wow these carbs are a pain!!

im used to sportbike down draft carbs i did alot of work on those but man these xj carbs are way harder! i never even found the pilot jets, at least i dont think i did. and drilling out those mixture screw caps was a biotch too! but im almost done i got one carb left and all it needs is the cap drilled out but i brok e the drill bit so ill have to wait on that till i get another one. and the float levels on this thing are way off each one of the floats is at a toatlly diff level. does anyone know the best way to get the proper float level and what is that level? 1985 xj 750 midnight maxim

 

If we're talking about Hitachi carbs, those are right out in the open -- the main jet holds the emulsion tube in place. The smaller jet next to it is the pilot jet. (We *are* talking about fuel jets, yes?)

Funny you should ask...

Not sure the year is right on that one... 83 or 84, maybe?

 

looks like you know more about my bike than me, yes 83, not 85 why was i thinking 85? anyway im trearing into them should have them done tomorrow i hope, even after reading that awesome guide you showed me im still alittle unsure how im gonna do it, i dont have a pvc carb holder and all that stuff. i think im gonna measure the distance from the carb case to the top of the float with the carbs upside down, that seems to be the easiest. does anyone know a ball park figure i should shoot for here?

 

according to the manual. 17.5 mm float height.

 

The "dry" method you're describing is only a starting point. Also, don't measure it upside down, just tilt the carbs enough so the float tang is slightly resting on the needle when you measure (the weight of the float can press in the sprung tab on the needle and throw off the measurement).

To correctly set the float levels, make sure your float bowl drain screws are able to be removed. Put the carbs back on, put the bike on the center stand on a flat surface. Take 6" or more of clear 3/16" vacuum hose and attach it to the "nipple" in the middle of the float bowl (one carb at a time).

Back out the float bowl drain screw 'til you see gas fill the tube. Hold it up to the where float bowl meets the carb body and ensure the gas level is 1-3mm below of the gasket surface.

If you are out of spec remove the float bowl, remove the float, and bend the tang on the float to adjust the height. Take a moment to figure out which way to bend the tang to raise or lower the fuel level. Very small increments! If you can see the amount you bent it you probably bent it too far.

Repeat the proceedure on each carb until all are in spec.

 

lou 627,
thank you for dummy proofing that for me, sounds very easy to do and well worth the time, ill keep everyone posted on the progress, thankfully yes the screws are easiely removable on mine

 

wondering why car carburetors use the dry method. with absolutely no way of measuring fuel height.

 

Thanks for the blow to my ego. If you knew how much time I've spent rewriting the blasted thing to make it more readable...

...and exactly what the writeup is suggesting you do. In graphic detail.

You mentioned lacking the PVC carb stand. If memory serves, the writeup says it isn't mandatory, but it does help. Same thing for the measuring tube with the markings on it, and the fancy auxiliary fuel tank. (Boy, do I like that fuel tank.) If don't have something that's listed in the writeup, make do with what you have.

1) You probably just answered your own question... no way to check the fuel level. These carbs have that.

2) We've been over this before. You do it your way, we'll do it ours.

3) You have a problem with the procedure, you go talk to Yamaha -- it's THEIR procedure, listed in THEIR factory service manual, fer crying out loud. For that matter, it's in the freaking Haynes manual that you're using to cite the 17.5mm figure.

 

hey smuck!! no no i wasnt trying to dis you at all, but to be honest lou just spoke my language a bit better, 8O but its because of that link i understood what he was saying at all. i knew id catch crap for not thanking you :cry: so anyway after shmuck, lou and snowy's advice i got all 4 carbs to perfect float levels!! it wasnt really that bad at all. i was excited to be getting that involved in the carbs now i can go try all this out on my fzr project. carbs are installed and those damn intake boots are installed! and guess what? the bike fired right up on the first touch of the button! ill ride it tomorrow and post what happens :!:

 

i was just saying that you all keep making the comment about floats not setting on there weights becuase the adjustments will be wrong and you all prefer carbs slanted and what not.

yet cars have been using the floats on there own weight for 85 years without any slant. they aren't slanted. tipped upside down or anything.

motorcycles are the same way. so what about honda, suzuki, and kawaski. or is that specifically a yamaha rule.

if the float height spec is there. then i'll use it. just like a car. and i'll be done in 5 minutes. and the manual i have is yamaha. printed in 1984. and it says nothing about fuel height.

 

And you'll be wrong.

 

...which is why I put the "sticking out my tongue" face at the end. No worries.

Imagine what I started with.

Carbs. You can do it... we can help. Now you're an expert at it.

To be honest, when I did them up before, I did let the full weight of the floats sit on the needles, because it didn't seem like they were pressing down on the spring-loaded part at all.

