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Gas smell when running

Started by SoftailDave, November 27, 2022, 10:24:24 AM

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SoftailDave

November 27, 2022, 10:24:24 AM Last Edit: November 27, 2022, 10:53:20 AM by SoftailDave
OK, this has been a puzzle for me for some time. Bike is 1997 Heritage Softail Classic with 24,000 miles. When running I get a smell of unignited gas from the exhaust. The front cylinder runs perfectly while the rear cylinder stutters at idle. My initial diagnosis was electrical. I checked the timing, replaced the spark plug and the the spark plug leads. Still same problem. I checked compression on both cylinders both were the same and good. Proceeding with my electrical diagnosis I replaced the entire ignition including the coil. This didn't resolve the issue.
I then turned to the carburetor out of desperation. Checked for leaks, no problem. Removed the carb and rebuilt it including a new slide. Still same problem.
A while back I installed a new EV27 cam and adjustable pushrods.
I am wondering if this issue could be due to the pushrods bring out of adjustment. There is no pushrod noise so if it is the problem I would assume one or both are adjusted too long.
Any thoughts would be appreciated.


Ohio HD

The bike has hydraulic lifters, so unless you cranked them down and bottomed the piston, they can't really be too tight. I'd look at a rear intake leak.
For your bike part needs, call Calif Phil   www.harleypartscheap.com

SoftailDave

Thanks, that makes sense.
I checked for an intake leak by spraying some wd40 around the intake. There was no change.
Forgot to mention I looked to see if the ignition was grounding somewhere.

Hossamania

Do you have a chrome cover over the coil? Make sure it is not rubbing on a plug wire or coil wire.
I want to suggest removing one plug wire at a time while running to see if there is a major difference between the two, but not sure how to do it and ground it out. Could try removing one, ground it, and try starting the motor. Then the other.
How is the gas mileage?
I ain't drunk, I'm just drinking

SoftailDave

The coil does have a chrome cover but nothing is rubbing. I have run the bike without the cover. I have run the bike on just each cylinder and the front runs like a charm but the back stutters. I don't know the gas mileage for sure but i suspect it isn't great. It seems to be running rich on the rear cylinder as there is black residue on the exhaust tip. When I rebuilt the carburetor I installed a knurled mixture needle for adjusting and I believe it is fine.
It makes no sense to me but is there some reason the rear cylinder could be getting more gas than the front?

kd

Quote from: SoftailDave on November 27, 2022, 03:25:24 PMThe coil does have a chrome cover but nothing is rubbing. I have run the bike without the cover. I have run the bike on just each cylinder and the front runs like a charm but the back stutters. I don't know the gas mileage for sure but i suspect it isn't great. It seems to be running rich on the rear cylinder as there is black residue on the exhaust tip. When I rebuilt the carburetor I installed a knurled mixture needle for adjusting and I believe it is fine.
It makes no sense to me but is there some reason the rear cylinder could be getting more gas than the front?

It sounds like carbon on the rear exhaust valve stem "may" be causing it to stick causing the problem.  It can cause the erratic idle miss and could also cause a rich mixture as it effects the compression at low idle rpm.  Do you notice the rear head pipe bluing up more than the front header pipe?
KD

SoftailDave

I didn't notice any notable bluing on the rear exhaust. However this sounds like a very likely cause of my issue.
The bike was running rich and it is very possible carbon has built up on the exhaust valve stem.  The bike hasn't had much use for the past couple of years.
Other than giving it a good run any suggestions ie gas additives etc that can clean the valve?

xlfan

Quote from: SoftailDave on November 27, 2022, 03:25:24 PMIt makes no sense to me but is there some reason the rear cylinder could be getting more gas than the front?
The rear cylinder always gets more gas due to the longer intake time on a carbureted 45 degree v-twin.

SoftailDave

XLFAN - That is interesting,  wasn't aware of that

JW113

I have to admit that trying to get my brain wrapped around the subtle different front/rear intake effects makes my head spin. Yes, there are some funny things going on that cause the front and rear AFR to be a little different, I believe it has to do with the fact that the intake dwell time (the time when neither valve is open and no air is flowing through the carb or intake manifold) is different between the two. But I think I'm fairly convinced that that has nothing to do with the issue you describe. Dunno, could be wrong of course.
 :SM:

My first question is, how do you ride this motorcycle? Baby it around like an old lady going to the grocery store or beat the living hell out of it every minute you're on it? Or something in between?

The next question is, please describe your start up process and how you manage the enrichener knob?

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

kd

 :agree: It's the far side of a 45 degree Vtwin.
KD

SoftailDave

I am almost 69 years old and usually have my wife on the back so I am like old lady driving to church on Sunday. On my own i am something in between.
Startup - I pull out the enrichener and let it warm up for a minute or two. Then off I go and push the enrichener until it will idle by itself, usually 1 or 2 miles.
Now, thinking about the enrichener, is it possible for the enrichener valve to malfunction?

