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Old 19 March 2009, 11:44   #1
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Yamaha 200VMax 2strokes carburatted damage?

Just to inform everybody in case you have the same motor.

My motor is a Yamaha 200VMax carburatted 2002 model which i have from new. The motor has done 426 hours in total.
So far the only thing I have done is to change the anodes in the cylinder heads and of course regular services as per book manual from the Yamaha main dealers in Greece.
However, after 426 hours exactly the following have been noticed:

1. White spots floating in the gear box lub oil. Which according the the mechanic means that I need new gear box gaskets.

2. When you bring the pistons in the top position and if you take one spark plug out and you press with a screw driver on top of the piston from the hole, the piston retracts by about 2-2.5 mms. This means that the pins have been warn. The engine must be opened, and pistons, rings, pins must be changed, new gaskets and all that. In case there is a damage in the cylinders, the block needs reboring and bigger pistons obviously. Someone told me that may be the crank shaft may have been damaged too.

Cost for all the above including the oil floater of the main oil tank, gaskets (all Yamaha original), and full piston kits (after market) all coming from the US with shipping is USD 952.75, labour costs in Greece EURO 600, if the cylinders need reboring have to add another Euro 30 per cylinder = Euro 180.

TOTAL in Euro 660 + 600 + 180 = TOTAL Euro 1440!! )

The question is the following:

1. For the gear box, I understand that this may be considered normal wear and tear

2. BUT for the engine, is this considered normal to have such a damage to have such a damage? Is this repair necessary? (I believe that it is). Is there any chance that the crank shaft may have a damage too?

I know that will find all out when I will open the motor (mid next week), but I am just asking to be prepared for the worst!
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Old 19 March 2009, 12:18   #2
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I'm not convinced. Take it somewhere for a second opinion-and get it compression tested too.It's highly unlikely all the gudgeon pins/small ends have damage.

I'd be a bit more cautious about the gearbox too-it's quite possible it's just in need of a new set of drain/vent screw gaskets. Get it refilled with fresh oil and new drain/fill screw gaskets and see if the problem recurs after a few hours use.
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Old 19 March 2009, 14:17   #3
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I agree with NOS4R2.
If you had that much play in the big/little ends surely it would be rattling like a bag of rusty spanners? the only thing that would make all cylinders fail like this would be autolube failure, and it would probably overheat and sieze the pistons in the bores before damaging the gudgeon pins or bigends. surely you would have noticed that spots of white in the gearbox is of little concequence at an end of season service, if the oil has a significant amount of water in it it will look yellowey white rather than golden.
I would get a second opinion on the engine wear, and just change the gearbox oil and fill/drain plug washers and check the colour after a day or two use,
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Old 20 March 2009, 05:15   #4
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Thanks guys, I have asked a friend hat is a mechanic on motorbikes and he said that most likely that the piston pins are worn out. This is a common fault with these motors (apparently).
The reason is that aluminium is rubbing against steel and they get worn.
Now I'm going to open the motor next week and see what I will find.

DREAD IT !!

PS: As far as the gear box lub oil white drops is concerned I am in agreement with you. Thanks
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Old 20 March 2009, 05:40   #5
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[quote=Manos;286947] most likely that the piston pins are worn out [quote]

I can't see how pushing down on the piston and observing it move is a diagnosis for worn pistons/gudgeon pins/crankshaft. To me, without further data, it defies logic. Pistons are meant to go down (and up) and even a piston at top dead centre will be displaced by a vertical load, especially in one that has done 426 hours and is therefore as friction free as it's ever likely to get. (By the way, poking a piston with screwdriver is probably not a great plan unless you know what you're doing...and why!)

There is no design issue with aluminium pistons running in different metal gudgeon pins. That is the norm...Lubrication is what facilitates it. Differential metal bearing surfaces occur everywhere.

Personally, I would have thought that 2,5mm of gudgeon pin float would have long since produced catastrophic failure, itself preceeded by god-awful noises (piston slap and little end rattle) as doggypaddle suggests.

You've told us what you think the solution is...but what is the engine problem you think you have to fix? In other words, why were you poking the piston in the first place?
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Old 20 March 2009, 05:49   #6
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The mechanic said that first mechanic I took the motor for the yearly service said that he could hear the engine ruttling. I went there and although he turned the motor on there was normal noise. The same mechanic said that 100% ins need changing as well as I would need to change pistons and rings and possibly i will have to rebore the cylinders and that may be there is a big damage.

Quote:
Originally Posted by Leapy View Post
In other words, why were you poking the piston in the first place?
The same mechanic suggested, since I said that I can hear the motor working in a normal way and I don't hear this rattling he was claiming (I have other 2-stroke outboards too on my other smaller boats and I think I know a little about them), ... he suggested to bring the pistons to the high point and he asked me to just give to one a soft poke. I did what he said exactly and the piston retracted. He said that this is the sign that the pins are warn out.
Also I decided to take 2nd and 3rd advise, and after talking to the chief mechanic in Yamaha Greece and another authorised mechanic by Yamaha they both said that this is a common fault of these motors. So as I am not an authority on outboards I hear what people with experience and knowledge have to tell me. They said what I wrote before, the damage is due to steel rubbing on aluminium.
I hope the above answers your question
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Old 20 March 2009, 05:56   #7
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If it isnt knocking or rattling or down on compression dont fix it!
as for aluminium pistons wearing out, well all engines have aluminium pistons thats not unique to yamaha, and yes they all wear out but not in 400 hours EVER unless there another problem, like no oil. In fact the rings usually go first and it is common to re-ring a piston and re -use to freshen an engine up before a rebore is nescesary.
You cant say there is definetley a problem because there is aparently 2mm play in the piston, you could have an acceptable amount of play in the main bearings, big end and small end, that added to a cold piston being like the proverbial knob in a shirt sleve and some sideways movement too could make it seem like the problem is worse than it is. it may just be the piston rocking because of the big skirt clearenge 2 stroke engine have especially when cold.
While its difficult to judge if there is a problem from your description my advice to you is be very weary of people willing to take your money off you. you know the sort, who cure a misfire by changing a plug lead, and then scratch around the headgasket with a nail to make it look like its been off and charge for a valve job.
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Old 20 March 2009, 06:00   #8
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If its officially buggered after 400 hours then thats poor. Pistons shouldnt rub the cylinder, they should float on a film of oil. do you get through enough oil?
I think i wouldnt trust an autolube anyway, much less to go wrong with premix
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Old 20 March 2009, 06:02   #9
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@ doggypaddle ... Thank ... I agree with you and this is the reason I wrote this thread as I thought on similar lines. However, when people (qualified mechanics) tell that you need this and say that the engine is about to seize (more or less) one wonders if he is wrong.

Well this is the power of a forum, I got what I needed.

Thanks guys.

I'm off to get a manometer to measure pressure this weekend and let you know the results.

Thanks again for the advise.
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Old 20 March 2009, 06:03   #10
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Quote:
Originally Posted by doggypaddle View Post
Ido you get through enough oil?
Autolub is working fine. No probs there. Checked it.
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