I did the overflow tubes in my float bowls and low and behold there is a very slight leak...well a hint of fuel on the drain ends. The garage stinks of gas when I come home for a ride and the wife says I better fix even though the smell subsides in a couple hours. When I did the overflow tubes I did a friction fit by tapping them into place and used J-B Weld as well. On two carbs I drilled through to where the drain screw sits, and on the other two I stopped short, but I don't know which are which. I have an idea what happened. Do you? I'll look into this, this weekend.
-
WOULD YOU LIKE TO BE ABLE TO POST? REGISTER FOR COG MEMBERSHIP
All registration must be done through the club's main webpage: To register / join COG, click here
For instructions to convert to full membership, click here
-
Can't post after logging to the forum for the first time... Try Again - If you can't post in the forum, sign out of both the membership site and the forum and log in again. Make sure your COG membership is active and your browser allow cookies. If you still can't post, contact the COG IT guy at IT@Concours.org.
Float bowl drain leaking
- Thread starter conando
- Start date
What a co-inky-dink. I was JUST getting ready to post the exact same concern. I get a drip or two out of each drain tube at the end of a ride and I thought the adhesive was failing at the tube-to-bowl junction. The funny thing is I only get a drip or two then it stops, never any more than that. Well, I just got through taking #4 bowl off to inspect and the JB Weld looks as good as the day I bonded them together. No degradation, no delamination, tube in there solid as a rock. Here's what I think is going on. I think there are gas fumes that are condensing in the drain tubes and dripping out. It may be that the latent heat of the hot engine when I return from a ride are causing a little evaporation in the float bowls that is condensing in the cooler tubes. Any other ideas? JMHO Dan
I am seeing the same thing. I pulled the carbs last night to recheck the fuel level. I did a quick check before I called it a night, but did not find anything. I will be taking a better look this evening and will report back if I find anything.
How high are you above the fuel level, which is ideally at the parting line? I set mine app 5/16". I think if they're much lower you'll be subject to slosh over. I know George Young suggested 4mm over, I think that's to low, and 10mm put's your drains even with the air correction jet, which IMO is a bit to high. I set up a cutoff toll to replicate tubes, and have a bunch cut to 1.450" now. I think I'm gonna offer it as a little kit, and / or an addition to the jet kit - Steve Shleper of the 7th gear unit and performance exhaust cam sprockets. My bike - "SHOODABEN" - 1109cc's of what an 04 concours "shoodaben"!
I have the copper tube and was intending to install this weekend, and fit my new float valves at the same time. I bought a bag of 4mm x 14mm allen headed bolts to replace the std. cross head bolts. If anyone wants a set let me know. I bought a bag of 100 so have a few spare. I was thinking of drilling a 1.5mm hole straight through then drilling the 1/8" hole only part way. I have a feeling the 1/8 tube is a bit too large a diameter so the 1.5mm restriction will reduce any vaporizing. But still be large enough to solve any overflow issue. Thoughts? The bronze tube is available at any decent sized model (train, plane, boat) store. Colin Prior Cogmos Administrator Lake Forest Park WA COG#7767
I cut my tubes at 40.0mm long. Using George's recommendation of 36.0mm and taking Steve's advice, I lengthened them a bit. But like a dumba$$, I didn't measure the height of said tube above the parting line after insertion and bonding. I'll pull #4 bowl off today and measure it. Stay tuned. Dan
I just figured out that the 2 left carbs have different float bowls than the 2 right carbs (duh). The boss you drill into for the tubes are different heights for left and right carbs. No wonder I stopped short on 2 and went through on 2. I had the drill bit marked with tape. This doesn't help the theory I had though. Back to the drawing board. I now think there are two separate issues. First is sloshing over into the tubes like Steve said. I got a good size curb bump at the end of my driveway which could allow a drop into the tubes. This would explain why I have a hint of gas on the drain nipples. Second is convection venting during cool off. The tubes introduce a second vent to the float area. I
Raycad
Moped
Last week, I found locally at Fastenal the Allen head screws (they had stainless only) and I was planning to do the install with the tubing that Dan Bergmen has graciously sent me. But whoa ! Better wait and see the outcome of this discussion ! Would the Service Manual of an older bike with the OEM tube help us? I checked the current Honda Common Service Manual and I found at page 8-4 a generic and not to scale drawing of a Float System with an overflow tube that is shown waaaay above the fuel level. The top of our tubes should surely be as high as possible, as mentioned before, just short of allowing fuel seeping into the cylinders. And I also think that creating a new vent with the tube can cause convection and condensation problems altough the dripping, in my opinion, should be at the end of the old vent if it's really condensation and not sloshing (when braking in the garage, leaning suddenly on the sidestand or even jacking on the centerstand). If the top of the tubing seems high enough, why not block the old vent and see what happens? What do our experts Dan, Steve and the others think?
I just got Steve's jet kit and overflow tubes and will be installing soon. The mention of condensation in the float tubes sounds possible to me, cold fuel and warm carbs could make sense. What about putting a trap in the drain lines coming from the drain plugs at the bottom of the bowl. Think of how your bathroom sink drain looks, water goes down then back up slightly then down for good. Some water stays in the curved up part "the trap" and keeps fumes from coming out your sink. If you could put a few up and down curves (Traps) in your plastic drain tubes might this do the same thing? The small amount of gas that condensed in the tubes might only make it to the traps and not to the ends of the tubes causing less of a smell after bike had been ridden. Let me know what you think. 1968 Honda 160 Scrambler, Sold 1979 Kawasaki SR 650, Traded in 1978 Kawasaki KZ 1000 Z1R Turbo 1986 Kawasaki ZX 1000R Ninja 1999 Kawasaki Concours
Steve; What am I missing here, I'm just playing around with this now, at 15mm tube is still not interfering with the underside of the carb bowl. yes its below/above the air correction jet but so what? I don't see capillary action or a siphon effect in play here. 5/16 (dang why can't you guys use metric LoL) 8mm does not seem that far from the fuel level given acceleration and deceleration and vibration is going to slosh the fuel around a fair amount. I think I'm going to go for 15 mm from the parting line, and will perhaps do a test by fitting a damaged float valve to see if the fuel leaks into the carb or not in an overflow situation. If its too long/high I can always cut them down.
