MAP sensor carbureted Eglide?
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Road Captain
Joined: Jan 2007
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From: under the bridge on the sunrise side
MAP sensor carbureted Eglide?
Whats it do? I have my bike apart right now trying to figure out why it runs so shitty below 2k rpm's and noticed it wnen I pulled the intake manifold off to check the seals. I am going to disassemble and clean/inspect the carb while I am at it. I wonder if an S&S carb would be a better option on a stock motor, I am at 60k miles and if worn beyond repair what my best route would be.
Road Warrior
Joined: Jul 2006
Posts: 1,532
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From: Rochester N.Y.
I had a 2006 FLHT (carbed) and didn't notice a map sensor....
Well anyway , the MAP sensor would tell the ECM what load the engine is at by the vacuum available in the intake manifold.
Low vacuum=high load high vacuum=low load
The reason it's not a vacuum sensor , is that ECM's don't do negative values well.
So they call it a MAP sensor AKA Manifold Absolute Pressure Sensor.
I would clean out the original carb , as it's probably the best and easiest carb to tune that you'll ever mess with.
Once jetted properly , you wouldn't need to play with it much ever , unless to clean crud out of the bowl on occasion.
Mick
Well anyway , the MAP sensor would tell the ECM what load the engine is at by the vacuum available in the intake manifold.
Low vacuum=high load high vacuum=low load
The reason it's not a vacuum sensor , is that ECM's don't do negative values well.
So they call it a MAP sensor AKA Manifold Absolute Pressure Sensor.
I would clean out the original carb , as it's probably the best and easiest carb to tune that you'll ever mess with.
Once jetted properly , you wouldn't need to play with it much ever , unless to clean crud out of the bowl on occasion.
Mick
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
what year bike?
map sensor?
The stock Keihin CV carb is a great carb.
the S&S was a good replacement for the carbs used by H-D previous to the CV--- only the CV is self adjusting for altitude.
an S&S or mikuni may work better at a specific altitude, then need re-jetting if you go up or down a couple of thousand feet.
( my pal with the mikuni'd 105HP roadking couldn't keep up with my stock 80" EG Classic if we went up to 5000', we live at 1400')
nightrider.com has good cv tuning and modding info in the biketech section.
the cv has a low speed jet, usually a 42 to 48, and main or high speed jet usually 170 to 195, and a needle which is suspended from the slide.
the 2 jets and the needle ( which moves in and out of the main jet, like making a circle with your finger and thumb and moving the other finger in and out of it--- the taper of the needle determines how much fuel is added to the air)
aside from blockages in the jets, worn seals and a pinholed diaphragm on the slide are about the only problems you can see on these.
( there is also an idle adjust under a plug- presence or absence of a plug indicate whether the carb has been monkeyed with)
the seals on the stock design intake manifold can be a problem, many of us changed to a solid manifold such as bartels, ramjett and S&S ( I've used all 3 ), which have better sealing.
Werte you able to check the manifold for leaks before you tore into this?
the carbed Harleys I've owned ( with electronic ignition) had only a vacuum operated switch with retarded ignition timing if vacuum was low ( "low" is dependent on model bike/ gearing/weight)--- this black plastic switch called the VOES is usually mounted behind the horn or on top of the intake manifold.
Mike
map sensor?
The stock Keihin CV carb is a great carb.
the S&S was a good replacement for the carbs used by H-D previous to the CV--- only the CV is self adjusting for altitude.
an S&S or mikuni may work better at a specific altitude, then need re-jetting if you go up or down a couple of thousand feet.
( my pal with the mikuni'd 105HP roadking couldn't keep up with my stock 80" EG Classic if we went up to 5000', we live at 1400')
nightrider.com has good cv tuning and modding info in the biketech section.
the cv has a low speed jet, usually a 42 to 48, and main or high speed jet usually 170 to 195, and a needle which is suspended from the slide.
the 2 jets and the needle ( which moves in and out of the main jet, like making a circle with your finger and thumb and moving the other finger in and out of it--- the taper of the needle determines how much fuel is added to the air)
aside from blockages in the jets, worn seals and a pinholed diaphragm on the slide are about the only problems you can see on these.
( there is also an idle adjust under a plug- presence or absence of a plug indicate whether the carb has been monkeyed with)
the seals on the stock design intake manifold can be a problem, many of us changed to a solid manifold such as bartels, ramjett and S&S ( I've used all 3 ), which have better sealing.
Werte you able to check the manifold for leaks before you tore into this?
the carbed Harleys I've owned ( with electronic ignition) had only a vacuum operated switch with retarded ignition timing if vacuum was low ( "low" is dependent on model bike/ gearing/weight)--- this black plastic switch called the VOES is usually mounted behind the horn or on top of the intake manifold.
Mike
Last edited by mkguitar; Oct 2, 2011 at 02:52 PM.
Cruiser
Joined: Mar 2011
Posts: 210
Likes: 6
From: N/A
Excellent answer, the ECM uses the map feedback to adjust the timing curve, not many failures with em.
After you get the intake seals installed also check or replace the carb to intake mount seal.
