For an 81 xs400. Anyone tried swapping out the worthless original carbs with a set of Honda CB carbs? This is my second xs400 and I would rather spend money on a new setup instead of wasting time on the the original non adjustable junk. This latest bike will run shorty mufflers and UNI pods. There are several companies selling CB360 carb setups featuring Mikuni vm32 carbs. Seems to be an ideal swap but am concerned about the available space needed to mount the new setup.
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carb swap
- Thread starter ksrebel
- Start date
did u try to rejet them?
lcgtr
XS400 Addict
Do a search, it's been done, I'm doing it now. VM32 carbs are too big for a 400.
Awfully aggressive for a second post ever, in response to your first response on the board ever, after asking a question you could have used the search function for...
We're all here to help, man.
The attitude in his posts suggests to me that he doesn't really want help, he wants to bitch. My teenage son shows more respect and humility when asking for help. And that is what it will take to get help...
Dave
Dave
sly409
XS400 Addict
hes too good for this forum, maybe he'll go off and create his own xs400 forum 
I have been doing a search. I did a very extensive search here and elsewhere before I ever posted. There is very, very little real information out there. Usually people offering an opinion on a subject in which they have no knowledge. Only one post concerning a swap with Suzuki carbs was helpful. If you guys would rather spend your time working on junk rather than riding, have at it.
I can't wait until you edumacate us on what works.
Maxim-umm
XS400 Addict
ksrebel, I've looked into this very subject extensively and you're right, there is little info about. There was a post about the Suzuki and I looked into that as well. They COULD work, but you could still have to modify the boots to fit. There was no definite answer that I could find here, or any other forum.
the first response to your question was simply an effort to gather more information. If you would like our help, please leave any attitude at the door. There's no need to bash on the bike or other members. Many of us on this forum have had great luck with these bikes and all the original parts, including the carbs.
Now, you want to run uni pods and shorty's. It's not a matter of original carbs vs cb carbs. If you're going to change the intake and exhaust air flow that much, you'll have to mess with the carbs anyway. Some carbs not as much as others, but in the end, you'll have to put in the time and effort to get it right. Research jetting these carbs and see if you missed anything before. If you did everything the same, then buy the cb carbs and see if you can get them to fit. That's the only SURE way you'll get your answer.
the first response to your question was simply an effort to gather more information. If you would like our help, please leave any attitude at the door. There's no need to bash on the bike or other members. Many of us on this forum have had great luck with these bikes and all the original parts, including the carbs.
Now, you want to run uni pods and shorty's. It's not a matter of original carbs vs cb carbs. If you're going to change the intake and exhaust air flow that much, you'll have to mess with the carbs anyway. Some carbs not as much as others, but in the end, you'll have to put in the time and effort to get it right. Research jetting these carbs and see if you missed anything before. If you did everything the same, then buy the cb carbs and see if you can get them to fit. That's the only SURE way you'll get your answer.
maybe you should just get a different bike all together since our carbs are junk the rest of the bike probaly is also.Besides that working on junk gets us prepared to work on the better carbs
I understand what ksrebel means.. im messing with carbs fo too long to be hapy with em. if i knew it, i would have bought some aftermarket ones much sooner. Second pair of carbs and there is always SOMETHING wrong. Its frustrating ... And real info on aftermarket ones is nowhere. Only unsure way to spend your money for flat slides on mikeXS (in my case i will have to pay an inport taxes as well) which is looking too modern installed on this bike imho.
A guy who lives nearby promissed me to get aftermarket carbs for me and tune them also as he races those bikes (i belive he has SOME experiences). He told me that every time he gets this bike for tune-up (or make it running as it SHOULD be running), he throws ours bs 34s away as its a waste of time if they dont run right after some standard maintenance.
He will not be aviable for 3 months now due to vintage racing so im in it alone again. With no information. With 2 sets of crappy carbs. With bike running badly. With so many hours spended on research, maintenance. With so much money spended. With no bright future.
I decided to go deeper. I've ordered a "color tune" sparg plug (can see whats happening inside a cylinder) and finally answer my carb issue. Im so curious. But sceptic on the fact they wil run well one day. At least not that particular ones i have at home. With "color tune" i can get aftermarket and tune em much easilly, but some info would be just great (where to start + range of jets to get for tune-up)..
A guy who lives nearby promissed me to get aftermarket carbs for me and tune them also as he races those bikes (i belive he has SOME experiences). He told me that every time he gets this bike for tune-up (or make it running as it SHOULD be running), he throws ours bs 34s away as its a waste of time if they dont run right after some standard maintenance.
He will not be aviable for 3 months now due to vintage racing so im in it alone again. With no information. With 2 sets of crappy carbs. With bike running badly. With so many hours spended on research, maintenance. With so much money spended. With no bright future.
I decided to go deeper. I've ordered a "color tune" sparg plug (can see whats happening inside a cylinder) and finally answer my carb issue. Im so curious. But sceptic on the fact they wil run well one day. At least not that particular ones i have at home. With "color tune" i can get aftermarket and tune em much easilly, but some info would be just great (where to start + range of jets to get for tune-up)..
