complicated carb problem

[El Gringo]

Another thing I would check is for wear on your emulsion tubes, if they are particularly worn you'll be getting too much fuel at the lower end which can upset the idle and low end running.

I've just bought new to replace mine and even a visual inspection shows how worn the old ones are

[ventYl]

not neccessarilly spark plug, but ignition. Incluging caps and wires.

[Squishy]

not neccessarilly spark plug, but ignition. Incluging caps and wires.

Yes that's why I said spark(plug) ;).

[gallant_pilot]

i sync the carbs abd they look good.this is exactly the one which is the refrence for sync the others.

[Squishy]

i sync the carbs abd they look good.this is exactly the one which is the refrence for sync the others.

There is not one carb to use as reference for the others..
You sync 3&4, then 1&2 and then 1+2 & 3+4

Make sure you use the throttle stop screw to set higher (I think its 1700rpm?) but in your case set it so they are all running.

[gallant_pilot]

guys today i noticed something new and it might be the problem!

1-the carbs i believe,they are good now as everything is set back to the stock setting.

2- i didnt have chance to do the compression test yet,but today i found some water mixed with kinda foamy oil leaking out of the engine which i guess coming from the gasket.

i upload the photo and will be waiting for tour comments.

if is the gasket, what is your suggestion? replacing the gasket or anything else?

[Squishy]

Might be coolant with oil... check the levels. Yes could be the result of a leaking gasket.

Unless the leak is very bad, it should still run. If you hold your hand in front of the exhaust while it's running.. do you feel vapor/oil/coolant?

[gallant_pilot]

i checked it out, and there is no oil or coolant coming out of exhaust,which i guess the leakage is not that bad yet.but still on idle the same pipe doesnt get hot.

[ventYl]

did you performed compression test? (if you already written about it, i am sorry, i didn't go through this topic very thoroughly) maybe you should to test with engine cold and then with engine warm. normally cold engine should give lower compression readings than warm but if you are leaking compression into oil / water lines you may see that this particular cylinder won't have compression increased accordingly to others.

[gallant_pilot]

as i said before !

today while i was riding it,the bike started jerking and i open the throttle,suddenly it just started to mess around and work on 3,no power at all. i rode it back home and i think the gasket is gone now.

but there is no smoke or steam coming out of the exhaust pipe.also i can see that leakage is still there.

now if you guys have suggestion about replacing the head gasket, plz tell me in details.

1- do i need to take the head for engineering or i can lightly skim it on marble and fine(1500) sand paper?

2- i cant find a brand new gasket here and the agent says i have to wait for 3 weeks to bring from Japan

3- do u suggest the copper gasket instead of SUZUKI steel gasket? my friends said the copper can work much better than steel so i have to get it cut  first if i use the copper.and it would be accessible for me.

4-in general.do you guys think the problem was the gasket from the beginning which made me think there is carb problem?

however after building the engine,i didn't put new gasket and used the old one,just sprayed it with normal  paint aerosol to seal it.

[TJS]

re - torque all head bolt and valve cover bolts.
If that doesn't work try new gaskets. While you are there, look for any cracks in the water passages.

[gallant_pilot]

guys any idea about using aluminum head gasket or copper?

i wanna get it cut asap and wanna know if the aluminum gasket is working!

[Thief400]

Wow leave for a year or 2 and the squids on here are still having carb issues!!! There are hundreds of back posts on how to get a 400 jetted correctly. Now 102.5 are too lean from stock period! So going even leaner is just stupid. A stock 400 is very happy with 110 mains, stock pilot, stock float height. Raise the needle one up from stock. Oh and use stock mikuni jets not some crappy jet kit.

[greg737]

Wow leave for a year or 2 and the squids on here are still having carb issues!!!

Carbs will always present issues, won't they?  I think that part of the difficulty we're seeing today with Bandit 400 carbs is the result of Emulsion Tube wear.

The problem is that emulsion tube wear is hard to see and identify: http://www.factorypro.com/products/Mikuni_needle_jet_buy.html

Now 102.5 are too lean from stock period! So going even leaner is just stupid.

This is probably a true statement, but only if the set of carbs don't have worn (oblong) emulsion tube holes.  Unfortunately the B400s are getting pretty long in the tooth and worn emulsion tubes are more and more common. 

Once the emulsion tubes begin to wear into an "out of round" state the carbs become richer and richer.  I don't know if you can actually tune around the situation but people sure to try which might explain what the Original Poster in this thread is trying to do.

Apparently Mikuni saw the emulsion tubes as a "consumable item", something that was just going to have to be replaced on a regular basis, but most owners of motorcycles with Mikuni carbs didn't get the message.

[Thief400]

I've got almost 40000km on my bike and thè emulsion tubes are as round as the day they left the factory! 2 things contribute to worn out emulsion tubes, the major factor is jet kit needles and to a lesser degree high levels of ethenal in the fuel.