Ok I have a 74 iron head sportster kick only right side shift. Rode to a swap meet about 4 hours away last leg of the ride on the way there started leaking oil from the oil pump kept a close eye on it keeping oil topped off when needed. Made it back the bike was running drove it up put it in the garage. the next weekend I went to start it and had no compression. looked like a leaky head gasket on rear cylinder. Replaced all gaskets in top end everything looked ok so I put it back together tried to kick it over and it had some compression but not what it usually has and it would try and fire then shot flames out the front exhaust. The pushrods seem to be ok. Where should I look now? Thanks

 

I'm no expert, but I'd run a compression test to see what the compression in each cylinder actually is. If it's low like you think it is, you need to find out why and fix it.

Again, no expert here, but if flames are shooting out the front exhaust pipe when you try to start it, it sounds like the front exhaust valve is open or partially open when it shouldn't be. Probably wouldn't hurt to check the timing to make sure the ignition's firing when it should be.

When you say "pushrods seem to be ok" do you mean you've done a pushrod adjustment with the bike stone cold and they're adjusted correctly?

And welcome to the forum!

 

Thanks man, Yeah I did a push rod adjustment but I will double check that. I was thinking valve too but wanted to make sure I didn’t overlook a possible easier solution. thanks for the response. New to this forum thing.

 

it more then likely over heated on the drive back - possibly intake leak and it leaned out and scuffed a piston or even warped a valve

 

Compression test first. Sounds like it will fail, but which cylinder or both? Proceed accordingly.

 

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.

 

Ironhead Push Rod Adjustment

Do this procedure with the engine stone cold. I usually do it first thing in the morning.

1. Remove the spark plugs. Remove A/C to make room to work.

2. Using a flat blade screwdriver pry the spring keeper off of each push rod; the bottom of the keeper pops out first, then the top. Alternately, use a 3/4" open end wrench to push down on the top of the spring retainer, then pry out the spring keeper with the screwdriver.

3. The lower push rod covers may be stuck tight against the bottom o-rings, but they can be loosened by pinching between thumb and finger [or carefully using a shop rag and a pliers] and twisting or rotating. Lift these up and secure each with a tall-S-shaped piece of 12 or 14 gauge household wire [not cable] [or a long piece of Plumbers solder such as 95/5 hooked over the rocker cover and under the push rod cover.

4. Jack up back end of the bike so that rear wheel is 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.

5. To adjust a particular push rod, its valve must be fully closed [the valve spring is relaxed]. Valve position for a particular cylinder is determined by observing the corresponding push rod of the other cylinder. For example, when the rear cylinder intake valve tappet is raised [valve fully open, spring compressed], the front cylinder intake valve is fully closed, and the front intake push rod can be adjusted.

6. Check [and adjust if necessary] the push rods:

[a] use the rear wheel rotate the engine so that the rear cylinder exhaust push rod tappet is fully raised. The front cylinder push rod is adjusted correctly if it has no vertical or horizontal play, and you can just rotate the push rod between thumb and forefinger with no trace of binding or dragging.

[b] to adjust if needed: hold the adjusting screw in place with a wrench; with another wrench loosen the split locknut. Then turn the adjusting screw using fingers only until the pushrod's ball end is seated in the tappet with a "slight amount of play". Then tighten further as follows:

Option 1: Adjust on the tighter end of the range: There should be no vertical or horizontal play, and you should be just able to rotate the push rod between thumb and forefinger with no trace of binding or dragging.

Option 2: Adjust on the looser end of the range: Set the adjusting screw to finger tight so that you cannot turn the push rod between forefinger and thumb. Undo it a tiny bit so that it is just barely loose. Then loosen it 1 "side" for an exhaust or 1/2 "side" for an intake. "Side" refers to one side of the 6-sided adjusting nut.

EDIT: Experience here is that Option 2 is the better and most likely the correct choice.

[c] hold the adjusting screw in place with the one wrench; with fingers then the other wrench tighten the locknut.

[d] recheck the adjustment; it is common for the adjustment to go out as you do step [c], in which case [b] and [c] must be redone.

[e] repeat for the other push rods.

[f] rotate the engine checking each pushrod.

7. Use a flat blade screwdriver to push the upper push rod covers up, and seat them into the upper o-ring or cork washer that is in the rocker cover.

8. Install the spring keepers, top end first, by prying them in under the bottom with a flat blade screwdriver.

 

Just as an add, they make scope attachments for your phone so you can look inside the cylinder via the spark plug hole. After some tests might be a good way to look around before taking things apart. Not saying this is the best one, just giving you an example:

https://www.walmart.com/ip/2-Meters-...&wl13=&veh=sem