Vapor lock

[hogv8]

Has anyone come up with a full proof way of preventing vapor lock ? I thought I had it licked but yesterday setting In 81 degree Daytona traffic I had what seemed to be vapor lock . Finally got the bike restarted but ran like shit until I let it set for a couple of hours to cool down .

[mmaupin]

On my first SB, a 1999 model, I insulated all of the fuel lines. Also, the fuel filter was on the suction side of the fuel pump. So with a little bit of differential pressure across the filter and a hot day equaled vapor lock. After insulating the fuel lines, I had no problems with it.

[hogv8]

On my first SB, a 1999 model, I insulated all of the fuel lines. Also, the fuel filter was on the suction side of the fuel pump. So with a little bit of differential pressure across the filter and a hot day equaled vapor lock. After insulating the fuel lines, I had no problems with it.

So your saying the filter should be after the fuel pump ?

[mmaupin]

No, just change the fuel filter once or twice a year and insulate the lines and filter. I think most of the electric fuel pumps require filtering ahead of the pump. I used the aluminum coated stuff like this: https://www.ebay.com/itm/Aluminum-Metal ... fqUzlPoG2w

[SQ4MN]

Jack, I think I'm the expert on vapor lock. Here in Las Vegas we have most days in July and August from 105 to 115 and some even higher. The pavement is much much hotter, you really can fry an egg on it at times. My bike used to vapor lock all the time when I first got it. I took the stock air tech pump which was brilliantly mounted on the bell housing and tossed it. I made a mount under the left side cover for a HOLLEY RED fuel pump and run uninsulated rubber fuel line. The bike has never vapor locked again no matter the heat or traffic conditions. Ten years on the same pump without trouble. This was a simple fix, nothing fancy.

[502wingman]

Jack, 81 is not that hot and your bike is in good shape. Usually when the "cool" gas comes out of the tank the vaporlock is gone after a couple of hundred yards of driving again. At least that is my personal experience.
My guess is that you still have a problem because of the bad gas you had lateley. May be the filter inside the carb or so.

[hogv8]

I run a Holley Red mounted on the left side off the side od the battery box . It normally shows about 5 to 7 lbs. fuel pressure until it gets hot while setting in hot traffic and I can watch the fuel pressure gradually drop as low as 1 to 2 lbs . When it gets to 0 of course it stalls . This never happens in NY state climate and runs perfect all the time with no problems . It just doesn't like Florida for some reason .

[hogv8]

I have my liquid filled fuel pressure gage plummed and mounted behind the right valve cover and after doing some research people are saying that if a liquid filled fuel pressure gage is mounted too close to a heat source it will not be accurate and to use a non liquid filled fuel pressure gage instead if it's mounted near a heat source for more accurately.
I think the best thing for me to do is better wrap all of my fuel lines including the tank crossover hose , make sure my fuel lines are tied up away from heat sources and replace my fuel pressure gage with a non liquid filled and go from there .

[The Mindless Philosopher]

I chased what I thought were vapor lock issues for a couple of years. Desert Southwest (close to sea level) with the same temp's as SQ4MN for 6 months out of the year.

I changed and modified fuel lines and filters, swapped in a pricey Carter fuel pump, installed a phenolic (insulated) spacer under the carburetor, and even started covering the main tanks with a reflective car sunshade that hooked onto my foot pegs. NOTHING WORKED!

The nasty little culprit turned out to be a cheap plastic inline fuse housing (fuel pump lead) that kept expanding when the trike would sit in the heat, then contract when I could get moving. Just barely enough airflow would get under there, but even that evenually stopped working. It was fine in the cooler months. I had no way on God's green earth of figuring it out until the fuse housing dry-rotted and crumbled inside the insulation.

The day it finally gave out, it was 110F outside. The Hoss kept hesitating and konking out. It would restart intermittently, so I rode it a few hundred feet each time for four miles until it passed out again. I had to call a tow truck one mile from home after it quit and wouldn't start at all (this after a half hour of trying to troubleshoot road-side. Glad I carry loads of water in the summer!)

I'm not saying this is your issue, but I'd get down into wiring weeds if you haven't already. Start with that 1 Amp inline fuel pump fuse if you have one? You never can tell.

