OK I have a question, it may have been covered once I looked all over forum but couldn't find an answer.

I have an 81 Ironhead, just rebuilt carb with kit from Ebay.Its a Keihin After rebuild I have a high RPM issue. As long as carb is choked it will run low rpms but after it warms up and disengage choke rpms continue to climb. I Did not let it go over 3k but it would have continued to climb I am sure. Could I have done something during rebuild to open main jet up and its now allowing to much fuel through?

I have ordered new jets from J&P should be here by Wednesday. Is there anything else I should look into buying before Wednesday,to have on hand. I don't want to have to tear everything down over and over.

 

if you took the throttel blade out you put it in upside down or backwards -- dont know if you did that its a guess

 

First is to get the idle speed and pilot screw settings settled. These can only be set when the engine is fully warmed up - as in take it for a ride outside of city traffic. So once it has warmed up reduce the idle speed using the idle speed screw.

If that does not work then there may be a problem with the throttle cable. With the air cleaner off examine the throttle plate at the back of the carb - it should close almost all the way; if it stays too open you will get exactly what is happening.

Setting the pilot screw is done with the idle speed approximately correct, with the engine fully warmed up. Simply, turn it in until idle speed stumbles, then out until it stumbles again - then set it between these two limits. Best is between about 1/4 and 1-1/4 turns out. If it does not settle in this range then the pilot jet is not the optimal size.

A usual cause of high idle or slow return to idle is an intake leak - air being sucked into the cylinders thru the manifold/cylinder head or carb/manifold connection.

Another possibility is bad parts in the carb kit. The worst in this regard is the new "float valve" - the needle that controls flow of fuel into the bowl. These often leak fuel; often the old part is better than the new one.

I do not think i have nailed this down here, just presented some ideas to consider.

 

You were correct I didn't even consider I also bought a new throttle and replaced it. Brand new from HD shop and it doesn't let the throttle plate close all the way. Noticed after the fact, replaced with old one, idle is fixed. Now I am waiting for new jets to rid myself of some other issues.

 

Awesome! What are the other issues?

Is it the stock Keihin butterfly carb? For 1981 the stock jets are main: 160, slow: 68. Here are some notes ...

Setting Slow Jet and 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, a half hour or so] before i can trust that the new results are reliable.

 

I wish the carb was the only issue, but I got the bike with the sole purpose of enjoying it all year not just riding season. Four months on the road 8 months in the air. LOL
I am working on brakes and clutch untill jets get here, I ordered a few sizes including the stock.

 

Well Jets got here and whatever the issue was with the idle wasn't contained in the throttle. After i put new jets in in started it up and went right back to high idle. Going to look into possible intake leak.

 

Intake And Exhaust Leaks Tests

You cannot get a good tuneup if there are intake leaks or exhaust leaks.

1. Check for Intake Leaks

With the engine idling spray propane gas or WD-40 around the carb/intake/cylinder head joints. Propane is best because it leaves no mess, and is most easily sucked in thru leaks. WD-40 is said to work well because it has very fine spray droplets. Be careful to not allow any of either to get sucked in thru the A/C as this will invalidate the results.

Any change in engine RPM is a leak which must be fixed.

EDIT: Experience is that this procedure will identify larger intake leaks, but it may miss very small leaks that also must be fixed. And that propane is the better choice.

EDIT: You have to do a lot of spraying to detect a small leak. Propane will be really clean. Anything else like WD-40, carb cleaner, etc will make a huge mess.

2. Check for Exhaust Leaks

Pour about 1/2 ounce of oil into each cylinder thru the spark plug holes. Run the engine at idle. You will get lots of smoke for about 5 minutes.

All smoke should come from the ends of the exhaust pipes/mufflers. Any other is a leak which must be fixed.

 

Should this be done with a/c on or off or does it matter?

 

I do it with the A/C on.