More performance from stock carbs?

jamesc2123 · New Member Joined: Aug 05, 2007 Posts: 6

Doing a full rebuild on my '82 xs right now, new pistons, rings, several other pieces that needed replacing. It currently has a set of high flow pipes and pod filters.
I'd like to know what I can do to the stock carburetor to get more fuel in and maximize power. I'm not very familiar with carbs, but there's got to be something i can to improve performance and not do something stupid like buy the $600 dellorto carbs on mikesxs... Twisted Evil

Any ideas/tricks?

Srinath

I've spent the last few weeks staring at these carbs, and here is my conclusion if you're taking off that air box and swapping to a free pipe.
I'd do +1 on pilots and +4-5 on the mains. So 45 bleed style pilots, and ~155-160 mains. Put 1-2 #4 washers under the needles, set air screws to ~3 turns out and put the float back to stock.
Cool.
Srinath.

xsjohn

Way off................... xsjohn

Srinath

OK so what do we run.
I am planning a pipe and staying stock air box and filters on mine, and I have +1 on pilots and +1 on mains.
I pulled out 132.5, so I got 135 in it, and I have 45 pilots, but I had to drill my 37.5's which were non bleed.
So what would be correct for a pipe only bike, and of course what is right for K&N and pipe. Thanks.
Cool.
Srinath.

xsjohn

It's in the needle taper with those BS34's........I have that down and even compensate for the hotter right cylinder...........I can't tell you how to do that I just build them ................

""""""but I had to drill my 37.5's which were non bleed""""""""" not sure I understand this .........non BS34 carbs or something.......?

xsjohn

Srinath

I have several 1000 non bleed pilots in the 37.5 size. I have done several 100 GS500 carbs and the pilots I swap for 40 non bleeds. The calculation form bleed to non bleed is approximately like this. 37.5 bleed is roughy the same as 40 non bleed. Bleed jets like the XS ones have holes on the sides, non bleeds do not.

I had a set of pilots I had to punch out in the 34 XS carbs. So I had to replace them, and since I didn't feel like plonking down 10 bucks and waiting a week I took my non bleed junk and drilled it to 45 size, .45 mm with a #76 drill. That leaves me with 45 bleed jet and I fitted 135 main's in it.

The needle I usually shim up but I didn't bother with this one. I figured +1 on pilots and mains should cover it cos the airbox on the bike is still stock. Pipe is all I am fitting, and on older bikes they didn't let em run that lean cos that was pre EPA.

I'd prolly guess my 45 non bleeds work like the 42.5 bleeds it had. 135 mains may be all it needs for pipe.
I should run it and see how it runs, I have no ignition box yet, so its not starting.

Needle is an obstruction in the emulsion tube. Main jet is the entry to the emulsion tube. Thinning the needle or lifting it works just like putting in bigger mains FWIW. That is why DJ can supply smaller mains than the stock and yet get the bike richer.
Anyway these carbs are simple, should prolly be able to formulate a jet pack formula for it like I do for GS500's.

Cool.
Srinath.

xsjohn

All the proof is in the pudding.........how it cruises without ratcheting and how smoothly it runs and how it goes down the highway and for how long.......these truths will be self evident......where have I heard that....

A fellow XSer sent me this.......... how true it is...........

DRILL PRESS:
A tall upright machine useful for suddenly snatching
flat metal bar stock out of your hands so that it smacks you in the chest
and flings your beer across the room, denting the freshly-painted project
which you had carefully set in the corner where nothing could get to it.

WIRE WHEEL:
Cleans paint off bolts and then throws them somewhere
under the workbench with the speed of light. Also removes
fingerprints and hard-earned calluses from fingers in about the time it takes you to say, "Oh, s***!"

SKILL SAW:
A portable cutting tool used to make studs too short.

PLIERS:
Used to round off bolt heads. Sometimes used in the
creation of blood-blisters.

BELT SANDER:
An electric sanding tool commonly used to convert
minor touch-up jobs into major refinishing jobs.

