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PostPosted: Wed Sep 04, 2019 4:16 pm 
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Current ride: 2007 Ulysses
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Well I've melted it.

Engine guy reckons it was probably down to overfuelling washing the oil from the bores.

I'm sure there is an 'on line map' debate somewhere that I should have read. Grrrfff!

Looking to put it together after a rebore etc.
Forged Pistons obviously better but are they better enough to justify 5* the price of cast ones.
What did Eric use in the stock Ulysses?

Thanks

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PostPosted: Wed Sep 04, 2019 7:30 pm 
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proff. patpending
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How did you melt them? Have you been playing with maps?

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PostPosted: Thu Sep 05, 2019 1:01 am 
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As a general rule, lack of bore lubrication is likely to cause a piston skirt seizure rather than a melted piston. Need more information to be sure. A picture(s) would help. However, a melted piston is usually characterised by a nice little hole in the piston crown and/or material lost from the piston at the lands of the piston ring grooves or the top edge of the piston diameter. The rings themselves are often stuck firmly in the distorted ring groove. A melted piston crown, in my experience is almost always due to an ignition timing and/or fuel lean condition. It can also be exacerbated by the wrong (too hot) spark plug grade. Under unfavourable conditions, that itself can damage a piston. Buell changed the plug grade (6R12 to 10R12 from memory) years ago partly because of some instances of piston issues, usually rear cylinder if I recall correctly. HTH.

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PostPosted: Thu Sep 05, 2019 9:56 am 
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03 wrote:
As a general rule, lack of bore lubrication is likely to cause a piston skirt seizure rather than a melted piston. Need more information to be sure. A picture(s) would help. However, a melted piston is usually characterised by a nice little hole in the piston crown and/or material lost from the piston at the lands of the piston ring grooves or the top edge of the piston diameter. The rings themselves are often stuck firmly in the distorted ring groove. A melted piston crown, in my experience is almost always due to an ignition timing and/or fuel lean condition. It can also be exacerbated by the wrong (too hot) spark plug grade. Under unfavourable conditions, that itself can damage a piston. Buell changed the plug grade (6R12 to 10R12 from memory) years ago partly because of some instances of piston issues, usually rear cylinder if I recall correctly. HTH.


Totally agree with you there 03.
Like you said a picture would help.
Over revving can also break the skirts on skirted pistons.

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PostPosted: Sun Sep 08, 2019 4:26 pm 
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pash wrote:
How did you melt them? Have you been playing with maps?


Nice free map from the people at buelltooth.

Can't say that it was definitely the cause so don't want to get into it.
I suspect it is the same map as the bike came with.

Once bike is together again I will put the stock map in and scratch my head for a bit.

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PostPosted: Sun Sep 08, 2019 4:32 pm 
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Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

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PostPosted: Sun Sep 08, 2019 4:32 pm 
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proff. patpending
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That’s the sting in the tail from free maps with no pedigree... Pistons don’t melt on standard maps on a well maintained bike...

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PostPosted: Mon Sep 09, 2019 12:49 am 
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pash wrote:
That’s the sting in the tail from free maps with no pedigree... Pistons don’t melt on standard maps on a well maintained bike...

Exactly.

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PostPosted: Mon Sep 09, 2019 5:43 am 
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Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.

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PostPosted: Mon Sep 09, 2019 5:28 pm 
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03 wrote:
Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.

:yt: and Its’ a wonder that with that amount of bore wash ,the over fuelling hasn’t diluted the oil and compromised it lubrication properties and done damage somewhere else

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PostPosted: Tue Sep 10, 2019 2:02 am 
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barney wrote:
03 wrote:
Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.

:yt: and Its’ a wonder that with that amount of bore wash ,the over fuelling hasn’t diluted the oil and compromised it lubrication properties and done damage somewhere else

Fortunately, it's a rolling element bearing engine so more tolerant than a plain bearing motor. Long term, no doubt the cam shaft bearing bushes would be worn (and the lifters and rocker arms) but I get the impression this motor didn't travel too far after the ECU had been monkeyed with?

