complicated carb problem

[El Gringo]

Having just replaced a set of emulsion tubes on a stock bike with standard needles and approaching 46,000 miles ~ 74,000 Kms I can only imagine its a combination of fuel and emulsion tube material.

New tubes have completely solved the massive richness issues I was having. As for tuning around the problem, you can to a point by leaning off the needle but eventually the tubes will need replacing.

On 750 and 1100 oil cooled motors Emulsion tubes are, as Greg says, consumables, made infinitely worse by harder needles be they Dynojet or otherwise.

I replaced 6 or 7 sets in a 2 year period at the Dyno place I worked at, mainly on Suzukis

Cheers

Chris

[Squishy]

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.

What makes you think that?
My 400 has 100 stock jets and runs great. (BST33SS)

[greg737]

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.

I agree there's probably a very wide range of possible lifespans for Mikuni emulsion tubes, probably influenced most heavily by various things people do to their carbs (performance mods and clumsy maintenance) that have the unintended effect of increasing the rate at which the emulsion tubes get worn.

I would bet that the emulsion tubes last the longest in carbs that are never modified.

When I bought my B400 last year and disassembled the carbs I found that they'd obviously been messed with quite a bit over the years.  First, the springs in each carb had been cut shorter than their original length by about 4 coils of the spring winding.  One of these shortened springs was installed upside down (with the cut end downward on the needle while all the others had the un-cut tight-coiled end on the needle).  Also one of the needles had a washer used in place of the original spacer.  I don't know if the needles were OEM or some sort of aftermarket brand, but they seemed unstable and waggled in their seats in the slides.  This would certainly allow them to rub against the emulsion tubes.

Obviously one of the prior owners of my Bandit was trying to get better performance out of it and we all know that the default assumption of the hobby level tuner is that "richer is always better".  This sort of thing is probably what causes Bandit 400s to eventually become completely un-tuneable and eventually end up stored away in a shed or pushed into a dark corner at the back of a garage.  Because modifications to richen up the engine when the emulsion tubes are fresh will end up making the bike unrideable and untunable when the emulsion tubes start to wear (which causes it to richen up even further).

[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.

What makes you think that?
My 400 has 100 stock jets and runs great. (BST33SS)

Hundreds of hour dyno tuning yes they "run" with 100 but they run better , run cooler, and make more power with 110. Oh and the Gsxr 400 where this engine comes from has guess what 110 mains stock Mmmmmmm. The only reason they came with 100's was to pass emission tests

[Thief400]

Having just replaced a set of emulsion tubes on a stock bike with standard needles and approaching 46,000 miles ~ 74,000 Kms I can only imagine its a combination of fuel and emulsion tube material.

New tubes have completely solved the massive richness issues I was having. As for tuning around the problem, you can to a point by leaning off the needle but eventually the tubes will need replacing.

On 750 and 1100 oil cooled motors Emulsion tubes are, as Greg says, consumables, made infinitely worse by harder needles be they Dynojet or otherwise.

I replaced 6 or 7 sets in a 2 year period at the Dyno place I worked at, mainly on Suzukis

Cheers

Chris

Where did you find a set of emulsion tubes for a bandit. Suzuki has been out of stock for years over here in Canada

[Squishy]

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.

What makes you think that?
My 400 has 100 stock jets and runs great. (BST33SS)

Hundreds of hour dyno tuning yes they "run" with 100 but they run better , run cooler, and make more power with 110. Oh and the Gsxr 400 where this engine comes from has guess what 110 mains stock Mmmmmmm. The only reason they came with 100's was to pass emission tests

Not saying I don't believe you :).  Just curious. My 400 does about 185km/h and pulls great. Only thing I've noticed is that after 12000rpm it drops in torque a bit.
Do you also have experience with the BST33 carbs? It might be different jetting wise compared to usa/can BST32.

edit:
This page says gsx-r 400 has 100 mains http://www.graniterock.co.uk/400manuals/GSX-R400_GK76A_Spec_sheet.pdf

Thanks

[El Gringo]

Having just replaced a set of emulsion tubes on a stock bike with standard needles and approaching 46,000 miles ~ 74,000 Kms I can only imagine its a combination of fuel and emulsion tube material.

New tubes have completely solved the massive richness issues I was having. As for tuning around the problem, you can to a point by leaning off the needle but eventually the tubes will need replacing.

On 750 and 1100 oil cooled motors Emulsion tubes are, as Greg says, consumables, made infinitely worse by harder needles be they Dynojet or otherwise.

