problems with carbs, xs400 1978

[DrHans]

seen pair of carbs from xs650 (they are 38mm mikuni) would it be good idea to put them instead of 34mm ?
would I need to change jets in carbs to adapt them to fit xs400 ?
will it have bad effects on engine ?
will it give reasonable increase in power ?

 

[xschris]

They are not spaced the same as the 400 carbs. If you did get them to fit it would be too much carb for the 400 as they are metered for a larger also different rpm'd engine

 

[DrHans]

They are not spaced the same as the 400 carbs. If you did get them to fit it would be too much carb for the 400 as they are metered for a larger also different rpm'd engine

do you know any replacement carbs I can use ?
Koso 34mm flat side ? are they any good ?

 

[xschris]

I have never used them Any sohc xs400 carbs will work or xs360's will bolt on.

 

[DrHans]

my carbs you saying from xs360, but to adapt them I need to put main 137 and 42.5 pilot jets - someone suggested.

will it work ?
and if it will will these fit in the jet slots in bowl (I mean size of thread and diameter of jets itself ?

cant measure carbs jet hole right now myself

theres no 137 only 137.5
http://www.ebay.co.uk/itm/NEW-PATTE...pt=UK_Motorcycle_Parts_13&hash=item43bbc95d48
http://www.ebay.co.uk/itm/NEW-PATTE...pt=UK_Motorcycle_Parts_13&hash=item43bbc97671

sorry for long post

 

[xschris]

If your carbs are the bs34's used on the xs360's then use the stock size pilot jet which is 17.5 and main jet witch is 135 if your bike is stock. I have a set on my 80 xs400 with a free flow 2-1 exhaust and k&n pods. I put 140 mains in with the idle mix screws set at 2 turns out and it runs great. Not sure if I even need the 140 main but I did it just to make sure. Those jets wont work on these type of carbs. The ones you want are the ones used in the 70-79 bs38 xs650 carbs. Main jet http://www.mikesxs.net/product/48-0216.html I don't see any pilot jets that will work at mikes but the xs360 carbs use a non-bleed stile jet ( see the pic) The 76-77 xs750 used the same pilot jets also http://www.ebay.com/itm/77-Yamaha-X...Parts_Accessories&hash=item336d4b3893&vxp=mtr

 

[DrHans]

If your carbs are the bs34's used on the xs360's then use the stock size pilot jet which is 17.5 and main jet witch is 135 if your bike is stock. I have a set on my 80 xs400 with a free flow 2-1 exhaust and k&n pods. I put 140 mains in with the idle mix screws set at 2 turns out and it runs great. Not sure if I even need the 140 main but I did it just to make sure. Those jets wont work on these type of carbs. The ones you want are the ones used in the 70-79 bs38 xs650 carbs. Main jet http://www.mikesxs.net/product/48-0216.html I don't see any pilot jets that will work at mikes but the xs360 carbs use a non-bleed stile jet ( see the pic) The 76-77 xs750 used the same pilot jets also http://www.ebay.com/itm/77-Yamaha-X...Parts_Accessories&hash=item336d4b3893&vxp=mtr

I think my carbs are Bs32, there is a picture in my first message. Im confused now, which ones I have ? and are there jets to adapt it to 400cc, being mentioned 137 main and 42.5 will not work ?

 

[xschris]

I think there is a guy on here that has a set of 32's on a 400 but not sure what jets he is using. The 42.5 will not work in these type of carbs 17.5 or 20 is what they used. The pilot circuits in these styles are much richer than what the stock 400 carbs used.

 

[xschris]

After some looking the members name in pork chop. He has a xs250 with 400 jugs in it. I thought the 32's where spaced different than the 34's for the smaller xs250 head

 

[DrHans]

will any 34mm carbs fit ? (I mean, fit In matter of jeting, compatibility with engine of xs400) ?

for example: KAWASAKI CVK 34MM CARBS, Suzuki GSX1100 ex et katana 34mm carbs, Gsxr 1100 Carbs
they are mikuni

physical connection to engine head can be adapted.

 

[xschris]

Every carb with work differently because they are setup for the bike they are intended. If you fit a non-xs400 set on your bike you with most likely have jetting issues. So if you are willing to spend the time messing with setups then go for it

 

[DrHans]

bought 4 carbs for cheap (keihin cvk 34mm) to adapt to xs400.
they should fit manifolds, will change spacing if needed

anyone used these carbs ?
what are jets (pilot, main) sizes for this carbs to fit xs400 (1 carb - 1 cylinder) ?
anything else should be adapted to fit xs400 ??

 

[DrHans]

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no one used or knows anything about Keihin carbs?

 

[Scorpio1963]

Nope others have sought info here about them and other brands but few people have info about them.The members who know have since went into hibernation or they tried walking a tight wire across the grand canyon and didnt make it.

 

[xschris]

I have never used them. You will be the first Making non-xs400 carbs work could be a challenge. Stock 400 carbs are getting hard to find for cheap.

 

[willem]

maybe the carbs are so dangerous to put on no-one lives to tell the tale..

be careful man I expect explosions, or a 1000 more horsepowers or something

good luck either way!

 

[DrHans]

just cleaned them, they seems to be in a good shape. dont know what condition are inner tunnels, lets hope in good and no blockage. will try to find right jet sizes soon.

 

[DrHans]

made it work yearstuday, my xs400 now running Keihin CVK 34mm carbs. manufactured correct spacing braket and elongated throttle control lever, still need to make throttle cable holder.

 

[xschris]

You should post some pics and a video when you get it running.

 

[DrHans]

it is running, will post pics later.
also made chocke lever (out of thick wire) and blocked unnescessary holes in carbs