Gremlin in motor

[ski22]

It's been sometime since I’ve posted but I know this is the place for answers. This is a long one: 1960 FLH, 50 over, Morris MM74E mag (recently refurbed by Morris), a recently rebuilt Linkert M74B (previously ran a Bendix with the same issues to be stated later), timing is correct (many different adjustments during the troubleshooting process), oil return is good (straight 60), tops done in '05 by someone I know and trust. It runs but here are the issues: I've been battling an extremely hot motor (timing is where it should be and I run the carb on the fat side) and a front cylinder that has compression issues (120 rear, sub 90 front). I've owned this pan for years and after riding it I expect to find a big glob of aluminum on the ground where there was once a motor. Have done comp tests and leak downs and the problem is always down not up. I have torn down the front too many times and I find rings that are not sealing and a jug that is on at least one occasion distorted. After new rings and/or a freshly honed and hatched jug I have temporary good compression. My obvious assumption is that the excessive motor temp is causing my cylinder issues. I've blamed air leaks (none in the obvious places), the bottom end (checked rod for straightness and slack), fins removed for mag clearance (somebody took off more than necessary), the head itself (which has been checked every time I do a tear down), and finally a gremlin that lives in the motor. I still talk to the previous owner who is a friend that I would like to sell this headache back to and who had the same issues before the tops were done. Over the years I have seemingly tried everything and have heard it all from the bar room wrenches to the pros. There's a dent in wall from beating my head against it. Any input besides give up or sell it (it has become a personal challenge) would be appreciated. Sorry for all the parentheses and the length of the post.

[steinauge]

Silicone wafers seeded well and dipped in 105R are generally appreciated by Gremlins.How are you telling that the engine is running hot?How high does your oil temp get? I suspect you diagnosed your own cylinder problem when you said "distorted" I would replace the cylinder.The problem likely occurred during the boring process but I would also be sure the case deck is flat while I was there.I would think that if you have been running the bike all this time and havent burned it down it maybe isnt as hot as it feels?

[Hauula Pan]

50 over should not cause heat issues but if you're sure the front cyl. is getting too hot and you're having compression & ring seating issues there are any number of things that could be causing them. Here is something you can try without tearing into the motor, Change the heat range of the plug in that cylinder and see if that helps it run cooler. That won't solve the compression issue but may help with the overheating. For the compression issue I'd suspect either the bore job wasn't quite perfect, or the rings aren't seating right, or the cylinder is damaged. Of course the only way to find out is tear it down again. I recommend using cast iron rings (Not chrome ones) they'll seat easier and do less damage to the walls over time, and ensure they're properly gapped when you install them. Check the cylinder in several places with a good gauge to ensure it is round and the bore is true from top to bottom. Until you're ready to tear into it I'd say If you are sure you don't have any leaks, and know the timing and mixture are all good about the only thing I can suggest is try different plug ranges and see if it cools down.

[fourthgear]

As stated ,how hot is the mtr. getting ? Is it causing preignition or pinging ? You said you checked for air leaks , did you check the spark plug fitment area ( you would be surprised how many leak there ) ,valve cover screws above the intake manifold ?

Hows the fit of the venturi in the Linkert ? (Cotten will hopefully jump in here ).Even though you said it acted the same with the other carb, they both could have the same problem of air infiltration.
I can't help ya on the timing of a Mag., never owned or played with one , but incorrect timing can cause a lot of problems, even though it may start fine .

What cam are you running , solids or hyd. lifters ?( had to ask ,cause even older mtr's can be converted to run hyd. ) Just because you are getting return , doesn't mean all is well with the oiling system.

[awander]

Hauula:

"Change the heat range of the plug in that cylinder and see if that helps it run cooler"

I think the heat range of the plug will affect only how hot the plug runs, not how hot the cylinder runs.

[FlatHeadSix]

Andy is correct, the heat range of the plug only tells you how hot the plug runs, NOT how hot the motor runs. If you install a plug with a heat range which is too high for the what the motor needs, or for your driving conditions, the plug will burn up, not the motor.

mike

[FlatHeadSix]

also remember that Harley plug numbers are backwards: Higher number = Colder plug. And, as stated above, putting a colder plug in will not lower the operating temp of the engine but it may increase the chance that the plug will foul out prematurely. Don't run out and buy a bunch of #5 plugs and think you are going to lower the engine temp, you're only buying trouble.

mike