BTW, I forgot to mention that the cylinders are bored .030 over if that matters at all.

 

Jets are a 165 and a 65. Gas squirt is just left of center.

 

Those jets are probably close. Here is the procedure to check the size of the slow jet and the number of turns out on the pilot screw [we always set the slow jet and pilot screw before messing with the main jet] ...

Setting The Pilot Screw on Your IronHead

If the carb is old and dirty the pilot screw passage may be gummed up such that you will not be able to "gently seat" the pilot screw reliably. If this is the case remove the carb from the bike and clean it up. Some guys try to do carb work with the carb in the bike. IMO this is a very bad idea.

In the pilot screw passage there should be, in this sequence: screw, spring, washer, o-ring. Occasionally POs have installed these parts in the wrong sequence; remember that the purpose of the washer is to protect the o-ring from being damaged by the spring]. The screw usually comes out easily. The other parts may require some work. The best technique is to stick a pipe cleaner in the hole, twist it around, and, like magic, out come the other parts on the end of the pipe cleaner.

EDIT: Some carbs, noteably 1966 to 1978 Sportster carbs, do not have the o-ring and washer in the pilot screw passage.

1. You need to have easy access to the pilot screw, easy enough to reliably judge "screw it in until gently seated". Loosen the front fuel tank mount bolt; remove the rear fuel tank mount bolt; prop the rear of the fuel tank up on a piece of 2X4; on some bikes this will not be necessary.

2. With the engine cold [so you do not burn your fingers] turn the pilot screw in clockwise until it is gently seated. Count the number of 1/4 turns as you do it; write the number down. Back it out to the original setting. You may need to return reliably to this setting after experimenting.

The "normal" starting point for this process is 1,1/4 [according to the 79 - 85 FM] or 1,1/2 [according to usual practice] turns out.

EDIT: An old HotXL magazine article recommends for Keihin butterfly carbs between 1/4 and 1,1/4 turns out. My experience is that this works best. If you are more than 1,1/4 turns out your pilot jet is too small.

3. The engine must be at full warm up. It will have very hot parts; to avoid burned fingers have a well lighted, comfy place to work.

4. Set the engine idling at about 1000 RPM. You want it to be idling at the slowest speed that is consistent with a smooth idle so that you can hear or feel slight changes.

5. Turn the pilot screw in clockwise until the engine idle becomes worse; tending to stall. Count the number of 1/4 turns as you do this. Then turn the pilot screw out counter clockwise until the engine idle gets good, then becomes worse, tending to stall. Count the number of 1/4 turns as you do this.

6. The best setting for your bike will be somewhere between these two settings. The FM says to use the leanest setting [most screwed in] consistent with a good idle quality. Some guys say to go between the two settings.

It should be between 1/2 and 1,1/2 turns out from gently seated. If it is not within this range you should change the slow jet.

EDIT: I follow the advice from the old HotXL mag article - set it between 1/2 and 1,1/4 turns out.

7. You may have to adjust the idle speed.

8. Make sure that the spark plugs are clean, then ride the bike. I usually go for a half hour or so ride outside the city, then ride home with the last 10 minutes at city riding speeds [so that it is on the "idle port", not the "idle transfer ports", the "mid range port", or the "main jet" [see carb diagrams in FM]]. Hopefully the plugs will come out a nice medium gray or tan color. If they are too dark you can screw it in another 1/4 turn; too light screw it out 1/4 turn, and try the ride again.

9. If they are really light or really dark the problem is not with the pilot screw setting. For example, too light might mean an intake or exhaust leak, and too dark might mean the pilot jet is too large [among other possibilities].

10. My experience with this process is that after making a change i have to clean the plugs and go for a good ride [say, an hour or so] before i can trust that the new results are reliable.

 

Thanks IronMick! Looks like I have some stuff to do this weekend.

 

Cleaning a Carb

1. Removing it from the bike should be straight forward. First thing when it is out is to check the pilot screw setting. Turn it all the way in until gently seated counting the number of 1/4 turns; then write this number down; then reset it.

2. I put mine in a vice to remove the screws, and for much of the following work. Wrap in a shop towel; close the vice gently taking extra care with the choke and throttle linkages. The vice is a needed extra pair of hands.

EDIT: A better choice than a plain vice ...


Better one ...



