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Wow, thanks for the detailed reply.  Yes, I do open the throttle slightly when starting, always have done for 56,000 km.

I will check the needle jets, thanks.
SUZUKI BANDIT 250 & 400 / Re: Dies immediately after starting when cold/wet
« Last post by greg737 on Yesterday at 11:27:20 PM »
I believe your problem is carbs that are running too rich.  If a carbureted engine will start from cold without needing any choke it means the carbs are running too rich.

The choke is a necessary item on a carb (by design).  On the Bandit's Mukuni carbs using the choke during starting provides both fuel and air (not just fuel) to properly balance the air-fuel ratio for a cold startup.  A set of carbs that are running too rich will only provide the extra fuel (not additional air) which means the air-fuel ratio is very likely to go too-rich during the startup.

This sets up a situation where you (the rider) might develop the habit of "cracking the throttle" a bit because you're very familiar with the bike and you know that you need to admit some extra air during a cold startup. 

This method of starting a carbureted bike creates a highly variable condition that could easily go "over-rich" and fail to start.

Because "Cracking the throttle" opens the throttle plates just a bit it has the effect of slightly reducing the vacuum pull experienced by the Main Jet, which reduces the amount of fuel that will be sucked up through it.  If the Main Jets are worn to the point where they are flowing too much fuel this slight reduction in vacuum might have the effect of lowering the amount of fuel delivered to a point where the air-fuel ratio is correct for cold startup.

If (by chance) you happen to "crack the throttle" just the right amount the bike will start right up.  If you "crack the throttle" too much you might have to crank longer because the air-fuel ratio will be on the too-lean side for a while.  But if you "crack the throttle" too little you could easily end up with one or more of the cylinders being fueled into an over-rich condition, which means a "flooded" condition (an air-fuel ratio that is too rich to burn).

So when the bike fails to start and then refuses to start, it's because one or more of the cylinders are flooded-out with fuel.  This is why waiting 30 minutes is the solution, because waiting 30 minutes allows all that extra fuel to evaporate away.

One of the things that causes Mikuni carbs to run too rich is when the soft brass metal of the main jets has been worn by the needles.  The wear from the needles causes the original round hole of the main jets to become oval and larger, which increases the amount of fuel the main jet can flow, causing the too-rich running condition.
SUZUKI BANDIT 250 & 400 / Dies immediately after starting when cold/wet
« Last post by yuckhil on November 17, 2019, 06:11:54 AM »
Hello everybody, I hope somebody has advice for me.  Bike always starts strongly first crank without choke.  No problem once the engine is warm.

When it is cold and/or raining, even if parked under cover, it immediately tends to die within 3-5 seconds.  If it dies then it will not fire AT ALL, just cranks over and over.  Leave it for 30 minutes, then it starts instantly.  If I manage to get moving, it runs very rough (sounds and feels like on 2-3 cylinders) and exhausts a LOT of vapour for about 1 km, then rides normal after that.  One day I rode into a rainy patch, and it became rough until I passed through the rain patch.

Bike is fully stock.  New plugs, battery, air filter.  Plugs, jets, oil looked clean at the last change.  Float valves were leaking; new float valves reduced the severity of the problem, but it still dies.

Any ideas?  Thanks.
Just picked up an 01 Bandit very inexpensively and want to improve her manners on dirt roads. I'm thinking the DL1000 fork tubes would slide right into the Bandit tripple trees, so if I can source a suitable rear shock and increase the ride height accordingly I'd be half way there. Anyone done this or contemplated the technical difficulties I'd face?

FWIW, I'm perfectly happy with the stock engine tune and have no interest in hustling down the road like it was a track day. I just want to be able to take any road I see with some confidence.

And I like the Bandit better than the Vstroms I've had   :grin:
BIKES/PARTS/GEAR for sale/wanted / '91 Bandit 400 looking for a good home
« Last post by suvari on October 07, 2019, 08:41:19 PM »
Hey there, I am at the stage where I am coming to terms with the fact that I will not have the time and setup to do justice to my Bandit 400. It is a 1991 I bought locally--in DC area--in 2012, and loved it. Haven't ridden for about 3 years now, and almost getting to forget why not. I know I wanted to rebuild front brakes. Clutch is not releasing fully, but it might be as simple as an adjustment.
The engine was running strong when I parked it. Carburator was good.
The tank was rusty when I bought it. Put a good liner in, but that was after stripping all paint, so tank looks uglyish now with an aging plastidip. But no dents. Tap is aftermarket high flow.
Got a bunch of parts as well.