Fugawee

I think that it is a safe bet to say that anything can malfunction.
But regarding Your Enrichener...assuming that the Carb is a Stock CV, I have seen some build-up on the Valve at the end of the Cable where it sits in the Carb's passage.  I removed it and cleaned it up, and the Carb itself.  Not saying that is Your issue, but it may be worthwhile to check out.  Pretty much the same thing if You are running an S+S...just a different style of Choke set-up.
As far as the Adjustable Push-rods...if You did the work, double check the adjustments.  It's not all that difficult, and You may get a surprise.
On My Bikes with Carbs, I try and use the Choke as little as possible.  Normally I don't need to use it unless it is really cold.
I think before I went to the Toolbox, and if You feel the Bike is OK to ride, I would take the Bike out on a lonesome stretch of road (if possible) and run it for a while doing some "big numbers" to see if maybe some build-up finds it's way out.
As far as a Fuel System Additive/Cleaner...I have never used any on a Bike so I can't comment on that.
Good Luck.  I know that this type of stuff can drive You nuts.  I hope that You find the Issue.

JW113

Based on the response for the riding style, that is my thought as well. Get it warm, find a long open highway stretch, and bang it off the rev limiter at WFO a few times in 3rd gear. A gasoline engine needs to be stressed on occasion to knock out some of the carbon build up from start ups, idling, and low speed riding. Back in the day, we used to get a squirt bottle of water, pull the air cleaner, rev the motor up and shoot some water down the carb throat. Sometimes it was quite amazing to see the cloud of black crap come shooting out the tail pipe...

Sounds like you're doing a reasonable control of the enrichener. My own practice is to start it up, push in to about 1/4 after it fires, idle for maybe 30 sec, then get rolling and push it fully in. I try to take it off the enrichener as soon as possible.

The other thing I forgot to ask, have you tried swapping the ignition wires at the coil to see if the symptom changes at all?

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

xlfan

Did you replace a stock type ignition with a stock type ignition? Like dual-fire coil, 3-wire ignition pickup and an under-the-seat ignition module?
Do you see any voltage drop at coil positive 12V?

SoftailDave

Thanks everyone for the help with resolving my problem. I am in Canada and the bike is now on my motorcycle trailer in my garage. We head to Arizona on December 26th.
Once there i will take it for a good run on the highway and try and blow out any carbon.
The ignition was replaced with a Dyna 2000i programable digital ignition system. I tried both the single and dual fire modes with no change.
I haven't tried swapping the ignition wires at the coil as i wasn't aware it would run properly doing that.
Voltage at the coil was OK.
You have given me some great ideas to resolve this issue. If you have any other suggestions please let me know.
I will provide an update later this month once I have the bike back on the road.
Thanks everyone!

Hossamania

What octane fuel are you running? It may like regular 87 over premium 91. 91 octane is technically a slower burning fuel, if the motor isn't set up for it compression-wise, it won't run as well. Not sure how the EV27 effects that. Also, the 27 is more of a midrange cam, not a cam to be lugged along like a 13, it prefers to be used a little harder than what it sounds like you've been doing.
Good luck!
I ain't drunk, I'm just drinking

SoftailDave

I have been running Regular which is 87 octane.

Hossamania

Then go hammer on it for a while and let us know how it works out!
I ain't drunk, I'm just drinking

SoftailDave

Will do! Looking forward to leaving the snow for the sun in Arizona.

Bunjie40

When you did the cam swap, who tuned the carb and what jets are in it..? A 180/45 if a CV carb still. Can you post a pic of the Spark plugs? Funny thing with carbed Evo's is the rear will run a little richer than the front..

kd

I just checked back in to  see if there was any progress.  I see by the previous post I must have missed there was a cam change.  If so what cam and air cleaner are you using?   After running it in a fashion that gives you the gas smell, if you stop. shut it off and give the air cleaner filament a sniff, do you get a heavy fresh gas odor? If the cam has enough overlap and duration it may be low RPM carb standoff.
KD

SoftailDave

Hi again
Just checked to see if there are other suggestions.
The cam is an EV27 and the air filter is a Kuryakyn Hypercharger with a K&N air filter.
I installed a Screamin' Eagle Dynojet Kit. Subsequent I read conflicting comments on this modification and thought this may be my issue. So I ordered a new slide and put the carburetor back to stock.
Unfortunately the bike is on the motorcycle trailer until I get to Arizona on December 28th.
I will check for gas smell from the air filter and take pictures of the spark plugs and post results here.
Thanks again everyone!

Hossamania

The hypercharger is not helping. From a performance standpoint, it helps even less.
I ain't drunk, I'm just drinking

JSD