Just my two cents.

[Wild Bill]

I’ve been saying it for 15+ years... my 502 vapor locks at Daytona Bike Week unless I use a small amount of octane booster. Period.

In Virginia, no problem. Pennsylvania, Maryland, North & South Carolina, no problem. Sturgis & points in between, no problem. Daytona —> vapor lock.

When I’ve brought this up over the past 15 years, it has been collectively dismissed. Everyone wants to try and solve with every other possible fix known to man. I get it... octane booster simply isn’t as manly as changing timing, insulating fuel lines, changing the fuel pump, etc.

I run a Holly Blue fuel pump mounted to the side of the battery box with an external pressure regulator and a fuel pressure gauge. Been running this set up for many years (since I installed nitrous more than a decade ago). Didn’t matter... still vapor locks at Daytona Bike Week w/o octane booster.

Hmmmm, come to think of it, maybe the problem is in the cam bearings, or the oil pump arm & I should change those out???!!! (LOL)

Naaaaa, I’ll simply stick with my time-tested $2.97 octane booster. Just 1/3 of a bottle per fill-up is all it takes.

WB

[The Mindless Philosopher]

Octane boost definitely comes in handy after mine's been sitting for long periods between repairs, and in blazing heat when the fuel wants to boil (I've seen it boil at least once). I add it as a preventive measure. I might well have learned of it through one of your posts, Wild Bill (likely on the other site), but I tend to forget exactly who posts what unless I go digging. Regardless of where I got the info, I do follow the octane boost advice. Thanx for the reminder!

[hogv8]

I’ve been saying it for 15+ years... my 502 vapor locks at Daytona Bike Week unless I use a small amount of octane booster. Period.

In Virginia, no problem. Pennsylvania, Maryland, North & South Carolina, no problem. Sturgis & points in between, no problem. Daytona —> vapor lock.

When I’ve brought this up over the past 15 years, it has been collectively dismissed. Everyone wants to try and solve with every other possible fix known to man. I get it... octane booster simply isn’t as manly as changing timing, insulating fuel lines, changing the fuel pump, etc.

I run a Holly Blue fuel pump mounted to the side of the battery box with an external pressure regulator and a fuel pressure gauge. Been running this set up for many years (since I installed nitrous more than a decade ago). Didn’t matter... still vapor locks at Daytona Bike Week w/o octane booster.

Hmmmm, come to think of it, maybe the problem is in the cam bearings, or the oil pump arm & I should change those out???!!! (LOL)

Naaaaa, I’ll simply stick with my time-tested $2.97 octane booster. Just 1/3 of a bottle per fill-up is all it takes.

WB

Thanks Bill , I will definitely try it !

[Ulyssesj]

I’ve been saying it for 15+ years... my 502 vapor locks at Daytona Bike Week unless I use a small amount of octane booster. Period.

In Virginia, no problem. Pennsylvania, Maryland, North & South Carolina, no problem. Sturgis & points in between, no problem. Daytona —> vapor lock.

When I’ve brought this up over the past 15 years, it has been collectively dismissed. Everyone wants to try and solve with every other possible fix known to man. I get it... octane booster simply isn’t as manly as changing timing, insulating fuel lines, changing the fuel pump, etc.

I run a Holly Blue fuel pump mounted to the side of the battery box with an external pressure regulator and a fuel pressure gauge. Been running this set up for many years (since I installed nitrous more than a decade ago). Didn’t matter... still vapor locks at Daytona Bike Week w/o octane booster.

Hmmmm, come to think of it, maybe the problem is in the cam bearings, or the oil pump arm & I should change those out???!!! (LOL)

Naaaaa, I’ll simply stick with my time-tested $2.97 octane booster. Just 1/3 of a bottle per fill-up is all it takes.

WB

You mean oil pump arms don’t cause vapour lock? Damn man, I have all these used arms just sitting around. In all fairness the engines ran better after the pump was replaced with a few other components. The vapour lock was gone and engine ran great. Must have been oil pump arm.
Ulyssesj

[mmaupin]

To keep the topic on a serious note:
http://www.militarytrader.com/military- ... r-gas-woes

This author also advises there are only two ways to prevent vapor lock – cool the fuel or raise the boiling point.
Also, he is NOT an advocate of octane boosters, as many are ethanol based.