Seems to me a that rebore and new pistons (no need to worry about how they're made) will be required along with an ECU re-flash back to stock as a minimum. Plus a couple of engine oil flushes once it's running again.

PS - I presume you've checked to see if the engine oil stinks very strongly of petrol?

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PostPosted: Tue Sep 10, 2019 7:00 am 
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Current ride: 2007 Ulysses
Location: Elmswell Suffolk
03 wrote:
Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.


I'm just trying to fix my bike and feed my children at the same time. I need an informed opinion on cast Vs forged pistons.
The overfilling (or whatever it was) will be dealt with once it is all back together.

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PostPosted: Tue Sep 10, 2019 7:07 am 
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03 wrote:
barney wrote:
03 wrote:
Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.

:yt: and Its’ a wonder that with that amount of bore wash ,the over fuelling hasn’t diluted the oil and compromised it lubrication properties and done damage somewhere else

Fortunately, it's a rolling element bearing engine so more tolerant than a plain bearing motor. Long term, no doubt the cam shaft bearing bushes would be worn (and the lifters and rocker arms) but I get the impression this motor didn't travel too far after the ECU had been monkeyed with?

Seems to me a that rebore and new pistons (no need to worry about how they're made) will be required along with an ECU re-flash back to stock as a minimum. Plus a couple of engine oil flushes once it's running again.

PS - I presume you've checked to see if the engine oil stinks very strongly of petrol?

:yt: Reminds me of the old days :old: in the motor trade ,when the mechanically driven fuel lift pump diaphragm would partially fail, and pump some fuel in to the engine crankcases .

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PostPosted: Tue Sep 10, 2019 8:16 am 
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Bublnsqueak wrote:
03 wrote:
Bublnsqueak wrote:
Thanks 03.

I've melted a few 2 strokes in my time and agree with your comments.

Pretty solid engine guy called it fuel washing straight away so I will go with his assessment. (He does rebores, head skims etc)

I would be grateful to hear from anyone who has cast pistons in their xb and any other views on that issue.

Obviously forged are better. But five times better?

I think you're kind of missing the point here. It matters not in the slightest how your pistons were made. If your fueling and/or ignition are compromised, then even if you make them from solid unobtainium, you will damage them. If you truly have cylinder bore washing then you are over fueled by some margin and what Dr Pashley says is likely near the truth. How the pistons were made is irrelevant in that case.


I'm just trying to fix my bike and feed my children at the same time. I need an informed opinion on cast Vs forged pistons.
The overfilling (or whatever it was) will be dealt with once it is all back together.

For what you are trying to achieve, it's irrelevant. (That's from a professional mechanical engineer of more than 45 years experience, I hope that's informed enough for you).

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PostPosted: Tue Sep 10, 2019 10:27 am 
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Current ride: Buell 1125R
I'm just trying to fix my bike and feed my children at the same time. I need an informed opinion on cast Vs forged pistons.
The overfilling (or whatever it was) will be dealt with once it is all back together.

I think you probably know the answer to your own question.
Forged pistons are much stronger in every way without doubt but cost a lot more to produce.
That's why they are expensive.
I fitted some forged slipper pistons in a Norton 750 Commando after breaking the skirts on standard ones due to over revving. It wasn't a problem after that but I had also put racing valves, springs & collets & also ported the head. The timing & carburation was was spot on which was the most important part.
I was revving the bollox off the Commando every where I went as I was 18 to 24 years old. Did this for 6 years with Forged pistons with no problems other than blowing the mains & taking out the stator twice.
Sorry if this is presumptuous but I think your question might be.
Is it worth the cost for what you are going to do with the bike, when getting a descent tune on the ECU would probably fix it with a set of standard cast pistons?
I would just go with cast ones & feed your kids unless you're gonna race it.

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