Floats

Can someone give me a good starting point on how to set up the floats while the carbs are apart before i re assemble them, when there upside down and i lift the floats the needles do not move but if i turn them right side up they function properly and i do not know if this is how they work or the settings are way off, do i need to rebend the tabs to a certain degree or inch or whatever, they are NEW needles and seats and i have not changed a thing on the floats since factory, i do not know if the new seats and needles are exactly the same as the old ones, looking with the naked eye they look the same but i am no expert and that is why iam here asking for advice and your know how.

 

You to do a wet adjustment. All you need to do is set the carbs up in a vice of some sort, make sure it is level, and run a clear tube from the float bowl drain. Hold it against the side of the carb and check the fuel level where it stops.

 

Only issue, One bowl has a frozen drain screw, the rest are all new.

 

There is no way to get accurate results without doing that. I had one frozen on mine, what you can do is try an assortment of things to try to free it up, let some carb cleaner soak in it, WD40 etc. After that, make sure you have the CORRECT flat blade for it. The best way to get it out is one of those impact screw drivers, you can set it on there, hit the back end of it with a hammer and it unlocks that thing like magic.

My attachment for mine did not work, so I held on to the float bowl while my father used a screw driver that he could put a wrench on. While pushing hard against the float bowl, he turned with the wrench and we were able to get it off with stripping it or damaging anything. I suppose you could do the same with a vice, maybe not. But an impact driver is a very worthy investment

http://www.harborfreight.com/7-piece-re ... 93481.html

 

An example of the clear tube method...

 

Heat works wonders on stuck drain screws. The float bowl is mostly aluminum and will expand more than the steel screw. I screw the float bowl to a block of wood, mount the block in a vice, then heat the area around the drain screw with a propane torch.

The float needles drop by gravity - they will not levitate out of the seat with the carburetors when inverted.

You can get an approximate dry setting on the floats, but you then need to use the clear tube method to check/dial them in.

You partially invert the carburetor so the float valve is closed but the weight of the float does not depress the plunger in the float needle. The bottom of the float (farthest from the carburetor body) should be 21.5 mm (+/- 0.5mm) from the float bowl gasket surface.

Similar to this picture where #1 is 21.5mm.

 

You just use a different bowl if one of the screws is fighting you. :wink:

 

carbs upside down. the weight of the float entirely on the needle. 17mm dry height. that will get you started. then check your fuel height.

the needles won't rise because you have a gap in that little pin that connects to the needle and wraps around the float tang.

 

He has a 550 with Mikuni carbs. The dry height is 21.5 mm. The 17.5 number is for the Hitachi HSC32 used on the 650s and 750s.

 

Carl's advice is spot on.

And while you CAN just move a good float bowl over to adjust the carb with the stuck screw, it's a much better solution to get the screw unstuck.

Being able to reach in with a long screwdriver and open all 4 drains while the carbs are on the bike is a maintenance PLUS. Best to fix it now, while the carbs are off the bike. Carl's method works great and you won't tear up the bowl in the process. Just go easy with the heat, it doesn't take much...

 

Ok so i have the carbs apart, I got a MM ruler, when the carbs are upside down and i measure i do not know where to measure accurartly because the floats are on a angle, where would be the best spot to get the measurement from ?

 

You might just as well use the clear tube method in the first place, cos you wind up doing it that way in the end.

 

You measure perpendicular to the float bowl mating surface. It's been awhile since I worked on 550 carbs, but I thought the floats were round? If they're round measure to the point farthest from the mating surface. If they're not round you'll have to wait for bigfitz to weigh in.

You also want to measure both floats and make sure they are the same height - yours wouldn't be the first carburetors where a PO had twisted the wishbone.

You said "upside down". If the weight of the floats start to depress the plunger your measurement will be off. It's a good idea to angle them like the picture I linked earlier.

 

the weight of the floats doesn''t depress the needle. it sits on the needle as the needle sits in the hole of the seat. the float is a floatation device. not a weight heavy device.

if you don't have the full weight of the float on the needle then your not getting an accurate measurement. putting the carb at an angle isn't putting the full weight of the float on the needle.

gas pours in and lifts the float untill the needle closes the hole. the carbs don't run on the bike at an angle. and gas don't act as a pressure device to push the float into the needle

measurement is taken at the base of the carb where the bowl sits on. to the top of the float.

i've rebuilt 100's of car carburetors when they existed. i adjust the floats the same way regardless of car or motorcycle. there are no special tricks between the two.

 

Well thanks for the tips, yeah these needles have a spring loaded pin on the backside so the weight of the floats really dont even move them, ill measure from the furthest point just to get it in the ballpark and get her running again, i killed my started lol.

 

While the floats are not "heavy" they can have enough weight to depress the spring plunger in the float needle. When that happens the measurement will be wrong. You need enough weight to close the needle - that's all.

They don't always depress the plunger, but it happens often enough that it can be a problem.

BTW, it's been a very long time since I've done an automobile carburetor but I don't recall them having the spring plunger motorcycle float needles generally have.

 

i don't recall motorcycles having spring plungers either. never seen em on any of my bikes.

regardless. if the weight is pressing the spring loaded plunger then the spring itself is no good. or some other problem that is preventing an accurate adjustment.

if things aren't working when the carb is empty. they won't work when the carb is full either.

 

Th float needles in mine have th spring, as did th original needles...I presume it's purpose is a bit like a shock absorber to even out th bumps. Otherwise with all th floats jiggling about as you ride th needle would be forever opening and closing but not because th fuel level was low.
...and as often said before setting dry is for starters, finish with fuel.

 

THIS is the most important thing to learn from this whole discussion. The "mechanical" difference between in and out of spec is so minimal as to be invisible; you have to let the fluid indicate the functional shut-off point, not the "measured" one.

 

ahh

 

it would seem to me though. that yamaha already did that favor for you. THUS the reason they give you the dry height spec in teh first place.

i don't they they'd just list any ole number and make you figure it out from there.

you all argue that the wet height is the ONLY way. and it's the yamaha way. you all ague that the dry height IS NOT the way. but yet it's listed by yamaha. becuase they already did the legwork and research for you.

so on one hand. you agree and go with the yamaha way.
on the other hand. you all argue with the yamaha way.

i've never heard of wet height untill i found this websight. and i've done a LOT of carbs.

i've found over that years that on motorcycles. it takes 4mm below spec for the float to run rich. 5mm and the carb floods out.

it takes 2-3mm above spec to not allow enough gas inside to run.

 

Hear ye, hear ye! Read all about it!

http://mok.fileave.com/setting%20fuel%20levels.pdf


Might wish to take special note of the following:

Also, the fuel level needs to be thought of as a "tuning parameter", in the same way as you would think about jet sizes, main needle sizes, vac piston performance, and pilot mixture screw settings. And you should "think" of them in that manner because that's how the designers (engineers) of carb systems think about them, and then specify the proper fuel levels for a particular set of carbs on a particular model bike. Please note from the above referenced file, on Page 10, the "cheat sheet" which references the proper fuel levels by carb and bike.

Careful study will reveal that the same "type" or "series" of carbs, when used on different bikes, require different fuel level settings.

In the detective biz, such information is what would be properly called "a clue"............

 

are you sure its 21.5 MM, thats over 10 inches. unless i am looking at my ruler wrong.

 

This is a Photo Of my Float Level.

 

you're looking at your ruler wrong, thats about 3/4".
you guys never learn, set the floats wet, using fuel & clear tube.

 

Iam still confused, Must be my A.D.D

 

Here it is again:

 

that looks like 23mm to me. your getting close!