Seriously, the fuel filter on our bikes is on the suction side of the electric fuel pump. If you have a dirty fuel filter, a vacuum will be pulled between the fuel filter and the fuel pump. On a hot day, that equals vapor lock.

[The Mindless Philosopher]

I'm still using the dreaded glass fuel filters so I can keep an eye on things, but they are not located in sport where they will likey get crunched (one for the main line and one for the reserve).

[mmaupin]

I'm still using the dreaded glass fuel filters so I can keep an eye on things, but they are not located in sport where they will likey get crunched (one for the main line and one for the reserve).

I would get rid of those glass filters as fast as you can. It is not breakage as much as they loosen up and leak. It is a wonder my bike did not burn because of one of those. If you want to keep those glass filters, carry a stick and a bag of marshmallows.

[The Mindless Philosopher]

HAHAHAHAHAHA! Gotcha. I'll do that! (New filters, not marshmallow sticks!)

[Greg S]

I wish that I had a solution of my own to offer, but I don't. All I can do, is relay what has happened to my own BH. It has a ZZ4 engine in it, and it has a never ending vaporlock problem. I have yet to try what Wild Bill suggested, but will do so this summer.

The vaporlock on my bike happens when the temperature is 50F or above, and is caused by one of two conditions. The first, is when I am at too many stoplights, for too long. Shortly after taking off from about the third light, the bike will start to lose power, and then quit running. The second condition, is when the bike is traveling at speeds of 25 mph, or less, for more than 5 minutes at a time. Under both circumstances, the only way to clear the vaporlock, is to sit at the side of the road and let everything cool down.

In an effort to resolve the vaporlock issue, the Carter pump was replaced with a Holley Red. A special bracket was made, to position the HR underneath the left hand side cover, at a low point on the bike, and away from sources of heat, as much as possible. A new ground wire was installed, as well as a new 12V line to the new Blue Sea fuse box. Then, all of the fuel lines were replaced with fuel injection grade fuel line. These lines have a little bit thicker wall thickness that may insulate against the heat a little bit better. All of the fuel lines were positioned, so that there were no high points in the lines. What started to go down, continued to go down. What started to go up, continued to go up. The end result, was that the vaporlock problem was still there. No changes.

Next, I bought a product called Firesleeve (https://www.grainger.com/product/2RLY2? ... 07154449:s), and put it around every linear inch of fuel line. This improved things a little bit. The bike would now have to sit at a few more red lights, or go for 15 or 20 minutes at 25 mph or less. The problem was diminished, but still there.

Different grades of gasoline were tried. Higher octane, lower octane. No noticeable differences.

I did not put a phenolic spacer between the carburetor and the intake manifold, as I was having a vaporlock issue, not a percolation issue. Even though the fuel bowl in the Edelbrock is rather small, it was unlikely that this had anything to do with it.

At that point in time, it was evident that my particular bike was cursed by God, and that there was not much more that I could do about it.

Then, along came the second bike. This one has a 502 engine in it, and wouldn't you know it - it has the exact same vaporlock issues. Since nothing seemed to work for the 350, I just left everything as it was on the 502. It only had 400 total miles on it, and everything was in pretty good shape. My solution for eliminating vaporlock, was to simply not ride where either of the two conditions may exist that were known to cause vaporlock.

Now, the twist. A few years ago, I started going to a few Boss Hoss get togethers. The gatherings were in other states, and almost exclusively in the south. After the first year visiting Pigeon Forge, I thought that I had gotten extremely lucky, in that my bike did not vaporlock. Keep in mind, that it is one thing to ride in the mountains, but completely another, to ride along the 14 miles of non-stop traffic lights in 90+ degree heat and high density altitude in Pigeon Forge traffic. I did both, and did not have any vaporlock issues. If I could answer the question as to why this was/was not happening, then perhaps the vaporlock problem could be beaten.