Pull the top on the carb while you have it off & thoroughly check the rubber vacuum slide boot. Be careful when you replace the top not to pinch it anywhere. a tiny hole in that seal will give the carb erratic idle poor low speed & acceleration performance.
Not sure what yr bike you have or if the motor is stock, but there are also some very inexpensive mods that can be done to a OEM carb that will help big time.
I would not suggest spending the dough for another carb, not just yet anyways...
After you get the intake seals installed also check or replace the carb to intake mount seal.
Pull the top on the carb while you have it off & thoroughly check the rubber vacuum slide boot. Be careful when you replace the top not to pinch it anywhere. a tiny hole in that seal will give the carb erratic idle poor low speed & acceleration performance.
Not sure what yr bike you have or if the motor is stock, but there are also some very inexpensive mods that can be done to a OEM carb that will help big time.
I would not suggest spending the dough for another carb, not just yet anyways...
Last edited by 05FLHTC; Oct 2, 2011 at 11:46 AM.
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Road Captain
Joined: Jan 2007
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From: under the bridge on the sunrise side
Well its all apart and inspected, waiting for the crappy carb clean they sell us today to do its magic. The carb looks to be in good shape no real wear on the throttle shaft and no heavy buildups inside. I will order a Genuine James gasket set tommorrow. I decided to completley go thru the fuel system while I am at it. 6ne thing I found while disassembling was a large buildup in the tank of silver colored slivers, they were so numberous that I all but destroyed the fuel strainer getting it out. I have decided to replace the petcock with a new one sans the vacuum shutoff. I am leaning toward a pingle, any thoughts? Thanks for the replys it verifys my hunch that it acts somewhat like an old style vacuum advance unit on an automotive distributor in that controls spark advance during periods of high and low vacuum conditions.
Last edited by ppilotmike; Oct 2, 2011 at 12:59 PM.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
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From: Phoenix '53, '88, '09 Big Twins
pingels' good, although for myself I use stock style--- I like not thinking about the petcock. last time i needed one, I got it from an "upgraded" Pal.
examine the slide diaphragm under strong light for pinholes
you may want to replace the float bowl screws, i use 4 mm allens, anti seize on the threads, makes easy for tuning.
can drop the float bowl with the carb in place.
voes switches come in different ratings, or you can get an adjustable and set it yourself with a vacuum gauge.
may want to test yours under vacuum for air leak, since you have it accessible
mike
examine the slide diaphragm under strong light for pinholes
you may want to replace the float bowl screws, i use 4 mm allens, anti seize on the threads, makes easy for tuning.
can drop the float bowl with the carb in place.
voes switches come in different ratings, or you can get an adjustable and set it yourself with a vacuum gauge.
may want to test yours under vacuum for air leak, since you have it accessible
mike
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Road Captain
Joined: Jan 2007
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From: under the bridge on the sunrise side
No Vacuum Operated Electric Switch in 01'. I included a pic of the MAP sensor and its location. From my research the VOES went away in 98-99'. MK you may be right about the petcock, I also like not having to think about it. What part of Phoenix do you live in? I lived there in the early 70's at the corner of 35th Av and Glendale, miss the desert, may have to move back some day.
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my 04's MAP sensor went bad at fairly low mileage as it was still under the 2 year warranty, I believe I had under 30,000 miles on it at the time any way as 05flhtc said it effects timing curve. the only reason I discovered it was bad was it would be really doggy when going WOT until the revs got up past 3500 or so. during normal operation I never really noticed any difference in driveablity. It was during a dyno base line run that it showed up. I did the diagnostic trouble codes and sure enough it came up a bad map sensor. Other then having to pull the tank to get to it it was easy to change and a cheap part. I had over 80,000 miles on it when I got rid of it and the carb was still fine.
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Road Captain
Joined: Jan 2007
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From: under the bridge on the sunrise side
Ok so I had a couple days off and got the old scooter running. Rode it a hundred or so miles and I am still not happy with the way it runs below 2K rpm. It is worse when the engine is cold and chilly OATs adds to the problem. It just seems to break up, and isn't smooth at all. SO what I now know. It has new plugs and wires. The carb had been mod'ed before I got it, the vaccum hole in the slide is larger than 1/8", the emulsion tube I believe is not stock as it is installed with a screwdriver as opposed to a wrench, the needle I also believe is not stock as it has a snap ring and several spots you can install it to raise or lower its position. I found a slow jet marked 45 and the main is a 180. The float level was low so I adjust that IAW the factory MM. When I ordered my parts I got a 48 slow jet just in case, I guess that is where I will go next. Turning the mixture screw out seemed to have helped but it is now 3 and 1/2 turns out and there isn't much pressure from the spring acting on it. So calling all carb experts, what do ya think, should I bite the bullet and go S&S or try to save this poor step child? I stayed with the stock petcock after all, seemed like the right thing to do. Also I have pulled the plugs a couple times and there is no sign of brown, just white deposits and not much of that. While I was doing all this I changed all three of the intake manifold seals, the cylinder head ones were tightened per the MM and I even torqued them to 10ft Ibs, and verifyed the flanges were installed with the front in the front. Well thats all I can think off.
Last edited by ppilotmike; Oct 10, 2011 at 07:09 PM.