carbs carbs carbs

this thread purpose is to discuss my carb rack situation (and I sure hundreds of others were started the same way on this site). I've gotten a lot of help with my common "checking cylinder compression" thread a long time ago when I put new rings on all four pistons as well as a new piston = a lot of time, sweat, and $$ obviously in addition to the learning curve behind these wonderful bikes. along with the money situation I rebuilt my carb rack on a '81 650 maxim non-YICS. this includes a full carb dip in napa carb dip as well as the following parts:

-new throttle shaft seals
-new fuel o-rings
-new pilot mixture screw o-rings
-new pilot mixture screw washers
-new main fuel jets #110
-new jets #40
-new copper spacer washers underneath main fuel jets
-cleaned enrichments
-slides are cleaned and clunk when dropped in rack
-lowered fuel level using clear tube wet method to proper level
-bench synced nearly 20 times
-pilot mixture screws set at 2.5 turns out for now
-rack put together twice using flat surfaces: level and steel table saw
-throttle cable line is loose and has no tension while running
-VALVES ARE IN SPEC

as the list shows I've put a lot of new parts & time into this carb rack. situation however is weird. and I've explained this before on some other threads: my carb sync will not balance #4 with #3. using carbtuner mercury sticks I borrowed from a friend, the vacuum cannot become balanced. before you tell me the procedure, I KNOW how it works. balance 4 to 3, 1 to 2, and then 2 to 3. thats fantastic; and better yet 1&2 are balanced with 3 currently!

also before you tell me to look for air leaks, I HAVE. either with propane or starting fluid sprayed all around. for verification I put the propane bottle nozzle towards the airbox filter hole and that's when the idle increased. never an increase anywhere else.

back to carb syncing: the vacuum in #4 is lower than #3 and the rest for that matter since 1&2 are balanced with 3. I turn the sync screw for #4 ccw to close the throttle blade thus increasing the vacuum raising the mercury level. however when this is done the entire idle increases and the vacuum & mercury level in all four increases and i can't adjust the idle to turn it down since the main idle adjustment is backed all the way out.

i'm tired of smelling exhaust fumes in the garage (door is open!) tired of trying anything and everything, tired of the load idle increasing and decreasing all the time (getting headaces) so I just ride it like this for MILES, MILES, MILES back and forth to work (38 miles one way). only other than I could tell ya is my gas consumption is horrible. 31~32 mpg so I want to see if this carb sync can be fixed hopefully increasing the mpg but to no avail have not gotten anywhere. hogfiddles (Dave) I may be taking you up on that offer to check out my carb rack. i just don't get what I'm missing

 

What do your plugs look like?

Kenneth

 

My mpg went from ~47 to ~54 mpg(imp) just by taking the carbs off and bench syncing, as well as resetting pilots to 2.5 turns on all 4 carbs.

Are you calculating mpg(us) or (imp)?

I always calculate L/100km (cause it's easier on a km bike lol) Then plug that into here:

http://www.tdiclub.com/misc/conversions.html

 

You may have an Occult Vacuum Leak on 4.

When you try to Balance the Carbs and get a differential that does not adjust right ... a Leaking Manifold at the Mating Surfaces that does not leak until the rpm rise.

Quik-Fix:
Run a bead of RTV all around the No.-4 Manifold. Use your finger tip and force Sealant in the line between Manifold and Head.

You may also have:
A Stripped No.-4 Sync Screw
A Sync Screw Spring out of place or missing

 

to my surprise plugs were all greyish white to a smooth light grey so I took it to be a favorable condition. grant it they are brown paper color yet but I'm still in the syncing process

that's great you had a rack of carbs that all you had to do was tweak some things around. but I'm talking from experience with my carbs. Two years ago I was getting roughly 40 mpg before I tore into this bike thinking I could do better for her. now after an upper engine restoration and carb overhaul its not providing me with positive even-results.. I broke things apart out of curiousity and now I feel like 'curiousity killed the cat' its depressing

Rick: I forgot to mention that new gaskets are between rubber manifolds and they are tightly sealed. I can put more sealant next to the head but I have a feeling nothing will change.

stripped screw? then how come when I turn it with a screwdriver the idle would change? obviously it would be working fine. plus like I said I've done the bench sync numerous numerous times

 

While we are hunting for why the Bike won't let 3 & 4 Balance.