HACKSAW:
One of a family of cutting tools built on the Ouija
board principle ... It transforms human energy into a crooked, unpredictable motion, and the more you attempt to influence its course, the more dismal your future becomes.

VISE-GRIPS:
Generally used after pliers to completely round off
bolt heads. If nothing else is available, they can also be used to transfer
intense welding heat to the palm of your hand.

OXYACETYLENE TORCH:
Used almost entirely for lighting various flammable
objects in your shop on fire. Also handy for igniting the grease inside the
wheel hub out of which you want to remove a bearing race.

TABLE SAW:
A large stationary power tool commonly used to launch
wood projectiles for testing wall integrity.

HYDRAULIC FLOOR JACK:
Used for lowering an automobile to the ground after
you have installed your new brake shoes, trapping the jack handle firmly
under the bumper.

BAND SAW:
A large stationary power saw primarily used by most
shops to cut good aluminum sheet into smaller pieces that more easily
fit into
the trash can after you cut on the inside of the line instead of the
outside edge.

TWO-TON ENGINE HOIST:
A tool for testing the maximum tensile strength of
everything you forgot to disconnect.

PHILLIPS SCREWDRIVER:
Normally used to stab the vacuum seals under lids or
for opening old-style paper-and-tin oil cans and splashing oil on your shirt;
but can also be used, as the name implies, to strip out Phillips screw
heads.

STRAIGHT SCREWDRIVER:
A tool for opening paint cans. Sometimes used to
convert common slotted screws into non-removable screws and butchering your palms.

PRY BAR:
A tool used to crumple the metal surrounding that clip
or bracket you needed to remove in order to replace a 50 cent part.

HOSE CUTTER:
A tool used to make hoses too short.

HAMMER:
Originally employed as a weapon of war, the hammer
nowadays is used as a kind of divining rod to locate the most expensive parts
adjacent to the object we are trying to hit usually smashing the thumb that
is holding the object that you are trying to pound into whatever it is that
you are working on effectively eliminating the need for manicure care on that thumbnail for weeks. See: Son of a b*tch TOOL

UTILITY KNIFE:
Used to open and slice through the contents of
cardboard cartons delivered to your front door; works particularly well on
contents such as seats, vinyl records, liquids in plastic bottles, collector
magazines, refund checks, and rubber or plastic parts. Especially useful for slicing work clothes, but only while in use.

Son of a b*tch TOOL:
Any handy tool that you grab and throw across the garage while yelling, "Son of a b*tch" at the top of your lungs. It is also,
most often, the next tool that you will need.

xsjohn

nj1639

Too funny, and how true.

jamesc2123 · New Member Joined: Aug 05, 2007 Posts: 6

Ok so forgive me if I don't know enough about carbs to really get what just happened....

What I got is that putting in larger main jets and pilot jets will allow more fuel in to compensate for the increased air mass with the pipes and airbox. It sounds like theres not an exact way to know how much to open the jets though....

What I don't get is what you're saying about the needles. If you put washers under them what exactly does this do?

acetek · Full Member Joined: Feb 24, 2008 Posts: 68 Location: PNW

your stock 34's dont have adjustment slots for clips and washers for the needle jets unless by chance you have canadian carbs or needles Xs John can spin you up some kustom needles for more adjustablity and cooler jug temps I have a set they work good.
You should probably read this carb guide from xs650 garage
hope its ok to post here xs650temp.proboards.co...thread=731

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

Quote::

I'd do +1 on pilots and +4-5 on the mains

I think up 4-5 on mains is too much try going in smaller incriments and raising the needle. I have stock exhaust and air boxes and it was too lean for sure but 2 up on mains killed milage. I have one of johns original needle sets and they are even better now. I would deafenatly suguest johns kit and or try some expeirimenting. John has years of expeirimenting alredy done for us.

Quote::

It sounds like theres not an exact way to know how much to open the jets though....

Exactly you have to experiment but someone with a similar set up could give you a good start point. I'd try 1 up on main and piolet and raise needle and try it. Look at plugs, temp, and milage. As compared to other settings.

Quote::

What I don't get is what you're saying about the needles. If you put washers under them what exactly does this do?

