New Katana 1100 carbs installed.

[Dan Hodges]

Bigger Carburetors

Originally posted by strom


AFAIK the japanese stuff mostly used either keihin or mikuni carbs. Neither of these companies can afford to make "cheap" carbs.
Next, try finding a nice suzuki katana 1100 in a pristine working condition. OK, any suzuki inline-4 up to 1990. I know of only one GSX 750, and even that one has a half of kawasaki parts installed.
Try the same with any yamaha.
And while you're at it.... polish the insides of your steel carb, adapter pipes. And for goodnessake put some K&Ns on.

LP

All FJ carburetors were not the same and even though the throttle plates all measure 36mm,there was one flavor for the 84,one for the 85 and one for the later models and the later ones are still available from Yamaha. How much air does a 34 mm CV Mikuni flow and how much air will an 1100 cc 4 cycle engine pump at 80% VE & 100% VE @ 9000 rpm? A stock 80-83 XS-XJ Yamaha's cams only have 235 degrees of duration and subsequently the motor does not require the airflow of a 36mm carburetor.Remember the Suzuki Madura,don't see many of them around do you.

[pggg]

From Dan " How much air does a 34 mm CV Mikuni flow and how much air will an 1100 cc 4 cycle engine pump at 80% VE & 100% VE @ 9000 rpm? A stock 80-83 XS-XJ Yamaha's cams only have 235 degrees of duration and subsequently the motor does not require the airflow of a 36mm carburetor"

Dan, that's so much B.S. matey, hold back on the figures and theories and try some 36mm carbs on your XS, I promise you'll like the results..

[Dan Hodges]

Basic math

Originally posted by pggg
From Dan " How much air does a 34 mm CV Mikuni flow and how much air will an 1100 cc 4 cycle engine pump at 80% VE & 100% VE @ 9000 rpm? A stock 80-83 XS-XJ Yamaha's cams only have 235 degrees of duration and subsequently the motor does not require the airflow of a 36mm carburetor"

Dan, that's so much B.S. matey, hold back on the figures and theories and try some 36mm carbs on your XS, I promise you'll like the results..

Of course these figures are not BS or theory and are covered in "The Internal Combustion Engine" by Charles Fayette Taylor,a professor of mechanical engineering at the Massachusetts Institute of Technology (MIT).I have not gone the 36 mm carb route because A. the numbers don't add up,B,nobody has shown me an a v. b dyno test and C,I can outrun any Eleven I have ever encountered.If I were running a drag bike,both Mikuni and Keihin make some very good smooth bore race carburetors that can be purchased from several vendors.I built my motorcycle for the street and so I prefer the CV carbs better for that application.I must say,I have about 1500 miles on my (new) 1179 XS now and it is a bad boy and to say it carburetes perfectly is an understatement.The Megacycle cams and Super/Trapp 4 into one header sounds so evil meandering slowly across the gas station lot in front of all the Harleys.

[JWSanders]

I imagine I will eventually get rid of these carbs, but I think I'll go the fuel injection route instead.

The kits just keep getting better (and cheaper!) with full ignition control (and replacement) as an attractive option.

I really like the idea of a self-tuning system.


Carbs suck more than just air......

[petejw]

dan, was just curious where u get 100% VE
from @9000 RPM, going from memory back in the days
i was at Tech, most vehicles were producing VE @ 80%
max and this was usually obtained @ a speed
of around 80km/50 mph
to get 100% or more u needed a turbo or a blower.

but in saying that ur bike is beautiful. :-)

personally i think our carbs when they arent worn,
that is slides, emulsion tubes, dodgy diaghrams etc are just as good as any other carb. imho

[Snow]

100% VE? 80% VE? Wow...my physics teacher must've lied to us!

[pggg]

Well, I'll leave the technical stuff to the experts, but you don't need smoothbores or hard out flatslides to improve the performance, a modern set of CV carbs perform brilliantly on an XS11, even a set of modern design 34mm (I won't get into flow rates and cfu's or vcm's whatever ) are gonna improve the fuel delivery, but don't go thinking the XS cylinder head is maxxed out on fuel/air flow as stock, bigger carbs get these old air-cooled 4's boogying... sayin' that, the stock carbs perform well enough, I never had any real problems with mine, consistent and reliable, a bit ragged at very low revs sometimes, actually those BS34's would last forever, they don't seem to wear the needles and nozzle tubes and have metal diaphragm slides, but surprises me how many people on this site seem to have a lot of carb troubles, old fuel residue and rusty grunged fuel tanks have gotta be the main culprits there.