Do a different "Preset" on your Pilot Screws.

Set the TOPS of those Mix Screws 4.75 mm below the Top of the Hole.
This means you should be bringing them all Up and Out a bit.
Fine tune from that position.

 

okay I read earlier somewhere that you have also used a flat golf tee and measured 11/32". I can try this I suppose. just curious though what the pilot mixture screws even have to do with this though (why the certain measurement)? since my sync is outta whack. like I mentioned they are currently 2.5 turns out like everyone else says to start.

anyhow I'll give it a shot. any suggestions are great thanks Rick

 

I've been playing with my carbs since last August when I got the bike. So I've done my fair share of trial and error. I, right up until a week or so ago, thought I could get more / better preformance out of her by tuning tuning tuning as well.

After a year of getting pissed off, and having a bike react differently than the conventional thinking it should, i said @#$% it, and reset to factory settings. And it runs really well. My plugs aren't paper bag brown, and i don't care so much. The bike runs better than it ever has.

My 400 was the same situation, I tried and fought and tried some more for brown plugs. Never could get it, unless I felt like soot fouling all my plugs when choke was on.

I put 20 THOUSAND km on that bike riding like that with no ill effects. (Meaning white plugs)

I guess my thinking to try and help is this: Reset everything to factory defaults and see what happens, then go from there.

Just relaying my experience and trying to help that's all moe

I'm very strongly siding with Polock in this thread:

http://www.xjbikes.com/Forums/viewtopic ... art=0.html

 

try a bench sync another way. on the engine side of the carb on top of the bore there are tiny holes, thats where the gas comes in, you should be able to turn the sync screws till all the holes are covered equally by the butterfly's, try for 1/2 covered, if the gap on one of the butterflys in relation to the bore looks different that's a problem. if you can't make all of them close the little hole all the way, thats a problem. use the idle knob to set #3 then the sync screws to set the rest, in the end the idle knob should be able to close off all the holes and open them 1/2 way. if #4 won't come around maybe try loosening the screws to the rails and moving #4 around.
with the holes 1/2 covered the idle should be real low and the sync should be real close.
make sure the enrichment lifting fingers don't touch the plungers at all and the plungers are seated well

 

How do you duplicate "factory defaults" in regard to sync, when you've broken the rack?

If you're talking mixture screws, then OK, maybe.

 

I agree there's no real "factory defaut" for sync, I meant bench sync without vac sync when i was saying that

 

Then I don't understand. The "factory default" includes a vacuum sync with the YICS blocked to properly sync the carbs.

Just doing a bench sync is NOT "returning to factory defaults." It's "stopping before the process has been completed."

Once the rack has been broken and the carbs completely disassembled, throttle shaft seals replaced, etc.; there ARE NO "factory defaults" to return to, except maybe setting all the mixture screws at 2 1/2 turns out to start.

What were you using to vacuum sync? "Factory default" is a 4-stick manometer; and YICS blocked with the "factory" tool.

I suspect you were simply WAY out of actual (vacuum) sync, and going back to your (visual) bench sync got you closer to where it needed to be.

 

2 things come to mind -
1) When you re-installed the #4 throttle butterfly, you somehow didn't get it to seat "square" and it's just not working right. Loosen and re-tighten.

2) The Pilot well and related holes aren't perfectly clean and you are idling on 3 CYL until you tweak #4 a hair, then the motor revs up. A colorTune or even water sprayed on the exhaust would reveal this. Re-clean the Pilot circuit, run a bread wrapper tie or wire brush strand thru the holes.

Don't be afraid to try a different setting on the Pilot of #4 while doing a running sync.

 

Bench Sync with as thin a medium as possible.
3X5 Card -or- Resume' Paper.
Enrich the Pilot Jets so that the Bike Idles on its own, ...
Not close to where a TWEAK will Open a Throttle and have the rpm's run-away.

