Setting HSC32 float heights dry.

Don't worry about it. Its their position when bowl is full you are concerned with. I can see how they would hang differently as there is nothing to make they exactly the same.

 

Good deal Bill, thank you. I sorta thought the same but it's always nice to have a second opinion.

 

You're fuel level is likely to be too low. 11/16 (17.5mm) is the setting.

 

Good catch I saw the 13/16th pop up a while ago not sure how it got introduced. 17.5 mm works great

 

Okay now I've confused myself. I think I meant 11/16ths but had 13/16ths in my head from reading earlier. I'll double check before I close them up. Thanks guys

 

HSC-series Hitachi carbs:
Height: 17.5mm (11/16th")
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): top of float
Fuel level measured via clear-tube method: 3 +/- 1mm


Also, I note for the few float heights that are specified for MIKUNI carbs, that the point-of-reference for the float height measurement differs between different versions of the Mikuni carbs.......on some, the measurement point at the float is the lower "plateau" area of the float, and for others it is at the very "top" of the float (and by "top", I mean the top of the float WHILE YOU ARE MEASURING IT----while the carb is actually upside down!----which, in reality, is the physical "bottom" of the float).

Okay, if you're read all of the above and are not fully confused, well, it means that you just haven't been paying enough attention..........

P.S. I do NOT have any float height measurement diagrams for Mikuni carbs, as I don't yet have all of the float height measurements by carb, nor the reference points. If someone can provide those, it would surely be appreciated. The table below summarizes all of the Mikuni info that I've been able to crib together, with missing info noted by the ??


550 Mikuni carbs:
Height: 21.5 +/- 0.5mm
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): ??
Fuel level measured via clear-tube method: 2 +/- 1mm


650 Turbo Mikuni carbs:
Height: 17.5mm +/- 0.5mm
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): ??
Fuel level measured via clear-tube method: 2 +/- 1mm


XJ700-X/750-X Mikuni carbs:
Height: 17.5 +/- 1mm
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): upper "plateau" of float
Fuel level measured via clear-tube method: 3 +/- 1mm


900RK Mikuni carbs:
Height: 22.3 +/- 0.5mm
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): lower "plateau" of float
Fuel level measured via clear-tube method: 5 +/- 1mm


1100 Mikuni carbs:
Height: ??
Measurement reference point 1: carb gasket base, without the gasket in place.
Measurement reference point 2 (at float): ??
Fuel level measured via clear-tube method: 3 +/- 1mm

 

If you check the Yamaha service data (1981 and before) it has the float height for HSC32 carbs specified at 17.5mm (+/- 1/2 mm). Somewhere I got the idea that that measurement should be take perpendicular to the gasket face (gasket removed) to the highest point on the float. I've always done them this way and came out at the low end liquid level (3-4 mm).

Since you're using 3mm more, and measuring to the parting line on the float body it seems to me your fuel levels would be way low.

The Mikunis on the 550 state 21.5mm (+/- 1/2mm). I only did one 550, and it came out right at 2mm fluid level.

 

May be a newbie question but, how much difference does the 2/16ths difference make whether they are set at 11/16ths or 13/16ths? I mean I know it must matter somewhat but what effect will it have?

Just curious

 

Where are you finding this info? I've looked in (original edition) service manuals and at the TSB's for the Hitachi-equipped models and cannot find it, help!!!

 

The Fuel Jets (Hitachi) or the orifices for the Jets (Mikuni) need to remain immersed in Fuel at all times ... including when the Engine is run at Full Throttle.
Should the Float Heights be incorrect; there is a possibility that the demand for Fuel could exceed that which an incorrectly Height Adjusted Float would allow into the Fuel Bowl, causing the Fuel Level to fall below the Jets or their orifices during peak demand, resulting in a Lean condition, or worse, Fuel Starvation.

Likewise, if the Float Height allows for too much Fuel to enter the Fuel Bowls; the Fuel will seek the level of its supply source and either spill out the Carb Overflows or seep above the Gasket Surface and flow out the top of the Emulsion Tube and into the Intake Manifolds where it will continue to flow into the Cylinder Head and through any open Intake Valves, down into the Cylinders and slowly begin to collect in the Crankcase.

Draining a Sump filled with Gasoline is costly.
Having the Bike run in a Lean Condition can cost you an Engine.
Being within Specs for Float Height keeps the bike running good all day long and spares you the expense of having to drain Gas from the Sump and trying to figure-out what the hell to do with it after its drained-out!

 

Len I have seen it in the factory manual and here it is in the Haynes...

 

If you go to the online parts fiche HERE and pick an 81 or earlier model you can find float heights in the fiche called "SERVICE DATA".

