Carb rebuild sucks

[seestheday]

You should be able to pinpoint the leaks by just filling the carbs up with fuel.  If you can fill them up and they don't leak, then you don't have a leaking problem.  If your carbs are working properly the floats should lift up and stop more fuel from coming into the carbs through the nipple.  If your floats are sticking, then you'll leak through the overflow tubes.

If you blow air in then I think you'll just force the fuel in the bowls somewhere.  If the jets are clean then the fuel would probably be pushed through them.  Normally fuel is sucked through the jets due to the lower air pressure caused by the vacuum in the throats of the carbs.  By creating an increase in air pressure in the bowls, the fuel would move to the lower air pressure area (outside of the carbs) via the easiest path (probably through the jets).

[clyde the ape]

I did not use a compressor, I did it (yuck).  I was barely using any pressure.  I have a test bottle I tried, I hung it on the handle bars & the line drooped down & I connected it to the fuel line that came from the tank.  Once I opened the valve on the tank fuel would just flow.  I will try to set it up again & see if I can pinpoint the start of the leak.

[seestheday]

If its coming out the overflow tubes at all then its stuck float valves.

Do you have tubes hooked up to the nipples on the bottom of the carbs? That is where the overflow tubes should connect to.

Sent from my BlackBerry device on the Rogers Wireless Network

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From: "clyde the ape [via Honda CB750'S]" <[hidden email]>

Date: Thu, 31 May 2012 11:08:30 -0700 (PDT)

To: seestheday<[hidden email]>

Subject: Re: Carb rebuild sucks

I did not use a compressor, I did it (yuck).  I was barely using any pressure.  I have a test bottle I tried, I hung it on the handle bars & the line drooped down & I connected it to the fuel line that came from the tank.  Once I opened the valve on the tank fuel would just flow.  I will try to set it up again & see if I can pinpoint the start of the leak.

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NAML

[clyde the ape]

There is nothing on the nipples on the bottom of the carbs.  Part of the reason why it was so hard to tell exactly what was leaking.

[clyde the ape]

OK have an intermittent leak from #2 overflow.  Also when I move the bike around I get a few drips from the overflow tubes, is this normal??

[clyde the ape]

Well tore into the carbs this afternoon.  Found a new accelerator pump, all the other parts including all gaskets look old.  Mismatched parts, it's a shame.  Looks like I will be rebuilding some carbs this weekend. Lol

[seestheday]

Old doesn't necessarily mean bad. I'm pretty sure my gaskets are original (31 years old) and they don't leak.

Or did you pay for a full rebuild? If so, that really sucks.

Sent from my BlackBerry device on the Rogers Wireless Network

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From: "Clyde the ape [via Honda CB750'S]" <[hidden email]>

Date: Thu, 31 May 2012 17:21:44 -0700 (PDT)

To: seestheday<[hidden email]>

Subject: Re: Carb rebuild sucks

Well tore into the carbs this afternoon.  Found a new accelerator pump, all the other parts including all gaskets look old.  Mismatched parts, it's a shame.  Looks like I will be rebuilding some carbs this weekend. Lol

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NAML

[clyde the ape]

OK got my carbs apart on the bench.  Want to check my float height, but I am finding two different ways.  What is the correct way to check float height??

I found another thread on here about floats on a 1981 cb750 not being adjustable, is the tan float one of those non adjustable ones??
Here is the thread:: http://honda-cb750-s.456789.n3.nabble.com/82-750k-carb-float-adjustment-td3984087.html

Here's a link to a pic of my carbs ::  http://s1151.photobucket.com/albums/o627/cb750carmine/?action=view¤t=carbs.jpg

[shultz_1978]

Looking at the picture of your carbs. I think the orange float is aftermarket and not adjustable as it is a plastic. The other three look original and are adjustable by bending the steel tabe that the float needle rides on.

The best way to adjust them is to put the tabe were you think it should be. Put the carbs back together and hang them level and put gas through them and look for leaks. Before you put them back on the bike.

Try hanging them close to the bike so you can hook up the fuel line from your tank the us the shot off valve on the bike. Remember to hang them a little lower then the tank.

Best of luck

 

[shinyribs]

I think the orange float may just be coated with rust residue I hold my carbs up side don and adjust the tab til the floats sit level without pushing in the inner spring on the needle itself. But that is just my way.Others work as well.

[robs750]

Looks like the float on the left side of pic is non adjustable and the other three are adjustable.My sons '82 K has the same brown plastic floats.The non adjustable are all plastic.The adjustable's will have a metal tab that can be bent to adjust the float level.

I believe the non adjustable brown plastic floats use a different float needle and seat,not the same as the adjustable's.

I checked mine the same way Shinyribs did.......... to check the float height,the carbs are turned upside down level.Then the measurement(.610")is from the base of the fuel bowl to the top of the float.

Someone changed out the float for some reason!

[robs750]

Here is a link that might help.....http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revE.pdf

There is a good pic of a non-adjustable float in there.

[clyde the ape]

Robs your right that is the one float, & yes the needle is different.    Would it be easier to just change all the carbs to the non adjustable style floats??    I tried adjusting the floats upside down, the needle sems to be worn.  If I move the float it doesn't spring back up to the same height.

[robs750]

If it was mine,I would look for one more adjustable float.I think the non adjustables are worthless.You will aslo need the correct float needles for the corrisponding floats.I think the '79 carbs came with the adjustable floats.

The float needles(at least on the non adjustables)have a little spring loaded plunger on the end.If yours have this ,make sure the plungers move up and down freely.Take a look closely at the float needle tips with a magnifying glass.The rubber tapers should not have any worn grooves and should be pliable.

Turn the carbs upside down.The floats should rest againist the float needles on their own weight.The float height be about .610".Almost level.

When I rebuilt my sons '82K carbs,he had bought two different carb kits.I did notice a difference with the float needles.The first set of needles I used,the float hieght was way below the .610" spec.Then I tried the other kit and the float height was pretty close to the spec.So there is a difference with needles.

[clyde the ape]

If I place the floats on the little spring they sit at one height.  If I moved the float up & down depressing that spring, the float comes to rest at a different height.  They sit lower once the spring is moved.  Shouldn't they spring back to the same height??  

[robs750]

Yes,the plungers should raise back up.
You dont want to push too hard,this may cause the needle tips to get wedged into the needle seat and damage the needle tips!You only want to press lightly to see if the plungers work.

The floats should raise back up after pressing LIGHTLY.The plungers only move about 1/16".

[clyde the ape]

What are you using to measure the floats with??

[Lucky 1]

There is a small O ring on the top edge of float bowl #2.
If that O ring is left off it will leak.
That hole feeds the fuel circuit for the accelerator ump nozzles.

[robs750]

I used a 6" scale to measure the height.

[clyde the ape]

Lucky, I think that o-ring is there.  I will have to double check