I bought an 81' Ironhead and it ran when I got it, but not for long, it started back firing through tthe carb, so I tried cleaning it bu that didn't help either. I purchased and installed a new Super E carb and it did start but quickily died, and then back fired after it quit running. I think it may have flooded, but I am not sure. I am a virgin when it comes to motorcycles so any help on where to start and what to look for would be a great help.

 

the first thing you need to do is check for intake and exhaust leaks,i am not a s&s fan at all so i cant hepl with it,but it sounds like you may have leaks, take a propane torch( not lit lol)and shoot propane around the intake while its running if the idle changes you have a leak, how long has it sat? may need to adjust valves, maybe clean the fuel system also, does it have points ?

 

I would put your first carb back on it. You know it ran with that one. The new one may need to be jetted to match the bike and you have other tuning issues that need to be fixed first before you start swapping carbs.
Get a manual.
check the ignition starting from the plugs and working back.
Use good premium fuel without the ethanol mix.
You have had the carb off, so, as previously indicated check for leaks and fuel flow.
check compression (a good indicator if the push-rods need adjusting...and other possible issues)
and check the timing.
Once the bike is running well and tuned you can change the carb if you wish. You will need to tune the carb to the bike...but at least you know it is only the carb that needs adjustment to get the bike running properly.

 

I bought the bike just over a month ago. I rode it before I bought it but only around the block. It seemed to run fine then, A few days after I brought it home I started it again. It started up with no problem. So about a week and a half later I got it legal and it was a nice day so I was going to take it around the block. It started up with a little hesitation and once it was warm it backfired once through the carb and two times out the pipes, then died. I was told by the local mechaniac that my carb would never hold a setting and that I should change it. He also told me to loose the points. After a little research I found that the 81 does not have points but a solid state. I put on the new carb today after work and it started, even sounded good for about three minuets untill it died. I tried to start it again and got a backfire and could not get it to start again. Here is where I am stuck if I cant get it to start how do I check for leaks? Do you think a new igniton plugs and wires would help. I really dont want to take it to a mechaniac because I need to learn this. Is the clymer manuel the same as or equal to the h-d manuel? I am at a total loss here and any advise is much apperciated. Thank you

 

I bought the s&s carb new. It suposedly came jetted for my bike also two sets of jets were included one ritcher and one leaner. Shepdog I dont belive it has points, my research shows that it runs a solid state. Thank you men. I guess on my way home from work tomorrow I will stop and pick up some new plugs and possibly new wires. the wife said that next friday I can order a dyna S ignition. Any thoughts or suggestions? Should I get a single fire or a dual fire? What is the deffrence between the two?

 

My advice if you are new to working on ironheads is to hold off spending money on new ignition, new spark plugs and wires etc.
I would also include buying a new carb but you already made that plunge.

The best money you can put into the bike as your first purchase is a factory service manual. Not a Clymer or some other such manual..........Buy an official factory manual.

Then you will be better prepared to find the problem you are having and how to fix it.
In addition to the ignition system, you need to set the pushrod clearance, time the ignition, adjust the carb, not to mention adjusting the clutch and a hundred other things the service manual will instruct you on, along with help from members here.
There is no problem that a member of this forum cannot solve, trust me.

Maybe the problem is air leaking at the inlet manifold O rings.
An easy way to check this is remove the 2 bolts holdnig the carb to the manifold.
Run your finger inside the manifold, feeling 360° around each of the O rings surface. If you feel any irregularity at all then you have an air leak for sure. The O ring is compressed between the head and the manifold and the surface of each ring should be smooth and even.
Check front and rear cylinders.

The backfiring can be caused by an air leak which makes the fuel/air mixture lean.
Improper ignition timing can be another cause of backfiring.
I would be very surprised if anything on the carb itself could result in backfiring.