The clue: When the bikes were in the south, the gasoline used in the bikes came from the south

Without making this thread even more obnoxiously long, the conclusion that I came to, was that the RVP (Reid vapor pressure) of the gasoline that I purchased in the south, had a lower level of vaporization than the fuel that came from up north. The northern fuel had a higher level of vaporization, in order to facilitate cold weather starting and operation. In order to test this theory, I brought gasoline back from Pigeon Forge, and ran it in Ohio. Guess what? The fuel from Pigeon Forge worked just fine up here. As soon as I would resume use of the fuel from Ohio, the problems would resurface.

RVP may or may not be the variable within the fuel that is making the difference, but it is my best guess so far.

[Orlando606VetteTrike]

Great story Greg. I too when first getting my 502 here in FLA would experience vapor lock. I moved my Airtek pump to the left side of my battery box, used fuel injection hose, and wrap my lines with the DEI heat protection hose wrap and from that point on never had an issue again. I even had used 3 different carbs, 1 1910 which I'm not a fan of, and 2 different double pumpers and no issues. Even with water temps reaching 210.

[Ron Radulski]

I wish that I had a solution of my own to offer, but I don't. All I can do, is relay what has happened to my own BH. It has a ZZ4 engine in it, and it has a never ending vaporlock problem. I have yet to try what Wild Bill suggested, but will do so this summer.

The vaporlock on my bike happens when the temperature is 50F or above, and is caused by one of two conditions. The first, is when I am at too many stoplights, for too long. Shortly after taking off from about the third light, the bike will start to lose power, and then quit running. The second condition, is when the bike is traveling at speeds of 25 mph, or less, for more than 5 minutes at a time. Under both circumstances, the only way to clear the vaporlock, is to sit at the side of the road and let everything cool down.

In an effort to resolve the vaporlock issue, the Carter pump was replaced with a Holley Red. A special bracket was made, to position the HR underneath the left hand side cover, at a low point on the bike, and away from sources of heat, as much as possible. A new ground wire was installed, as well as a new 12V line to the new Blue Sea fuse box. Then, all of the fuel lines were replaced with fuel injection grade fuel line. These lines have a little bit thicker wall thickness that may insulate against the heat a little bit better. All of the fuel lines were positioned, so that there were no high points in the lines. What started to go down, continued to go down. What started to go up, continued to go up. The end result, was that the vaporlock problem was still there. No changes.

Next, I bought a product called Firesleeve (https://www.grainger.com/product/2RLY2? ... 07154449:s), and put it around every linear inch of fuel line. This improved things a little bit. The bike would now have to sit at a few more red lights, or go for 15 or 20 minutes at 25 mph or less. The problem was diminished, but still there.

Different grades of gasoline were tried. Higher octane, lower octane. No noticeable differences.

I did not put a phenolic spacer between the carburetor and the intake manifold, as I was having a vaporlock issue, not a percolation issue. Even though the fuel bowl in the Edelbrock is rather small, it was unlikely that this had anything to do with it.

At that point in time, it was evident that my particular bike was cursed by God, and that there was not much more that I could do about it.

Then, along came the second bike. This one has a 502 engine in it, and wouldn't you know it - it has the exact same vaporlock issues. Since nothing seemed to work for the 350, I just left everything as it was on the 502. It only had 400 total miles on it, and everything was in pretty good shape. My solution for eliminating vaporlock, was to simply not ride where either of the two conditions may exist that were known to cause vaporlock.

Now, the twist. A few years ago, I started going to a few Boss Hoss get togethers. The gatherings were in other states, and almost exclusively in the south. After the first year visiting Pigeon Forge, I thought that I had gotten extremely lucky, in that my bike did not vaporlock. Keep in mind, that it is one thing to ride in the mountains, but completely another, to ride along the 14 miles of non-stop traffic lights in 90+ degree heat and high density altitude in Pigeon Forge traffic. I did both, and did not have any vaporlock issues. If I could answer the question as to why this was/was not happening, then perhaps the vaporlock problem could be beaten.