Sorry for the spotty information. I will look to the parts box, and post pictures too. just trying to see if the forum is alive, and if there are local people who would be able to revive a beautiful machine. I am easy to deal. Say hi if this interests you at any price at all. If not, I guess it is a non-running donation  :yikes:

SUZUKI BANDIT 250 & 400 / Re: Jap B400 VC carb jetting question
« Last post by Ivandit on September 20, 2019, 04:38:14 AM »
That's really helpful, thanks a lot!!

I contacted 6Sigma and they have no idea at all IMO, as their reply was something like "yeah, do it that way then" :roll:

Obviously, the service manual is correct and now it all makes sense.

Anyway, I recently got my hands on a Yoshimura MJN kit so I'll be re-jetting according to the instructions in it...fingers crossed!

 :thanks: :thanks: :thanks:
SUZUKI BANDIT 250 & 400 / Monoshock oil capacity
« Last post by chamarang on September 18, 2019, 09:23:52 AM »
Hi any one know about the suzuki gsf250 rear monoshock oil capacity
SUZUKI BANDIT 250 & 400 / Re: Jap B400 VC carb jetting question
« Last post by T2098 on August 29, 2019, 02:33:25 PM »
When I jetted my 400VC I followed the factory service manual and did it as they specified, with the larger jets on cylinders 1 and 4.

The Bandit engine is liquid cooled and pretty cool-running at that from the factory with the 170 degree thermostat.   The two cooler cylinders likely have cooler cylinder heads and intake ports as well, and the cooler an intake port and its associated valves are, the less it atomizes the incoming fuel.

This lack of complete atomization is one of the main reasons why a cold engine needs to be run richer, both with fuel injection and carbs.   The cool intake port walls and intake valves leave an awful lot of little liquid fuel droplets un-vaporized, which just get pushed out the exhaust port as unburned hydrocarbons.

So the answer as to what the correct jets are for which cylinders depends on whether you're looking for nice even air/fuel ratios across cylinders (like Suzuki did with the Bandit, since it has zero issues with keeping itself cool) or whether you're trying to use the excess fuel to keep hot running cylinders cool and from overheating.  On a 70s-80s air cooled 4-cylinder it wasn't uncommon to see richer jets used on the hotter running inner cylinders to allow them to run a bit cooler - even if that meant the air/fuel ratio was perhaps richer than ideal for combustion and it cost you a little bit of fuel economy and some higher hydrocarbon emissions.
SUZUKI BANDIT 250 & 400 / Re: GSXR 750 Rear Shock Swap UPDATE
« Last post by panakos on July 28, 2019, 07:38:02 PM »
I just mounted an 06 gsxr shock, only a touch longer than stock, had to grind the rocker a bit for clearance for the larger spring, also relocation of the stock overflow is necessary (mine already was), I may lengthen the dogbones a bit to tweek ride height, will report back when the bike is back together and on the road.

That's probably too old, but with the k6 gsxr 600 shock, did you have any clearance issues when it fully compressed?
SUZUKI BANDIT 250 & 400 / Jap B400 VC carb jetting question
« Last post by Ivandit on July 01, 2019, 04:59:33 AM »
Hi there!

So last year I got a 6Sigma jet kit for my '94 VC, installed and running (apparently) well with a K&n air filter and stock exhaust.

The fitting instructions tell you to replace the stock jets with 105 on #2 and #3 and 102,5 on 1# and #4, which kinda made sense to me after reading about how that difference compensates the different cooling conditions on inner and outer cylinders, adding a bit of extra fuel to help #2 and #3 cooling:

But then...last week I was reading the japanese service manual prior to a valve clearance check and got a bit shocked when reading the carb specs:

So, apart from them being the same size (what's the point with the kit then??)...they are supposed to be fitted completely the other way around!! That is 105 on #1 and #4, 102,5 on #2 and #3.

Any thoughts/experience on this?

So far I've had different opinions, from "stick to the manual" (why the outer cylinders are set to be richer then??) to "the manual info is wrong" (hard to believe IMO...).

I just want to go back to stock jets, but I just don't know which is the right way...any help is much appreciated!! :beers:

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