If you are as close as you say, ... marrying 3 & 4, ... It can't hurt to Pulll the 4 Sync Screw and inspect the Threads for being stripped.

If this is a YICS Bike and the Passage isn't blocked, ... All the other Carbs are going to contribute to an increase in vacuum if the Passage is clean.

 

does anyone ever read the question '81 650 maxim non-YICS

 

No. We don't. We just look at our note and see whats underlined or highlighted.

Often, ... a General Comment applicable to the situation gets included from what we might find written in italics.

 

i see, that's kind of like setting a valve on a runny delaminated sink that goes clunk when the pods get stuck in the alternating brushes.
right?

 

I like the words "don't be afraid". at this point I've gotten a couple ideas to try something. thanks to Polock, TIME, Rick and Krs thus far. lets keep the conversation back in line though...

it just doesn't make sense. I can get carbs 1-2-3 balanced and 4 is sorta close but once it becomes nearly balanced with the other three the idle increases and increases. I have the idle adjustment screw backed out so no more chances of lowering it. therefore at this point I'm stuck with just riding it with 3 outta the 4 balanced. which doesn't seem to be a problem. I have ridden nearly 2 weeks of work time 38 miles one way like this and the acceleration and idle was nice smooth riding.

anyhow i won't be riding in the next few days either way since the forks are off and newly remodeled ones from a '82 are in the works of completely new rubber seals from Len so until I can tweak things and take it for a spin I won't bother making changes. I tend to type a lot so my whole tuning process is explained. plus you can always remember my avatar and situation because I live on a honeybee farm and dad sells honey out the back door

 

Brand New Carbs

Anybody need some new carbs??

 

if only $ grew on trees... jeez

 

well I can get 4 to balance with 3. I can get 1 to balance with 2. but getting all 3 to balance with each other and #3 at the same time sends the rpms too high 4k. i'm really baffled and frustrated. spent 2 hours tearing the carbs off the bike again (for the 50th time) observing the return springs, and even trying your suggestion Rick about the 4.75 mm which was impossible because there is no clearance to even measure in that dinky hole. even measured a golf tee but could see the line on the tee since there is no room to work around on these *%$#ing carbs

 

I'm sure he's measuring in mpg, since the avatar says "OHIO". Well.... I guess there could be an Ohio, Canada; or Ohio, India; or something.......

Moellear, I've asked before, I'll ask again........did you doublecheck to make sure that you have the airjets underneath the diaphragm in the correct holes? It is easy to install those two reversed.

On the thought of the diaphragm, I'm sure you've already checked to make sure there are no pin holes. Did you also check the slide needle to make sure that it is straight and smooth?

Dave Fox

 

ya its Ohio, United States (EST.)

airjets under diaphragm: #195 above #50 which are both above the hole for the shouldered screw holding the plate that covers 'em. in other words, #50 is in the middle.

no pin holes seen anywhere in the diaphragms. the slide needle for each one of them is not *perfectly* straight. if you were to drop the diaphragm assembly & the slide needle down the emulsion tube I have to guide the needle into the tube but how perfectly straight can they really be? mine may be off by a few degrees and just barely misses the emulsion tube hole so I was never worried about that. they were disassembled during carb overhaul and cleaned/sharp tip like a needle

 

the needle is ok, the small spring inside the slide, along with the little nub on the nylon piece at the base of the needle cause it to go to the side like that. No problem there from the sound of it.

Now here's a different question.... have you checked for air leaks yet?

Oh wait......that was the wrong one. I meant: Do you have any other xj-owners near you that might let you swap a set of carbs in just for trial? I mean, you may find that it's not the carbs. Rather, something like a squirrel got into an exhaust pipe, or you have a bad valve, even though the shims measure out correct now, you know.....something other than carb. Swapping the rack will tell you one of two things--either the problem is still there ,or it went away.