The clue: When the bikes were in the south, the gasoline used in the bikes came from the south

Without making this thread even more obnoxiously long, the conclusion that I came to, was that the RVP (Reid vapor pressure) of the gasoline that I purchased in the south, had a lower level of vaporization than the fuel that came from up north. The northern fuel had a higher level of vaporization, in order to facilitate cold weather starting and operation. In order to test this theory, I brought gasoline back from Pigeon Forge, and ran it in Ohio. Guess what? The fuel from Pigeon Forge worked just fine up here. As soon as I would resume use of the fuel from Ohio, the problems would resurface.

RVP may or may not be the variable within the fuel that is making the difference, but it is my best guess so far.

This is just my opinion, but did you ever think about installing fuel injection to your bikes? Barry Radu has had good results doing conversions in both small and big blocks.

[Jack]

How about a regulated return to keep the fuel flowing and not sitting and getting hot?

[Greg S]

Ron - This will shock most people, but I really like the quadrajet, in all of its quirkiness. Given the choice of a quad, that lets loose all of the sudden, vs fuel injection, I will always pick the quad. The reason for this, is the fun factor. Yes, EFI will turn better ET's, get better fuel economy, and so on, but I really like the kick in the butt from the quad.

Jack - That exact thought has gone through my mind. I just never did it yet. Not sure if an adjustable flow valve would be necessary, or, just a simple orifice.

The Holley Red is good for 97 gph freeflow, 71 gph at 4 psi, and a maximum pressure of 7 psi. The bike with the ZZ4 engine would need to see a flow rate of about 25 gph at full load (ballparking it with 1/2 pound of gasoline per HP-hr). With this fuel pump, a properly sized orifice should work just fine.

[mmaupin]

[attachment=0]Holley 12-801-
The Holley Red is good for 97 gph freeflow, 71 gph at 4 psi, and a maximum pressure of 7 psi. The bike with the ZZ4 engine would need to see a flow rate of about 25 gph at full load (ballparking it with 1/2 pound of gasoline per HP-hr). With this fuel pump, a properly sized orifice should work just fine.

Just for fun, I ran an orifice calc recirculating 40 GPH. It came out to be a bore of 0.124 inches. See below:

INPUT DATA
Fluid Type: Custom Liquid
Fluid Name: Gasoline
Pipe I.D.: 0.375 inch Base Pressure: 14.696 psia
Pressure at Flow: 4.000 psig Base Temperature: 60.00 F
Temperature at Flow: 100.00 F
Absolute Viscosity: 0.48000 cP
Isentropic Exponent: 1.000 Base Density: lb/ft3
Compressibility at Flow: Atmospheric Pressure: 14.696 psia
Density at Flow: 43.6564 lb/ft3

Flow Rates:
Minimum: 0.00 USGPH
Normal: 40.00 USGPH
Maximum: 45.00 USGPH
Full Scale: 71.00 USGPH

CALCULATED DATA (Calculation Performed at Normal Conditions.)

Orifice Bore Size: 0.124 inch Pipe Reynolds Number (Normal): 8189
Gas Expansion Factor: 1.0000
DP at Min Flow: Psi Permanent Pressure Loss
DP at Normal Flow: Psi at Normal Flow: 3.50 Psi
DP at Max Flow: Psi at Max Flow: Psi
URV (DP at Full Scale): Psi Velocity at Max Flow:
Beta: 0.3300
Discharge Coefficient: 0.6480

[Greg S]

The Reynolds number surprised me a little bit, but this is not something that I have calculated for a very long time. Maybe I am remembering the Re for laminar flow through the hose, instead of the orifice.

If this is a program that you used, would you be able to input a flow of 10 and 20 GPH for the orifice, with the remaining flow being available to the carb at 4 psi? Your number probably makes more sense, since 71 - 40 = 31 GPH, which is still greater than 25, but I am curious.

[mmaupin]

If this is a program that you used, would you be able to input a flow of 10 and 20 GPH for the orifice, with the remaining flow being available to the carb at 4 psi? Your number probably makes more sense, since 71 - 40 = 31 GPH, which is still greater than 25, but I am curious.

Sure, at those conditions a bore of 0.064 for 10 GPH and 0.089 for 20 GPH. In all of those calcs, I used 1/2 PSI for back pressure, assuming the recirc would go in the bottom of the fuel tank.