Stalling, bad mileage, vapor lock?

[Orion]

Greetings, first post on the board so be nice. I've searched through existing posts and have plenty of ideas on the bad gas mileage issue (around 20mpg), my carbs certainly need a cleaning/rebuild. I have also recently had a serious "vapor lock" type issue. Last time I was driving home from work, after about 6 miles of highway the bike completely died, pulled over, waited 3-4 minutes, starts up, rides for another couple of miles, dies. Repeat all the way home.

81 XS1100
32k
recent routine maintenance completed (plugs, filters, inline fuel filters, etc)


I have ridden about 200 miles since I purchased the bike with only one previous stall of similar nature on a cold, damp morning. That's Colorado summer cold, about 65 degrees @ 6AM.

It appeared to be heat provoked as it was quite hot that day, however I was not in traffic and it did the same thing once on the drive in to work in the morning as well, again, summer cold.

The bike appeared to be running fine other than that since I bought it. My only complaint would be lack of power and bad gas mileage. I'm very familiar with automotive work but this is my first bike. Any suggestions are appreciated, thanks in advance.

[79XS11F]

That sounds like fuel starvation so check that the air vent in the gas cap is clear and make sure your fuel petcocks are working properly. Also make sure that the fuel petcock screens in the fuel tank are not plugged. What's the condition of the inside of the tank? When fuel is flowing crap will be drawn to the screens only to fall away after the engine stalls when there is no fuel leaving the tank.
You could test the fuel petcocks by going for a run with them set to the prime position so not vac is required to allow the fuel to flow. If the engine still stalls then check the gas tank vent. Clean the carbs VERY VERY well as soon as you get a chance.
Rob

[TopCatGr58]

Re: Stalling, bad mileage, vapor lock?

Originally posted by Orion
Greetings, first post on the board so be nice. I've searched through existing posts and have plenty of ideas on the bad gas mileage issue (around 20mpg), my carbs certainly need a cleaning/rebuild. I have also recently had a serious "vapor lock" type issue. Last time I was driving home from work, after about 6 miles of highway the bike completely died, pulled over, waited 3-4 minutes, starts up, rides for another couple of miles, dies. Repeat all the way home.

81 XS1100
32k
recent routine maintenance completed (plugs, filters, inline fuel filters, etc)


My only complaint would be lack of power and bad gas mileage. I'm very familiar with automotive work but this is my first bike. Any suggestions are appreciated, thanks in advance.

Well, I will....usually, but don't expect it from PROM!

First, please edit your sig/profile to include the actual MODEL! An 81 what, Special or Standard...makes a difference in what we recommend!

Secondly, glad you have been searching the FORUM, but have you looked thru the TECH TIPS, from Main Page, scrolling down to the 4 sections, Maint., Repairs, Mods, Misc! Lots of info there about the carbs as well.

Thirdly, lack of power! You definitely have problems IF you have a lack of power!

I wouldn't jump to vacuum lock so much as perhaps lack of fuel flow, again depending on MODEL determines where this may be occuring, either petcocks, or Octopus, or as has been mentioned, blockage of gas tank CAP vent!?

Are you positive it's running on ALL 4 cylinders, spritzed water on pipes to check for sizzle....IF some are NOT, again which ones will determine troubleshooting paths!

SO...more info please!?
T.C.

[mro]

What TC said plus

sync the carbs.


mro
Newbie...cool
got any pics of your XS ?

[Orion]

Great, thank you for the newb lenience. The bike is an SH. One other thing I neglected to mention is the apparent "tank suck". I can hear the tank sucking air in after riding, and if I open the gas cap and put my hand over it, it certainly pressurizes, is this normal? I can also see bubbles coming up from the back (closest to seat) of the tank. Would this be an indicator that the vent hole is not working correctly? I know that the gasket on the fuel cap is bad so it leaks air anyways.

It looks like I have to do some actual work though huh I'll start with the fuel tank, pet cocks, fuel filters, and carb. I THINK it's running on all 4, but ya know what, I better check. I'll be busy tomorrow that's for sure.

Thank you everyone for your help, I'll be lurking around the forum from now on.

[wa407mpp]

vapor lock ?

A buddy had a ghost in one of his bikes a few years ago.that turned out to be in one of his pick-up coils. It would short out only when the bike was warmed up and then heal when it cooled. So read up on how to do a meter check on the coils and go for a ride and when it quites do the test while it's still hot . His coils only shorted out when ridden not just sitting and running ,also check your leads if there is'nt enough slack in they can separate, but they do'nt normaly heal.

[prometheus578]

Greetings, first post on the board so be nice.

