anyone have bendix tuning insructions?
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From: Houston Texas
RE: anyone have bendix tuning insructions?
cds4682......
I started the bike up again and took the air cleaner off to look inside to see whats going on. I have never seen so much gas being given. It really seems like I need to go to a smaller jet. I wasable to cross the jet numbers to more modern #'s I have a 1.10mm jet right now, I can go as low as .95mm
First of all, the excessive fuel you are seeing is from the accelerator pump, not from too large a jet.
Let me explain to you how this (and any other) carb works:
The fuel sits in the float chamber. The carb has a venturi that pulls suction when the engine is running.
The fuel is pulled from the float chamber and is routed through the idle tube to the top of the carb, then it is routed through the low speed adjustable jet (this is the needle closest to the engine) and at this point it has become an air/fuel mixture, and it dumps into the venturi to mix with the air the engine is sucking through the carb venturi. This 'dump' is done through 4 different small holes located in the roof of the venturi.
At first the fuel comes through hole #1.
As the throttle is opened further it comes through #2, then #3 and finally #4 as well.
At this point we have a bit of throttle rolled on.
A Bendix has an accelarator pump (some carbs do not) used to move fuel from the float chamber directly into the venturi when you suddenly crack the throttle. This is the 'excessive fuel' you are seeing. However, it is not excessive, but only appears to you that it is.
So far at this point, we have the engine running on nothing more than the idle/mixture screw (low speed adjustment), the air being sucked into the carb, and the accelarator when the throttle is quickly cracked open.
As you open the throttle up the engine starts to draw fuel through the main jet and the low speed adjustment becomes a background thing.
So, to sum it all up......
If you are sooty fouling plugs at idle speed or very small throttle opening, this will be corrected by adjusting your low speed needle. There is no jet to change out.
If you are out on the highway running 60 mph and the plugs foul with the sooty black coating then it is either that bad O ring (not in this case as you said the O ring was good) or you need to change out the main jet to a smaller one. I seriously doubt that is even a remote possibility.
Back to adjusting the low speed needle....
First start the bike and warm up to operating temp. Set the idle speed to 900 to 1000 rpms
You adjust the low speed needle (air/fuel mix) to obtain the highest rpm.. If it picks up to more rpm then reset the idle to 900 and adjust again. Turn the needle in until the engine falters. Stop. Turn the needle out until the engine falters. Stop. Return the needle to midway between these 2 points. Your low speed is now perfectly adjusted.
If you differ over this explanation,, then simply go buy yourself a smaller main jet size and install it.
Now go ride it at 60 mph and see what it does in regards to fouling plugs and see how well it runs (or does not run)...........pg
I started the bike up again and took the air cleaner off to look inside to see whats going on. I have never seen so much gas being given. It really seems like I need to go to a smaller jet. I wasable to cross the jet numbers to more modern #'s I have a 1.10mm jet right now, I can go as low as .95mm
First of all, the excessive fuel you are seeing is from the accelerator pump, not from too large a jet.
Let me explain to you how this (and any other) carb works:
The fuel sits in the float chamber. The carb has a venturi that pulls suction when the engine is running.
The fuel is pulled from the float chamber and is routed through the idle tube to the top of the carb, then it is routed through the low speed adjustable jet (this is the needle closest to the engine) and at this point it has become an air/fuel mixture, and it dumps into the venturi to mix with the air the engine is sucking through the carb venturi. This 'dump' is done through 4 different small holes located in the roof of the venturi.
At first the fuel comes through hole #1.
As the throttle is opened further it comes through #2, then #3 and finally #4 as well.
At this point we have a bit of throttle rolled on.
A Bendix has an accelarator pump (some carbs do not) used to move fuel from the float chamber directly into the venturi when you suddenly crack the throttle. This is the 'excessive fuel' you are seeing. However, it is not excessive, but only appears to you that it is.
So far at this point, we have the engine running on nothing more than the idle/mixture screw (low speed adjustment), the air being sucked into the carb, and the accelarator when the throttle is quickly cracked open.
As you open the throttle up the engine starts to draw fuel through the main jet and the low speed adjustment becomes a background thing.
So, to sum it all up......
If you are sooty fouling plugs at idle speed or very small throttle opening, this will be corrected by adjusting your low speed needle. There is no jet to change out.
If you are out on the highway running 60 mph and the plugs foul with the sooty black coating then it is either that bad O ring (not in this case as you said the O ring was good) or you need to change out the main jet to a smaller one. I seriously doubt that is even a remote possibility.
Back to adjusting the low speed needle....
First start the bike and warm up to operating temp. Set the idle speed to 900 to 1000 rpms
You adjust the low speed needle (air/fuel mix) to obtain the highest rpm.. If it picks up to more rpm then reset the idle to 900 and adjust again. Turn the needle in until the engine falters. Stop. Turn the needle out until the engine falters. Stop. Return the needle to midway between these 2 points. Your low speed is now perfectly adjusted.
If you differ over this explanation,, then simply go buy yourself a smaller main jet size and install it.
Now go ride it at 60 mph and see what it does in regards to fouling plugs and see how well it runs (or does not run)...........pg
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RE: anyone have bendix tuning insructions?
thank you for all of you help. I plan on getting a service manual as soon as I can stop buying parts. When I bought the bike I had planed on getting one right away but ended up having to sink a lot of money into just trying to get her to run. Thank you again. Without this site I most likely would have already sold or blown up my bike. Just kidding about the blown up I probably just would have set fire to it.
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RE: anyone have bendix tuning insructions?
ORIGINAL: csd4682
thank you for all of you help. I plan on getting a service manual as soon as I can stop buying parts. When I bought the bike I had planed on getting one right away but ended up having to sink a lot of money into just trying to get her to run. Thank you again. Without this site I most likely would have already sold or blown up my bike. Just kidding about the blown up I probably just would have set fire to it.
thank you for all of you help. I plan on getting a service manual as soon as I can stop buying parts. When I bought the bike I had planed on getting one right away but ended up having to sink a lot of money into just trying to get her to run. Thank you again. Without this site I most likely would have already sold or blown up my bike. Just kidding about the blown up I probably just would have set fire to it.
As far as the service manual thing.
You will find that having the "factory service manual" and the "Factory parts catalog" when you start will save you mucho time and aggravation. It will also go a long way toward preventing mistakes and needless waste of $$$ on parts.
The manual is important because it clearly outlines the way to go about installing, removing and troubleshooting things.
The parts catalog is very important as it not only has detailed exploded views of every section of the bike. But it shows the order they go on in, all the washers and such and list all the correct bolt sizes and part numbers. And on top of that, it will tell you what parts cross over to work on what years.
So always get the parts catalog with the widest model years covered.
So get those manuals/catalogs now..........then get back to work. You'll never regret it.
On Ebay you can get good, clear copies for about $20 each if you look and shop right. Just do a search on Ebay for Harley Service Manuals. You'll figure it out from there.
Enjoy that Ironhead!
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