5 year old post.
But I'll give you this- stock carbs work fine. Mine ran perfectly fine with no airbox and open exhaust. Needed minimal adjustment. They will work even better on a stock airbox and exhaust though. I don't know why people have issues with them. You'll get more headaches with aftermarket carbs. Stay away from the MikesXS, they are just Oko style Chinese PWK knockoffs and have tons of problems. Another issue with most aftermarket carbs is that they were designed for 2 strokes, and don't play well with a 4 stroke. You can get them to work no problem, just have to size them properly. I see tons of people buy them too big and then they wonder why they can't jet them right. If you have 'a guy' that does carbs, then by all means try a set of VM28's or something of that nature. You'll enjoy the throttle response once they are set up well.
But I'll give you this- stock carbs work fine. Mine ran perfectly fine with no airbox and open exhaust. Needed minimal adjustment. They will work even better on a stock airbox and exhaust though. I don't know why people have issues with them. You'll get more headaches with aftermarket carbs. Stay away from the MikesXS, they are just Oko style Chinese PWK knockoffs and have tons of problems. Another issue with most aftermarket carbs is that they were designed for 2 strokes, and don't play well with a 4 stroke. You can get them to work no problem, just have to size them properly. I see tons of people buy them too big and then they wonder why they can't jet them right. If you have 'a guy' that does carbs, then by all means try a set of VM28's or something of that nature. You'll enjoy the throttle response once they are set up well.
Most have issues with stock carbs because the bikes they are using them on are not stock. I have never had any issue with a stock setup bike with stock carbs. I would say the the xs360 carbs is the only good alternative for these bikes with stock setups. You must use stock filters and stock H-pipe hooked to the carbs. Along with factory exhaust tuning is easy as can be. My last 400 i picked up ( my fifth one) is all stock set to factory specs and runs perfect. All I needed to do was sync the carbs with a set of mercury stix and done.
My bike is complete stock. Why im having issues is just mystery or im completely out of luck on getting some working ones.
And yeah, 5 year old post, but why should i create new and fragment all the information around? If i create new one bunch of people will write "search the forum". I have searched
And yeah, 5 year old post, but why should i create new and fragment all the information around? If i create new one bunch of people will write "search the forum". I have searched
I will... What do you want to see?
But first of all i will describe that bike by words.
-Cylinders rebored to some standard oversized pistons i had from other engine (very nice compression now)
-primary chain changed (split case - checked everything)
-valves lapped, added new seals (and of coure clearance was set)
-new contact breaker points
-new air filter
-new carb boots
*****************************************
Carbs:
Cleaned in ultrasonic wash twice. Sprayed with carb cleaner milion times, flushed with compressed air (I have quite a powerful compressor). Flushed again with technical petrol (pressure from car's fuel pump, I could feel the petrol flowing through every hole). So it might be superclear.
Got an aftermarket rebuild set with this setup:
pilot jet: 42.5
main jet :142.5
needle 5Z1 in 3rd position (doesn't matter for low rpm anyway)
floats: 26mm
additional rebuild parts:
-new butterfly seals
-new diaphragms
-sealed choke plunger
*******************************************
I have set the bike "garage style".Static ignition timing, bench-synced cabs and home made tool to sync em correctly. I'm determining my mixture richness/leanness from the colour of the spark plugs. Now i'm waiting for strobe light timing tool, mercury-based carb synch tool and that transparent spark plug... We'll see, but i have no expectation. Im pretty sure the bike is set correctly or very close. After longer ride my spark plugs were really nice. But starting procedure is a nightmare. Once started, It behaves as no problem was ever there.
But first of all i will describe that bike by words.
-Cylinders rebored to some standard oversized pistons i had from other engine (very nice compression now)
-primary chain changed (split case - checked everything)
-valves lapped, added new seals (and of coure clearance was set)
-new contact breaker points
-new air filter
-new carb boots
*****************************************
Carbs:
Cleaned in ultrasonic wash twice. Sprayed with carb cleaner milion times, flushed with compressed air (I have quite a powerful compressor). Flushed again with technical petrol (pressure from car's fuel pump, I could feel the petrol flowing through every hole). So it might be superclear.
Got an aftermarket rebuild set with this setup:
pilot jet: 42.5
main jet :142.5
needle 5Z1 in 3rd position (doesn't matter for low rpm anyway)
floats: 26mm
additional rebuild parts:
-new butterfly seals
-new diaphragms
-sealed choke plunger
*******************************************
I have set the bike "garage style".Static ignition timing, bench-synced cabs and home made tool to sync em correctly. I'm determining my mixture richness/leanness from the colour of the spark plugs. Now i'm waiting for strobe light timing tool, mercury-based carb synch tool and that transparent spark plug... We'll see, but i have no expectation. Im pretty sure the bike is set correctly or very close. After longer ride my spark plugs were really nice. But starting procedure is a nightmare. Once started, It behaves as no problem was ever there.
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