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Air-cooled: Running too lean?
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calo1956
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PostPosted: Mon Dec 31, 2018 11:53 pm    Post subject: Air-cooled: Running too lean? Reply with quote

Ok first, Happy New Year to all! Its been awhile since i posted a question here, a good thing indeed. So I have noticed that my gas milage has gone down to the point of 10 -11 mpg I check it every fill up, and its been consistent that way for several months now.

So the back story. I did some mods to the AFM to rich up the fuel mixture, fearing it was running to lean based on mostly spark plug color. Thats around when i noticed the mpg's going down. So today, I decided to return what i changed back to the factory settings, thinking that it must be running to rich based on my poor fuel economy. After doing so, i decided to pull the plugs to see their color. They varied somewhat, but none looked rich at all, in fact all were light with no fouling, and #4 had the whitest porcelain and the electrode was white as well.

So if im not, as many of you will probably suggest, to alter the inner workings of the AFM, how do i richen up the mixture? The air bypass screw? I have a LM2 that i connect to the tail pipe, but i can't seem to get any steady reading what so ever, so im just going by the plug color. The van has been running good, other than it won't hold a idle till it warms up, and the poor mpg's. I have used a smoker to look for vacuum leaks, and have fixed any i found.
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PostPosted: Tue Jan 01, 2019 12:03 am    Post subject: Re: running to lean Reply with quote

I would leave the AFM alone and go right after all your grounds. Throughly clean every ground, especially the ones for the EFI system that are mounted on the top left side of the motor. Then the main strap under the coil. See what that does for you. Don’t forget the dielectric grease.
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calo1956
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PostPosted: Tue Jan 01, 2019 12:08 am    Post subject: Re: running to lean? Reply with quote

Thanks Bus Junky, the motor has less than 5000 miles on it, and its pretty pristine, and I replaced the old harness, so all my connections are clean
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PostPosted: Tue Jan 01, 2019 12:22 am    Post subject: Re: running to lean? Reply with quote

Indeed! Looks nice! I was also under the impression it was a waterboxer. My bad.
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PostPosted: Tue Jan 01, 2019 1:18 am    Post subject: Re: running to lean? Reply with quote

The sooty base ring indicates your mixture is rich. Bad camera angle on the electrode so it's hard to tell timing/heat range. What plugs are you using?
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Wildthings
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PostPosted: Tue Jan 01, 2019 5:11 am    Post subject: Re: running too lean? Reply with quote

They took the lead out of gasoline forty years ago that used to leave a whitish coat on the plugs and exhaust, and have added other stuff that makes the combustion more complete eliminating soot, the two of which make it very difficult to tune an engine using plug color. If you look at a modern gasoline powered vehicle you will not even see any color in the tailpipe at all, just bare metal. You pretty much can not tune by color any more and haven't been able to do so for decades.

To use an A/F meter get a bung welded into your exhaust prior to the muffler if feasible with your exhaust layout, or as close is reasonably possible to the exhaust in the tail pipe. The bung needs to go near the top of the pipe. You could also make an extension for the tail pipe if you were still getting any air pulsing that far back up the pipe.

The mixture adjust screw only effects the idle/off idle mixture. If you adjust the cog wheel then hopefully you made a paint mark at your starting point. If your engine was running strong before you messed with the cog wheel then a tooth or two would have been all that was needed to move your mixture to the rich side. In general once you begin to see a drop in gas mileage you have gone too far.
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PostPosted: Tue Jan 01, 2019 7:50 am    Post subject: Re: running too lean? Reply with quote

I think maybe you are basing your lean diagnosis on the bone white porcelain of the plug. That's a common misconception. It's the "base ring" that is the tell here- black and sooty = rich. The porcelain really only tells you if there is pre-ignition going on due to early timing. The ground strap will tell you if your heat range is correct based on the position of the heat mark- if the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then it means that the plug heat-range is "too hot", because heat is not being transferred/cooled from the strap to the base ring quickly enough. Lots of this kind of plug reading is from drag car tuning, but you are running rich for sure, and I'll bet you are running a lot of ignition advance.

Nice looking engine.
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calo1956
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PostPosted: Tue Jan 01, 2019 8:52 am    Post subject: Re: running too lean? Reply with quote

Thanks Wildthing, it wasn't running great before i loosened the tension on the large cog, and was a marked increase in performance after i ended up moving it CCW 4 teeth. I had also moved the small cog one tooth, that is supposed to richen the mixture across the the board. That i returned to the factory location. Im going to see if the milage goes back up, and will look more closely at the base ring of the plug rather than the porcelain. As always thanks for your help and advise. Im going to give the LM2 another shot as well..
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PostPosted: Tue Jan 01, 2019 8:59 am    Post subject: Re: running too lean? Reply with quote

Thanks Igeo. Im not sure i understand what you mean in regards to the ground strap. Do you mean the washer on the spark plug? And as far as the timing is concerned, I have it set to factory specs. I do agree that it is running rich, i can smell it, and now that you mention it the base of the plugs are somewhat fouled. As i mentioned, i have returned the one setting in the AMF, ill see if the MPH go up
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PostPosted: Tue Jan 01, 2019 9:06 am    Post subject: Re: running too lean? Reply with quote

The ground strap is the bent piece of metal that is attached to the base ring. It's grounded, and the spark jumps between it and the electrode embedded in the porcelain.
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PostPosted: Tue Jan 01, 2019 9:22 am    Post subject: Re: running too lean? Reply with quote

Thanks, my buddy just explained that to me, so based on my pic, it looks good, only the tip was white
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PostPosted: Tue Jan 01, 2019 10:40 am    Post subject: Re: running too lean? Reply with quote

First off I would add some FI cleaner to your fuel tank to get the injectors spraying well, and would set the timing to 28° BTDC @3500+ rpms, hoses off and plugged. Remember to reinstall the hose(s) when done.