I did make a stepped whole with the through hole being only 1mm. and the 1/8th being drilled in 7mm. The overall tube with this combo is 45mm but I'm measuring each one individually. Colin Prior Cogmos Administrator Lake Forest Park WA COG#7767
Today I plugged the original vent tubes and went for about a 135 mile ride. Plugging the vents caused no performance issues so that part is good. After parking in the garage I did not notice any fuel smell and there was no hint of fuel on the float bowl nipples. We should probably note here that the high for the day was 7 degrees Celsius or 45 degrees Fahrenheit. I left for two hours and came back and found the garage smelled of fuel again but maybe not as bad. It seems that plugging the original vents had helped, but only slightly. Then I checked the float bowls nipples again, and only then found a hint of fuel on them. So it seems Bergmen is correct on the condensation thing. There is still a possibility that drops of fuel sloshed into the tubes at the driveway curb bump or setting up on the center stand, and then taking some time to come down the tubes past the drain screws to the drain nipples. Hopefully others here will test as well and report their findings.
My bowls are curing over night yes that's bowls not bowels! I should have it tested tomorrow. Re 1mm diameter hole being large enough, its a fair question. Here is what I figure, the flow of gas into the carb is quite restricted by the needle valve so I'm confident a 1mm orifice will be fine. Note however that a 1/8 tube has a 2mm dia internal bore and the flow dynamics show, if you set the flow rate constant then: 1mm tube 1 m/sec flow rate 2.8 litre/Hr Volume 2.0 mm tube 1 m/sec 11.3 litre/hr If you halve the diameter you 1/4 the flow. So hopefully if condensation is the issue then in theory the condensation ought to be 25% less. As we use our garage as our primary entrance and the CFO has a "sensitive" nose I'm trying to keep the fumes to a minimum. Colin Prior Cogmos Administrator Lake Forest Park WA COG#7767
I should have it tested tomorrow. Re 1mm diameter hole being large enough, its a fair question. Here is what I figure, the flow of gas into the carb is quite restricted by the needle valve so I'm confident a 1mm orifice will be fine. Note however that a 1/8 tube has a 2mm dia internal bore and the flow dynamics show, if you set the flow rate constant then: 1mm tube 1 m/sec flow rate 2.8 litre/Hr Volume 2.0 mm tube 1 m/sec 11.3 litre/hr If you halve the diameter you 1/4 the flow. So hopefully if condensation is the issue then in theory the condensation ought to be 25% less. As we use our garage as our primary entrance and the CFO has a "sensitive" nose I'm trying to keep the fumes to a minimum. Colin Prior Cogmos Administrator Lake Forest Park WA COG#7767
Colin - the reason the air correction jet location is a landmark to me is becuase that's where fuel will discharge out of the bowl first as the level rises. that's why some guys report fuel in the airbox. Remember that the A/C jet is crossdrilled into the emulsion tube well, which is going to have the same fuel height as the bowls do (which is the exact reason fuel level is critical for jetting). Also someone mentioned blocking the stock vent system. Well now you know your bowl vents are open, if not the bike would shut off when the vent hoses were blocked. BTW, My vents are app 5/16" over the parting line. I've been riding alot lately, and haven't had the first hint of of a problem. I do have a clear hose and "t" system venting the bowls into 1 discharge point. Steve Shleper of the 7th gear unit and performance exhaust cam sprockets. My bike - "SHOODABEN" - 1109cc's of what an 04 concours "shoodaben"!
Many thanks again Steve, I'm on the same page now. Yes when mine leaked it was into the air-box. Not the engine. Which raises the point why is it some including my original basket cases hydrolocked? I guess its possibly a mixture of the bikes being parked on a slope or the stuck float is leaking faster than the Air Correction Jet can drain. I cut mine at 8mm and reassembled only one float needed adjusting. Here is the rig I used for the float adjustment, the step ladder makes a good stand. The bottle could be a bit bigger, but otherwise the siphon system works well and its easy to drain the bowls back into the bottle. Note the level and the wire connected to the throttle cable fixing that I use to check that its level in both planes. <a href="http://good-times.webshots.com/photo/2416037820100596652gUqBxM"><img src="http://thumb12.webshots.net/t/73/173/0/37/82/2416037820100596652gUqBxM_th.jpg" alt="Carb Float Level 005"></a> <a href="http://good-times.webshots.com/photo/2297975860100596652MaLiLA"><img src="http://thumb12.webshots.net/t/74/74/9/75/86/2297975860100596652MaLiLA_th.jpg" alt="Carb Float Level 007"></a> I'll slip the rack back in tomorrow. Time to watch Top Gear on BBC America LoL
Colin Prior Cogmos Administrator Lake Forest Park WA COG#7767
I have a very similar drain tube system, except I have the final drain tube coming off the left side after carb #1. I haven't had any draining or scent issues at all. steve Shleper of the 7th gear unit and performance exhaust cam sprockets. My bike - "SHOODABEN" - 1109cc's of what an 04 concours "shoodaben"!