Truly, I have no idea whatsoever.

Hrm. Would I be correct in guessing this is a supplemental service manual? Reason I ask is that according to your .sig, you've got a 650J (among many others); AFAIK, both it and my 750J use the same base service manual, that being for the 650G... which explicitly specifies measuring and setting the fuel level.

 

Just a follow up/chime in; I learned how to set my float heights from shmucks tutorial. What I posted is just a simplified description of what you are trying to accomplish, though not enough to take to the garage and work from.

Besides, my post will have you removing and reinstalling the carbs for each adjustment (you can't adjust a float with the carbs on); It'll add 4X the time it takes to build the stand and get an external tank hooked up.

 

yes it was a pain in the ass and i did remove it 3 times, i got lucky on one of them it was spot on the first time. yall should have seen my aux tank, it was my girlfriend holding up a funnel! haha thats what i call working with what i have! anyway i got all the measurements solid but after i got the bike running cold with full choke it was revving normally then i belive once it got hot and let off the choke it died! once i got it started back up it wouldnt rev below5 grand. oh man, and i did a generic sync with the buisness card. giving it throttle only makes it stall. once warm with the choke off it revs at 5 grand, wtf?

 

It sounds like it is time to do a complete sync on the bike and that should help with the idle.

Kenneth

 

explain to me how i would be wrong. if i use the yamaha spec of dry. but you all prefer the yamaha spec of wet. is that the same when you all said i was nuts becuase there is no way my tci would be the problem i was having with my yamaha. that i must have wiggled the rectifier wires and that's what got the bike running. yet the bike ran like crap with the old tci plugged back in. 17.5mm dry height is teh exact same spec as the 3mm fuel height. + or - 1 mm as the specs say. dry AND wet. i'll set my floats and i'll have 3mm. if all 4 are off 1mm. DOESNT MATTER, cuz specs give 1mm leeway. will the performance of the bike be effected. i didn't notice one bit of difference between 14mm and 18mm.

i've rebuilt well over 500 carbs on cars. back when i was a certified mechanic and fixing cars for a living. dry height specs as the instructions give along with the paper ruler supplied in the kits. i do my motorcycles the same way.

the 3mm wet height is a good idea. if you want to see what it's doing or if you don't have the specs. dry height works just as good. and isn't time consuming.

if the specs are available. one can never go wrong. the only floats i've replaced on bikes are brass floats. but every car i do gets a new float. and they all get adjusted with dry spec. cuz cars have no way to check for wet. nor do they have wet specs available.

if i'm wrong, then yamaha is wrong. and you've all been doing it wrong too. cuz yamaha has both dry and wet specs. just like cars come with dry specs. yamaha doesn't say IT'S THE RECOMENDED PROCEDURE. they just say it's the spec. and they give it 2 ways to do it.

i'm not knocking any procedure down. but mechanics don't spend all day doing a 5 minute job.

 

Don't know anything about your TCI, but I do know, by experience, that if you the float heights dry, no matter how carefull you are, if you then check with the clear tube & gas, 9 times out of 10 they will be off, how much small differences in fuel level make to performance I wouldn't know, I just try & get as near spec as possible.

 

No they just charge you for a full day of labor.
*SNICKER*

 

damn it i gotta buy or make a carb sync tool. can anyone help me with a parts list i need and ill go get it? i know ive heard of people using bottles but i have no clue otherwise

 

Apologize (don't know how to Hyper-Link )! Go to the XJ FAQ SUGGESTIONS board. On the first page there is a post "How to: Make 2 bottle synch tool", GREAT how to. It's what I used to make mine. I used ATF for the liquid. Bench synch carbs first and you ought to be pretty close. That way there shouldn't be wide variations...

skillet

 

skillet, dont be embarrased i have no idea how to hyperlink either! haha no very computer literate. ok ill go check it out, thanks, in your opinion whats the best method to bench sync? i used a buisness carb and felt like it was good and close but now its idleing at 5 thou. i might have torn a intake manifold putting the carbs on, ill have to check for air leaks first. thanks for the help

 

I used a paper clip. Don't think (not sure) if it makes a difference, only that they're all DAMNED close. Catch the light coming through the crack in the butterflies. Easy to tell if that way. Hopefully you didn't tear intake manifold :cry: . GOOD LUCK :wink: !!!

skillet

 

My $.02... I think snowwy66 is on to something regarding float height. I seriously doubt Yamaha checked the float heights wet, it would take to much time in a production environment not to mention, the exposure & fire hazard. I have worked in manufacturing for 29 years at 6 different companies and they all built things as efficiently as possible. Now with that, I'm not saying it's wrong to check them wet for verification after you have them set correctly dry... However, this is just a hunch, but I would suspect that the reason why some people have to go round and round with dry/wet checking is because they have sticky needles, seats or floats. Do it right the first time by cleaning all contact surfaces, set them dry and then verify wet and I'll bet the dry setting will work more often then not... When I did my carbs last winter, either I got terribly lucky by setting them dry or because I made sure all the moving pieces weren't sticking or both, I'll never know but I agree with Snowwy66 for the most part...

