Float height and other adjustments

[arm]

Hey guys, finally I got my shiny new parts for my carbs

I'm curious as to how high to set the float heights, in the last image the black line on the paper is 26mm without the gasket.

I saw in this video that I need to tilt the carbs till the floats are sitting in the needle then measure then adjust, any tips on how to get the right height and what method to use?

Also for the big idle screw and the small brass screws with springs underthem on each carb, how much should those be set to? I think my bike ran a bit rich cause it smelt very strongly of gas, any ideas on how to diagnose rich vs lean and what to adjust? Thanks!

 

[kebabs]

hi did u get your carbs fixed

 

[arm]

hi did u get your carbs fixed

Hi yeah,

I put in the new floats and adjusted the tang to be 26mm from the top of the float to area where the gasket sits.

I found a mixture of information, some people said 32mm some people on here said 26mm so I stuck with 26mm and hoped to god I wouldn't have to take off my carbs again.

I used this video

around 37 mins in he'll get adjusting the tang and such.

So yeah, luckily enough my float bowls don't overflow with gas anymore and all is well as far as it comes to fuel

 

[kebabs]

Hi yeah,

I put in the new floats and adjusted the tang to be 26mm from the top of the float to area where the gasket sits.

I found a mixture of information, some people said 32mm some people on here said 26mm so I stuck with 26mm and hoped to god I wouldn't have to take off my carbs again.

I used this video

around 37 mins in he'll get adjusting the tang and such.

So yeah, luckily enough my float bowls don't overflow with gas anymore and all is well as far as it comes to fuel

thats not so bad.good video. I set mine at 26mm didn't work for me.fuel flowing out the filters I set them at 32mm ,all is good now.used a gauge similar to the video.
I wish I had a dollar for every Time the carbs have been off.I could strip and rebuild with my eyes closed now

 

[kebabs]

I think it's important to that you have the float needle opening and shutting at the correct times.

 

[arm]

thats not so bad.good video. I set mine at 26mm didn't work for me.fuel flowing out the filters I set them at 32mm ,all is good now.used a gauge similar to the video.
I wish I had a dollar for every Time the carbs have been off.I could strip and rebuild with my eyes closed now

ah, interesting, In one of my posts (that's insanely long at this point) a user suggested 26mm and so far this forum has been correct about everything and yup, I no longer have fuel flowing out of my air boxes either.

And yes your right, the float height is important since its job is to push up and close the needle when the bowls are full of fuel.

If I had a dollar for each time I took of my carbs id have about $3

 

[GuyS]

I’m not getting why 32mm and 26mm? They’re BS34’s so things should be one or the other (either 26mm OR 32mm). Making sure the needle and tang are just touching (as the Rocky video describes,…. means that’s the basis of measurement), there’s a center of gravity determined by the exact time the floats moves the pin.

 

[avemachina]

The 32 vs 26mm is because the measurements are different depending on whether you have brass floats or rubber floats. 26 is for brass. The rubber ones have an odd swoopy shape to them, so the volume it occupies in the space of the float bowl is a little different.

 

[kebabs]

The 32 vs 26mm is because the measurements are different depending on whether you have brass floats or rubber floats. 26 is for brass. The rubber ones have an odd swoopy shape to them, so the volume it occupies in the space of the float bowl is a little different.

mine are brass .26mm didn't work for me fuel over flowing into the cylinder and air filter..32 was good

 

[GuyS]

Is it possible that where and how you measure” is the difference? I’m just about ready to disassemble my BS34’s The video link above where it says “video” in Arms first post, suggests measuring at the point the needle and tab start to interact. Other’s had the carbs laying flat on a table.

I have never adjusted a carb float before so it seems confusing. Maybe its not when you actually do it!

 

[kebabs]

I found it best to measure with the carbs flat on the table with gasket off.for me the most important thing is having the needle opening and closing at the correct intervals. with carbs in there natural position floats hanging the needle only needs to be out its housing a couple of mm.if the needle is out to far to much fuel will enter the float bowl and the needle wont shut off.its like a toilet cistern. to achieve this bend the tang that the needle rests on.hope this helps.

 

[kebabs]

set your float level first then adjust tang if needed

 

[GuyS]

Great thanks. I’ve now disassembled the carbs…ugh do they ever need cleaning! I found the float needle on the right carb doesn’t move. The other one does. They’re going in the ultrasonic tomorrow.

 

[GuyS]

Would anyone have the O ring size for the connector?

 

[kebabs]

Would anyone have the O ring size for the connector?

looks like 8mm.whats that off

 

[GuyS]

It’s the fuel connector between 2 Mikuni BS34 carbs off of my 1982 XS400J Maxium 15G. The OD of the aluminum tube is 9mm. I have some MIL spec fuel O rings of various sizes so just wanted to make sure I am replacing the old with similar if not exact. If you look at my disassembly picture above, you can just see the connector at the top left of the righthand carburetor. It’s what transfer full to the other carburetor.

 

[kebabs]

It’s the fuel connector between 2 Mikuni BS34 carbs off of my 1982 XS400J Maxium 15G. The OD of the aluminum tube is 9mm. I have some MIL spec fuel O rings of various sizes so just wanted to make sure I am replacing the old with similar if not exact.

pull um off and check

 

[kebabs]

hi.did you get your carbs bk together

 

[GuyS]

Yes mostly back together. I bought a carb kit from Mike XS. It provided new float needles, main jets, pilot jets and carb gaskets. When I took the jets out I discovered a #120 on the right side and a #127.5 on the left. From what I read the XS400J (maxim) stock should be 115 and 125. That was 2 of the options in the rebuild kit from Mike XS, so I changed them to stock. The float needles did not have a little basket on the end like the old ones but do have a screen at the bottom. I tried to put the old baskets on the bottom of the new float needles but they did not seem to want to go on. The new float needles do have a small screen on the bottom so I figured that was a replacement for the “baskets”. Now I have encountered a problem. The floats are WAY, WAY off. Apparently 28mm is the measurement (from the carb without the gasket to the top of the float. My floats measure 24mm. I am surprised they are so far off. And the tab is already bent down I’d have to bend it even further. Since this is my first time rebuilding things like this are “red flags” to me. I’ve read the original tabs were almost level with their metal bracket.

Mar 17. Note that I have discovered the XS400 J main jets should infact be 127.5 and 117.5. Not the 125 and 115 I suggested in the post above.

 

[GuyS]

pull um off and check

I’m a little nervous of pulling them off. They seem to be quite brittle. And I’m concerned they may be some kind of none available odd ball! There’s two each side so some redundancy for sealing. I don’t think it’s leaked “YET”.