Dave

 

update: carbs are balanced. thanks to you fellas for putting up with me

new problem: bike runs excellent upon cold start. choke and over the course of 5 minutes I have to slowly let choke off. when I get the bike idling nearly 1050 rpm purring like it should I then give it some blips of throttle. as it begins to get hot (10 minutes into running time on centerstand) the idle takes a longer time to return back to normal. by this time I give it nice smooth throttle blips and then it stays high near 4k and takes forever (a minute or so) to slowly drop. I also found that quick blips of throttle occasionaly drops the idle down.

it seems like the vacuum is causing it to run fast (holding the butterflies open) and as it reduces vacuum pressure the idle slowly drops back to normal. however sometimes the idle will not return back to 1050~1100. I'm stoked to get this far. please give me some advice other than check for air leaks. I've literally sprayed carb cleaner on every square inch of the carbs and rubber manifolds. no change in idle.

am I chasing my own tail? seems like this process is never ending for me.

 

Your slides are still sticking. Well, maybe anyway, there are other possibilities.

Vacuum doesn't hold the butterflies open; that would be the pink monkey with his paw wrapped around the throttle (you.)

Vacuum DOES hold the slides up. As do slides that don't want to go "clunk" once warm. Are your carb bores polished shiny smooth?

When you rebuilt the carbs, did you disassemble the slides, and be sure the holes and passages in them are clean too? (I believe that's where the Hitachis release their vacuum.)

(I'm fishing for a reason for it to not "release" the vacuum operating the slides, or for a reason that they might not be returning on their own.)

The other possibility is that there is an issue with one of the pilot mixture circuits causing one carb to run overly rich or overly lean when it's not on the mains. It only takes one to "hold up" the whole program, idle wise. Or one "misbehaving" float valve allowing a higher (or lower) fuel level than it should. You should be able to see it with a ColorTune, and I'd bet it's #4.

Do you have/have access to a ColorTune? I would honestly loan you mine but it's a 12mm version for the 550s.

 

took the slides out tonight and gave the bores a brief shining with Mothers. they look very clean and have a shine to 'em.

before I took apart the brass slide and the plastic screw holding the long needle, I noticed that 2 of the 4 needles tend to stick after being depressed down. almost as if they were holding a small spec of dirt or something and not allowing the spring to extend back out under normal conditions. here's a close-up of 1 of 'em with a small area of black near the base of the needle and bottom of the brass slide.

second picture depicts my needle itself. any reason why I should remove the screw? I figure all it does is hold the plastic retainer on the needle.

in regard to the needle itself, I'm guessing it should be as pointy as a nail (?) so if not use fine sandpaper...?

 

i think you'll find those brass slides are really anodized aluminum, stained with old gas.
that's not a screw in the needle, it's a split that spreads open to hold the plastic cap on.
once the needle is in the slide and the screw on the spring there's nothing to push it up to get it stuck, don't worry about it

 

Polock's right; and you need to clean those slides. Don't polish them, but get some good carb cleaner and get them not "brass" looking anymore.

Don't sand the needles, but do get them clean. All those black deposits need to go by-bye.

I hate to ask, but are there any other parts of the carbs you maybe failed to get microscopically clean?

 

the stain on the slides is actually below the surface of the anodize, it may not come out.
be sure the o-ring and washer on the idle mixture screw are right. if the rpm's hang, push the throttle linkage down with your finger just to be sure there is no binding there.
10 minutes running on the center stand is a long time without a good fan
right on the motor

 

*looking at my carbs saying $#%# you!*

if someone has their slides out, lemme take a look at what one without stains look like. I honestly believe you fellas, just curious how different mine looks compared to others since I've always had these that look yellow and brass color

believe me, I will be taking my time to get these slides in perfection order. I'm really hoping this is my only culprit. new o-rings and washers from Len are installed in correct order. many thanks to you XJ Wizards. your input means a lot to me...

 

all of mine look more or less like yours, anodize is porous and silver color untill it's stained and sealed, then the only way to change it is remove the anodize with lye, you don't wanna do dat

 

The Stains on the Diaphragm Pistons are of no consequence.

If the Piston is Shuddering, Slow-moving or Binding, ... the Inside Diameter of the Pistons Bore needs to be refinished.

