Found My Vacuum Leak, Finally
wjamesfl:
I recently rebuilt my carbs and all 6 of those hoses were severely cracked! Something to look out for. Not sure if it was old age or if the previous person that opened these carbs up didn't remove them before spraying carb cleaner.
98valk:
Quote from: Mooskee on August 21, 2025, 09:17:39 PM
Quote from: dan7uk on August 21, 2025, 07:03:02 PM
Quote from: Mooskee on August 21, 2025, 12:23:32 PM
Good thing it was #5. You can get to it and #2. The others are between carbs.
Very lucky it was carb #5 easy to get to vac hose and replace, 5 minute job.
Wonder what is involved to get to carb #1, #3, #4, & #6 Air Cut Valve vac hose. I would say the tank would have to come off along with the air box, not sure what else.
All that, and remove carb bank. Then split carbs. You would at least have to replace the fuel and air rail O-rings because they will have taken a set from my experience. There is one guy on here that swears O-rings never go bad, but that isnot my experience. Basically if you go that far, you might as well refurbish. Otherwise you might be doing all that work again.
they go bad due to people using off the shelf fuel additives that eat away at the OEM Buna-N o-rings. that's it. It has nothing to do with AGE and/or 10-15% ETHANOL IN THE FUEL.
Mooskee:
Quote from: Mooskee on August 21, 2025, 09:17:39 PM
Quote from: dan7uk on August 21, 2025, 07:03:02 PM
Quote from: Mooskee on August 21, 2025, 12:23:32 PM
Good thing it was #5. You can get to it and #2. The others are between carbs.
Very lucky it was carb #5 easy to get to vac hose and replace, 5 minute job.
Wonder what is involved to get to carb #1, #3, #4, & #6 Air Cut Valve vac hose. I would say the tank would have to come off along with the air box, not sure what else.
All that, and remove carb bank. Then split carbs. You would at least have to replace the fuel and air rail O-rings because they will have taken a set from my experience. There is one guy on here that swears O-rings never go bad, but that is not my experience. Basically if you go that far, you might as well refurbish. Otherwise you might be doing all that work again.
I was looking at a carb set yesterday with this conversation in mind. I think I could change the AVC tubing without breaking apart the carbs. It would not be that easy, but to avoid breaking the set apart, I think it is possible. You would probably have to remove the choke links for a little more room. It would help to have some very thin needle nose or hemostats.
If you determined your vacuum leak was caused by a leaking ACV tube it might be worth it. Not easy but much less expensive and extensive than taking everything apart.
Mooskee:
"they go bad due to people using off the shelf fuel additives that eat away at the OEM Buna-N o-rings. that's it. It has nothing to do with AGE and/or 10-15% ETHANOL IN THE FUEL."
98Valk, I totally agree with you, contrary to what you probably think. In fact I respect your engineering knowledge and experience. I have actually read almost all of your posts. I worked as a technician for 46 years in the Navy and Nuclear Power. I have worked closely with many engineers, and respect the craft.
That said I have a lot of hands on experience on equipment. The point you make about the O-rings being damaged by using inappropriate additives is a good point. I agree.
I also get carb sets that are in various stages of failure. I am not sure just how many 25 year old Valkyries have never had any fuel additives in the tank. Very often when people report their machine not running correctly, they receive advice to put in additives. Some of those additives will clear up circuits that are not too clogged. Perhaps at a price of an eventual carb rebuild. Or maybe you get away with it and get years more service out of them.
I get a lot of carbs that have been sitting for extended periods with ethanol fuel in them. New riders inherit their dad's or grandfather's bikes, or buy a Valkyrie that has been sitting due to the owner not being able to use it and selling it after some time. The carbs are all gummed up and often leaking on the fuel rail; especially at the fuel tees. Perhaps because of movement of the tees with the fuel lines connected. I don't see it as often on the front fuel rail tubes.
I do not think the ethanol attacks the O-rings. Ethanol does have a big effect on the functionality of the carbs if left sitting in there too long without running the engine.
What I see is the fuel turning thick, then leaving a yellow green deposit in the carb bowls and slow circuits. It can look like dust, or lacquer, and can get so bad it is difficult to remove even using an ultrasonic cleaner. There is often what I call a "fungus" because it is a greenish fuzzy deposit in and on the bowl components. It builds up and clogs the circuits; especially the slow circuits.
I have even seen some cases where the goo had the main needles stuck such that the crossover arm cannot operate the butterflies. I have 100's of pictures of all these conditions because I take pictures for my customers during the rebuild process.
In summary I agree that it is additives that attack and destroy O-rings. I agree that the O-rings can withstand ethanol fuel. I submit that ethanol fuel left sitting in the carbs for long periods will cause blockage of the slow circuits and if gone long enough will even clog main jets and freeze the main needles in the seats.
I use Marine Stabil in my fuel when sitting up for any length of time. My trike has to have high octane fuel because of the compression ratio. That fuel is generally ethanol free.
I welcome your feedback and input on what if any additives are recommended for use.
I also would appreciate your input on what to use to lubricate new O-rings when installing them. The Honda manual just says "oil".
Respectfully
Dave
Jess from VA:
Mooskee, I have some 35 carburetors at my house, including two Valkyries. I am incompetent as a carb repairman (but have used a gifted motorcycle mechanic and a lawnmower shop from time to time).
I burn no ethanol gas in any of them.
My county and others close-by do not allow the sale of non-ethanol gas, so about quarterly I drive 100 mile round trip to get about 40 gallons of it to bring home to use in my machines. I have always dosed this gas with the proper amount of Marine grade Stabil (1/2 oz per 5 gallons), but also have added a "slosh" of both Seafoam and Berryman's B12 to each 5 gallon can. Of course I've done this to make the fuel last. And it generally gets used up in 3-5 months, then replaced, but it's been my understanding that it should be good for 1-2 years. It sits out in a shed in high heat all summer, winters are mild.
The area I can get the nonethanol is where I always ride (out in beautiful horse country, not in urban traffic where I live), so I usually fill the bike I'm riding before the 50 mile trip home. But some rides are shorter and then I top up from my storage gas at home.
I've been doing this for years, and never had any problem with either of my '99 Interstates, or any of my other equipment from using this treated gas (as far as I know).
But after reading this thread and your posts, I'm wondering if you think the Seafoam and B-12 is a bad idea? Overkill?
Navigation
[0] Message Index
[#] Next page
[*] Previous page