92 Bandit 400 idle and throttle lag.

[Wunder]

Hi there, My name is Shaun and I currently ride a Suzuki 92 Bandit 400.
I live in the upstate area of South Carolina.


Heres my issues, In the mornings when its somewhat cold out the bike is alittle tough to get cranked.
Like for example. It's 31 Degrees out, I've gotta full choke the bike to ignite the engine, After it cranks half choke the engine whilst it idles or else it'll just die off.

I'll let it run for about 8- 10 minutes to ensure its nice and toasty. However, Once I hop on and start towards my destination the engine will start bogging down at 7 rpms. This is what bothers me the most. I've had the bike for roughly 3 and half months and it's recently started this.

It runs alittle better in warmer weather like the low 60's.

So far, I've replaced the plugs (Wires I've yet to replace).
rans about 2-3 shot glasses worth of seafoam in the fuel and added some high octane racing fuel (103 octane level to be exact)

What else can I do? I've asked a few people who are decently knowledgable on motorcycles and they given me a wide veriaty of answers from Carbs need cleaning to Plugs are bad.

As to what plugs I'm using I'm using some standard plugs bought from Auto Zone, Is this my problem?

Thanks for your time, Gentleman.

Ride safe!

[r_outsider]

The bike is a little lean in the cold, dense air. Try richening it up on the airscrew and needle, see if it helps.

[Wunder]

Thanks, Outsider.

I'll give that a go

[apollonrop]

WAIT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Wunder before you adjust something that has nothing or at least very little to do with your problem, let me explain something to you.  Your carbs will have betwn 3 and 4 circuits that control how they operate.  The idle adjustment screws are designed primarily for adjusting your IDLE circuit.  They will affect to some degree your mid range rpms and fuel ratio but thats it.  At 7k rpms your dealing more with the needle jet and jet needles and your main jets than anything else.  

IF YOU ADJUST YOUR IDLE MIX SCREWS THERE IS A VERY GOOD POSSIBILITY THAT YOUR GOING TO HAVE A WORLD OF TROUBLE TO DEAL WITH AND IT IS UNLIKELY THAT YOUR ISSUE AT 7K RPMS WILL GO AWAY.  

However, if you have already adjusted the idle mix screw hopefully you documented exactly how many turn outs each one was from the closed position before you opened/closed them any more.  

So here's what your going to need to do if you want to deal with the bogging down affect at 7k rpms.  First I am assuming that since you've only had this bike for 3.5 months that it had sat before you got it.  If thats correct then you definitely need to clean the carbs.  The more time it has sat for the more likely it is that you need to clean the carbs and adjust the floats.  However, if you knew the guy you bought the bike from and you know he used to ride it like every other weekend then you're probably looking at doing a float adjust.  

I won't lie to you, float adjusts are a bitch to get right.  Even experienced mechanics (who ARE thorough) don't enjoy them.  Here's why, floats aren't hard to adjust.  But you have to check and often times (on older bikes like yours) replace alot of the seals.  Over time they mold to the shape of the thing they are sealing and they stop sealing properly.  PROBABLY WHATS GOING ON IN YOUR CASE.  But once all the seals have been checked/replaced then they have to do a plug chop test on the systems that are in question in order to ensure that the mixture has been set correctly.  Like I said float jobs done right are a BITCH.  But on the bright side if you learn how to do it and you do it right you will know what your issue is far better in the future.  Man I JUST LOVE FUEL INJECTION.  Anyway...

As for the spark plugs, yes you do need cold weather plugs.  If you have the manual it will specify the exact type you should use.  This would be my first suggestion in the course of to dos.  But I would be surprised if you don't need more to get the bike right i.e. a good carb cleaning and float adjustment.  By the way you don't need to change the spark plug wires.  Most of these bikes made by Suzuki back in the day carry SOLID CORE spark plug wires.  That means that they will be all copper (or what ever metal strands that they happened to use at the time) and they don't deteriorate like current car wires do.  In other words instead of having a hose that has a small stream of water (symbolic of common day wires) running through it, the water representing the metal inside the cables, you have a fire hose worth of water.  Unless they've been severed, they're fine.  Also, your rough idle will probably get much better after you clean the carbs.  Adjusting my idle mix screw is the last thing I want to do when I buy a new old bike, mostly bc that system is very particular and the least susceptible to change over the years.  If that makes sense.