I replaced 6 or 7 sets in a 2 year period at the Dyno place I worked at, mainly on Suzukis

Cheers

Chris

Where did you find a set of emulsion tubes for a bandit. Suzuki has been out of stock for years over here in Canada

Ordered them through Robinsons Suzuki in the UK, Mine is a Canadian import from what I can tell, so I ordered on the US part no. although I think from what they said I had the last 4 in Europe, the UK spec ones were on 5-6 week back order from Suzuki Japan.

They are still available but seemingly becoming unobtainium

[vintagemilano]

Partzilla says they have needle jets available. Could be an experiment for someone.

[gallant_pilot]

wow,i see this post is going into new things.
i never knew the emulsion tubes can cause problems,however after checking them recently.i still see them in very good condition,all the holes are perfect and its rounded shape completely ;
anyways!

i had to strip the top end myself ,and i found 6 valves are leaking.specially on # 3 which wasnt getting hot,2 intake and on ex were leaking badly.

i lapped them all and the seal properly now,also i got an aluminum gasket cut and also did some skimming on the head at home.

my bike performs nicely with 95 main jets and fuel economy is better with them, i also cleaned that little hole from the main passage to the pilot jets which i never knew they do exist .

i am gonna reassemble the head before weekend and test it.

one thing i noticed that there was petrol in my oil after flashing it.i can easily smell the petrol in it.

so guys, u still think its the emulsion tubes which need to be replaced?



 

[andrewsw]

petrol in the oil is often a sign of a stuck float needle. The needle will stick open and gas will just fill up the cylinder, leak around the ring and fill up the crankcase.

A

[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.

What makes you think that?
My 400 has 100 stock jets and runs great. (BST33SS)

Hundreds of hour dyno tuning yes they "run" with 100 but they run better , run cooler, and make more power with 110. Oh and the Gsxr 400 where this engine comes from has guess what 110 mains stock Mmmmmmm. The only reason they came with 100's was to pass emission tests

Not saying I don't believe you :).  Just curious. My 400 does about 185km/h and pulls great. Only thing I've noticed is that after 12000rpm it drops in torque a bit.
Do you also have experience with the BST33 carbs? It might be different jetting wise compared to usa/can BST32.

edit:
This page says gsx-r 400 has 100 mains http://www.graniterock.co.uk/400manuals/GSX-R400_GK76A_Spec_sheet.pdf

Thanks

The 5 gray market bikes I worked on all had 110 mains stock! If your only getting 185kph then your missing a lot of top end power, mine did 225 before I started to play with the engine. This was with the 110 mains. And yes I've a lot of experience with the 33mm carbs as canada has alway gotten unrestricted bikes!   

[Squishy]

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.

What makes you think that?
My 400 has 100 stock jets and runs great. (BST33SS)

Hundreds of hour dyno tuning yes they "run" with 100 but they run better , run cooler, and make more power with 110. Oh and the Gsxr 400 where this engine comes from has guess what 110 mains stock Mmmmmmm. The only reason they came with 100's was to pass emission tests

Not saying I don't believe you :).  Just curious. My 400 does about 185km/h and pulls great. Only thing I've noticed is that after 12000rpm it drops in torque a bit.
Do you also have experience with the BST33 carbs? It might be different jetting wise compared to usa/can BST32.

edit:
This page says gsx-r 400 has 100 mains http://www.graniterock.co.uk/400manuals/GSX-R400_GK76A_Spec_sheet.pdf

Thanks

The 5 gray market bikes I worked on all had 110 mains stock! If your only getting 185kph then your missing a lot of top end power, mine did 225 before I started to play with the engine. This was with the 110 mains. And yes I've a lot of experience with the 33mm carbs as canada has alway gotten unrestricted bikes!

225km/h? That's the gsxr400?

No way the gsf400 can do 225... many sv650 can't even go 225.
Maybe i'll get myself some 110 mains and see what happens....110 with stock airbox...yes?

[Thief400]

Umm yes a bandit can do 225 and the Sv's round here are good for 240ish. By the at I've owned my bandit since new! By the way your riding the wrong bike if you want good gas mileage.

[Squishy]

Umm yes a bandit can do 225 and the Sv's round here are good for 240ish. By the at I've owned my bandit since new! By the way your riding the wrong bike if you want good gas mileage.

Final post before we hijacked his topic too much 
At the moment I'm doing 20KM on 1 liter..
Just to be sure #110 mikuni size right? (because I know Dynojet/factory pro sizes are different). And stock airbox/filter?
Thanks.

[Thief400]

Buddy your beating a dead horse if your trying for good mileage. If you want mileage get a passport 70. The best you will get on a "properly" running 400 is mid 30 mpg. Period! This engine puts out more specific HP than the Gsxr1100 of the same vintage. Don't be so "F"ing  lazy and search out the hundreds of posts on here about jetting and mileage!