Author Topic: Keihin PD diagram?  (Read 8904 times)

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hawkeye

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Keihin PD diagram?
« on: July 16, 2005, 12:54:43 PM »
Hey all, I just got my bike running well enough to ride but I'm having some trouble with idling.  I have the shop manual for my 750f but the carbs they cover in there are not the same, at least it doesn't look like it.  I'm trying to figure out how to adjust the pilot screw and it seems like it's at a different location on my bike than in the manual.  I was wondering if there were any PD diagrams online somewhere that would help me out.  Sorry for such a stupid question, it's just that I just got my 750 and have never worked on motorcycles before.  Thanks for any suggestions you guys can offer.

Offline jtb

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Re: Keihin PD diagram?
« Reply #1 on: July 16, 2005, 07:16:30 PM »
Hawkeye, the screw is at the front of the carb, in a molded recess.  Start with the screw 1 3/4 turns out.  If your experience is like mine, you'll be able to remove the carbs, tear them down, reassemble and remount them in under 2 hours.  ::)

John
1977 CB750F
1985 V65 Sabre
1986 VFR 750 (gone but missed greatly)

Offline Steve F

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Re: Keihin PD diagram?
« Reply #2 on: July 18, 2005, 09:45:22 AM »
Hawkeye, the screw is at the front of the carb, in a molded recess.  Start with the screw 1 3/4 turns out. 
John
That all depends on what year you're talking about. if you have a '77 or later, the adjusting screw is on the "engine" side of the carb.  '76 and older have the adjuster on the "filter" side.  The '77's used a fuel adjuster, and the 75-76 used an air adjuster.  Turning out an air adjuster will lean, turning out a fuel adjuster will richen the mixture. confused now?  ???

hawkeye

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Re: Keihin PD diagram?
« Reply #3 on: July 19, 2005, 08:24:30 AM »
Thanks guys for the replies.  My laptop's motherboard blew up on me so I haven't had internet access at home.   >:(

Anyway, mine is a '77 and there is a big brass knob on the right side of the engine side of the carb, I'm guessing this is the fuel adjuster?  I have to fiddle with it to start, then fiddle with it when I'm stopped at lights and stop signs because it seems to want to race up to about 3k rpm on me until I turn it out a little bit.  Then it seems to do it again the next time I stop.  What I usually have to do is turn it in a few turns to get the bike started then gradually turn the screw out as it warms up.

Offline TwoTired

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Re: Keihin PD diagram?
« Reply #4 on: July 19, 2005, 08:59:30 AM »
I think we have a terminology problem here. The big knob you are turning is simply a lower travel adjustment for your throttle twist grip.  This is set when the engine is at full operating temp for an idle speed of 950-1050 RPM.

The pilot screws are located, one, on each carb, centered and slightly forward of the float bowl housings.  These adjust fuel mixture at idle speeds.

I suspect what you are really after is a choke adjustment.  At the base of the choke knob is a friction adjustment so it will hold a setting while the engine is running.  There is also a fast idle cam adjustment linked to the choke knob so that the idle speed is increased as the the choke knob is pulled out.  This fast idle cam also changes the lower travel adjustment for your throttle twist grip. Fast idle speed is 3000-4000RPM at is maxium.


Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

eldar

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Re: Keihin PD diagram?
« Reply #5 on: July 19, 2005, 09:50:15 AM »
Adjust your brass knob (idle) when engine is warm.  The screws control your air/fuel mix for idle but NOT idle speed. If you have good response when pulling on the gas from ilde, leave these screws alone.

I know what tied says about the choke adjustment. It is not mandatory but unless you set it, you will have to keep monkeying with the gas to keep the bike running.