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