vf750rdr Posted May 26, 2009 Share Posted May 26, 2009 Hello all! My name is Tom from Buffalo, NY....I am the proud owner of a 1980 XS 400 Special, with just 4500 miles on the clock. I found theis forum on a Google search, and have so far found it to be quite interesting and informative...I'm looking forward to hanging out here and learning much about this bike form all of you! My first dilemma: the previous owner hacked up the carbs pretty badly. It appears that he tried to do some sort of work to the floats, and broke the support that holds it. So...I now have a useless carb. My question is: can I replace the carbs with units from another model, or is this unit unique to this model? Aside from needing a set of tires, it looks to me like it's a pretty solid machine.... Thanks in advance for any advice you can give me, and I'm looking forward to a long tenure on this forum!! Tom Link to comment Share on other sites More sharing options...
JimR Posted May 26, 2009 Share Posted May 26, 2009 Hello all! My name is Tom from Buffalo, NY....I am the proud owner of a 1980 XS 400 Special, with just 4500 miles on the clock. I found theis forum on a Google search, and have so far found it to be quite interesting and informative...I'm looking forward to hanging out here and learning much about this bike form all of you! My first dilemma: the previous owner hacked up the carbs pretty badly. It appears that he tried to do some sort of work to the floats, and broke the support that holds it. So...I now have a useless carb. My question is: can I replace the carbs with units from another model, or is this unit unique to this model? Aside from needing a set of tires, it looks to me like it's a pretty solid machine.... Thanks in advance for any advice you can give me, and I'm looking forward to a long tenure on this forum!! Tom Hi Tom, I would try to source so more XS400 carbs, as XS400's are sensitive to their carbs you may spend more in time, effort and money getting something else to work on the bike ... I guess not impossible but a bit of a job ! Regards Jim to the forum Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 26, 2009 Moderator Share Posted May 26, 2009 Tom from Buffalo you can get new carbs if your so inclined (not original spec) a company sells the modern mikuni on ebay for xs650's but I'm sure they will jet them for a 400. drewps Link to comment Share on other sites More sharing options...
JimR Posted May 26, 2009 Share Posted May 26, 2009 Tom from Buffalo you can get new carbs if your so inclined (not original spec) a company sells the modern mikuni on ebay for xs650's but I'm sure they will jet them for a 400. drewps Hi Drewps, how are they going to fit into the inlet manifolds/airbox without a struggle ? and then the problems of the larger venturi, so fitted 400 size jets into 650 carbs may not work to well but perhaps I only sold XS bikes & you restore them you will have more knowledge on modern replacements than me ! Regards Jim Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 26, 2009 Moderator Share Posted May 26, 2009 Hi Drewps, how are they going to fit into the inlet manifolds/airbox without a struggle ? and then the problems of the larger venturi, so fitted 400 size jets into 650 carbs may not work to well but perhaps I only sold XS bikes & you restore them you will have more knowledge on modern replacements than me ! Regards Jim the 34 mm ones I am assured, will fit not the 38mm!! i know some of our german xs owners have used a delorto carb! Link to comment Share on other sites More sharing options...
JimR Posted May 26, 2009 Share Posted May 26, 2009 the 34 mm ones I am assured, will fit not the 38mm!! Hi Drewps, I would guess there are very few people left with working XS2 carbs (34mm 650). but you need to take into account that the XS400 manifolds were/are staight where as the XS2/XS650 are slightly offset and may not produce a seal within XS400 the manifolds, this would hold out as the older carbs (34mm) will 'sort of' fit and as the offset is increased on the larger venturi there is no chance ! If they do fit & are jetted to suit what happens with the progression holes/ports in the carbs ? if they don't match the motor/o.e spec there is a chance the bike will drop 'into holes' when the incorrect holes/ports take over the carburation but as you have improvised I would guess you know how to over come that problem. Regards Jim Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 27, 2009 Moderator Share Posted May 27, 2009 Hi Drewps, I would guess there are very few people left with working XS2 carbs (34mm 650). but you need to take into account that the XS400 manifolds were/are staight where as the XS2/XS650 are slightly offset and may not produce a seal within XS400 the manifolds, this would hold out as the older carbs (34mm) will 'sort of' fit and as the offset is increased on the larger venturi there is no chance ! If they do fit & are jetted to suit what happens with the progression holes/ports in the carbs ? if they don't match the motor/o.e spec there is a chance the bike will drop 'into holes' when the incorrect holes/ports take over the carburation but as you have improvised I would guess you know how to over come that problem. Regards Jim i'm fitting new dohc carbs to my sohc engine and had to make new brackets which isn't hard. I have the engine running but now need to dial in the carb settings which I'll do on a dyno with a fuelling curve print out!! I go in the choppor underground forum and these guys build their own manifolds for single carb installations on xs400's and 650's , crazy but they work!! Link to comment Share on other sites More sharing options...
JimR Posted May 27, 2009 Share Posted May 27, 2009 i'm fitting new dohc carbs to my sohc engine and had to make new brackets which isn't hard. I have the engine running but now need to dial in the carb settings which I'll do on a dyno with a fuelling curve print out!! I go in the choppor underground forum and these guys build their own manifolds for single carb installations on xs400's and 650's , crazy but they work!! Hi Drewps, dohc & sohc XS400's do have more in common than old XS650's. the single carb/manifolds were looked at it the 70/80's and disregarded as it (at that time) was difficult to get an SU carb to to run on a 'modern' engine but as the 'modern' engine is now old I would guess that this is now possible, but tbh I would prefer the orginal twin carb set up. Regards Jim Link to comment Share on other sites More sharing options...
Vincent Moy Posted May 27, 2009 Share Posted May 27, 2009 Hello all! My name is Tom from Buffalo, NY....I am the proud owner of a 1980 XS 400 Special, with just 4500 miles on the clock. I found theis forum on a Google search, and have so far found it to be quite interesting and informative...I'm looking forward to hanging out here and learning much about this bike form all of you! My first dilemma: the previous owner hacked up the carbs pretty badly. It appears that he tried to do some sort of work to the floats, and broke the support that holds it. So...I now have a useless carb. My question is: can I replace the carbs with units from another model, or is this unit unique to this model? Aside from needing a set of tires, it looks to me like it's a pretty solid machine.... Thanks in advance for any advice you can give me, and I'm looking forward to a long tenure on this forum!! Tom Hey Tom, Have you tried looking at carbs on ebay? http://cgi.ebay.com/ebaymotors/82-XS400-SE...p4506.m20.l1116 Vincent Link to comment Share on other sites More sharing options...
vf750rdr Posted May 30, 2009 Author Share Posted May 30, 2009 Yep, sure did! I bought a set for 50.00....should be here any day! I can't wait to get this baby on the road!! Hey Tom, Have you tried looking at carbs on ebay? http://cgi.ebay.com/ebaymotors/82-XS400-SE...p4506.m20.l1116 Vincent Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 30, 2009 Moderator Share Posted May 30, 2009 if you go after market carbs, give this vendor a call to see if they fit your bike Link to comment Share on other sites More sharing options...
JimR Posted May 30, 2009 Share Posted May 30, 2009 if you go after market carbs, give this vendor a call to see if they fit your bike Hi Drewps, they may fit but as the photo shows there is the XS650 intake 'splay' which is some what different to the 400/360/250 if you have fitted this can you give me the info so I can put the info into the 'database' Regards Jim Link to comment Share on other sites More sharing options...
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