 

The 17.5mm gives you 3mm fuel height below the gasket line. 21.5 would be 4mm lower, a world of difference in terms of fuel level. See Ricks reply for why that is vital...

 

Excellent explanation there Rick on the effects of different float levels.
Thanks

Bill I see you have the same year/model as my bike so you set yours at 11/16ths (17.5)?
Thanks

 

Yes then verified using the tube. Works great if you are careful. The ones I had to adjust I found were not set correctly. I was probably rushing through it. But once at 17.5 they seem to sit at 3mm below the gasket line.

 

Oh, THAT service data......

 

I think I'm right here but tell me if not. I have the carb rack and my tank off the bike. I can set my carbs level on a table with my tank slightly higher, set to PRI and run a clear hose to each nipple and hopefully all the carbs fuel level will match and be about 3mm below the gasket line. Is this correct?

 

Absolutely but make sure the rack is level side to side. Now for some more controversy. Some say tilt the carbs front to back to the angle they sit in the bike. Some say level them. I angled mine - I figure they should be adjusted as they run...

By the way 3mm +- 1mm don't be too fussy you will drive yourself nuts.

 

*lol* Okay thanks for the reminder because I can be a little "Monk"-ish with my OCD.
I agree with you on the "angle" since that's how they'll ride on my bike.
Thanks

 

The service manual specifies raising the front wheel of the motorcycle until the carburetors are level front to back.

I just measure them in normal position, at the centerline (front to back) of the bowl.

 

This thread is incredibly helpful.
I was going to throw my carbs back on after cleaning without checking the floats because I'm just not ready to mess with gas flowing through the tubes and yanking the carbs off and on to make minute adjustments.

This I can handle.
Thank you XJ forum.

 

Just pulled my bowls off and did a measurement if I am doing it correctly I am sitting at about 11mm you can see where 17mm is on the scale. This bike hasnt been run in 13 years, and I know that they havent been touched in that time, do I bend the tang that holds the seat to keep the floats at 17 where the scale is sitting? Thanks.. I can't figure out pics

Keith

http://i60.photobucket.com/albums/h30/N ... ure193.jpg
http://i60.photobucket.com/albums/h30/N ... e194-1.jpg

 

Ok here is where its gets funny. I understand and have set the last 4 sets of carbs this way and it seems to have nailed it.

Tilt the carbs so the weight of the float is not depressing the little spring loaded pin in the needle. At that angle set the float height to 17.5 mm by bending the tang on the float. In my case it has put the float height right on spec. Hope that helps

 

Well I figured out part of my issue, I replaced the seats with the carb repair kit HCP1 XP1915. If you look at attached picture the float on the right is stock seat which is at 17mm. The one on the left is replacement which has the flaot at about 11mm. So, should I just bend the tang which holds the seat to take it up to 17mm thanks

http://i60.photobucket.com/albums/h30/N ... ure196.jpg

 

Thanks MN-Maxims for your response, I was thinking that the replacement seats where just a bit different thats why it slipped my mind when I said they havent been touched in 13 years. I guesss the floats need to be adjusted when I went to these seats.

 

Ok, Since I got my own segment going here, I did a measurment with the carbs on thier side with the tang just touching the seat adjusted to 17mm. Then put the carbs on thier back and the measurement went to 13mm, I could see the seat being depressed. MN-Maxims I understand what you are saying and I am not contradicting what you are saying but what is the proper way by the manual. Your directions make sense but I am just wondering when they say to set them at 17mm in the manuals if they are taking into consideration the seat being depressed. Does this make sense?

Keith

 

The thing being depressed is not the seat, the seat is the part that screws into the carburetor body.

The little spring plunger is to protect the seat and the tip of the needle from vibration. You want to set the float height without the spring depressed at all. You did it correctly when you had the carburetors tipped just enough to close the needle but not depress the spring plunger.

 

So which is it? Do we measure to the parting line or to the bottom (which is now the top since the carbs are turned upside down)? I understand that we measure from the gasket surface without the gasket but what do we measure to?

 

http://www.youtube.com/watch?v=_CX9bN4AJvc

Here it is a good video about setting the Float height. Different set of carbs but same technique.

Carvall

 

u go to the online parts fiche HERE and pick an 81 or earlier model you can find float heights in the fiche called "SERVICE DATA".[/quote]



I couldn't find XJ 900's at the Yamaha site

 

+1 to 11/16 from mating surface to casting mark in float. 2 years ago bought new seats and valves. Could not get it right for the life of me. Gave up for awhile and after setting my floats to this spec it runs like a charm. Thank you!!!!!

 

Im super new too and dont really have a clue what Im doing love the Q tip thing, so the 17.5 mm is from the shelf with no gasket to the top of the float or the "mold line" half way between thhe black part of thr float?

