Stale Gas? (Harley carb troubleshooting content)

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
Another question for the Backstage experts...
What are the symptoms of "Stale fuel"?

Finally attempting to get my bike back on the road for the (short Canadian) season. Got it running a few days ago but it wasn't running well (spitting and hesitating off idle). So - figured bad accelerator pump or clogged jets, pulled carb and cleaned and replaced some bits and pieces.
Got it back together and if anything it is worse. Pretty certain it is running way too lean - only way I can keep it running is if I keep the choke (enrichener) engaged.
So - before I pull the carb again in frustration I'll go get a jug of fresh fuel.
While I make a fuel run - any other words of wisdom?
(for reference it is a 2000 Harley - was running reasonably ok when I mothballed it last fall)
 

LP121

Senior Member
Joined
Jan 22, 2014
Messages
6,442
Reaction score
16,398
My guess is that you didn't use fuel stabilizer? How high is the ethanol content in the gas in your area?

Here, it can be as high as 10%. Fuel is only good for, at the most, 2 months around here in things like lawn mowers and weed eaters. You can get away with using it in your car, though I wouldn't.

Just try the fresh gas and see what happens. It'll probably clear up since you already went through the carbs.
 

six-string

Senior Member
Joined
Oct 1, 2009
Messages
6,997
Reaction score
14,667
gas can leave a residue on carburetors and other engine parts over time.
that's why most mechanics recommend you run the engine dry before putting it up for the winter.
there are fuel cleaners and additives that can help to reduce this problem.
talk to your local mechanic and see what they recommend.
sometimes just a bit of fresh fuel and nice long highway ride can clean things up nicely.
 

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
Sounds like a plan - new jug of high octane has been purchased - need to drain the last bit of the old crap
 

dave b

Senior Member
Joined
Oct 20, 2010
Messages
3,617
Reaction score
7,513
ALWAYS start with the spark plugs. Easy, cheap, and quick to check/change. Also the cause of LOTS of problems of this sort, even when they look good.. That said, if it NEEDS choke to run, 99% of the time it's the slow (idle) circuit blocked. Could be an air bleed circuit, the pilot jet itself, or related to the mixture screw. Saying you "pulled carb and cleaned, and replaced some bits and pieces" doesn't tell me anything that helps. It does tell me the carb is the first place I'm going, cuz A: We're pretty sure that's where the problem is anyway, and B: The customer fucked with it himself.:laugh2: (Not slagging on your mechanical ability S, but I've been doing this for a very long time. Motorcycle carb work is my thing.) What 'bits' did you replace? It matters
 

jkes01

Senior Member
Joined
Jan 10, 2011
Messages
4,035
Reaction score
3,780
Fresh gas with fuel stabilizer is an easy test. I cannot run my riding mower in the summer without stabilizer in the fuel.
 

Mike I

Gold Supporting Member
Joined
Jan 11, 2010
Messages
2,315
Reaction score
2,819
Smell the old gas.

I Bet it smells like bad fuel.

Fresh gas and an approved carb cleaner may fix you up, since you said it was running fine before you stored it.

Good luck! :thumb:
 

Pop1655

Gold Supporting Member
Joined
Aug 24, 2014
Messages
14,364
Reaction score
41,292
How old is the bike? Common older boat issue is non-ethanol resistant fuel lines. They self destruct from the inside out. You'll never see it. A fuel line replacement has cured many an outboard.
 

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
I think dave b is on the right track.
The customer (me) shouldn't have fucked with it :)

Completely drained the fuel - went with fresh stuff and ran it for quite a while (neighbors must love me).
It will idle without the choke but giving it any throttle it pukes, sputters and will die unless I grab some choke.
Taking a break as I tend to make things worse when I work in frustration.
Gut feel is I messed up and will likely tear it all down again (tomorrow)

For reference: (hoping dave b is following along )
2000 Harley softail - basically stock first year of the twin cam.
Dealer did the "Stage 2" kit when I bought it (If memory serves - high flow air cleaner, a re-jet and freed up the idle mixture screw). I upgraded the pipes (Vance and Hines big shots with the quiet baffle). Other than that - stock drivetrain.
While I had the carb off - I cleaned it all up, inspected the jets and replaced the accelerator pump diaphragm). Cleaned and inspected everything I could pull apart.
I never really paid much attention to the workings of the HD Kleihn CV carb - but here is a vacuum actuated slider valve that regulates airflow as the throttle is opened up. I kind of suspect I should see it moving as I open up the throttle - but it doesn't budge (granted I didn't go wide open but still??)
Gut feel - I messed up the assembly of the main vacuum diaphragm.
Spark plugs look ok - but maybe I'll order a new set anyway.
Will do some reading tonight before getting back in to it tomorrow.
 

dave b

Senior Member
Joined
Oct 20, 2010
Messages
3,617
Reaction score
7,513
Double check that the slide diaphragm is in its groove at the top of the body. Double check that a handful of throttle delivers a squirt from the accell. pump nozzle (they can take a while to prime) The slide diaphragm assy doesn't regulate airflow. The butterfly valve that the cables are hooked to does that. The slide simply raises and lowers your jet needle in the needle jet, thereby regulating FUEL flow from the main jet.. Sitting there idling, give it some throttle, you should see it rise a bit.
Idling properly, then dying under ANY load could be fuel level in the bowl. More critical than most people realize. I check the float height on ANY carb I have the bowl off. Hope some of this helps. you're too far for a house call.
 

