Damaged exhaust manifold o-ring surface

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Yes, while it's out, the balance shaft oil will be easy to drain and replace.
With engine in normal upright position I fill to just under the plug threads with mercury premium gear oil or you could follow shop manual for volume and type.
 
Sportster-2001-951C-Stock said:
Yes, while it's out, the balance shaft oil will be easy to drain and replace.
With engine in normal upright position I fill to just under the plug threads with mercury premium gear oil or you could follow shop manual for volume and type.
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The engine is still inside the hull can it be done without pulling the engine?
 
The 951 is one of the lowest pr
jborr8 said:
The engine is still inside the hull can it be done without pulling the engine?
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You can just top it off or check fluid level while in the hull, I top mine off as needed, twice now might need it again. If you can see oil it's a good feeling, 1st time I couldn't see any.
 
jborr8 said:
I will. In your opinion will the work that I have done help in any way to improve the short life span of the 951?
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Mostly what happens is the piston and ring clearances will get sloppy and blowby begins to destroy the oil film. The large clearance doesn't transfer heat into the cylinder wall effectively, piston runs hot and it goes spiraling downhill from there. If a piston gets torched and galls badly or breaks apart the crank bearings are dusted with debris if it doesn't toss a rod and just throwing a top end on after the bearings are contaminated is unlikely to last any time.

Crankshaft outer seals can become leaky as well, resulting in a lean air/fuel mixture and piston-eating detonation begins to occur. In this case the engine might tend to run away on the trailer or it will be impossible to nail low speed fuel mixture as the crank seals will leak one moment and not so much the next, upsetting stability of air flow and vacuum signals in the carburetor.

Compression is an effective way to judge this wear or even better, a cylinder leak down test. I haven't seen any data from a 951 leak down test, only a hundred or so compression tests, which is also how we quickly determine the health of EVERY outboard and 2-stroke that comes into our shop before submitting a repair quote.
 
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While the head is off, post up a pic of your piston crowns, if you will please. The crowd might want to see the color and pattern of deposits on the crowns, I know I'm curious. Also check the underside of the crowns for deposits, if the pistons were running hot there might be some carbon there.
 
Sportster-2001-951C-Stock said:
While the head is off, post up a pic of your piston crowns, if you will please. The crowd might want to see the color and pattern of deposits on the crowns, I know I'm curious. Also check the underside of the crowns for deposits, if the pistons were running hot there might be some carbon there.
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Image1561669176.487741.jpg definite carbon build up and a small dent on right side piston
 
My original plan was to do top end re-build but from searching on the forum it seemed that with 175 hrs the bottom end would be too tired to handle a new top end
 
175 hours kinda depends on your preference I think. If you prefer not to mess with it again in a couple years then do it now. The one thing to keep in mind is if a bearing locks up it could break a rod and punch a hole in the cases, tearing them up. If the ski was putting around recently, there will be a little extra carbon on the plugs and such, this tends to occur due to engine temp as well, not just fuel mixture alone. 1st picture is detonation from being too lean, looks to me like the crown was cleaned for the picture.Piston Detonation.jpgpiston wash.jpgPiston wash 1.jpg
 
Your engine was running lean, see the last picture above the Sporster posted.

The 951 was the last of the carbed engines once the emissions requirements hit so it being a leaner, cleaner 2-stroke gives it a shorter life also.
 
Those crowns look okay to me, I don't see anything obvious going on. Maybe a little lean if anything but was there any throttle hesitation? Hesitation is indicative of fuel system issues, specifically lack of fuel. Dirty carbs or fuel line air leaks are a couple causes.
 
mikidymac said:
The 951 was the last of the carbed engines once the emissions requirements hit so it being a leaner, cleaner 2-stroke gives it a shorter life also.
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I agree with this, which is why it fits well with my personal preference of fattening up the air/fuel mix slightly. This holds true IMO, across the board with 2-strokes, fatten them up then back off it need be.
 
Sportster-2001-951C-Stock said:
I agree with this, which is why it fits well with my personal preference of fattening up the air/fuel mix slightly. This holds true IMO, across the board with 2-strokes, fatten them up then back off it need be.
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Agreed, I would rather replace a few fouled plugs than melted pistons.
 
It appears that I am running too lean which would make sense because the last owner never changed grey fuel lines or rebuilt/cleaned carbs. Without a compression test I guess I’m rolling the dice on these pistons. What is your opinion on doing a top end only job? I’ve read on here before that once these 951s reach around 200 hrs it’s all or nothing
 
You read correctly. With the added stress of fresh cylinders and pistons and the increased load the tired cranks usually punch windows in the cases.

If it was mine and I was going to keep it for a few seasons I would spent the $400 on a new OEM crank and ride it for another 20 years.
 
Sportster-2001-951C-Stock said:
One really nice feature about a 2-cylinder is there are fewer parts needed for a rebuild and if one cylinder is having issues, it's more noticeable.
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That's why I don't touch the Yamaha, Kawasaki or Polaris triples. More parts, carbs and when one cylinder goes the other two keep running until the cases get a hole in them. Not to mention those giant Yamaha pipes, my knuckles hurt just thinking about them.
 
You've gone this far, it's kind of a crap shoot putting it back together with just a light hone and new rings then hoping for the best. I personally don't like the idea of slapping just a fresh top end on considering by the time you spend this money and time may as well do the whole thing?

Don't overlook you'll need the alignment fixture to set the engine back in place and get it straight with the pump, can't just toss it in and bolt it down.
 
Also with that many hours pistons and a hone are not going to help. Your cylinders will be worn also and need an actual overbore with new oversized pistons fitted.
 
mikidymac said:
You read correctly. With the added stress of fresh cylinders and pistons and the increased load the tired cranks usually punch windows in the cases.

If it was mine and I was going to keep it for a few seasons I would spent the $400 on a new OEM crank and ride it for another 20 years.
Click to expand...

So that brings up another point. I’ve also read on here that a complete rebuild can’t be done cheaper that a reman with a warranty. I would love to do it all myself and I think I can probably handle it but is it really worth it when a reman is $1500?
 
Sportster-2001-951C-Stock said:
Those crowns look okay to me, I don't see anything obvious going on. Maybe a little lean if anything but was there any throttle hesitation? Hesitation is indicative of fuel system issues, specifically lack of fuel. Dirty carbs or fuel line air leaks are a couple causes.
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Slight hesitation but then again I only rode it once on the test ride before I began tearing it apart. The tempo lines were filled with green goo and the carb filters were dirty
 
In my opinion yes. The remans are good but they don't use the top quality parts.
If you can do it yourself it will be a better engine.
OEM crank, pistons & rings, seals, gaskets and reeds will be $900. $150 to have both cylinders bored and honed and you are at $1050.

Seadoo also sells a complete reman for $1330.
 
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