 

Make a Tool.
Mechanics Pocket Ruler
Toothpick
Red Magic Marker

Badda-bing; badda-boom!

 

Thanks rick, You are the man

 

Hey rick question. On the picture on the left. The top line should not line up with the top of the bowl. Should not be higher?

 

I know this is an old thread, but if I am going to be using aftermarket float needles and seats, does the 17.5mm measurement still stand?

 

It should.

K&L Supply distributes a needle and needle/seat set manufactured by Keyster. I suspect this is what you're going to end up with in an aftermarket set.

If I correctly recall a conversation I had years ago with Chacal the needle sold for the XJ650 by K&L is longer than the stock needle. He was having fits getting a float level set. The problem won't be that the level is different but that the float tang will be cockeyed on the end of the needle giving inconsistent results.

Now it is possible K&L simply has a problem in their cross reference. I know that needle is an exact fit in another carburetor they list it for (a 750 Virago, I think). So perhaps another distributor is really selling a different needle, but I doubt it. As far as I know K&L is the only distributor handling this stuff in the U.S.

You may be able to get a long needle to function consistently by bending an S curve in the tang so it sits square against the needle. It's not something I've tried.

Be interesting to hear from Chacal on this......

 

Yes, it would be very interesting as I ordered them from Chacal....

God I hope I don't have problems setting the float heights, I've come this far with too many snags already. No more! It has been fun though!

 

viewed the u-tube video and tried to replicate the measurement. Is 17.5mm at center of float top (bottom) correct setting for 83 xj750?

I'm having heck of time setting at this distance! Way too much as I see it.

 

You set it to whatever gives you the correct fuel level measurement. If it's 17.5mm, then great. If not, then set it to whatever DOES give you what you're looking for.

 

Just trying to get the dry setting close so that wet - set is at least close. Have not started the wet-set yet. As I recall the XJ 650 and XJ 750 float bowls are identical so either they are identical or the xj 650 data is all I have to work with.

 

anyone still watching this thread? Im replacing needles an the aftermarket is 1mm longer than stock, does this make my float height +1 or -1?? why is this so confusing. it seems like its double upside down lol

 

The "dry set" is only meant to get you close.
Here's what I did, I did the dry set at 17mm, then did a wet set on one carb bowl. Once I got that first bowl zero'd in I just copied the other three to it...did the wet set again...tweaked the ones that needed tweaking, and rechecked on the wet set...
Finally, when you do the wet set, fill and drain, and refill each bowl a couple of times before you take your measurements...it'll be more accurate....let's the valves actually get seated.
Good luck

 

Hey guys, newbie here, thanks for all the great info. Bill, looking at your photos, it says you're at 22m on your ruler, but aren't we supposed to have them set at 17.5? I'm in the process of doing this myself and just want to make sure

 

Chopper, make sure you are adjust to the correct measurement for the correct carbs for the correct bike.
What bike are you doing?
If you prefer, send me a private conversation, and I'll talk you through it. Also, I'm only a few hours east of you.........

Dave F

 

I'm working on a 1981 XJ650, trying to find out the correct float height measurement so I can adjust before putting the carb bowls back on. Also, I'm unsure if I should bench synchronize the carbs, or if I should just try them as they are and see if they're already synced by previous owner? What do you think?

 

Chopper,

The dry setting is indeed 17.5mm for your initial setting.

Yes, you should bench sync. That way you KNOW where they are starting at. If you're not sure how to do that, I can talk you through it.

Send me a private conversation with your phone number, and I'll give you a call. I'll have a lot of free time for a few days to be able to talk.

Dave Fox

 

Thanks for replying so quickly dave. I know how to bench synch, and I guess I will most likely end up bench synching them, but First I'm going to try them the way they are, and maybe they're already synched correctly to the bike (wishful thinking), if not, I'll pull the carbs back out and bench synch them. I'm in the process of trying to remove the brass caps so I can clean the fuel mixture screws, trying to pry them up with a razor blade but so far not having any luck. Any tips on that?

 

Carefully drill a small hole in the top, remembering that it's only about 1/10" in thick or so, and the screw is juuuust underneath.

Use increasingly larger bits, going slowly as you want the get the bit to 'grab' the brass. On

Once it 'grabs', use the bit to 'turn and pull' the plug up and out. Don't leverage it sideways, as the pressure can damage the aluminum

 

New problem: trying to install new brake pads on the front last night...I depressed the piston all the way open with a C clamp, put new pads on, but now I can't get the mouting bolt for he caliper to line up, because the pads are too thick. I also noticed the slant on these pads run opposite of the slant on the old pads, does that matter? What should I do, grind these pads down a bit? The mounting bolt is missing the hole by almost 1/4 inch