I really lost myself this weekend
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Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
Yea, you'd think I'd learn. Well, at least I'm getting pretty good tearing thru Harley engines. At least my 95" TC build I did for my dad is still together.
I already upped the jets. One step richer needle, raised one notch, and a richer emulsion tube. I got the fattest main in there, wondering if I should buy more. Is your 260 main in a Mikuni HSR?
I already upped the jets. One step richer needle, raised one notch, and a richer emulsion tube. I got the fattest main in there, wondering if I should buy more. Is your 260 main in a Mikuni HSR?
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Grand HDF Member
Joined: Nov 2009
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Likes: 1,663
From: Tampa
Second, that's a stretch. I've NEVER heard of so much fuel in the cylinder that it washes off the minimal amount of oil on the cylinder walls to cause this. Especially since the oil rings keep oil off the cylinder walls.
Edit: For reference, I still doubt it but: https://www.hastingspistonrings.com/...faqs/fuel-wash
This was caused by an overheated piston, plain and simple. In the RPM range I was at I neglected to check the wideband since I was trying to slowly get around someone and was watching traffic. My bad, hindsight and all that... At that time the carb switched to more needle jet and jet needle (yes, they're two different things), which I neglected to adjust from when I used that carb in a 1200 Sportster. The AFR's went into the 15's, piston got hot, expanded, and there you have it.
BTW, I checked the rear cylinder and there's .004" clearance. For cast iron cylinders and forged aluminum pistons, that's where you wanna be.
For what it's worth, here's an article from Axtell explaining the detail of what happened to someone else's bike:
http://www.axtellsales.com/files/PDF...ngine-Heat.pdf
Last edited by Mattbastard; Apr 9, 2018 at 08:55 AM.
Seasoned HDF Member
Joined: Aug 2008
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From: Ohio
This is what we call BS.
Grand HDF Member
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From: Toledo ohio
Just putting my 2c worth. Allow me to introduce myself. I worked at Jasper Engines for 17 years, held 17 ASE Certs with 2 Masters. I worked in Tech diag and troubleshooting on Gas and Diesel Engines, Transmissions, differentials. I attended several advanced training classes at Federal Mogul in St Louis. Doing advanced diagnosis and electronic troubleshooting. So,,, I was just offering what we see in the Automotive industry as fuel wash, when an injector is stuck open in a fuel injected car, the excess fuel washed the oil film brought up by the oil seal rings, there is a top and bottom to rings "can" cause what I see in that photo. We switched to
Hypereutectic piston
A hypereutectic piston is an internal combustion engine piston cast using a hypereutectic alloy–that is, a metallic alloy which has a composition beyond the eutectic point. Hypereutectic pistons are made of an aluminum alloy which has much more silicon present than is soluble in aluminum at the operating temperature.
If you don't believe me, fine, if you want to conclude it was overheating, fine. I just wanted to offer my experience as a possible cause to look at so it don't happen again. Just trying to help out brother.
Hypereutectic piston
A hypereutectic piston is an internal combustion engine piston cast using a hypereutectic alloy–that is, a metallic alloy which has a composition beyond the eutectic point. Hypereutectic pistons are made of an aluminum alloy which has much more silicon present than is soluble in aluminum at the operating temperature.
If you don't believe me, fine, if you want to conclude it was overheating, fine. I just wanted to offer my experience as a possible cause to look at so it don't happen again. Just trying to help out brother.
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Grand HDF Member
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From: Tampa
While I do appreciate your input, I regret to inform you that this has happened to me before. Fortunately I've successfully rebuilt more HD engines than I've broken and when the jetting is correct the break in is perfect.
I will NEVER AGAIN use Hypereutctic pistons in a Harley, or any engine for that matter. Them Keith Black pistons are ****!
I used them in a Sportster. The design is so bad in order to maintain integrity the crown had to be thicker than forged that the oil rings actually can't be installed until after you have the piston installed on the rod. You also have to take a few degrees out of the timing. Garbage!
I will NEVER AGAIN use Hypereutctic pistons in a Harley, or any engine for that matter. Them Keith Black pistons are ****!
I used them in a Sportster. The design is so bad in order to maintain integrity the crown had to be thicker than forged that the oil rings actually can't be installed until after you have the piston installed on the rod. You also have to take a few degrees out of the timing. Garbage!
Last edited by Mattbastard; Apr 10, 2018 at 08:40 AM.
Seasoned HDF Member
Joined: Mar 2010
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From: Poolville
I have heard that before.......
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From: Haslet Texas
While I do appreciate your input, I regret to inform you that this has happened to me before. Fortunately I've successfully rebuilt more HD engines than I've broken and when the jetting is correct the break in is perfect.
I will NEVER AGAIN use Hypereutectic pistons in a Harley, or any engine for that matter. Them Keith Black pistons are ****!
I used them in a Sportster. The design is so bad in order to maintain integrity the crown had to be thicker than forged that the oil rings actually can't be installed until after you have the piston installed on the rod. You also have to take a few degrees out of the timing. Garbage!
I will NEVER AGAIN use Hypereutectic pistons in a Harley, or any engine for that matter. Them Keith Black pistons are ****!
I used them in a Sportster. The design is so bad in order to maintain integrity the crown had to be thicker than forged that the oil rings actually can't be installed until after you have the piston installed on the rod. You also have to take a few degrees out of the timing. Garbage!
Granted a compression test came in a bit lower than I thought it should be but the bike ran good so I wasn't real worried about it.