 

Great debate about float height vs fuel level and I think you are all correct (mostly) Snowny said he use to work on cars and when he overhauled carbs he replaced the floats, car parts are usually cheap. I don't know if he remembers but back in the late 70s early 80s one of the car carb kit companies sold a chart and a balance scale that had float weights (some plastic floats can absorb gas after extended time and become heavy) I have seen this a couple of times on older bikes, tech cleaned carbs, replaced needle and seats, set float height, was synching carbs when they started to overflow. After he rechecked everything and reset float height to a higher level it still did it replaced floats sat level to standard and problem cured, so if you are using new floats then float level is OK but old floats I would use fuel level measurement to be on safe side.

 

i read some great stuff in the faq section about needle seizing and carb syncing im gonna try next chance i get, but i got to thinking and i think one of the needle sliders is jaked up cause when i first started the bike it idled great but after touching the throttle she flew out the roof. and i did the wet and dry methods for float hight so im gonna check em again looking for that heavy float, thanks for the tips yall. i will keep everyone posted

 

I'm sure you're right, with all the components coming off the line exactly the same they wouldn't even measure them, the settings in the book are for bikes that have done some work.

 

Holley has a plug in the side to check fuel level. Wet spec is furnished for variations in the parts that Yamaha has no control of. Yamaha factory did not check wet float height they did not need to . As far as replacing floats that little hanging scale to test car floats had other uses too.

 

Waldos right on both points!!! But as far as a heavy float causing a high idle that is not going to do it. If throttle butterflies are almost closed I would sure recheck the slide diaphrams to make sure you have them in right sounds more like an air leak and I don't the spray test would show you that one.

 

Sorry about last post, last part was for guy with 5000 rpm idle not yours.

 

i was gonna comence to tearing into the carbs again but first i made sure the floats were still correct, they were so i tryed to start it again and it idled fine. but once i messed with the throttle a few times, not right away but after a few hits, the rpm shot up and so i shut it off, restarted and it idled fine. right now its idling perfectly, but i know if i go out thre and mess with its happy spot its gonna freak out again, so now what? if anything im gonna tear the carbs apart again :cry:

 

ok thanks to all you guys and this forums faq section i think ive narrowed down the problem child. after bike flips out and i shut it off, i hit the carbs with my hand and after i start it up it purrs like a 27 year old kitten, im thinking the slides are hanging up. now i need to muster the enthusiasm to take the carbs back off

 

If you don't know when the carbs were last cleaned,...
Then, ... YOU have to do them.

Carb Cleaning is Maintenance.
If, for no other reason than their AGE, ... you should clean them.
After time the Diaphragm Piston Bore requires scrubbing clean.

Cleaning the WHOLE Rack seems like a daunting task; but there are many fine articles, which Members have contributed, some with pictorials, ... to walk you through the process of Cleaning the Carbs and doing Fine Tuning afterwords.

The Carb Cleaning Job can be made less intimidating if you approach the process in a simplifying manner.

Don't so the whole Rack in one sitting.
Do one at a time.
If you do one at a time ... you have less parts to deal with.
You learn where each part goes and become familiar with the design.

By the time you do your third or forth one, ...
You know the ropes.

 

hey rick, i just got done cleaning them, in fact i was chatting with you on the other post you wrote about the slides. yeah they are clean but i didnt pay much attention to that part of the carb, i never have on any bike, but you showed me the light, and so have the rest of these fine folks

 

Rick will show you the way! I followed his advice with my 650 and what a great difference afterward.

I'll be following his advice with my XS1100 carbs this winter too.

 

Rick is right on with carb "maintenance" clean, polish, scrub, tweek whatever it takes to make the carbs like new to get your engine to run thev way its supposed to. I have found you just need to keep after them even if you have done them a few years ago. They should be pulled and maintained to keep things right.

MN

 

i've heard of the balance scale but that was way before my tenure in the profession. i do recall plastic floats but that was a rare occasion. so were the black floats. can't think of the word those things were made of but i didn't replace them much. never seen one go bad. the brass floats on the other hand. always get replaced. i've seen them go bad way to much to even consider reusing them. cars OR bikes.

back in the day when i was turning wrenches. all the carb kits came with instructions and paper rulers to adjust the floats with. along with replacement bearings and gaskets and accelerator pumps and what not.

