Topic: carb post fix, and other carb questions

[bcbillings]

I have a 1981 CB650c so you know what bike i am talking about.

the previous owner paid a lot of $$ to have someone replace almost everything on these carbs and in the process the guy snapped off his float post. it makes this bike dump gas on me like its free... but the weird thing is it comes out of either 2 or all 4 at the same time ... not just the one pictured. in an effort to make a temp repair i drilled  a whole and used aluminum wire to make a stay for the float rod. even with that the bike still floods out like mad.



any idea if it its still just this carb that is the issue or if its something else? I know my petcock leaks some but its not enough to account for all the fuel that dumps out of the carbs when the bike runs.

I have a set of 1982  carbs that i will have to take all the way apart and swap most of the parts from the 81 carbs over ( i have a new set of screw in slow jets as well) should i just replace the one broken body in the 1981 rack with the corrisponding body from the 1982 rack or swap everything over to the 1982 rack? or do you think that fix is good enough for the float bowl and i should be doing something else to stem the flow of fuel out of every hole these carbs have?

[bcbillings]

I am at a crossroads where I either rebuild the 82's with the 81's parts, or replace the one 81 carb with the corresponding 82 carb body, or if you have some ideas outside the broken carb or a setting to adjust to stem the fuel please let me know so I can decide what way to head

[Stev-o]

Call Jim....

http://www.jmfmicroweld.com/

770-367-7320

[bcbillings]

I have talked to him, but i have no money at all to put into this. I have to make it work with what i have!  Jim's prices are great i just cant do it.

thanks for the imput!

[scottly]

Billings, your repair looks to be functional, and since the other carbs are also overflowing, I doubt that is the problem. Look at your float needles and seats. Loose seats and/or damaged/dirty needles can cause flooding. Pay close attention to the tiny spring-loaded plunger in the needle (if your carbs have them), as I've seen weak springs that caused flooding.

[bcbillings]

I think i have 4 brand new spare ones, i will swap them out. but like i said it appears a vast majority of the peaces that could have been replaced on the broken set had been, could it be possible they installed the wrong seats?

[scottly]

Who knows what was done. Just saying, I've seen seats that weren't firmly screwed in, float needles with weak springs, and crud from the gas tank all causing similar symptoms. You get to play Sherlock Holmes and try to figure out why your floats aren't controlling the fuel level in the float bowls properly.

[tomkimberly]

Have you cleaned the float valve seats? Use a mild polishing compound and Q-tips.


Tom

[phil71]

those particular carbs are a nightmare for this. First, see if the needle plugs the hole with no float attached, or if it seeps around it. If it does, the needle is shot, or there's debris in the seat.
   If it's dry, then the float is warped. There is an adjustable rubber/steel float for that carb body that was on the CM450 nighthawks I think, and they fit and work so much better than that #$%*ty plastic one. After 30 years they sometimes get out of shape and sag, and therefore don't close the valve all the way.

[bcbillings]

those particular carbs are a nightmare for this. First, see if the needle plugs the hole with no float attached, or if it seeps around it. If it does, the needle is shot, or there's debris in the seat.
   If it's dry, then the float is warped. There is an adjustable rubber/steel float for that carb body that was on the CM450 nighthawks I think, and they fit and work so much better than that #$%*ty plastic one. After 30 years they sometimes get out of shape and sag, and therefore don't close the valve all the way.

can you or anyone else say for certain if the the CM450 nighthawk floats would work? i dont want to try to find some if they are not the correct ones! i will do some research and see what i can find as well. I know the needles are fine as they are all brand new, However it never hurts to check.

thank you for the input!

[phil71]

you don't say if you tried keeping the hole plugged with the needle and your finger without the float. if it seeps , you have to do some lapping on the seat

[phil71]

this is the guy> http://www.ebay.com/itm/78-83-CB400-CX500-CB750-CM400-CBX-GL1100-CARBURETOR-FLOAT-SET-79-80-81-82-81-82-/390495039043?pt=Motorcycles_Parts_Accessories&hash=item5aeb516e43&vxp=mtr

the part doesn't cross reference to your bike, but it fits fine, and works better than the original

[chewbacca5000]

this is the guy> http://www.ebay.com/itm/78-83-CB400-CX500-CB750-CM400-CBX-GL1100-CARBURETOR-FLOAT-SET-79-80-81-82-81-82-/390495039043?pt=Motorcycles_Parts_Accessories&hash=item5aeb516e43&vxp=mtr

the part doesn't cross reference to your bike, but it fits fine, and works better than the original

+1 The non adjustable floats are the pits.  Also weak float needle springs could be to blame, but if you can ajust maybe you have a chance.  These are powerful carbs when they are properly tuned.  Also a PITA.

[bcbillings]

Im extremely busy because of my job and have not been able to do anything at all with them yet, i was told that toothpaste with baking soda would work the same as polishing compound. I have not the slightest idea where to find the real stuff, but i do have toothpaste lol

[K3Owner]

I haven't seen 650 carbs but expect the seat is brass like the rest. I use brass polish like Brasso on a q-tip. Make sure then that the needle is clean and does not stick when applied to the seat. Check the needle pin for wear. This reminds me of my KZ650 carbs. They never failed to dump on a ride.