Anyone ever see cylinder wear like this?

[hemiheadharley]

Hey guys,this is my first post here after reading all I could the first month or so. After 25 years of being around drag racing both cars and bikes I have been completely astounded by the wealth of knowledge here. It has been very humbling to realize how little I know about what I thought I knew about.

I am hoping someone can tell me what happened here and more importantly how to prevent it from happening again. These cylinders are from my 46 Harley race bike purpose built for drag racing. The engine is an 84 CI knucklehead,11.25 to 1 static CR with 128 cc hemi chambers and 50cc dome pistons. I can give the cam specs if it helps but I think the events leading up to disassembling the engine will be enough.

After the initial start up and heat cycling the first test ride resulted in a stuck exhaust valve. The timer/distributor on these engines is advanced manually and in my excitement I forgot that detail and put the bike under moderate acceleration for about a mile. I got it shut down just about the time I heard the tap tap tap. The front head was pulled,guide and valve replaced,valve lapped and put back together.

Second test ride covered about 10 or 12 miles and the bike ran flawlessly. At this point I installed a custom dual linkert carb set up that just never would run right. It was delivering way too much fuel at all throttle positions and after about 30 minutes of trying to sort it out the single carb went back on. Around this time my engine builder swung a leg over to take a ride and said "it's getting easier to kick,that's not good". We decided to pull it apart and discovered this wear pattern on the cylinder walls.

REAR.jpg

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FRONT.jpg

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The cylinder cross hatch was glazed off in relatively uniform vertical stripes. The scratches in the one cylinder are only visual and can't be felt with your finger tips or thumbnail. There was no scoring on the piston skirts and no sign of detonation on the piston tops or plugs. Even though kicking the bike became much easier it still ran well. We are re-ringing it and re-honing the cylinders but we would still like to know what caused the striping on the cylinder walls. I appreciate any and all opinions. Thanks!

[underhead valve]

I had a similar wear pattern when I firs started rigid honing and the hone chattered---- the high spots wore shiny--- I was using a aamco hone and learned to put cardboard shims under the guide felts

[bentvalves]

are the rings butting?

[hemiheadharley]

The rings came with the forged pistons in a set from S&S and were gapped to their specs. The honing was done with a drill mounted spring loaded honing tool with 2 floating stones and 2 floating wipers. The final finish was done with a ball type hone.The final wall clearance was .004, again S&S recommended spec. My builder has done around 20 of these hot rod engines over the last couple of years and none have had the cranking compression loss that we saw in this engine.

[af2]

are the rings butting?

Again are the rings butting? Put one in the bore and measure!

[BillK]

hh,
I would also say you need to see if the rings are butting. You can usually tell by looking at the ends of the rings. If they are real shiny they were probably too tight.

The other problem is with the type of hone you used it is impossible to make the cylinder round if it is not that way when you start.

My one main Harley customer bought torque plates and they do make a difference. Every set of jugs I do for him get the plates bolted on.

[hemiheadharley]

The ring butting will be the first thing I check Friday when I am back at the shop. The cylinders were brand new and from the same manufacturer that most of the other engines were built with. Reproduction quality can be suspect for sure but no issues have been apparent until now. I definitely appreciate the info so far guys, thanks!

[Truckedup]

Harley, what did the cylinder walls look like when you pulled the head for stuck valve? I race vintage Triumphs and if the timing slips back the engine often suffers a soft siezure...It might be minor but it usually get a bit worse with time...You are sure the stuck valve was not from a non concentric seat ? I use torque plates but if the engine heats up the round becomes unround....And the carbs, did it over fuel and possibly wash the cylinder walls?
Do you know Frank Spittle?

[HDBD]

I have the proper plates with studs down for the knuckle cylinders. Some guys dont allow enough clearance when using forged pistons and the full cast iron sleeves. Yours may have seized or as others have said not enough ring end gap. In a racing situation the clearance needs to be opened up

[hemiheadharley]

Truckedup, the cylinder still looked good when the stuck valve was repaired. These heads were prepped and raced on another engine last year with no issues. As far as the carbs it was over fueling so bad that when the throttle was closed and the rpms were coming down fuel would spray from the bores as if coming from water pistol. I have asked a few guys about the cylinder wall wash being an issue because of the over fueling ,the consensus being the pattern wouldn't be so uniform if that had occurred. I would add that they were all modern Harley guys (all Aluminum engines) who have never been around the old stuff. I don't recall having ever heard the name Frank Spittle. Is he an older Harley guy? (older Harley not older guy)

HDBD, I will pass this info along to my builder. BillK mentioned the torque plates also. Your newspaper pic is exactly what this bike was built for! October can't get here fast enough!

[Truckedup]

Spittle drag raced fuel Harley's back when ...He's from the North Carolina I believe, maybe 75 or so years old........

[modok]

It's probably out of round.
Hones can produce high order distortion like that, I really doubt that anybody would have caught it tho if you weren't specifically looking for it.

But MAYBE you could hear it while honing.

[bentvalves]

he mentioned a spring loaded hone of some sort....

[HDBD]

Honed with a CV616 they are straight, true, and on size. The bike in the photo won its race and used the same S&S pistons @ .006 clearance. The previous go around the owner seized them just like yours. Honed with a lisle drill motor hone.

[Dutchman]

There appears to be scuffing 360 around the bores. It looks even enough to agree with the rings butting. Off shore cylinders are a crap shoot at best. Lately I have used a ductle iron sleeve from darton sleeve and bore until the spigot is gone,cut off the flame ring.The flame ring is about .060 bigger than the spigot so it acts like a stepped sleeve. .004 press fit.
Sleeves are about the same cost as import cylinders. With the knuckle bolt pattern not many options.
I'm not sure if s&s makes chili dears now with there kn program.
You may have picked up a frequency when honing,it is difficult to get the spigot straight where there is no support, I have a vertical hone but a lot of the time I do finish Harley cylinders on a horizontal hone with a an600.
Dwell at the spigot is needed and is a pita sometimes with the vertical.
Worked on t/f modified and pro street Harley's for a lot of years,ductile iron is the choice for a race cylinder every time.
Good luck on your project, sounds like a fun one.