3. You must be very careful handling the float so as to not change the level. You should have the official specs for setting the level as in the FM, and check it, every time you dismantle the carb, as the last thing before putting it back together.

4. The jets are made of brass, a soft metal that is easily damaged. Use an exact correct size screwdriver. I ground a medium flat blade screwdriver down to exact size on my bench grinder to access the slow jet.

5. The general appearance of the inside of the carb is not necessarily a good indication of its condition. It can look spotless and have clogged jets, or look cruddy and have clear jets.

6. Clean each individual part. Do not allow any solvents to contact any rubber parts [tip of needle, o-ring seal for bowl]

7. Make a list of all of the jets and passages for your carb using the carb manual or the FM for the bike. Then ensure that you can blow either compressed air or carb cleaner thru each one.

8. Remove the pilot screw and clean the parts and the passage. The passage contains in this sequence: pilot screw, spring, washer, o-ring. These are very small parts, especially the washer and o-ring. Usually the spring will easily fall out. One time i thought the spring was not in there because it would not fall out; i obtained a new spring and could not get it in! The technique for removing the washer and o-ring is to use a pipe cleaner: stick it in the hole, twist it around, remove it - you should see the washer and o-ring on the end of the pipe cleaner.

EDIT: the washer and o-ring are part of the pilot screw assembly for 1979 on. They are not in the 1978 and earlier Keihin carbs.

Remember that the purpose of the washer is to protect the o-ring from the spring and you will always get them back in in the correct sequence.

9. Dismantle the accelerator pump assembly noting carefully the sequence and orientation of the parts. Clean and inspect the parts. Replace the diaphragm if it is cracked.

10. Check the float level then carefully put it back together. I personally find it very confusing trying to decide which way to bend the tang if it is not correct. If the fuel level is low is the float high or low? Do i need to bend the tang up or down? On the bench the carb is usually upside down, adding to the confusion. Sort all this out before making an adjustment.

Best to replace the original Phillips screws for the bowl with stainless steel socket head screws.

 

Mick,
Do you have the float specs for this carb? My FM is older and only has the Bendix in it. I searched online yesterday and cam up empty handed.

Thanks.

 

Hold the carb so that the float is hanging down to your left. Angle it a little if necessary so that the needle is just seated. You are looking at the choke plate. The fuel inlet is at the top. The distance between the top edge of the float [which is now on the left] and the edge of the carb should be 16 to 17 mmm, or .63 to .67 inch.

 

Mick,
Ok, so I adjusted the float and checked the sequence of parts on the pilot screw. While it was out I cleaned it with a pipe cleaner and sighted through to make sure it was open. I put the carb back on and started through the instruction on how to adjust the pilot screw. It makes no difference where I turn it, there is no change in the idle. Now, to clarify, I do not have a tach on this bike so will it effect it if I am idling too high? I can try to rig an electronic tach of some sort if needed.

On another note, I followed your instructions on cleaning/checking my generator (I commented about the dead battery on the post). Anyway I just wanted to thank you! You just save me a $100 rebuild. I cleaned it with contact cleaner and cleaned the copper contact on the armature (which were totally black) and it works great! What a relief!

Thanks again!
Dave

 

In my experience this means that the pilot screw is too small. If it were too large the engine would stall with a very small turn either in or out. Do not change the main jet, just the slow jet. It is currently #65.

J&P Cycles has Keihin slow jets in sizes 54, 60, 65, 68, 72, 75, 88, 100. i would go up to a #75.

68 is too small a difference from 65, virtually no different at all. So going to 75 is about like skipping one jet size. They cost about $8.00 each so you could order 72, 75 and 88. That would cover it for sure. If there had been some response to adjusting the pilot acrew i would perhaps suggest a #72.

There has been at least one case where a new jet from J&P was manufractired incorrectly and would not screw into the carb. If it will not go in easily do not force it. You will have to send it back and order from a different company. Best if you can order thru a local indie motorcycle shop.

 

I changed butterfly Keihin carb to my 1969 Sportster. Main jet is 170 and flow jet 88. Air/fuel mix valve opened 1 turn. Engine is getting so much gas spark plugs are black and there are big flames coming out of pipes when accelerating? Float level should be OK and checked intake sealing which also looks just fine. Any idea why it's getting so much gas because jets are pretty normal size?