carbs off a 900

[goldcoastguy001]

Hi guys this is my first thread so i thought i'd start with something i played with today......I have had some mixture probs of late and to make it brief........everything in carbs is stock.....all cleaned and triple cleaned.....sync'd......has stock A/Box and 4-2 pipes.
Problems; stumbling off the line from idle, rich mix and fouling plugs when hot, WOT test rich mix, mid range flutter in revs about 5000rpm.

Cure; had a set of mikuni's of a 900 sitting under the bench.
checked the jets all are the same except for the mains they were 102.5 instead of the 110's i had in the 1100 carbs, so i swapped them over. Ran like s**t. swapped the springs over in the slides and checked the length were all the same, test rode. awesome of the line smoked the tyre!! ran like crap after 2500rpm. pulled emulsion tubes and needles swapped for 1100 ones, ran like crap still, swapped them back to 900 ones.....had a smoke and figured well it still runs really rich?? so i tried the 102.5 mains from the 900. so to re cap we have a set of stock 900 mikuni's running xs1100 springs ontop of the slides. took it for a run s**t myself when the thing smoked the tyre in 2nd gear up to bout 3500rpm and then launched itself like a rocket all the way to redline! checked the plugs still slightly black.....I removed the baffles in the pipes and fitted my pod filters on the carbs now she runs with the best tanned plugs i have ever seen in any bike???


any ideas why this all worked out so well??
Do the 900 carbs flow a faster mix?
will post some pics of my bike, like most i wanna show it off being new and all.....lol

I'll go more into explaination if someone is interested.

[tjfisher30]

900 ?

OK first nice post second what 900 what model? year ? you got to give us something to work with ..

[81xsproject]

if it is a kz, the carb spacing is different and so is the size of the intake. With that said, there is a coversion kit on ebay right now to use smooth bores on the 11. I can see how it compensates for the intake diameter, but I don't know if it does anything about the carb spacing. The kz's have intakes that come straight off the head and a big space between the inner two center carbs, while the XS has intake boots that curve in so that the spacing between each carb is the same. I don't know why anyone would want to go to smooth bores. Even the almighty carb guru, Wired George, from the KZRider.com forum recommends coverting the old smoothbores to, you guessed it, the BS-34 for better performance and ridability.

[81xsproject]

Well, after reading your WHOLE post I noticed that you had them installed so they must not be off a kz. Sorry, jumped the gun a little bit.

[goldcoastguy001]

Carbs are off a 1988 XJ900 I had bought them awhile back for another project that never got off the ground, they were rebuilt by a carb shop and had been sitting wrapped in plastic under the bench. Well just finished sync 'ing them this morning and took it for a ride I can't fault it, it rides really responsive and seems to rev much faster to redline it also seems heaps happier to do so...really have to hang on to the bars now...


I have tried to see what numbers are on the carbs but i cannot find any neither inside or outside the carbs so although i know they are Mikunis i dont know what model carb-They look identical to the xs1100 carbs but internals look slightly newer technology

[50gary]

goldcoastguy, isn't the XJ900 the bike you and the Brits call the 900 diversion? Have you had a chance to check the fuel economy?
Cheers, 50gary

[goldcoastguy001]

50gary,

Yes thats correct a friend had a XJ900 Diversion which is what prompted the project that the carbs were for...I havent noticed any great differences in the fuel economy although it runs awesome I have just been running road town in short trips till Im comfortable that all is working ok, will be doing a trip bout' 200km tomorrow so i'll be able to tell you for sure, but at this stage around town its hard to see any change in economy. I have noticed that it seems to like the 6000premium fuel better than the 4000premium, but it dislikes the 8000rated premium fuel. Not sure what those work out to be for your guys fuel ratings.

[goldcoastguy001]

well got back from the test milage ride and i thought it went well.....the old xs1100 carbs gave me bout' 8.1kms/litre (worked out on getting 202.5kms on 25 litres of fuel before in ran dry), the xj900 carbs are giving me more grunt/response and 10.6kms/litre (worked out on getting 265kms on 25 litres before it ran dry) both tests were done on the same highway, not sure what that is in miles/gallon but if someone has a conversion for me that'd be great...

cheers!

[Just In Case]

Originally posted by goldcoastguy001
if someone has a conversion for me that'd be great...

cheers!

ok, 8.1km/l is 18 mpg (US) or 22 mpg (rest of the world )

10.6 km/l is 24 mpg (US) or 29 mpg (rest of the world )

[goldcoastguy001]

Hey thanks a heap for that, my conversion knowledge doesnt stretch any further than cm to inches....lol.....next question would be is that milage respectable?...or how does the tests on the carbs compare to other xs1100's

obviously the 900 carbs are better overall but sounds like the old xs1100 carbs werent really that good on economy for my bike anyway... or would they be comparable to other xs1100's in that case it would mean the XJ900 carbs are better to use anyway..?

[mro]

compare to other xs1100's

My stock 80G gets low 30's around town and high 30's highway.

Just checked.
About 50 miles on Freeway 70mph.
About 30 miles going 55/60 mph
Another 44 miles 35 to 45 mph
used 3.4 gallons >US

36.5 mpg


mro

[81xsproject]

goldcoast, from the numbers, it doesn't sound like either set of carbs are tuned as well as they could have been. That mileage is pretty low, unless you ride like I do and look for every oppotunity to give THE JUICE!!

[SG-Olli]

(rest of the world )

I dare to object!

For some part of the rest of the world it is:
8.1kms/litre = 12.35 l/100km
10.6kms/litre = 9.43 l/100km
Still it sounds like you you know where the throttle is located.

[81xsproject]

I have to be having some SERIOUS fun to get my milage down to the low 20's and I know mine could be better tuned.

[goldcoastguy001]

lol....I have to admit we have some nice roads here and i definitely push the limit on most of them......I also ride alot thru the hills and ranges.....around town i think the milage seems to be much better....probably cause i'm usually around the 3/4 throttle in the outback areas.......whoo hoo she goes well though....lol..the plugs are the best color tan i've every seen so they cant be that far out tune can they?.......