15 ~ 20 years or more of Aluminum Oxidation builds-up in the form of a light-gray film on the surface of the Bore. Enough to shrink the I.D. and cause the Piston to be encumbered.

ScotchBrite Scrub <==> Dremel <==> Polished Bore

 

piston bores are cleaned and shiny as a mirror. problem still exists

PROBLEM: IDLE IS HIGH AND WON'T RETURN TO NORMAL CONDITIONS ONCE THE BIKE GETS HOT (EITHER RUNNING DOWN THE ROAD~10 MILES AND/OR SITTING IN THE GARAGE RUNNING)

the bike runs well on the road. smooth acceleration, no boggyness or stuttering. dad thinks it is something that expands because he listened upon a cold start as the bike warmed up in the garage. it was a nice purring around 1000~1200 rpm. but when I came back from a ride ~10 miles, the idle would soar. no throttle linkage in catching. no air leaks because it doesn't change idle speed til the bike is warm. so could the sync screws be expanding just enough to hold it open?

also, if you push down (even a micrometer) on a single or multiple sync screws as the bike is running properly would your idle drop? my idle drops to the proper rpms when I push down on the two outside screws when the idle is screaming and it idles beautiful. this problem has been in existance all summer for me. dad says I have WAAAYYYYY too much patience for this. but I'm on my last hope here and even just got off the phone speaking with an owner (never met him in person; seen his sales on CL) who happens to be selling three different XS models who happens to live 5 miles away from me. he couldn't think of any other reason than what I've gotten assistance on here. help me guys

 

could it be?........ after it's hot, and the idle is high, adjust the idle knob till you get 1100, snap the throttle a few times to make sure it stays there.
always adjust the idle speed hot

 

idle knob is backed out all the way once again. I've snapped the throttle and it would sometimes drop 500 rpms or so. idle speed cannot change physically with my hands. something more serious wrong than that

 

When I had the problem of my rack running to lean and not being able to get my fuel air ratio set right. We found that the vacuum tube plugs. The ones you hook your gage up to for a vac sync. Well they where leaking air and guess what, even using propane did not detect the air leak. When I replaced the rubber caps ALL my plugs except number 3 where black. Had to start the carb air/fuel setting ALL over.

 

Hey Mole - Ear <snicker>,

I found the problem.....you only have three carbs. Your title should say "Carbs Carbs Carbs CARBS". Without that 4th carb, you're gonna suck in a lot of air and have an incredibly lean condition.

Well, seriously--I am sorry to see you're still having the problem. As I said before, the offer stands if you wish to send the rack out and I'll take a round at it it, too, once the riding season is over. Now, question--have you tried a different rack of carbs yet?

Dave fox

 

only going to ask two questions:

1. the propane trick: release propane around the carbs and rubber connections when the bike is warm (too hot to touch headers) or just after a hot ride down the road when my bike will be soaring around 5k rpm?

2. If you push down (even a micrometer) on a single or multiple sync screws (the throttle shaft linkages holding the four carbs together) when the bike is running properly around 1000~1100 rpm would your idle drop low enough to perhaps kill the engine? ... I've noticed when the bike is at 4~5k rpms I can do the same thing to lower the idle to a more reasonable idle and I'm wondering what the case is on a proper running bike

 

1: Do it under whatever conditions are contributing to your issue.

2: If I push on my linkage when the bike is idling, nothing happens unless I MASH on one hard enough to overcome the little linkage springs. BUT that's on a bank of Mikunis. A Hitachi equipped bike owner needs to chime in.

 

There are a host of issues that could contribute to incomplete closing of the Throttles.

1) Bent Throttle Cable End Mount.

2) Linkage alignment (Align Rack)
3) Throttle Plate Drag (Throttle Plate scraping Venturi. Reposition.)
4) Dry Shaft Bores / Seals -- Dried needing lubricant.
5) Swollen Throttle Shaft Seals
6) Improperly placed Linkage Return Springs
7) Weak Springs
8. Missing Spring(s)
9) Improperly routed & adjusted Clutch Cable. Cable Stay misplaced applying undo pressure on rack.
10) Throttle Plates mixed after overhaul. Throttles swapped.

