Mikuni BS26SS - informations/parts?

[Guest]

Some time ago I asked about idle but I went another route after still having more problems in GSX 400 F katana. The problem is: Idle now runs fine and she keeps it, but... I have radiculous gas mileage, it burns more than 7L per 100km(should burn 4,5L/100). It burns more than my car which has 1.6L engine just wtf, sorry for that. I did one more test. I went on trip riding 120 km/h on 6th gear for longer distance then went back to garage not having it working on idle(as soon as I arrived I turned off the engine while still being on road). And... I unscrewed spark plugs... 3 out of 4 cylinders are running very, very rich despite fact that all of 4 carbs are set identical(needle row set, pilot screw, float height).

I am trying to find any parts, but there are none, british shop has none parts even needle valves are gone there. In netherlands they have incomplete set of parts and very expensive. I stopped riding I don't want some valve to just be stuck because of all the gunk being produced by conditions it works in.

So yes, this katana would run fine if she had working carbs. But I don't have another set of 4 in nicer shape. I tried to find any, none are for sale.

One option I have is to ask carburetor rebuild magician(yes, there are people like this in poland) who rebuilds carbys for very old cars/motorcycles and makes every part himself. So far I am out of ideas where to find complete set to rebuild or where to find x4 BS26SS in good shape.

Maybe you have something to help me out there?

Thank you in advice,
Himer

[tom203]

So you want to give up on these CV carbs and opt for a set of VM's..... A bunch of uninterested/inexperienced "mechanics" have a had a go at your carbs - who knows what they did. I'd pull the carbs and check- maybe they got wrong main jets installed or maybe they forgot to change the o-ring under each float needle seat messing up the running fuel height. This is where I'd investigate first with a rich condition.

[hugo151]

Hi , they might be the same carbs as gsx 250, but they only have 2 carbs. Try N R P in manchester , england. They will have jets / slides / diaphrams etc.

[Nessism]

Is the bike stock or modified? Pod air filters and header by chance?

First thing I'd do is fully go through the carbs. Tutorial linked in my signature. Also, adjust the valves and check compression. Check valve timing at the cams. Check the ignition advance to make sure it springs smoothly. Brakes are not dragging. When going through the carbs take an inventory of all the various jet sized and compare that to the factory service manual for your bike. Maybe someone upsized the jets for some reason. Also, get factory Mikuni jets, not cheap aftermarket crap jets.

Good luck

[Himer]

Yes, motorcyle is fully stock. Whole air intake is factory one without any leaks with only one diffrence it now has genuine meiwa filter like it should be. Previously some idiot used vaccum cleaner hepa filter as an air filter in the airbox. Gas mileage was even worse with that "thing" - 12L per 100.

It consumed about 5.5L per 100 max BEFORE I hired 3 diffrent people to solve carbys problems. And I know that last idiot ordered jets blindfolded, he didn't even check what should fit there he just randomly bought jets for them. And I also know... I have this bike for more than a year and before touching carbys it had enrichment problem I could clearly feel on race track that engine is flooded, it was just flooded with gas and it wouldn't rev smoothly on gear instead it jumped and sounded weirs to my ears.

I suspect a mechanical problem in needle jet and whole needles themselves. How can I explain then that cylinder no 3 has very nice spark plug colour and all the rest is just coal - too rich. Before even posting we tinkered with my cousin on it and we checked float first in there. And the float closes right like on the book on all 4 carbs. It is not overfilling and not acting funny. Also carbys react through whole spectum on pilot screws. Problem is only when riding - when needle is moved up. For my eyes and thinking those carbys have either worn out slider springs and soft rubber just works like mad in there because there is tension problem or needle jet with needle is worn out on 3 carbys and there is easy check for that - just measuring them.

I called all magicians and when they heard CV they said no, every one of them so I am left with those carbys alone. I'll try to dismanlte them asap and post some pics here. I will also check those jets.

I have found needle jet, main jet and pilot jet on cmsnl along with the slider springs I'll try to order them in this week. For needles I have a source - buying complete sliders from GN125 - it had same carb, well almost identical in means I can't combine those in 4 like ones I have on this GSX.

[tom203]

When you get those sliders/diaphragms from the gn125, you be able to compare them to what you got in your set- who knows what those 3 hack mechanics have done (and left you with).

"Problem is only when riding - when needle is moved up. For my eyes and thinking those carbys have either worn out slider springs and soft rubber "

hold the vacuum diaphragms up to the light and look for pinholes that would interfere with their rising. Personally, I doubt it's a worn out spring issue.

[Himer]

Suppliers in my country list full sizes of all areas on those slider assemblies so first I'll take one from my carbys measure it if it is correct I am gonna order all 4 with diaphragms attached to them. Probably those are interchangeable. I am only having problem with needle jet in cmsnl. There are two GSX 400Fs in there. One list is from 81, second from 83 and only this part has diffrent number and I am having trouble should I order those from 83 version like mine or those from 81. For the version of 83 there is no pic for me to compare only number on schematic but schematic is really bad.

First I am gonna check if I need even those jets, maybe they are ok in there, just a matter of checking markings.

[steveb922]

Might be a daft question, but are you sure the BS26 is the correct carb? I'm probably wrong, but I seem to recall BS29s on your bike.

While you're going through your carbs, you might find this useful:

http://www.thisoldtractor.com/dr350_manuals/service_bulletin_carburetor_jets_2004-01-30.pdf

[Himer]

Steve,

Manual says what is in there. Even the looks of GN125 carby are the same, same dimensions. Only diffrence is in "SS" on the end. GN125 had BS26, mine has BS26SS x4. From what I was able to dig, suzuki made changes themselves in the factory not even informing Mikuni about that for this model. Whole slider assembly which I will get from one of my carbys will make everything clear. If dimensions are the same as slider from GN125 then I have new route to look for some parts. If not, then I don't know myself what to do with this.

To prove carby model, here is spec from manual for this motorcycle:

carbys.jpg



Another EDIT:

I am saved!

http://www.ebay.pl/itm/81-SUZUKI-GSX400F-GS40X-CARB-REPAIR-KITS-CARBURETOR-4-REPAIR-KITS-20-GS40XCR-/253033993468?hash=item3aea0054fc:g:8DUAAOSwImRYFQH6

Found complete kit in affordable price. I won't close this topic it will probably arrive in a like 2 weeks or so. We''ll continue when I'll get the kit.

[Himer]

Package from japan arrived before weekend. I still miss needle jets x4. I tried to find them on CMSNL but... None are correct... https://www.cmsnl.com/suzuki-gsx400f.../#.WZnyDShJaUl not this one, not this one: https://www.cmsnl.com/suzuki-gsx400f.../#.WZnxpChJaUk no pic, wrong numer 0-8 instead of P-0. Carbys look very bad, so yes. They didn't clean those. Needle jets along with needles on cyl no 1 3 4 are worn, I measured them that is the cause of too rich mixture while on gear constant speed. One carby had too much float level but doesn't change the fact I need some actual parts. I have correct jets and needles plus pilot screws new.

Maybe someone here will be able to find those needle jets I need I am still trying to find them and I made ticked in CMSNL maybe they can help too.