Mikuni BS36 CV carbs for XS1100

[pgnz]

go 45 pilot jet and/or bump the slide needles up one notch(half a mm)

[makzy]

I,v just fitted a set of bs36 carbs off an fj 1200, carbs came with 104 mains 42 pilots, runs very good but has a flat spot just above idle, by ear and color tune idle doesn,t come good till the mixture screws are about 4 turns out, replaced mains with 110 and pilots 42.5 still doesn;t run any better at idle, screws still 4 turns out at least before idle settles down, float levels set at 5mm, flat spot goes away with a very small amount of choke, any ideas on where to go now would be appreciated thanks.

[AussiXS11G]

the latest on the BS36 carbs on my machine.....
14.5km/litre for the whole 1245km trip Brisbane to Bellingen and back -
see more about that here
http://xs1100.com.au/forum/index.php?topic=1703.msg10680#new
16.0km/litre for the transport stage between home and Casino on Friday
12.71km/litre for the Gwyder Hwy between Grafton and Glen Innes (yes - I was fairly up it)

yep - I am happy

Main Jets 160
Pilot 45
Pilot Air Jet 135
Needle in centre

[petejw1966]

great stuff bryan,
so what settings  did u end up with
float heights/jets etc....

[AussiXS11G]

Geez Errol.....I don't think a graph is going to happen.
as you say though, any excuse for a fang....
Having ridden the machine now, I can't believe that I thought it was going well on the ride to Bourke and back in May.

[Christian Raith]

XSellent work Bryan, looks like I may have to do the same when I am back on the road

[Eveready1100]

Gee, Bryan. I guess you'll just have to go out and ride it at a higher average speed to find out then, eh?? Any excuse for a fang, mate.
How about a series of runs done at various speeds so you could do up a graph to display the various results. Of course all testing would be done in a safe and controlled environment like Morgan park (fun!) or Willowbank (handy but a bit boring)

I am really impressed by your current figures though. You've got it really dialled in now.

[AussiXS11G]

very happy indeed.....
the best I got out of the BS34's was abt 250ish
I wonder how it will do at an average higher speed ....if you know what I mean

[Jonesy]

gotta be happy with that, pert near the same as bog stock out of the factory with the added advantage of about 20% + more horses

[AussiXS11G]

OK - first tank of fuel since re-jetting......
around town and highway (down to the Gold Coast n back -110km/h runs)
305km from full to reserve!!!!
 

[steptoe]

it,s amost always the simple things, great news,

[AussiXS11G]

Well now........I've been a bit quiet on here for the last week and a bit.....I came home from dynoing my machine feeling pretty frelling smug.....107hp n all.....
One of the breathers from the float bowls into the airbox was broken (at the airbox) so I rang around and asked what blokes did with them when pod filters are used in lieu of the airbox... "just run them up under the seat and put a small filter on them so nothing gets in" was the general advice.
So I modded the airbox thus and re-assembled the machine ready for last weekends ride.



Suffice it to say that the machine started, idled and ran well up to abt 5000 revs then misfired v badly.
After considering that it was spark and unrelated to the breathers, testing coils, checking all connections, swapping out the TCI unit, the regulator etc, etc a colleague suggested that I return the machine to the state it was after dyno tuning.
So from my "parts bike" I took the airbox, removed the crankcase breather circuit and fitted same, took the bike around the block and hey presto - problem solved.



To say that I am amazed is an understatement - my amazement is bordering on stupefacation......
The machine was simply drowning in fuel - the air/fuel mix so rich that it would not burn - completely sooting the plugs.
I suspect that if the machine had been tuned with the breathers not into the airbox all would have been well.
I am disappointed I didn't get to take the XS away last weekend but the KTM was AWSOME....

BTW -  KIwi....nice write-up about the Kwaka carbs - I ran 140 mains in my BS34 XS11 carbs to great effect (with the state of tune of my lump)

[pgnz]

howzat....

mines got the keihin 36mm CV carbs off a ZRX1200, the barrels and slides are sleek and streamlined inside, they were jetted so lean with #95 main jets as standard,  shows how stifled some stock ZRX1200's are.  For the 8-valve aircooled XS11(1196cc) and with a ported cylinder head 4-1 k&n filter dynacoils etc... I re-jetted the 36mm keihin carbs to up around #140 size( that's a lot of sizes) and she revs to redline in a blink with a ton of torque everywhere and the fuel delivery is faultless and delicously smooth!  A good set of carbs changes the whole ride and feel of the engine.  With chaindrive and light wheels/discs so weighs quite a lot less than normal means good milage(for a thirsty XS11) at about 14 - 15 kms per litre average unless you're thrashing it constant, and if trying hard will get up to 18kms per litre on a 100kph cruise. 

I found with the 78' XS11 34mm (137.5 main jet) carbs with hot-rod engine, they won't perform if you try to upsize any more than 2 or 3 sizes main jet maximum.  Basically bugger-all happens as far as extra stomp goes.  Anything over 142.5 is a backward step It'll just drink fuel like crazy and every increase up in size equals lower and lower top speed.   They can't flow enough air to dilute the extra fuel.  The later XS11 34mm carbs with skimpy 110 - 125 main jets must be pretty bloody stifling though

STANDARD


PORTED



 

[steptoe]

motorcycle, 1, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,back tyre zilch,,

[SCARFEY]

Much better thank you Baldy