[Wunder]

WAIT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Wunder before you adjust something that has nothing or at least very little to do with your problem, let me explain something to you.  Your carbs will have betwn 3 and 4 circuits that control how they operate.  The idle adjustment screws are designed primarily for adjusting your IDLE circuit.  They will affect to some degree your mid range rpms and fuel ratio but thats it.  At 7k rpms your dealing more with the needle jet and jet needles and your main jets than anything else.  

IF YOU ADJUST YOUR IDLE MIX SCREWS THERE IS A VERY GOOD POSSIBILITY THAT YOUR GOING TO HAVE A WORLD OF TROUBLE TO DEAL WITH AND IT IS UNLIKELY THAT YOUR ISSUE AT 7K RPMS WILL GO AWAY.  

However, if you have already adjusted the idle mix screw hopefully you documented exactly how many turn outs each one was from the closed position before you opened/closed them any more.  

So here's what your going to need to do if you want to deal with the bogging down affect at 7k rpms.  First I am assuming that since you've only had this bike for 3.5 months that it had sat before you got it.  If thats correct then you definitely need to clean the carbs.  The more time it has sat for the more likely it is that you need to clean the carbs and adjust the floats.  However, if you knew the guy you bought the bike from and you know he used to ride it like every other weekend then you're probably looking at doing a float adjust.  

I won't lie to you, float adjusts are a bitch to get right.  Even experienced mechanics (who ARE thorough) don't enjoy them.  Here's why, floats aren't hard to adjust.  But you have to check and often times (on older bikes like yours) replace alot of the seals.  Over time they mold to the shape of the thing they are sealing and they stop sealing properly.  PROBABLY WHATS GOING ON IN YOUR CASE.  But once all the seals have been checked/replaced then they have to do a plug chop test on the systems that are in question in order to ensure that the mixture has been set correctly.  Like I said float jobs done right are a BITCH.  But on the bright side if you learn how to do it and you do it right you will know what your issue is far better in the future.  Man I JUST LOVE FUEL INJECTION.  Anyway...

As for the spark plugs, yes you do need cold weather plugs.  If you have the manual it will specify the exact type you should use.  This would be my first suggestion in the course of to dos.  But I would be surprised if you don't need more to get the bike right i.e. a good carb cleaning and float adjustment.  By the way you don't need to change the spark plug wires.  Most of these bikes made by Suzuki back in the day carry SOLID CORE spark plug wires.  That means that they will be all copper (or what ever metal strands that they happened to use at the time) and they don't deteriorate like current car wires do.  In other words instead of having a hose that has a small stream of water (symbolic of common day wires) running through it, the water representing the metal inside the cables, you have a fire hose worth of water.  Unless they've been severed, they're fine.  Also, your rough idle will probably get much better after you clean the carbs.  Adjusting my idle mix screw is the last thing I want to do when I buy a new old bike, mostly bc that system is very particular and the least susceptible to change over the years.  If that makes sense.

Man, I'm sure glad I'm lazy. In all honesty I've yet to get around to adjusting anything due to a clutch cable going bad.
Thank you, Apollorop for the write up!
However, I don't believe the bike sat dorment, The previous owner used this bike as a trick bike, as well as a weekend commuter.
Though, I would still like to clean the carbs since I'm going to be messing around with them anyhow.

But the plugchop test looks to be rather simple test, after watching a short youtube video on how to test and what results mean what.

Again, Thank you Apolloonrop.
You I believe you just saved me a HUGE headache, Bud!

[Chris H]

Hi Shaun,
Should have posted in the B4 section and the guys would tell you it runs CR8EK plugs and the B4 is Known for bad carburation when the o'rings in the carbs go hard with age and then dont seal correctly. Could be worn needle/emulsion tube but most likly the o'rings.