Ironhead Engin is Missing and compression difference

[clacker24]

Would a bad gasket cause missing and the difference of a compression test? Here is a little background, I did a check of my compression and found that the front cylinder is running around 85 and the rear is running 110 or so. My bike is also missing and by checking the plugs it looks like the front cylinder is the culprit. I have a bad head gasket due to the oil on top of the front cylinder. What I’m looking for is confirmation that a bad gasket would cause all this.
Thanks
Clacker24
1985 XLX-61 1000cc

[Fe Head]

Welcome to the Forum

Yes the disparity in compressions could be the root cause for the miss firings.

I would suggest adding some oil to each cylinder and repeat the tests.

If they stay the same it will point you towards the valve(s) as the main cause. The leaking of oil at the head gasket area while not a good sign will not be the main reason for the low compression as you would have a high pitched chirp emminating from there when the engine is running. It would also progressively get worse quite quickly.

The lower compression on the front would also not be drawing in the A/F mixture as strongly as the rear thus compounding the naturally shorter duration after the rear cylinder fires.

If on the other hand the compression(s) increase significantly with the added oil you may well have a broken or failing set of rings.

Thirdly there is also the possibility of a hole starting in the piston.

The other areas to check are the push rods to be sure there is adequate clearance or rotation when the cylinders are at TDC (top dead centre). This is easiest to do with a cold engine.


Overall it looks like your in for a top end dismantle and repair. It is not a difficult process and there will be a lot of help should you need it.

The compressions should be within 10% of each other and between 130 -150 PSI when hot and with a WOT (wide open throttle & choke).

Cheers;

[cantolina]

I could not have stated the situation better than Fe Head did...

Spot on...

[Shu]

Are you sure the bad gasket you have is the head gasket and not the lower rocker cover gasket between the rocker and the head? The reason I ask is because those would cause an oil leak moreso than a head gasket.

The difference in compression readings needs to be investigated. Run the test again. Did you hold the throttle all the way open when you cranked the engine? ANyway then add 1 oz of oil to the cylinder and ruin the test again. If it raises dramatically then it is likely to be rings. If not then it is likely to be valves. Does it burn a lot of oil under throttle? Regardless you are going to have to pull it apart to identify the cause and most likely its time for a complete upper end rebuild; pistons, cylinders (new or bored), heads rebuilt, etc.

[clacker24]

Thanks for all the info...Ill let you know what I find out...

[clacker24]

Originally Posted by Shu

Are you sure the bad gasket you have is the head gasket and not the lower rocker cover gasket between the rocker and the head? The reason I ask is because those would cause an oil leak moreso than a head gasket.

The difference in compression readings needs to be investigated. Run the test again. Did you hold the throttle all the way open when you cranked the engine? ANyway then add 1 oz of oil to the cylinder and ruin the test again. If it raises dramatically then it is likely to be rings. If not then it is likely to be valves. Does it burn a lot of oil under throttle? Regardless you are going to have to pull it apart to identify the cause and most likely its time for a complete upper end rebuild; pistons, cylinders (new or bored), heads rebuilt, etc.

It is the rocker gasket that is leaking. I found the center bolt behind the spark plug to be loose and tightened that up but i still have the issues. Thanks for the help.

[MetallHed]

Originally Posted by clacker24

Engin is Missing

well you better find it! dam!