The way I adjust the AFM is this:

First I adjust the wiper so it is at the maximum position, barely but still on the resistance strip when the vane is wide open. This will give you the maximum fuel when the pedal is dead to the floor at high speeds. I then set the cog so the engine is responsive but not overly rich at part throttle at around 40-60 mph in high gear.

You need to verify that your fuel pressure regulator is giving the correct pressures with the vacuum hose installed and removed.

If you have a dependable buddy, you can have him drive while you move the vane back and forth with your fingers as different loads are put on the engine. In general the wiper should be about centered in the sweet spot for any driving condition.
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PostPosted: Tue Jan 01, 2019 11:35 am    Post subject: Re: running to lean? Reply with quote

calo1956 wrote:
Thanks Bus Junky, the motor has less than 5000 miles on it, and its pretty pristine, and I replaced the old harness, so all my connections are clean
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calo1956
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PostPosted: Tue Jan 01, 2019 2:54 pm    Post subject: Re: running too lean? Reply with quote

Thanks Wildthing, Sounds simple enough, ill try adding some FI cleaner. I double check the timing, but unless it changed from the AFM re-adjustment it should be spot on. I had it out for a good run on the highway today, ran fine, but i noticed the CHTemp up. It usually runs 300 to 350 as per my gauge on the highway, and it looked more in the range of 350 to 400. I wasn't expecting that, the oil temp was up somewhat, but it has been below its norm since the cold weather set in. Tomorrow is another day, Ill check the timing, add some FI cleaner, and see how it goes from there...
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PostPosted: Tue Jan 01, 2019 3:02 pm    Post subject: Re: running too lean? Reply with quote

LM2 requires a bung. You will get very different readings between the bung and the end of the tail pipe. End of tail pipe was not successful for me.
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calo1956
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PostPosted: Tue Jan 01, 2019 3:19 pm    Post subject: Re: running too lean? Reply with quote

Thanks AZ, I don't know why that is, i watched some vids, mostly motorcycles and it worked fine fo them. Like you, i haven't had that luck. I don't get it, its not like im just sticking the hose in my tail pipe, I bought the special adapter from the manufacture for that purpose. Im gonna give it a shot again, and see. I t came with the bung, just i have a SS exhaust, so i can't weld it myself. With my set up i can just drop the muffler and have it welded on the short pipe between the flange and the muffler..
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PostPosted: Tue Jan 01, 2019 4:02 pm    Post subject: Re: Air-cooled: Running too lean? Reply with quote

With the tail pipe piece I got a massively fluctuating reading. This also happens as a result of an exhaust leak. With the bung and all leaks closed up I was able to adjust my A/F ratio to my desire. This was four years ago now so my memory is faint. I do know that I finally got the ratio to where the motor ran strong and stayed cool but had real bad MPG. Adjusted to where MPG were better made the engine run real hot. In the end I was drawn to the dark side.
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calo1956
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PostPosted: Tue Jan 01, 2019 4:14 pm    Post subject: Re: Air-cooled: Running too lean? Reply with quote

Yea AZ, i hear that. I already took a good running motor that ran cool, and smooth as a baby, and now its rough, mainly at idle, and already running hotter. I can't believe just returning the smaller of the 2 adj on the AFM back to factory would cause so many issues. Well ill figure it out, with help, i always do, thats why im still driving it 38 years later..
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PostPosted: Wed Jan 02, 2019 7:47 am    Post subject: Re: Air-cooled: Running too lean? Reply with quote

Just spent 4 hours on my van chasing the same deal. I have a o2 sensor I was able to yank out for the test though! (Cali spec, I think you have federal right?)


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Then I ran it to the front to the battery and was able to watch while driving:

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I got it to not run hot per say, but I am going to go back and lean it out a bit more because it won’t cold start correctly under 40 degrees because I set it too rich. Been waiting for a thread like this to pop up to try and get an answer as to where to set my numbers!

Idle I have at 14.7
No load rev is around 13.5
Full load is around 10.5 at the most heavy throttle.

Was gonna back the full load off to about 12 and see how it responds unless someone has some difinitive numbers I should set it at.
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PostPosted: Wed Jan 02, 2019 10:25 am    Post subject: Re: Air-cooled: Running too lean? Reply with quote

Well at least you got a steady reading, i think that is the target #'s you want, I do have a Federal, and no bung to tap into so its the tailpipe adapter or have a bung welded in. With the little change i made, it threw everything off, but my gas milage was horrible, so i leaned it out a bit, going back to where it was set in the factory. Im going to get out there and check timing etc. Nice Westy you have there!
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