Honda Twins banner

1 - 19 of 19 Posts

Registered
Joined
147 Posts
Discussion Starter #1
Well my cb350 k3 has been running great for the last 10 months after carbs were refreshed. About 2 weeks ago I pulled into the garage after a 60 mile ride and there was gas coming from the left carb overflow tube. It stopped of course once I turned the petcock off which i always do when turning off the bike. So I finally pulled the carb off last week (3D carbs) and the float itself was full of gas due to a hole. I replaced with a new OEM Honda float, set the height of float to 26mm, and reinstalled. Gas continued to pour out. 馃槨 Carb off again replace float seat and float needle, reset float height 26mm......but this time i hooked up my little auxiliary tank and checked on my workbench as it is a real pain to put everything back on the bike. It continued to leak unchanged!!! 馃槨馃が馃が. Carb apart again...checked brass overflow tube in the bowl to be sure the brass tube was ok and no leak so it is fine. I closed the float needle and no air will pass thru when closed...so it is closing. I then thought if I set the float height higher it may stop the overflow. So I set it to 28mm.put everything back together and tested.......still leaking!!!!!!!........ Reset float height again to 29.5 mm thinking it should close the needle but still leaking !!!!!! FOUR STRIKES...I'm out . What am I missing????

Any help would be great for my blood pressure and help stop the cursing under my breath.

Thanks
 

Registered
Joined
4,456 Posts
open up the carb bowl and inspect the overflow tube. If this is cracked it would allow fuel to leak into the overflow.
Can be repaired by soldering.

Edit - Nevermind I didn't read the part where you said you checked the overflow tube already.
 

Registered
Joined
4,456 Posts
Run me through the steps you took to set your float height

There are only 2 possible ways for fuel to leak from the overflow, either float height is wrong or overflow tube is cracked or broken.
 

Registered
Joined
751 Posts
Is it possible that the float is sticking or hanging up on something? You{ve got an o-ring style seal for the float bowl, so iit's not a swollen gasket, but have you looked at how the tang on the float interacts with the valve? Or could something else be impeding the float's motion? Gunk on the float pin?
 
  • Like
Reactions: jkv45

Registered
Joined
147 Posts
Discussion Starter #5
76Twin thanks for the reply. Your statement about the ways it can leak we my thoughts also but i worried that the float seat or needle could be leaking but it closes air tight.
To check the brass tube in the bowl I filled the bowl right up to, but just shy of the hole on the tube it's self and no leak.... so I think its ok. To set the float height i used calipers measuring from the the edge of the carb body(where the gasket sits) to the top of the float with the tang just touching the float needle. Am i thinking of this backwards....that is the higher the float height is set the less fuel should be in the bowl and the lower the float height the more fuel in the bowl.


Thanks
 

Registered
Joined
147 Posts
Discussion Starter #6
Is it possible that the float is sticking or hanging up on something? You{ve got an o-ring style seal for the float bowl, so iit's not a swollen gasket, but have you looked at how the tang on the float interacts with the valve? Or could something else be impeding the float's motion? Gunk on the float pin?
Carnivorous,

I do not think the float its self is impeded. It moves freely and once i put everything back together if i gently move the carb up and down before putting fuel in I can hear the float freely move in the carb bowl. The float seat is clean and new so no gunk or debris i can find and the float needle spring seems to move fine. I guess the tang is interacting as it should with the needle itself . Is there something specific i should look for??? Thanks
 

Registered
Joined
4,456 Posts
did you set the carbs on their sides while you checked/adjusted the float heights? the float tab should just touch the needle and not pressing into it.
 

Registered
Joined
147 Posts
Discussion Starter #8
did you set the carbs on their sides while you checked/adjusted the float heights? the float tab should just touch the needle and not pressing into it.
Yes tilted to where the tang just touched. One thing I noticed was the original float needle spring was a little 鈥渟ofter鈥 than a replacement one I had on hand. So I even changed between the two of them and it made no difference. They both allowed leaking. I鈥檓 wondering if I some how missed a leak in the brass overflow tube in the bowl? I checked it with water not gas. Then dried it well with compressed air. Maybe I should check it again. I guess I could duct tape the small hole in the brass and fill the bowl and gently blow air up into the brass tube thru the distal end of the brass to look for bubbles?
 

Registered
Joined
751 Posts
Carnivorous,

I do not think the float its self is impeded. It moves freely and once i put everything back together if i gently move the carb up and down before putting fuel in I can hear the float freely move in the carb bowl. The float seat is clean and new so no gunk or debris i can find and the float needle spring seems to move fine. I guess the tang is interacting as it should with the needle itself . Is there something specific i should look for??? Thanks
sometimes a small groove gets worn into the tang of the float. But since you replaced yours with new that doesn't make sense. But sometimes this can cause the float to stick. But corrosion or gunk on the pin or towers can also impede movement. IF you've checked it, you've checked it. Sounds like verifying the overflow tube might be the next step. Assuming you've tried having fuel flow with the float bowl off, and have lifted the float to make srue fuel stops?
 

Registered
Joined
147 Posts
Discussion Starter #10
sometimes a small groove gets worn into the tang of the float. But since you replaced yours with new that doesn't make sense. But sometimes this can cause the float to stick. But corrosion or gunk on the pin or towers can also impede movement. IF you've checked it, you've checked it. Sounds like verifying the overflow tube might be the next step. Assuming you've tried having fuel flow with the float bowl off, and have lifted the float to make srue fuel stops?
I have not checked stopping fuel flow with bowl off but will do that!! Thanks
 

Premium Member
Joined
24,208 Posts
Water has heavier viscosity than gasoline and won't flow thru a crack. The pipes also crack at the very base going into the bowl. Filling the bowl, capping the top of the stand pipe with your finger and blowing into the drain fitting should show any leak.
 

Registered
Joined
147 Posts
Discussion Starter #12
Thanks all for your help! Turns out it was the brass drain tiny hole about 2-3 mm up from the base! Filled with water gently blew up the distal end of the drain and air bubbles identified the small hole. I couldn鈥檛 even see it with magnifier!
308385
 

Registered
Joined
751 Posts
Always good when there's a happy ending.
 
  • Like
Reactions: ancientdad

Registered
Joined
4,456 Posts
Like I said there are only 2 possibilities for the leak from the overflow.
Good job.
 

Registered
Joined
7 Posts
76Twin thanks for the reply. Your statement about the ways it can leak we my thoughts also but i worried that the float seat or needle could be leaking but it closes air tight.
To check the brass tube in the bowl I filled the bowl right up to, but just shy of the hole on the tube it's self and no leak.... so I think its ok. To set the float height i used calipers measuring from the the edge of the carb body(where the gasket sits) to the top of the float with the tang just touching the float needle. Am i thinking of this backwards....that is the higher the float height is set the less fuel should be in the bowl and the lower the float height the more fuel in the bowl.


Thanks
Check Common-Motor.com on uTube
 
1 - 19 of 19 Posts
Top