FT9.9 AE X Cylinder head removal

[panasonic]

Prior to fitting head checked with straight edge and there does appear to be some warping so will have to get this skimmed. Is there some way of knowing the maximum the head can be skimmed?
The block seems to be OK.

Also on the diagram here:

1998 T9.9MLHW Yamaha Outboard CYLINDER CRANKCASE Diagram and Parts

There is an O ring part number 38. Where does this go?

Although the new gasket has built in sealant is it worth using some extra and if so what?

Any advice would be appreciated.....

Well do you know how much the head is warped? Service manual gives .004" limit, and then procedure to flatten it if not to badly warped.

Also what are you using for a straight edge? Are you sure it is dead straight and it is not warped itself?

Item #38 is a grommet...not an O ring. Is there a threaded hole that it might sit on as show in diagram and something bolts to that cover. The grommet serving as a damper maybe....I am not sure.

Put head gasket on as is.

[TownsendsFJR1300]

This pic from earlier:

http://www.yamahaoutboardparts.com/a...7621-block.jpg

Looks like possible a white o-ring/grommet and it's BELOW the lower cylinder(as in the parts diagram)..

In the block, close to where the power-head meets the mid section...(about 2/3's over in the pic)

It's about the only place it can go.



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[cleddau1]

Thanks for replies. It is part 34 not 38; senior moment for me; I think it goes over one of the oil pump orifices.
German made precision pristine straight edge.
Have noted the sandpaper method and seen the videos but not sure about this technique. Eyeballing warpage is way over tolerance in several places but will measure.
Thread is getting long so will start new one if further queries.

Diolch yn fawr

[TownsendsFJR1300]

PLEASE KEEP IT ON THIS THREAD.. It's easier for us...

Part #34 is what I was talking about, I refer back to my last post re the location....

I would think it'd be partially machined inward...

Re the warpage, that certainly helped with the head gasket / leakage failure...



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[99yam40]

Thanks for replies. It is part 34 not 38; senior moment for me; I think it goes over one of the oil pump orifices.
German made precision pristine straight edge.
Have noted the sandpaper method and seen the videos but not sure about this technique. Eyeballing warpage is way over tolerance in several places but will measure.
Thread is getting long so will start new one if further queries.

Diolch yn fawr

I have used this method for cleaning and resurfacing heads on 2 strokes many times before.
main thing is to keep even pressure and turn often to keep from taking too much off on one area.
I kept a small amount of running water on the paper to help wash the cuttings off,So the paper would not plug up on any certain spots.
If the part is too big for the sheet of sand paper it will be difficult so may want to have it done a a machine shop

[cleddau1]

The head was 5 thou out, high in the centre, had it resurfaced for £30 and finally got it all back together.
Motor started instantly and warmed up nicely, good water flow and no overheating but not run under load. Revs up nicely but misfires when held at high revs.
Also disappointed that compression only 115psi although same on both cylinders.

[pstephens46]

Take it to the lake and run it.....

Or the firth.....maybe wrong country...

[cleddau1]

Milford Haven estuary........
That is what I had in mind also, to put it back on the boat and give it some welly....

[TownsendsFJR1300]

The head was 5 thou out, high in the centre, had it resurfaced for £30 and finally got it all back together.
Motor started instantly and warmed up nicely, good water flow and no overheating but not run under load. Revs up nicely but misfires when held at high revs.
Also disappointed that compression only 115psi although same on both cylinders.

I hope your NOT opening the throttle fully in neutral.

That's a great way to make an anchor...

[pstephens46]

I hope your NOT opening the throttle fully in neutral.

That's a great way to make an anchor...

Wonder if a 9.9 has a rev limiter?

Might make for a misfire!

[pstephens46]

Milford Haven estuary........
That is what I had in mind also, to put it back on the boat and give it some welly....

Googled the estuary. No little spot of water there. Probably gets a bit nautical at times.

[99yam40]

in gear out of the water is about the same as neutral on an outboard in my opinion.
but then we do rev up chainsaws without load on them except the chain running around on the bar.
but at least I do not hold it there very long.

is in gear/out of water and the chain out of wood enough of a load not to hurt the motors when reving?

has anyone seen a chainsaw with more than one cylinder?

[pstephens46]

in gear out of the water is about the same as neutral on an outboard in my opinion.
but then we do rev up chainsaws without load on them except the chain running around on the bar.
but at least I do not hold it there very long.

is in gear/out of water and the chain out of wood enough of a load not to hurt the motors when reving?

has anyone seen a chainsaw with more than one cylinder?

How was your vacation Yam?

[TownsendsFJR1300]

in gear out of the water is about the same as neutral on an outboard in my opinion. AGREED..
but then we do rev up chainsaws without load on them except the chain running around on the bar. I don't but a short burst(two stroke too designed to be run WOT) won't hurt that..
but at least I do not hold it there very long.

is in gear/out of water and the chain out of wood enough of a load not to hurt the motors when reving?

has anyone seen a chainsaw with more than one cylinder?

It'd be way too heavy to handle.. Not needed anyway. The power to weight ratio has increased over time.


The blowers, etc (TWO STROKES), I fix and fine tune to max RPM often hit at LEAST 8,000 RPM STEADY, often 10,000 RPM's (especially the blowers-designed to be run WOT with NO load (just the "fan").

That outboard isn't designed to rev way past its red line with no load..
Valves float, different beast...

Most mowers are governed to 3,600 RPM's or lower. You can easily push the governor, open the throttle and get double that RPM. I wouldn't do that but for a second or so, or count on buying a new short block...

It really depends on the machine, what it's used for, and how it's designed.

Now my 600cc, 95HP, in-line 4 cylinder, FOUR STROKE, Yamaha motorcycle engine does have a rev limiter I hit once (in gear). First and second gears (WOT) pick up the front wheel (no clutching, just throttle-about 90MPH) motorcycle has a 14,000 red line.

[panasonic]

It'd be way too heavy to handle.. Not needed anyway. The power to weight ratio has increased over time.


The blowers, etc (TWO STROKES), I fix and fine tune to max RPM often hit at LEAST 8,000 RPM STEADY, often 10,000 RPM's (especially the blowers-designed to be run WOT with NO load (just the "fan").

That outboard isn't designed to rev way past its red line with no load..
Valves float, different beast...

Most mowers are governed to 3,600 RPM's or lower. You can easily push the governor, open the throttle and get double that RPM. I wouldn't do that but for a second or so, or count on buying a new short block...

It really depends on the machine, what it's used for, and how it's designed.

Now my 600cc, 95HP, in-line 4 cylinder, FOUR STROKE, Yamaha motorcycle engine does have a rev limiter I hit once (in gear). First and second gears (WOT) pick up the front wheel (no clutching, just throttle-about 90MPH) motorcycle has a 14,000 red line.

What do you mean you only hit the Rev limiter once? That bike will wheelie starting at 50 mph....they are rocket ships.