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
Double check that the slide diaphragm is in its groove at the top of the body. Double check that a handful of throttle delivers a squirt from the accell. pump nozzle (they can take a while to prime) The slide diaphragm assy doesn't regulate airflow. The butterfly valve that the cables are hooked to does that. The slide simply raises and lowers your jet needle in the needle jet, thereby regulating FUEL flow from the main jet.. Sitting there idling, give it some throttle, you should see it rise a bit.
Idling properly, then dying under ANY load could be fuel level in the bowl. More critical than most people realize. I check the float height on ANY carb I have the bowl off. Hope some of this helps. you're too far for a house call.
Appreciate the advice... didn't consider the float. I think I can do that without removing the carb. (dealer had messed up one of the float bowl screws so I also replaced those with allen head bolts - so easy to access)
But... slide doesn't budge when I give it some throttle - It moves freely but won't move on it's own when I crack the throttle. Kind of suspect I messed up seating the diaphragm when I put it back together (sucks because the carb has to come off to remove the slide)
 

dave b

Senior Member
Joined
Oct 20, 2010
Messages
3,617
Reaction score
7,513
But... slide doesn't budge when I give it some throttle - It moves freely but won't move on it's own when I crack the throttle. Kind of suspect I messed up seating the diaphragm when I put it back together (sucks because the carb has to come off to remove the slide)
Do that.....don't touch anything else, and try it. (If you had it apart, by all means check the float height. If you didn't, it ran fine before, remember.) Sucks, but, that's the drill.
 

Crotch

Triggered
Gold Supporting Member
Joined
Jan 13, 2012
Messages
27,377
Reaction score
67,553
Smell for sure. If gas is old, you'll know it immediately. My first job out of high school was a small engine mechanic. First snow every year we'd be buried with snow blowers that wouldn't start. Drain the gas, change the plug, 35 bucks for 15 minutes of work. Sometimes get close to 100 in a day.
 

Uncle Remus

Senior Member
Joined
May 5, 2016
Messages
1,684
Reaction score
3,557
New fuel and a bit of seafoam. Run the shit out if it and see if it picks up. Does it just fall on it's face when you put the coal to it? Does it get better after it warms up? Is it worse on a cool morning? All things that would help to find the cause.
 

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
New fuel and a bit of seafoam. Run the shit out if it and see if it picks up. Does it just fall on it's face when you put the coal to it? Does it get better after it warms up? Is it worse on a cool morning? All things that would help to find the cause.
First time I've fired it up since last fall and... it isn't running well enough that I'd dare actually taking it out on the road.
So, having said that... it will idle with no choke once it warms up but:
- blip the throttle and it pukes and sort of backfires
- slowly increase the throttle (guessing maybe 2000 rpm) and hold steady - give it maybe 10 seconds and it starts to puke and sputter, rpms drop. Grab some choke and it recovers.

Still doing some reading and youtubing... pretty sure I messed up the install of the main diaphragm as it does not move when giving it gas.
Also I'm wondering if the low speed jet isn't quite clean. Could see light through it but just a pinhole.... I think I should be able to snake an unwound G string through it? (#45 low speed jet).
Assumed the low speed jet wasn't really relevant as I thought the main jet was the working circuit once I got away from idle... but after reading it seems that assumption was wrong.

Think my battery is on it's last legs as well... guessing that isn't helping (Not sure if it is relevant though?)

Will remove the carb again tomorrow and:
- recheck the low speed jet
- recheck the fuel needle valve and float level
- ensure I get the main slide diaphragm installed correctly
Probably change the spark plugs for good measure
Probably replace the battery if it doesn't blow my budget

So, back at it tomorrow.
Dave b has me figured out.... I'm probably the typical mechanical hack that ensures his job security as I end up having to pay the pros to fix my damage :)
I enjoy the process of wrenching (helps me relax) but my batting average for actually making things run better is pretty low.
 

Uncle Remus

Senior Member
Joined
May 5, 2016
Messages
1,684
Reaction score
3,557
Definitely running lean any of those things could cause it. Pretty sure you're going in the right direction. Sitting kills bikes. I always made a point to take at least a short ride once a month when I had a bike, but I don't live in Canada. Get 'er fixed and use a little Stabil next year
 

Skeletor

Senior Member
Joined
Dec 5, 2009
Messages
836
Reaction score
1,519
Well - pulled the carb (much quicker the second time around) - stripped it all down and rechecked the bits I assumed I messed up but... all looked good and within spec.
- Float level - check
- Low speed jet - clean and clear
- Main Jet - clean and clear
- slide seems to work as it is supposed to - diaphragm looked good - not pinched
- Accelerator pump - sprays as expected
- Pulled the idle mixture screw for good measure - nothing unusual there
Float bowl was full when I pulled it

Any other thoughts before I put it back on the bike? :)

Move on to ingredient 2 - Spark?
(Figured Spark would exhibit different symptoms so I hadn't considered it)

Time to order some new spark plugs I guess
 

dave b

Senior Member
Joined
Oct 20, 2010
Messages
3,617
Reaction score
7,513
Well - pulled the carb (much quicker the second time around) - stripped it all down and rechecked the bits I assumed I messed up but... all looked good and within spec.
- Float level - check
- Low speed jet - clean and clear
- Main Jet - clean and clear
- slide seems to work as it is supposed to - diaphragm looked good - not pinched
- Accelerator pump - sprays as expected
- Pulled the idle mixture screw for good measure - nothing unusual there
Float bowl was full when I pulled it

Any other thoughts before I put it back on the bike? :)

Move on to ingredient 2 - Spark?
(Figured Spark would exhibit different symptoms so I hadn't considered it)

Time to order some new spark plugs I guess
New plugs for sure. When you reassemble, inspect the intake manifold closely. Some Harleys are prone to intake leaks. When it's together and running at idle, spray a shot of brake cleaner or propane at the carb/manifold joint. If there's a vacuum leak, you'll know.
The reason I mention the vacuum leak is the fact your slide wasn't rising before. Pressure differential is what makes it happen.
Good luck.:fingersx:
 


Latest Threads



Top