Can someone point me in the right direction? -video of 73 Ironhead running rough
 

Looking for a little help. For the last 30 years I've had a dirt bike, crotch rocket, or 4-wheeler in the garage. This is my first Harley. It's a rebuilt Ironhead with less than 4k miles. The bike has been running perfectly. I was at a stop light and it sounded like it was idling a little high. I reached down and adjusted the carb and it hasn't been right since.

It seems like it's running a rich but for the life of me can't get it back to the way it was. I replaced the plugs and have adjusted the carb back and forth to no avail.
I removed the air cover and this is what I see... Lots of exhaust and oil coming out... What do you think?


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you have to start in the begining - adjust the valves - set the points - check for dirt in the float bowl if so replace the low speed jet --- replace the intake O rings < they are always an issue and 4000 miles its time - than see what it does -- it to me is a tuning issue -- johnjzjz

Thanks Johnjzjz.
I didn't have anything to do with the rebuild and acquired the bike trough a trade so that's helpful advice. I'll spend some time in the garage tonight and see how it turns out.

Your bike in the video sounds a lot like mine did the first time I started it up after an engine rebuild. Especially the "pop pop" sounds. My problem was a massive intake air leak because I didn't get the O-rings installed correctly when I installed the intake manifold.

I can't tell if you have a carb support bracket installed or not, but you should have one to keep the carb and the intake manifold from shaking loose.

Do you have the factory manuals yet? You need these two ...

99484-78 Service Manual
99451-78B Parts Catalog

eBay and Google searches should turn them up. Or a local indie motorcycle shop or HD shop.

We cannot see what carb is on there. Typically the only external adjustment you can do while sitting on the bike is the idle speed. On a few carbs you can also adjust the slow speed fuel mixture. See if you can get a couple of pics of the carb, maybe front and back.

I would start with adjusting the pushrods. Remember to do this with the engine stone cold. I do the preparation steps the night before, then the actual adjustment first thing in the morning. Here is a good video ...


This needs to be checked every 2000 miles. They do not always need to be adjusted, but they do need to be checked. Especially after a new top end rebuild - they need to be checked at 100 miles, 500 miles, and 1000 miles; then every 2000 miles.

Man you guys rock. Thanks for the service manual numbers too. I've been watching youtube videos up to this point.

Here are a couple more pics... The adjustment I made was to the top screw.

Test compression.

I am not familiar with that carb - i know only the Keihin and the Mikuni VM. If someone else can ID it [Bendix perhaps?] we can provide more info.

Here's my notes on measuring cylinder compression and leakage. I do the compression test regularly, about as often as oil changes, and keep track of the results. If a cylinder measures low i immediately suspect a pushrod is out of adjustment, usually too tight.

The neat thing is that it is much easier to do a compression test than to do a pushrod adjustment check. So i do it immediately after a ride. I even have the tools etc set up beforehand so i do it at full operating temperature.

Cylinder Compression And Leakage Tests

A compression test should be done as part of each tuneup. Record the results and follow any changes over time.

A cylinder leakage test should be done any time you are considering taking down the top end. This test gives you useful information regarding what you should look for when you have it apart.

Each of these requires a tester which you can buy at an auto parts store. A compression tester could be found for about $40.00 more or less, and a clyinder leakage tester for somewhat more than that amount. With the cylinder leakage tester you will also need a small air compressor. Should be able to find a small sausage style for under $100.00.

Use these tools once and they have paid for themselves, compared to paying $50.00 to $100.00 per hour at a shop. Buy a slightly larger air compressor [look for about 5 CFM @ 90 PSI] and you will be able to use it with air tools.

Compression Test

1. Ride the bike to get the engine to get it up to operating temperature
2. Disconnect and remove both spark plugs; insert them into the leads and place them on the cylinder heads for grounding [they are hot so be careful]
3. Screw the compression tester into the spark plug hole for either of the cylinders
4. Hold the throttle open, and ensure the choke plate is also open [choke knob pushed in]
5. Crank the engine through several rotations until there is no further increase in reading at the tester gauge
6. Record the final reading
7. Repeat for the other cylinder

The difference between the two readings should not be more than 10 psi. A low reading on one cylinder indicates possible valve or ring damage to that cylinder. To determine which, pour about 1/2 oz of oil into that cylinder through the spark plug hole and repeat the test. If the reading returns to normal then valves are good, rings may be defective. If compression does not return to normal then valves may require service.


Cylinder Leakage Test

This test will tell you what to look for at the top end tear down: worn exhaust valves, worn intake valves, leaky head gaskets, or worn rings.

This test is usually done immediately following a compression test. So the engine is at or close to normal operating temperature, and the spark plugs have been removed.

1. Remove the pushrods to ensure that the valves are closed.

2. Set the cylinder to be tested at or near top dead center [TDC] as this is the wear area for the rings ...

a] rear wheel off the ground, shift to 2nd gear, rotate wheel until it clicks, repeat until you get to 4th gear. Now by rotating the rear wheel you are rotating the engine. Almost impossible with the plugs in; very difficult in lower gears. For the following it helps to have either a shop assistant or a wide "wingspan".

b] you can see in thru the spark plug hole, especially with a flash light. You can also try inserting something soft like a pencil and watch it rise and fall as you rotate the engine with the back wheel; but be careful it does not break or get stuck! You will have to hang on to the pencil with left hand while rotating the rear wheel with the right.

3. Turn on the compressor, connect the gauge to the air pressure, and adjust the gauge
4. Thread the adapter into the spark plug hole and attach to the gauge
5. The gauge now shows the amount of leakage
6. Listen at each exhaust pipe. Excessive hissing here indicates the respective exhaust valve is not sealing
7. Listen at the A/C intake. Excessive hissing here indicates intake valve[s] not sealing
8. Listen at the timing plug hole. Excessive hissing here indicates the rings are not sealing
9. Listen around the cylinder/head connection. Excessive hissing here indicates the respective head gasket is not sealing


Notes

A mechanics stethoscope [with the probe removed for this test] makes a good listening device, as does a length of oil line hose.

Greater leakage results in a sound of lower pitch.

There will always be some leakage, especially past the rings.

I also have a 73 shovel with the original carb which is a Bendix.I did install an aftermarket adjustable main jet and got it running well.wHILE i DID REBUILD THE CARB WATCH OUT WHAT PARTS THAT YOU PUT BACK IN TO IT AS THERE IS A LOT OF JUNK OUT THERE...

AS was said its a bendix carb one of the best harley ever had, kits are reasonablly priced But the E Blows kits are the bottom of the pile from china

you could convert it to an adjustable main BUT you said it ran just fine till to me the O rings went away - do up a complete tune if you keep it you will need to become good at it to keep it in top tune --