If you put a washer under the needle it will raise it which will allow more fuel in as compared to where the slide is, the slide raises and lowers the needle in the main jet and needle jet which allows fuel into the throat of the carb. I think a simple version would be if it is lean when going to wide open throtle raise main jet sise. If it is lean at cruis rais needl height.

xsjohn

The problem with shimming those log needles and large main jets is that you will wash the rings at heavy throttle and still be starving for fuel at moderate throttle.......... guess you guys will just have to find out...

The trick for making these last is to quell the temps ..........ah what would I know.....to think that a Toyota gets hundreds of thousands of miles on almost identical cylinder liners and pistons and rings.........what would be the wild card...........HEAT...................

For example at 75,000 miles my compression is the same as day one....150....except I have lowered it a bit purposefully ..........and it has never run better with cylinder temps averaging 210 on a 65-70 degree day and so on as it gets warmer.......and getting 55mpg......ah what would I know...I was making these run right before most of you were born........

xsjohn

Srinath

If its rich enough to wash the oil out of the walls it will definetly be too rich to run right on hot days and after it gets warm. But yes, definetly possible to get it too rich in one spot and too lean in another, not just on an XS, but on almost any bike/car.
I actually have seen bikes that were jetted so badly that you can throttle wheelie while closing the throttle while it gasps and falls on its face when you open throttle.

So yes you can screw yourself 14 ways from sunday. However the 1 step at a time approach would work (patience and 1 change at a time to study it), and suggesting the 4-6 up may have been a little of jumping the gun, after all my XS will not even tick over at this time even though its my second and the first was great in stock form wiht all around +1's for jetting. I still have to experiment with pipe and what ever proper.

Cool.
Srinath.

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

I gues the original needles would have to be shimed so much that it will let to much fuel in? I just experiment till its corect for my riding and terain.
I would suguest a needle made to be adjusted.

Srinath

I doubt that. I believe the stock needle may be too fat 1/2 to 3/4 way to the tip and too thin @ the tip.
That would however leave it too lean till 3/4 throttle and to right above 3/4, but if you put in larger mains, you can get that up to 3/4 throttle part right but have the gas wash off the oil off the walls past that. The remedy may be to sand the needle from the 1/4 to the 3/4 length only, however I will really make 1 change at a time, make many many observation runs before concluding anything. In fact, I will put an O2 sensor in the pipe and run it before I sand the needle.
Anyway longer needle wont do much, neither will a DJ style stepped needle. You need a thinner all the way but same thickness as stock in the last 1/4 ... maybe. I wil lrun it and see ... if I can ever get this thing running ... Mad

Cool.
Srinath.

suiteo

Only one thing to do for stock carbs in my opinion. Listen to xsjohn, and get a set of his needles. Just rebuilt mine, and after several newbie mistakes, and getting the correct info from folks here, my bike runs better than ever. Running open style UNI pod filters and stock pipes with the baffle plugs punched out. Worth the effort of cleaning and rebuilding.

Jay

650skull · Support Staff Joined: Jul 19, 2007 Posts: 1186

Well you could look up "XSJOHN'S NEEDLE KITS FOR BS34 CARBS 80-84" in the Vault Wink

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

Quote::

Only one thing to do for stock carbs in my opinion. Listen to xsjohn, and get a set of his needles.

cant realy go wrong here. There are years of experience, trial and era saved going this route[code]

gordo

James, I have an '80 with the so- called "terrible" BS34 carb's. Yes, they do suck in the stock form. I tried using the needle kit from Mike's, doing all kind's of different setting's with them, to no avail. Alway's ended up lean or rich somewhere in the rpm range. Then I got a set of John's needle's, installed them excactly as he stated, and the engine run's great. I have the mod's you mentioned, pod filter's, 2-1 pipe, freshened up top end. Like John stated , what the hell doe's he know. Well, he know's these carb's. And like the Pamco mod on the ignition for the older bike's, set 'em & forget 'em.BTW, I get between 50-55 mpg. No oil consumption between change's.

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