Being new to an Ironhead and wanting to start a new project I thought i would try for a little help in the trouble shooting department. The bike will start and run at an idle when its cool, ride it for an hour or so and shut it off and it wont restart. If you let it spend an hour or so cooling down it will fire right off again. This is the first issue the second being that while your riding the bike it will take a smooth throttle but when you put more than about a quarter throttle into it, it starts to sputter until you back off the throttle. Any help or ideas would be greatly appreciated

 

Do you have the factory service manual 99848-85 and the factory parts catalog 99451-85A? You need both of these. Get them anywhere - local indie bike shop, HD dealer, J&P Cycles, various internet and eBay sellers, etc.

Problem #1 ...
See what others say.

Problem #2 ...
Bogging down is typically a problem of too much fuel. Sputtering is typically a problem of too little fuel. It could be that the fuel filter is clogged or the fuel level in the carb float bowl is too low. Here's some notes ...

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.

 

welcome to the forum

if it starts well cold...fails to start hot. that is likely a ignition coil that needs to be replaced.

an easy check is ride it until it is hot....make it home before you shut it off...then cool the coil with cold water (carefully) and see if it will start again while the rest of the motor is still hot.

 

ill bet it will start hot if you hold the throttle wide open( fuel bleeds down past the needle and seat) floods the motor, sounds like you have a dirty carb as mick posted his notes on, a passage blocked partway would make it run rough also, try shutting the fuel valve off and let it run out of gas let it sit then open the vale and see how it starts

 

I'm leaning toward the ignition coil too. My only concern about it is typically the coil winding has a break in it that when cool, makes contact and as the coil heats up, the windings expand and it looses it's connection and the motor stops. The whole thing about it running and not restarting until cool doesn't fit the 'mold'. Maybe the residual heat with out the air cooling it causes the condition. When this happens, pull the plugs and check for spark by plugging them into the wires and grounding the base of the plug against metal on the bike. Try to 'start' the bike and see if the plugs spark or not. If not, then you know it is the ignition system. DO NOT attempt to hold the plug while doing this unless you are using pliers with rubber handles or a piece of wood. It will knock you on your a$$!

The fuel thing....I don't know if Mick mentioned it in his post or not, but he is usually quick to point out that if you have an external fuel filter, especially one from a car, it will restrict your fuel flow as they are not designed for gravity fed systems. Check your internal filter by draining your tank and removing the petcock. It will be a screen over the tubes inside the tank. If this filter is good and clean you have no need for an external one.

 

Thanks for all of the replies tried to start like mentioned above after I got bike good and hot with throttle wide open sure enough it eventually started. Also just tried shutting the fuel off letting it die and turning it back on to see if bike would restart but immediately shut it down as I just got covered in gas as did the side of the bike. So it looks like off to pulling the carb apart now thanks again for the starting points we will see what happens after this step.

 

there is crud in the needle and seat, when i got my current gas tank the po had got paint inside of it, so for a while i was getin crap in the float bowl,make sure the tank is clean maybe replace fuel lines,alot of guys say not to run a in line filter but i have ran a good glass in line filter on every on of my iron heads forever and never had a fuel feed problem just have to get a good filter, you may want to look into a cv conversion, they do start and run alot smoother