[Dan Hodges]

VE

Originally posted by petejw
dan, was just curious where u get 100% VE
from @9000 RPM, going from memory back in the days
i was at Tech, most vehicles were producing VE @ 80%
max and this was usually obtained @ a speed
of around 80km/50 mph
to get 100% or more u needed a turbo or a blower.

but in saying that ur bike is beautiful. :-)

personally i think our carbs when they arent worn,
that is slides, emulsion tubes, dodgy diaghrams etc are just as good as any other carb. imho

I was using 100% VE as a best case scenario regarding air flow as most modified street engines would be 85% VE or less.In regards to this VE thing,it is possible to achieve 100% VE in a race engine naturally aspirated on carburetors.I have a 555 C.I. big block Chevrolet in my drag race Camaro and when the motor was dynoed with a modified single 1150 Holley Dominator carburetor it was at 102% effiencey @ 8500 rpm which means it was pumping more than a stock 1150 Dominator would flow however said Dominator is not stock as it has been modified by Barry Grant carburetors and now flows over 1300 cfm.These high dollar race motors are dynoed in a dyno cell, not some goffy tire smoking chassis dyno.These test monitor the carburetor air flow,A/F ratio,VE,fuel consumption,EGT,engine vacum and HP and torque.The carburetors on my Eleven have new Yamaha slides,"O" rings,floats,gaskets and new donuts that go on the end of the needles.The slides were $125 each from Yamaha and I didn't add up what the other carb parts cost.Actually,I have at least half a dozen sets of Yamaha slides with various size vacum holes that I have experimented with to find it's sweet spot.There is always more than one way to build a motor and mine might not be the only way nor the cheapest,but it works and when the tach needle hits 6000 rpm I know it was money well spent. A Mikuni carb is just as good as a Keihin,no better,no worse and both are junk when they are worn out.

[pggg]

Seeing such a tricked out motor being restricted with the poor old clunky BS34's seems such a waste...

[MAXIMAN]

Patrick

Showing your ignorance again I see... ...not surprising.

When I rebuilt my Maxim I gained from 72 hp to 94 hp at the rear wheel. That is a MEASURABLE 32% increase...via dyno. Not some BS seat of the pants feeling froom some snake oil additive you put in your gas tank. If you read the thread you know all that was done to the motor (big bore, ported intake and matched exhausted, Web cam...blah blah blah)

The truth is when we installed the FJ1200 (36mm carbs) I thought we were "killing the witch". But Dan told me I really didn't need the 36mm...the 34mm bores would flow ample air for any Eleven....trick or other wise.

Like you I questioned this logic. However UNLIKE you I did not insult Dan and I did not think I hadit all figure out. SO Unbeknownst to Dan I installed the 34mm Mikunis just to see what would happen.

I lost about one half of one horsepower at the very peak...but gained a little in the mid section. In reality the curves were almost identical.

When I compare you and Dan as authorities on internal combustion engines an analogy comes to mind.

pggg is to racing what this guy was to comedy.



Dan Hodges is to drag racing what EF Hutton is to the stock market. When he talks...people listen.

[pggg]

Hey maxxy boy, you know you make a great toady dont'cha? Gonna do your abuse and run trick again huh?

[pggg]

BTW, with four brand-new carb slides 125 bucks each, I wouldn't be swapping carbs in a hurry either...

[MAXIMAN]

Abuse? If anyone is abusing it is you Patrick.

pggg said:

Dan, that's so much B.S.

The only BS I see is coming from a kiwi. So why don't you do like me and put your money where your mouth is. Put that "BIG BADD" Eleven of yours on a dyno. make a few run with the stock tuned carbs. Then make a few with your overhype ZRX carbs. You won't be impressed with the results and neither will anyone else.

Secondly Patrick...what makes my ZRX do wheel stands at 100 and bury the needle into the 160 range isn't the 36mm carbs. If you'll give me your address I'll gladly send you a buck so you can buy a clue.

Oh yeah...and have a nice day.

[petejw]

I wasnt 2 far off
and tech was 20 yrs ago. :-)

the only reason i would try other carbs
is cause of the cost of the replacements
parts for the originals.

[Snow]

Looks like I was just a little confused - I was thinking of thermodynamic efficiency, which for a gasoline engine is typically around 25% thermal efficiency.