Hi guys, I'm was sniffing for trouble and found a 1984 Sporty (11-83 production date) for sale. The bike had sat for 10 years in a garage and the guy selling bought it and changed out the old gas, put in a new battery and changed the oil (SAE 60), i just took it for a ride and it runs great, but when cruising at part throttle it makes a metallic wrapping noise in the engine and the faster you go the louder the noise gets but at idle it does not make any noise at all. After getting down close to the engine and listening to it at about 2,000 RPM it makes the noise and it will keep making the noise but at idle like I said it goes away completely. After listening to it really closely with my ear next to the cylinders I came to the conclusion that it is coming from the front cylinder the rear is quiet do you have any idea what could be possibly making this noise?

 

If you use a mechanics stethoscope you might be able to isolate the source of the sound more accurately. Is it in the cylinder or the combustion chamber or the cylinder head?

These stethoscopes are a simple device and inexpensive [probably $10 to $20] and very handy. Some guys use a screwdriver but the correct tool is much better.

One time I have such a sound, coming "obviously" from the rear cylinder head. While riding one day a leaned forward to get a better listen - the sound went away !

I sat upright and it returned. OK - it was a loose snap button on my helmet.

 

Thanks for the help IronMick, I will get astethoscope, after reading around on the subject I am not as scared about itand told the guy I will take it. I will keep this post updated with what Ifind. I am sure I will have some more questions for you IronMick, as you arethe authority on Ironheads.

 

I also had a funny rattling noise on my ironhead. Turns out the tank was vibrating against the frame. It was sitting just a little too close.

carl

 

I was listening to it with the stethoscope I bought, the noisiest spot was the front cylinder exhaust tappet block. So I took it apart and it as well as the lifter look fine, so I will put it back together and run it again. I checked the adjustment on all of the valves and they are right on too. I think I will check the timing as well, I bought a timing hole clear plug. Here is a picture of the bike, by the way I am up for the "renter of the year" award with the bike in the living room.

 

Here is a YouTube video of my good looking, good running, good sounding IronHead. Note the sound especially when the camera is close to the cylinder heads, both sides. The mufflers are quite loud, but you can always hear the actual engine sounds. These are noisey engines...

 

I really went at it with the stethoscope again this weekend and still cannot find the noise, it really sounds like a spark knock but it does it sitting in neutral too. I was thinking timing so I checked the VOES to see if it was working with my multimeter and sucking on the tube and it does go from open with no vacuum to closed circuit with suction. Also I opened the filler for the primary to see if maybe the noise was in there but no dice, then I did a compression test and at has 200psi in the front and 205psi in the rear cylinder. Any other ideas?

 

Those compression test numbers are unrealistically high - unless this is a very hi-tech engine. Typical good numbers are between 120 and 180 psi. Here is the correct procedure...

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.

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 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. Best to use a clip to attach them to the heads, especially if doing a kick start
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 **** 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%. 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. 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.

 

Hi Mick, I used my friend’s Craftsman compression tester kitand those are the number I got, I did warm it up (I did it the first time coldand only got 120psi) and opened the throttle and choke all the way too. I didnot check it again with putting oil down the cylinders since the numbers wereso high, as I mentioned it really sounds like a loud spark knock, the searchcontinues.

 

If the numbers really are that high you are dealing with a compression ratio in the neighborhood of 12:1 that would cause knock. Extreme carbon buildup? Shaved heads?