 

its stil doin it!! i just made sure the slides for the needles were moving freely and they were, just like the post says, they go clunk! so i discovered a few things when i had it runnin. if you only rev the bike up wit 1/4 throttl it will rev back down great, but if you give it more throttle to rev it the revs will hold at 5 grand, but if i hit the carbs with my palm bike idles back down, i can do this repeatedly over and over if i want. so i doubt its jet related or anyting like that. what other than the slides and floats can i dislodge by hitting it? this is CRAZY man! i will tear back into the carbs again but i just dont know what to look for, its all good i even rechecked float hight and its great

 

Im having the same problem with mine. I was told by other users on here that it is out of synch behavior. So look into making a quick 6-8 dollar manometer. I will probably be trying to synch mine today. I will see what happens I guess.

I wouldnt say its slides. There is no way mine can be hanging up, those things are like mirrors in there! Haha.

The only thing that could probably be dislodged is floats by hitting it.

If your going to tear it off, look for someones advice on a bench synch.

 

raven, acturally sync kinda makes sence. if the throttle plates hang open i can see the idle going up. but man i have my doubts. but anyting is possible ill pull em and see if i can get the throttle plates to hang open. i appreciate the help

 

Well I can tell you I tried it today and it did not really do much. It started to idle better but any time I tried the throttle it just raced up to 5k. I took them off and Ill wait until I hear some good advice on here or something I guess.

 

sync won't cause the problem.

since you've got the carbs off. move the throttle fully upwards to see if it comes back down. which i think you've down already. not the slides but teh whole throttle.

then check the throttle cable. you say it only does at past 1/4 throttle. the cable might be frayed or kinked so it's jamming up inside the insulation.

put the carbs back on but keep the throttle cable disconnected. see what happens by using your hand to open the throttle.

 

You might have bumped the Rack in some way while they were off the Bike that has the Linkage "Out-of-alignment".

If the rpm's are elevated and you get them to "Come-down" by giving the Rack a nudge or swat, ... that might indicate a couple of things.

> One or more of the Carbs is misaligned.
> The Throttle Shaft Pivots are dry and need a few drops of lube.
(Marvel Mystery Oil applied to the Shaft Pivots)
Then, ... test the movement to see if they all shut or one keeps them all from closing.)

Set a Level in a Vice with the bubble centered-up.
Place the Rack on the Level with the Hats and Diaphragms out so that the Bodies will set on the edge of the level and see if any of them are "Way Out"

 

raven, i think snowwy is on to something, i just got my carbs off and will try a better sync, stay with it man i know how ya feel, snowy, i think you might have it my good sir me hitting the carbs might be what is freeing up the cable in the sleeve. ill post my findings

 

rick, notated il lube the pivots and get my hands on a level and let you know what i find out, thanks you

 

Hmm, well my rpms dont seem to go down, it seems to do it on its own and I dont know why.

MN-Maxims said :

Have you messed with your throttle blades at all?

 

raven, mine only do it if i touch the throttle, but only if i use more than 1/4 throttle, other than that itll idle all day. only ting i did with the blades was a bench sync, im gonna try to do the paperclip method as soon as i get some, i cant belive i couldnt find any in the house! tonight i opened up the carbs again and gave them another once over, blowing out passages and checking my floats and needle slides, all was still perfect. but did you see what rick posted about carbs being out of line? i used a ruler a min ago and mine are straight, but ill prob go get a more reliable straight edge before i put em back on the bike. also he said to lube the throttle shaft too. try all that, but im sure your throttle blades open and close fine right? also snowwy said to unhook the throttle cable and use your hand to rev the bike, that will test if its the throttle cable sticking. man this has turned into one hell of a project huh? hey have you tried hitting your carbs as the bike over revs? mine will idle right back down if i do, try that to

 

Ya I will be lubing up the linkage up before I put them on next. I dont think they are out of line now. It is possible for my throttle cable to be getting stuck though.

Ya, its being a pain having things worse before you took them off!!!

 

she runnith and she runnith good! i removed the carbs again and gave em another once over and didnt really discover anything out of the norm. so i decided to resync them. last time i did it i used a card. it wasnt very effective for me i guess cause i resynced them using the paper clip meathod listed in the FAQ and now its perfect. so i think my problem WAS a bad sync. reason i belive this to be true is while i was going through the tutorial i noticed while i had all the sync screws bottomed out the throttle would hang really bad, but when you get em synced its all good again. so i must have had one carb slightly off causing a hang up. but now im done and my "fun" with the carbs is over. next i need to remove the front end and rebuild it, already got the seals ready to install, and i got tires for it too. but alll that will go on new posts, thanks alot everyone,
oh raven, did i beat you to it?! :twisted:

 

perfect sync is using vacuum with the motor running.

 

Damn you!!!!!!!!!