1940 chief oil leak at head

[jn1972]

I have an oil leak on my chief that I could not find. Today I pulled the tanks an the oil leak is coming from both 9/16 bolts at the top motor mount. The bolts for the motor mount did not have Any washer on them.could this cause my leak and does the thick washer go between the top motor mount and the head or does the thick washer go on top of the motor mount ? Thanks jerry

[PRG]

Howdy sir,

If that "oil" is a thick black tar looking substance it is unburnt hydro carbons from your combustion chamber and is a breach of your head gaskets. Likely the bolts in question bottomed out in the cylinders before sufficiently clamping the head(s) down giving a false torque reading. Normally Chief head gaskets fail at the exhaust port area but not entirely uncommon to yield here.
.

[tfburke3]

I agree that bottoming out is a potential cause,especially with non original bolts.I like to tighten a head bolt with a standard washer,which is thinner than the head bolt washer to make sure it snugs,then you know you will clamping head when using correct washer.
The washer goes under the bolt head.Check the bracket lays flat on the head,adjust if needed,then shim to frame after torqueing.
Tom

[T. Cotten]

Its more tragic for Sport Scouts, Folks..

....Cotten

[PRG]

Howdy sir,

If there is any question you may have head bolts bottoming out all need to be checked. Running these and Fours with bottomed out bolts will result in the cylinders cracking radially between the cooling fins at the base root of the threads.

Might also mention if it is in fact breached gaskets you need to remove and replace as a re-torque on flat heads with their known hot spots will likely not hold, particularly with fiber gaskets. Now, speaking to the general population and straying from convention here, seeing as we're now dealing with 70 plus year old parts and metal fatigue I'd highly recommend copper replacements and heads torqued to only to 35 ft lbs or so on perfectly flat heads and cylinder decks. The punishing torque values specified for Chiefs and Fours traces specifically to the poor gasket material of the day that had to be crushed into submission to survive the excessive heat and thermal shifting at the exhaust port area. Copper is far more durable.

Decades of 50-55 ft lb of clamping force in conjunction with thermal expansion/contraction is now resulting in increasing head failure in Fours which are regularly ridden, mine are torqued to 28 and my Chiefs to 35.

[jn1972]

You are correct about the bolt bottoming out I measured the top motor mount,the head,the copper gasget and the hole depth it comes out to 1.49 inches without torque ,the bolt with the thick washer measures 1.57 inches .i will have to remove at least .14 inches from the length of the bolt thanks for the help

[Tom Lovejoy]

always good to put the head on and bolts in and just snug them up with no head gasket. If they pull the head down snug and don't bottom, your good to go. Put it back together with the head gasket and torque it down, agree with less rather than more torque - good luck.

[exeric]

I had a lot of head problems with my '40 Chief during it's break-in, but I concur with everything said here, and would also add, to make sure the threads in your cylinders are good.

Tom Lovejoy, I was just reading the article you wrote in the 'Winter 2003' issue of 'The Antique Motorcycle' about your trip to the Yosemite National Park. Sorry for the late review. Without going into a lot of detail, I like to read our past club magazines while I meditate in my special tiled meditation room