings might be shrinked and either leaking fuel or air. it is always a good idea to rebuild the carbs if they were sitting for years. I agree with greg that sooner or later problem will arise and you will end up with carb rebuild anyway. Adding to written above: it is possible (and I would bet for that) that while bike was losing it's ability to run the previous owner tried to "tune" it. It is always the case: "Hey buddy, your bike not running properly? There are the fuel screws at the bottom of the carbs, try to turn them out. Sure; your bike runs lean". And instead of fixing the problem they completely wreck carb setup without fixing the issue itself. And then the bike ends up in the back of garage in worse condition that it had when it all began. So my advice would be: dismantle them completely (there's no need to dismount them from rack, just remove all removable parts and keep bodies in rack). Clean them; replace all O-rings (including the secret one under slide holder) and perform basic carbs setup (values are written in the shop manual).

Replace HT cables too. They cost few bucks (it is being sold in quantities of meters here, you can cut them to proper lengths and replace original ones on your own). Even visually good looking cables might get you a poor spark. With B4 CDI which is notoriously known for failing it is important to have the ignition path in as good condition as possible. You only need wires itself, caps are of screw-on type and could be re-used if not damaged. 

also, pay attention to fuel tap. i have an experience that original needles in carbs are good if they have to hold fuel with fuel tap which is not not leaking but if fuel tap doesn't close fully they might leak fuel into carbs and engine. it is nothing worse than dismantling hydrolocked bike at office parking lot so you can get the fuel out of cylinders instead of making short trip before coming home from work. OEM fuel tap is rather expensive and cannot be rebuild but I think that it pays itself off (ruining your mood when you hear that engine is hydrolocked is priceless).

Doing all the above and using fresh fuel I bet that it will run after first crank. Then you have to ballance the carbs, change oil and filters and enjoy the ride :)

[jayb]

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!