Mk1 Bandit 600 carb troubles

[Sketch424]

Hi Gents,

Short story time!

I have a mk1 bandit 600, I'm having issues with the carbs, still. 

The mods on the bike are as follows:

Dynojet stage 1 kit
DJ104 jets
Simota Filter
airbox mode 44mm hole - Currently covered for testing.
Full blackwidow system with a full length can
dyna coils
4 degree Ignition advancer

I set the carbs to the default settings for dynojet kit, 2.1/4 A/F screws and e-clip on position 4 on the needle. larger DJ104 needles as I have a full system and free flowing filter. I have altered the float heights to 18mm from the standard 17mm to try and reduce richness, however this hasn't helped! (intentionally tested at 16mm and found to increase richness severely)

I've had a Mk1 B6 before with the same mods, except a standard system, that was the same settings on the needles, didn't check the jets. and it ran absolutely amazingly. even compared to another mk1 I rode at the time. 

I'm tapping into some wisdom here to see if there's anything I've overlooked?

Edited to add the actual problem I'm having...That helps! 

when I first start riding the bike is sweet as hell, pulls hard doesn't stumble, it's great! however on an extended run of low rpm bimbling combined with full throttle full rev testing, I come across what feels like almost flooding cylinders, revs will sit high, like around 2k for a while on idle, I leave the bike for a couple of hours, come to start it again and it's fine. Coming onto the power from low RPM results in a flooding stumbling feeling. I have stripped and cleaned the carbs a few times now to ensure everything is clean. I've also balanced the carbs after each strip and rebuild.

I think there's a slight scent of petrol in the oil as well. 

I have yet to do a compression test.

Thanks guys!

 

 

 

 

 

 

Edited August 11, 2018 by Sketch424

[wsn03]

Needle float valves!!!

Buy a remote tank from.demon tweeks.

Put carbs on bench, turn on tap and watch them piss fuel everywhere. This is the classic symtoms you are describing. If so buy either OEM  (order from USA to save a fortune) needle float valves or try Wemoto (people saying they are good). 

Change your oil if so, its now got a lot of petrol in it.

Your air filter box is probably full of fuel so be very careful. 

Edited August 11, 2018 by wsn03

[Sketch424]

 

By needle float valves, do you mean this little ali parts with the rubber tips that seat when the float closes? 

Tell you what, thats one thing I didnt do, I have a remote tank and I've had the carbs off loads.

Thats something to try, my airbox is dry though

[wsn03]

3 hours ago, Sketch424 said:

 

By needle float valves, do you mean this little ali parts with the rubber tips that seat when the float closes? 

Tell you what, thats one thing I didnt do, I have a remote tank and I've had the carbs off loads.

Thats something to try, my airbox is dry though

You've got it. Its really good to test these anyway. The bench test proves your float levels are ok and that the needle float valves are doing their job

Every aftermarket set Ive tried are shite btw. Guys on here saying wemoto work. Mikuni are made in Japan, so are Wemoto...sounds like might be the same.

If buying OEM order from US or Japan,  Makuni parts,  if you dont want to be well and truly bummed by the GB Suzuki dealers. Get the part number first

Edited August 11, 2018 by wsn03

[Sketch424]

Afternoon wsn, so took carbs off and setup a remote tank, and there are no leaks.

So far this is what I've done and it feels better. 

Lifted needles by a clip position (leaner) 

Reset a/f mixture to 2.1/4 as suggested by dynojet. 

Balanced the carbs by eye while they were off.

Bike idles really well now. Hunting is near enough gone, it actually idles instead of constantly nearly cutting out. I do have some high speed runs to test as well. 

[Gixer1460]

1 hour ago, Sketch424 said:

Lifted needles by a clip position (leaner) 

Lifting needles makes them richer - not leaner.

[Sketch424]

Apologies, lifted needle clip position... Dropped the needle down.

[wsn03]

On 8/19/2018 at 3:30 PM, Sketch424 said:

Afternoon wsn, so took carbs off and setup a remote tank, and there are no leaks.

So far this is what I've done and it feels better. 

Lifted needles by a clip position (leaner) 

Reset a/f mixture to 2.1/4 as suggested by dynojet. 

Balanced the carbs by eye while they were off.

