Mikuni drain hose wet but not dripping

pcspecialist · 07-28-2016, 07:48 PM

I never paid any attention to drain hoses in the past, is it normal for them to be wet with fuel but no noticeable dripping. I opened up the drain screw some and held the end of the hose up to see where the fuel level in the carb is and it appears to be almost level with the top of the bowl.

w0ss · 07-28-2016, 09:25 PM

funny you mention that, I saw the same on mine and just assumed it was normal. I never see it leaking but almost looks like it's weeping or something.

pcspecialist · 07-28-2016, 09:50 PM

I wonder if it is just fumes condensing? If a few more say they experience the same thing, it's a safe bet that's exactly what's happening.

Ariel Red Hunter · 07-30-2016, 01:33 PM

Quote:

Originally Posted by pcspecialist

I never paid any attention to drain hoses in the past, is it normal for them to be wet with fuel but no noticeable dripping. I opened up the drain screw some and held the end of the hose up to see where the fuel level in the carb is and it appears to be almost level with the top of the bowl.

Yes it is normal. When the bike goes over a bump, the float tends to flutter, letting in too much fuel. The fuel bowl is small, so as to prevent sloshing. A bigger float bowl would obviate the need for an overflow drain, but experience has shown that losing a little fuel from the over flow is better than having a large amount of fuel sloshing around in the float bowl, upsetting the fuel delivery. The original carburetor this one (and the Mikuni) is derived from had a totally different float and needle system that was pretty impervious to flutter.

But costs a lot more to make.

pcspecialist · 07-30-2016, 07:23 PM

Normal when going over bumps, but, I'm asking if it is normal when parked?

I'm also curious at what level should the fuel be? As I stated earlier, mine is about even with the top of the bowel.

Ariel Red Hunter · 07-31-2016, 07:29 AM

Quote:

Originally Posted by pcspecialist

Normal when going over bumps, but, I'm asking if it is normal when parked?

I'm also curious at what level should the fuel be? As I stated earlier, mine is about even with the top of the bowel.

Normal when parked? Only for a few seconds. The bike is off of vertical when on the side stand. Yes, the fuel level is very high all the time. That's one of the reasons you should turn off the fuel when parking the bike. A little hint ~ If you turn off the fuel before you shut off the engine, it should not drip.

jct842 · 07-31-2016, 02:29 PM

Leaks..........probably not in this case but I have had and others also, a leak that is so little that it doesn"t drip but you can smell it in the garage and will empty the gas tank if left alone by itself.

Ariel Red Hunter · 08-01-2016, 06:21 PM

Quote:

Originally Posted by jct842

Leaks..........probably not in this case but I have had and others also, a leak that is so little that it doesn"t drip but you can smell it in the garage and will empty the gas tank if left alone by itself.

Hmmn. This has happened to you with the gas shut off? If so, it is a defective petcock.

I have read elsewhere about carb bowl boiling from proximity to hot exhaust pipe. This won't answer the problem of emtying the gas tank. If it is really emptying the gas tank, take out the oil dipstick and smell it for a gasoline odor. If you smell gasoline, don't start the engine. Change the oil before riding again.

Ariel Red Hunter · 08-03-2016, 08:43 AM

A possible reason for Mikuni's to have wet ends on the drain hose, and smell up the garage with gas smells is if the float level is too high. You have to be super careful when changing jets to not in-advertently bend the float arm just that little bit to over fuel the float bowl. When you turn the carb upside down with the float bowl off, measure from the machined ridge on the carb body to the farthest point on the float. Should be between .6 and .66 inch. The little metal plate that touches the needle is where you adjust float height. Take the float out in order to bend the tab. These float and needle and seat parts are very delicate, so be careful.

mtiberio · 08-03-2016, 08:49 AM

ethanol changes the specific gravity of fuel, and some floats needs to be lighter so they float with more force and seal the float valve better...

Weldangrind · 08-03-2016, 11:17 AM

Quote:

Originally Posted by mtiberio

ethanol changes the specific gravity of fuel, and some floats needs to be lighter so they float with more force and seal the float valve better...

Interesting! I hadn't thought of that.

Ariel Red Hunter · 08-03-2016, 11:42 AM

Quote:

Originally Posted by mtiberio

ethanol changes the specific gravity of fuel, and some floats needs to be lighter so they float with more force and seal the float valve better...

Me neither. But I would run non-ethenol 90 octane, which is easily found around here.

mtiberio · 08-03-2016, 02:07 PM

I deal a lot with antique moto guzzis, and we find the lighter float trick works well on 40 year old carbs...

Ariel Red Hunter · 08-04-2016, 02:27 PM

Quote:

Originally Posted by mtiberio

I deal a lot with antique moto guzzis, and we find the lighter float trick works well on 40 year old carbs...

Yes, and the DellOrto is another great carburetor.

07-28-2016, 07:48 PM	#1
pcspecialist Join Date: May 2016 Posts: 583	Mikuni drain hose wet but not dripping I never paid any attention to drain hoses in the past, is it normal for them to be wet with fuel but no noticeable dripping. I opened up the drain screw some and held the end of the hose up to see where the fuel level in the carb is and it appears to be almost level with the top of the bowl.
	0

07-28-2016, 09:25 PM	#2
w0ss Join Date: May 2016 Posts: 231	funny you mention that, I saw the same on mine and just assumed it was normal. I never see it leaking but almost looks like it's weeping or something. __________________ Hawk 250 with following performance mods: 17t, Mikuni with 110/25, Uni filter, Exhaust.
	1

08-03-2016, 08:43 AM	#9
Ariel Red Hunter Join Date: Jun 2016 Location: akwesasne, NY-13655 Posts: 2,220	Mikuni drain hose A possible reason for Mikuni's to have wet ends on the drain hose, and smell up the garage with gas smells is if the float level is too high. You have to be super careful when changing jets to not in-advertently bend the float arm just that little bit to over fuel the float bowl. When you turn the carb upside down with the float bowl off, measure from the machined ridge on the carb body to the farthest point on the float. Should be between .6 and .66 inch. The little metal plate that touches the needle is where you adjust float height. Take the float out in order to bend the tab. These float and needle and seat parts are very delicate, so be careful.
	0

07-28-2016, 09:50 PM	#3
pcspecialist Join Date: May 2016 Posts: 583	I wonder if it is just fumes condensing? If a few more say they experience the same thing, it's a safe bet that's exactly what's happening.
	0

07-30-2016, 07:23 PM	#5
pcspecialist Join Date: May 2016 Posts: 583	Normal when going over bumps, but, I'm asking if it is normal when parked? I'm also curious at what level should the fuel be? As I stated earlier, mine is about even with the top of the bowel.
	0

07-31-2016, 02:29 PM	#7
jct842 Join Date: Jan 2015 Location: arkansas Posts: 297	Leaks..........probably not in this case but I have had and others also, a leak that is so little that it doesn"t drip but you can smell it in the garage and will empty the gas tank if left alone by itself.
	0

08-03-2016, 08:49 AM	#10
mtiberio Join Date: Jun 2016 Location: Arlington, VA Posts: 258	ethanol changes the specific gravity of fuel, and some floats needs to be lighter so they float with more force and seal the float valve better...
	1

08-03-2016, 02:07 PM	#13
mtiberio Join Date: Jun 2016 Location: Arlington, VA Posts: 258	I deal a lot with antique moto guzzis, and we find the lighter float trick works well on 40 year old carbs...
	0