 

4.) i used pure silicon grease (Napa blue tube) and lubed them
5.) what would cause the throttle shaft seals to swell?
7.) define "weak spring". dad posed that same scenario to me last night when he was giving me 'weird off-the-wall' suggestions
10.) even if the throttle plates got mixed (mine did not) wouldn't a proper bench sync solve that problem?

Rick, this list great and I do appreciate it. Don't take offense to me asking about certain situations that may be unexplainable. These bikes operate under a certain "science" that keeps me interested to at least store mine rather than sell it. although I must admit there have been numerous times when I told myself... if only I got rid of this #@^! thing

 

unhooked both cables (throttle and choke)... still races around 4krpm

put as much propane around the carbs as I could til I got tired of smelling it. went somewhere else and lit the propane to be sure it was working fine. it does. no air leaks in/around the carb rack... still races around 4krpm

made certain my choke plungers are all the way down even with cable unhooked.. still racing

I'm done. carbs are coming off this evening and I'm stripping it down. butterflies comin off, throttle shaft seals coming out, mixture screws coming out. the whole thing... like I did 9 months ago and replaced everything then. 'cept this time its all coming apart for inspection. not gonna purchase anything cause that was an expensive ordeal back then. scary part is loctite is on my *new* butterfly plate allen head screws which better not slip or fuss with me.

i'm disgusted

 

rack is apart. i'm getting fast at handling the carbs. all that is left are to remove allen head screws holding the plates in each carb. noticed on the backside plate (the side of the plate between the slide piston/needle and the plate itself) of #4 its caked black. like its been burning excess gas inside?

any takers?

 

Crap. Wasn't fast enough. I was going to ask you to take a close-up pic of the whole rack showing the linkage side so everyone could take a look and see if they could spot anything.

My rack snaps back to "home". There is no ambiguity or hint of hanging up whatsoever. In other words, it would take a whole lot of friction to keep my carbs from reaching full stop. I know that doesn't directly help you much, but that's how they are supposed to operate.

As an aside, are you sure the black on plate #4 is new? Are you sure you got all the plates installed in the correct direction?

 

Throttle Shaft Seals will become "Swollen" if introduced to solvents that are absorbed by the seal. Mineral Oils and harsh chemicals in DIP Cleaners, plus Propellants for some Cleaning Products will ruin a Seal in seconds.

Weak Springs are ones that have either lost torsion or have been installed without preload or have slipped off tangs or anchor points.

The Throttle Plates can Bind if:
Not correct Plate.
Not "Centralized"

The Butterfly needs to be installed with precision if the holes allow for even the slightest adjustment.

When tightening the Throttle Plate to the Shaft ... Strips of 35mm Film positioned at 10 - 2 - & 6 O'Clock will help prevent binding.

 

Yes. black is new and is like a cakey/smeary residue that I'm able to wipe away. plates are *when i installed them just like they were before* in right direction. I marked up arrows the last time and have done so tonight.

where does the film go? between the plate and the shaft? between the shaft and the carb body? sorry I'm lost. I would understand the use of preventing it from binding, once I understood where it goes during the assembly process

 

maybe it's too late but heat loosens locktite, + 1 to Rice, the throttle should snap shut with a bang,like don't get your finger in there kind of bang.
i like to tighten the butterfly plates till the screw just touches then snap the throttle a few times to let them center themselves, maybe help them along if they need it.
if your rack is together this is where the sync starts, you can't get the plates right if the sync screws are holding them open even a little.
reread this whole thread the answer has to be here somewhere

 

upon further inspection at the location where the butterflies come to a close and return (where the springs snap them back), there is a small ring of black residue on all four including the excess black smudge inside the horizontal carb bore (not where the piston/needle travels up and down). this ring happens to be right at the same location as one of those 3 very very small holes

what's causing the gas to burn inside the carb? remember the bike was racing so I wouldda thought everything should be clean.

btw: throttle shaft seals are in excellent shape as if I bought them yesterday

 

did you ever get a back fire or even a gentle poof? that could be the cause of the black stuff and there's really nothing to wipe/wash it away so it just stays there