Bike idles really well now. Hunting is near enough gone, it actually idles instead of constantly nearly cutting out. I do have some high speed runs to test as well. 

Hello Sketch

Sounds like you're winning.  Delighted there are no leaking valves, thanks for letting me know. 

If you buy a carbtune balancer it will completely change your life. My Bandit 1200 carbs go out from perfection say every 2000 miles. I have her like a sewing machine...that device has made it rideable.

[Sketch424]

I did think about the carbtune balancer.

Maybe a Christmas present to me!! Hahaha! 

So after some testing, there is still a very narrow part of the throttle range where it's lumpy. This is at just cracked throttle, so for bimbling around town.

The throttle is also quite snatchy down there. So some fine tuning is needed, however some advice on what might cause the snatch is appreciated

my thoughts are that it's too rich down in the idle area still, I have my secondary airbox hole covered currently, so thats the next test

Edited August 23, 2018 by Sketch424
To add some extra info.

[wsn03]

On 8/22/2018 at 7:29 PM, Sketch424 said:

I did think about the carbtune balancer.

Maybe a Christmas present to me!! Hahaha! 

So after some testing, there is still a very narrow part of the throttle range where it's lumpy. This is at just cracked throttle, so for bimbling around town.

The throttle is also quite snatchy down there. So some fine tuning is needed, however some advice on what might cause the snatch is appreciated

my thoughts are that it's too rich down in the idle area still, I have my secondary airbox hole covered currently, so thats the next test

First thing I always do is set everything to standard, so get the airbox to original. Next mixture screws, I think on the 1200 its 2.5 turns out, just make sure all are the same. Then balance with carbtune...anything other than perfect balance makes my 1200 run like a pig - by sight or sound is near impossible in my experience with 4 carbs. 

 

Before i do any of this I set the tapets and always always always fit new plugs. I was battling with mine once at v low mileage and a mechanic said new plugs. Dumb I thought, they were perfect.  He was right, they seem to be really sensitive to plugs, very odd.

[Sketch424]

Thanks dude, I'll investigate further

[wsn03]

Welcome mate,keep us posted 

Edited September 2, 2018 by wsn03

[Sketch424]

Thanks WSN, 

So, a bit more testing. A/f screws at 2.1/4 turns, slightly snatchy throttle.

Set at 2.5, less to zero snatch, but bike felt a bit lumbery (too rich)

set at 2 turns, very snatchy, less lumbery, but the snatch is dangerous mid corner. 

I'm thinking, despite dynojet suggesting DJ104 jets for my setup, im going to test with DJ100s. As it feels too rich potentially.

[wsn03]

Did you do plugs, balance carbs and rappers? You'll never get it right if those aren't done first

[Sketch424]

Plugs are CR9EK, carbs balanced as well as can be done. Tappets were done not long ago

so put in the dj100 jets, set needle heights back to standard, it runs alot better. Still a bit bubbly at just on throttle, but, it's definitely a lot better. 

I have noticed that one of the plug holes does seem to be threaded, whats the best way to repair this? 

[Gixer1460]

For a 600 DJ104's sound big - from memory they are about the size used in 1200's - could never understand that as my GSXR1100 used DJ136/8's and used less fuel than a M8's 1200 - its all Dark Arts - I'm telling ya!

Plug thread - Helicoil kit - done carefully will outlast the rest of the engine.

Edited October 6, 2018 by Gixer1460

[wsn03]

On 10/6/2018 at 9:06 AM, Sketch424 said:

Plugs are CR9EK, carbs balanced as well as can be done. Tappets were done not long ago

so put in the dj100 jets, set needle heights back to standard, it runs alot better. Still a bit bubbly at just on throttle, but, it's definitely a lot better. 

I have noticed that one of the plug holes does seem to be threaded, whats the best way to repair this? 

Nice one. Im willing to bet even after a few miles you can re-balance the carbs finding them to be out. I find they take a while to settle...odd!

Are the plus NEW? NEW really changes things, I mean BRAND NEW. Forget low mileage or good condition...fit BRAND NEW. I dont know why but makes a big difference on Bandits...really odd

[Sketch424]

Thanks for your advice gents

the bike still runs a tad rich on th3 ifle circuit, so a dabble with the a/f screws should resolve that