Oh, this just begs for abuse!
Why'd you have to warn him, T.C.?
I agree with everyone else. Disassemble the gas cap. make sure the little vent passageway isn't plugged. yes, it'll vacuum lock the tank.
Vapor lock, no. Vapor lock is when the fuel in the line(or fuel pump) heats and vaporizes. no part of our fuel system is anywhere near anything hot.
Also agree with pulling the tank and disassembling the petcocks. I've seen them so plugged with rust and crap that only a little fuel seeps through to fill the bowl. You'll run out of gas in a few miles, but the bowls will fill again in a few minutes.
Next time it does that "vapor lock", immediately get off the bike and open one of the drains on the float bowls. If nothing comes out, there's the problem.

[Orion]

Re: What TC said plus

Originally posted by mro
sync the carbs.


mro
Newbie...cool
got any pics of your XS ?

I added to this thread

Pictures

[mro]

Cool pics
I happen to have an 81 special also.
Been sitting in the pallet rack tho as a dust collecter
Stole a couple parts for my LG off it but the LG been collecting dust lately too

Too many projects.....so little time


mro

[TopCatGr58]

Hey Orion,

Caught your pictures, great find for great price, that aftermarket seat alone runs ~$200.00! And it has Telefix forkbrace as well!

Okay, the special has that pesky Octy, and you could have some cracked vacuum hose that goes to it, so that it's not opening enought to permit the fuel to flow properly and fast enough to keep the bowls filled like Mr. Nice Guy Prom stated! Also, it can just corrode and rust and get stuck, so the vacuum hose may be intact, but the valve isn't moving! So...you can test it along with the petcocks, and you can take it OFF, and take it apart and check out it's innards, and get a repair kit, OR you can just chuck it away and bypass it entirely like many of us have!

A preliminary test would be to put the petcocks on PRIME and see if the problem keep happening, if NOT, then it points to the Octy, but could still also be petcocks!

You can see bubbles WHERE?:confused Once you open the tank's gascap the pressure is equalized so you shouldn't see any bubbles inside there.....OR are you saying that you have CLEAR FUEL LINES, and you see bubbles rising up thru them towards the petcocks/tank?? Please remember we can't see what you see without VIVID details of what you are looking at, etc., no detail is too small or insignificant!

Have fun, and report back your findings, etc., please!
T.C.

[Orion]

When I say bubbles, I mean in the gas, in the tank, like water when it first starts boiling or putting a tire with a hole in it under water.

Octy? I'm all about removing unnecessary parts, less weight right

[79XS11F]

If you have air bubbles in the fuel in the tank you have a leak somewhere in the fuel line system, fuel level device or petcock gaskets or in the tank it's self. Your going to want to find that leak even if it's not the cause of or related to your current issue. You don't want fuel dripping onto your hot engine.
Rob

[Orion]

Sure enough, I just went to the grocery store to pick up some "supplies" for this evenings party and ran it on prime. One of the petcocks leaks on this setting only. Additionally, I've found that #4 is not firing. The gas cap air hole is fine, but the gasket is trashed and I have ordered a new one.




It seems the consensus is a resounding no for vapor lock, yet with the inline fuel filter setup I have, the fuel lines come down to and touch the casing underneath. Just though I would throw that out there one more time before I'm told "no Dave, not vapor lock" one final time.



Getting there, I have a laundry list with the rest of the suggestions which I will be going through over the next couple of days. Thanks again to everyone thus far!

[TopCatGr58]

Hey Dave,

Okay, those fuel lines could be a bit LOW, the carbs are only gravity fed, and not vapor lock, but just the inability of the fuel to adequately flow back up hill into the bowls! IF you decide to remove the Octy, then cross the lines from right petcock to left pair of carbs and vice versa, and remove excess line so that the loops are just about even with the carb fuel "T" fittings, or just slightly below, but not all the way to the bottom of the bowl!

Without the Octy, you will only need the back petcock nipple, the front one is for PRIME, but it will flow in the ON and Reserve positions from the rear nipple, so cap off the front nipple!

With only 1 cylinder not firing most likely a clogged pilot/idle circuit in that carb,(CLEAN) but pull the spark plug and check for spark on the "dead" cold cylinder, and see what the plug looks like, dry or wet/oily? Dry=no fuel, wet=fuel but possibly no spark!

If no spark, pull cap, check for corrosion in end of wire, cut off 1/4" or so to expose uncorroded wire. Check the resistance of the plug cap, ~5k is normal, but internal resistor can go bad preventing spark getting thru. Also a bad plug can happen!

Yep, lots to do to recondition engine components, but will be well worth it in the end....hold on for some arm yanking power when you get all 4 working!
T.C.