2011 F115 TLR head machining

[zenoahphobic]

I think you might be way over thinking this, machining the head such a small amount will not allow the valves to hit the piston....IF the timing is correct, if machining that amount off allowed that, the compression ratio would be so high that standard fuel would be unusable. Machining tolerance may be related to other possible "issues". Thicker gaskets were/are common to maintain factory specs and have been available for years for all sorts of engines.

And just think, would a commercially built engine allow less than .020 inch clearance between the valves and piston top? A bit of crankshaft, big end, little end wear, and some carbon deposits would soon have such a gap close and the engine in trouble!

[99yam40]

I assume it means the big holes in the gasket won’t be a problem with bores drilled out .020 to .060

Well, I did not get that from it, but it would make sense.
I thought they would show a thickness in there some where.

[ausnoelm]

Where have you been?

If you're referring to me, I have been "lurking" but I have been away on holidays for quite a while, plus some family "stuff" has kept me busy and various other life "things" have come my way.

[tttraveler]

Thanks all for the notes
anyone know where I can get said .020 over thickness head gasket?
This would be a huge win if I can find it and move on.

On the 2011 there is a note on some parts to go to another page for pro 0510
can someone confirm that this means for a motor manufacture date of 01/11 that we use the pro 05/10 parts

[99yam40]

Thanks all for the notes
anyone know where I can get said .020 over thickness head gasket?
This would be a huge win if I can find it and move on.

On the 2011 there is a note on some parts to go to another page for pro 0510
can someone confirm that this means for a motor manufacture date of 01/11 that we use the pro 05/10 parts

I am just guessing that Boscoe is the one that can come up with a part number for the thicker gasket.
I am not sure what thickness a regular head gasket is,
but I think the .073" is the overall thickness of the thick gasket, since the .020 to .060 looks to be the piston hole diameter it covers.

[boscoe99]

Yamaha does not offer oversized (thickness) gaskets that I am aware of. An internet search will be your best bet. Maybe try Jasper Engines as they are known to overhaul Yamaha outboard motors.

https://www.jasperengines.com/node/1008

[tttraveler]

Thanks all for the info I’ll start searching now for a gasket
if anyone has any suggestions please post.

[zenoahphobic]

Yamaha (and other manufacturers) deal with “new” components. This means if something has gone out of specification, they recommend replacement.
Probably they do not want to spend R and D on various repairs in regard to reliability. I’d imagine a thicker gasket is more vulnerable to failure than a thinner one. New manufacturers want to limit warranty.

[zenoahphobic]

Also, remember machining only takes off the “high” spots, there will be untouched surfaces left (thickness within specs).
This means you may actually be reducing the original compression ratio for some cylinders by adding an extra 20 thou gasket! (adding a problem).
Takes a skilled judgement as to how much to shave off and what thickness gasket to then use, if at all. Calculations/ number averaging may be in order, not that simple at times.
Eg the torque on the head bolts determines how much the warp in the head can be corrected, and allow sufficient sealing compression of the head gasket. You don’t shave away all the warpage but rather down to manufacturers maximum out of tolerance spec. Engineers designed that figure.
Sorry.
Thinking/ analysis sometimes is beyond mechanics, no matter how “master” qualified they are. It takes a higher level tech/ engineer to see pros and cons when a certain thing is embarked on.

[99yam40]

just a thought, but what about the block itself?
How flat is that?
could some of the head warpage be the result of the block surface not being completely flat and the head modified itself to fit that?

Just something else to make you worry about.

[zenoahphobic]

just a thought, but what about the block itself?
How flat is that?
could some of the head warpage be the result of the block surface not being completely flat and the head modified itself to fit that?

Just something else to make you worry about.

Interesting thought.
But I don’t think one can flex a cylinder head in that situation to leave a permanent distortion. The block would have to be way out. But you could, if you have the press with precise thin spacers, bend it back; in theory atleast.
My understanding about warping or permanent distortion, comes about by high heat unevenly distributed such that internal forces change the shape. This occurs in situ and only is discovered fully when taken apart. The OP had (eventual?)gasket failure that alerted him to this permanent distortion. What came first is a vital question.

In any situation where material is removed from the head, as to whether a thicker gasket is called for, one needs to know about the engine and the octane rating of the fuel to be used. It would be nice if one can turn back time and test run that engine with varying octane to see how sensitive it is to knocking.

This is atleast interesting to me, some people are anal and add octane raisers, that would be an option for the OP if he can only use a standard Yamaha gasket, and goes down that route and actually has knocking.

[panasonic]

I honestly do not think that taking 0.013" off that head will have any negative effects on valve/piston clearance using the original size head gasket. Do I know that for sure? No I do not...but I would bet the farm on it that it won't.
A single strand of hair off my head is 0.004" so 3 hairs will be 0.012"...that's not much in the grand scheme of things here.
If there are no machined counterbores in the tops of the pistons for valve clearance then those pistons are not coming anywhere near those valves...relatively speaking.
If there are counterbores on top of the pistons then I would be a little bit concerned and would take some measurements to see how much clearance there actually is.