Does the bike have the carb brace that bolts to the air cleaner backing plate and the other end bolting to the tappet base?
If not, then this will cause an air leak because the weight of the unsupported carb and air cleaner will cause the carb/manifold to rotate and this racks the O rings.

There are a number of things but I urge you to start with a factory manual before you start turning to many bolts and nuts.
pg

 

+1 on all of this. The factory service manual is part number 99484-85. You will also benefit greatly from the factory parts catalog 99451-85A. You can order these thru any HD dealer, from any of the on-line catalog stores such as J&P Cycles, thru a local indie bike shop, or from various eBay sellers.

These books should be your very first purchase. They are your most important tools. You will need to spend several hours reading and studying.

It is not sound procedure to buy parts to solve these problems. Any 30 year old vehicle, and especially an IronHead, will have many problems caused by many previous owners. You need to solve these systematically.

Most likely there is more than one problem. Do not think that, "o boy, i just have to fix this air leak [or whatever] and it will be good to go". A most unlikely situation.

You need patience; right now, and for an unknown time period, you will be enjoying the wrenching and the reading/studying and the learning about your ironhead. The riding will come later.

It is far better to spend a few hundred dollars on good tools and to spend time on these forums than to spend several hundred [or thousand!] at a shop.

Here is my proicedure to check for air leaks. Do this then come back for more suggestions ...

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 definetly 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.

 

Mr. N-Texan, The gentlemen that posted above me, are like ironhead gods..if they cannot help you diagnose your bike, chances are you need to burn it. lol They are all EXTREMELY knowledgeable on what they say about the ole-mighty-ironhead. they've helped me numerous times, and gave me much appreciated opinions so buy a manual and start doin what they said. lol as for your points ordeal, are you sure it aint got points?! my 81 has points. (i just adjusted them the other day matter of fact..) And as for the idea that it runs for a little bit (as to say...till it warms up?) and then shuts off..makes me kinda wander it it is "valves" or "Spark" related.. especially with the bang pop that its doin. Coil gettin hot, loosing contact? or points N condenser goin bad? as for your S&S, good carbs i think, but sorry to hear ya dumped a few hundred bucks on something that didnt fix ya up right away. Im sure by now, you've learned that HD stands for Hundred-Dollars when it comes to fixin stuff. haha. WHen i swapped my carb out for a newer sporty carb (CV40) i replaced the intake seals as the "gods" had stated and then sealed my exhaust pipes as well. and lemme tell ya, wooow! big difference now buddy!

SO go with what they say, buy the HD manual, and get to turning some wrenches! you'll have it fixed inna few days time.. and don't buy nothing fancy till ya get it running properly and consistently!

 

I have been reading on this forum for some time now and have came to realize that pinion and ironmick are very knolagable when it comes to Ironheads. I feel blessed that they are giving me advise. Just got off of work and will be spending the afternoon with the family, but tomorrow morning I will be headed out to the garage to check for intake leaks. Do I use the small propane tortch that one would use for soldering(blue bottle)? Should I put the origional carb back on to test this? There is no brace on the new carb. I will be ordering both the parts manuel and the and the service manuel on friday. Should I buy spark pluggs in the mean time, or should I put the project on hold untill the manuels arrive?

Thank You Men

 

I would do both the intake and exhaust leaks tests. Yes, use the propane torch that you have for the intake leaks test, but of course do not light it, eh [heh heh].

I use lots of propane. I find it unnerving working on my bike in my small shop with the engine running. Lots of noise and vibration etc. But i just go for it. I work the propane from both sides of the bike and aim it into the joints between the cylinder heads and the manifold and the carb.

It will be useful to have a known good set of spark plugs on hand.

I do not know which carb would be the best choice.

BTW, here are my carb cleaning and pilot screw setting notes. These are written for the Keihin butterfly carbs, but the principles are the same for all carbs. You can check this against what you did with the original carb ...

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 ...


3. Be very careful handling the float so as to not change the level. 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.

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.