Cylinders wall woes

[TriNortchopz]

On that Eastern piston kit, it's hard to tell what style of wrist pin keepers you used... circlip? Spirlox?
Are the ends of the wrist pins flat or is there a chamfer at each end?

This Eastern Parts piston kit looks to use the spiralox:





https://www.ebay.com/itm/165876755660

[montuckymatt]

On that Eastern piston kit, it's hard to tell what style of wrist pin keepers you used... circlip? Spirlox?
Are the ends of the wrist pins flat or is there a chamfer at each end?

This Eastern Parts piston kit looks to use the spiralox:





https://www.ebay.com/itm/165876755660

That's the kit I have^^^. Spiralox and a chamfer on each end of the wristpin.

[farmall]

Even if you don't need it this time it's worth noting modern cylinder recoating services exist and may be worth it for specialty cylinders. They beat sleeving because they don't require deeply boring the original casting and can be repeated in future.

The bad old days of blistered stock Guzzi bores are ancient history. You'll need to find a dealer as apparently the usual idiots were not worth the hassle unfiltered.

https://www.usnicom.com/plating/cylindersCompanyInfo

https://www.usnicom.com/plating/pricing

[montuckymatt]

Even if you don't need it this time it's worth noting modern cylinder recoating services exist and may be worth it for specialty cylinders. They beat sleeving because they don't require deeply boring the original casting and can be repeated in future.

The bad old days of blistered stock Guzzi bores are ancient history. You'll need to find a dealer as apparently the usual idiots were not worth the hassle unfiltered.

https://www.usnicom.com/plating/cylindersCompanyInfo

https://www.usnicom.com/plating/pricing

Thanks for the links farmall. I've been looking into those guys for a couple years. In the future I'll have to locate a dealer. As soon as my cylinders get to the .060 range I'm gonna get serious about it. 13 fin big flatty cylinders are getting hard to find.

[TriNortchopz]

On that earlier pin retainer spit-out, was looking to find out more possibilities - as noted, rod rock due to unequal big end clearances, or pin not parallel. You confirmed the pin parallel to the deck.
Have you confirmed that the cylinder bore is square to the cylinder base? Is there any visible asymmetrical piston wear pattern?
and I saw one site saying their spiral-wound retainers(spirolox) could interchange with round wire-type circlips... hhmmm... but the spiral-wound retainers need a square section groove in the piston boss...that's why I was asking about your retainers - are the grooves square for the spirolox?
found this, although it is from an industrial engine, the info is relevant:

"...If the circlips fracture or their ends break off, this is due to excessive loads or improper handling while inserting the circlips. The circlips are only subjected to axial loads if the piston pin has an axial movement forced upon it. This occurs if the connecting rod is misaligned or is oscillating in a mostly asymmetric fashion, which causes the piston pin axis and the crankshaft axis to no longer be parallel. The piston pin then strikes in a very rapidly alternating sequence against the piston pin circlips and gradually forces them out of the groove...
Axial thrust of the piston pin during engine operation caused by:
- Bending or twisting of the connecting rod.
- Connecting rod eye bored at an angle (axes not parallel).
- Cylinder axis not perpendicular to crankshaft axis.
- Excessive connecting rod bearing clearance, particularly in conjunction with asymmetrical connecting rods.
- Connecting rod pins not parallel with crankshaft axis (machining fault).
Use of old or damaged circlips.
Improperly installed circlips.
https://www.ms-motorservice.com/en/t...pin-retainers/

[montuckymatt]

On that earlier pin retainer spit-out, was looking to find out more possibilities - as noted, rod rock due to unequal big end clearances, or pin not parallel. You confirmed the pin parallel to the deck.
Have you confirmed that the cylinder bore is square to the cylinder base? Is there any visible asymmetrical piston wear pattern?
and I saw one site saying their spiral-wound retainers(spirolox) could interchange with round wire-type circlips... hhmmm... but the spiral-wound retainers need a square section groove in the piston boss...that's why I was asking about your retainers - are the grooves square for the spirolox?
found this, although it is from an industrial engine, the info is relevant:

"...If the circlips fracture or their ends break off, this is due to excessive loads or improper handling while inserting the circlips. The circlips are only subjected to axial loads if the piston pin has an axial movement forced upon it. This occurs if the connecting rod is misaligned or is oscillating in a mostly asymmetric fashion, which causes the piston pin axis and the crankshaft axis to no longer be parallel. The piston pin then strikes in a very rapidly alternating sequence against the piston pin circlips and gradually forces them out of the groove...
Axial thrust of the piston pin during engine operation caused by:
- Bending or twisting of the connecting rod.
- Connecting rod eye bored at an angle (axes not parallel).
- Cylinder axis not perpendicular to crankshaft axis.
- Excessive connecting rod bearing clearance, particularly in conjunction with asymmetrical connecting rods.
- Connecting rod pins not parallel with crankshaft axis (machining fault).
Use of old or damaged circlips.
Improperly installed circlips.
https://www.ms-motorservice.com/en/t...pin-retainers/

I will definitely check to see what shape the square groove in the piston boss and for any asymmetrical piston wear.

What is a practical way to check and ensure my cylinder bore is square to the cylinder base? I did a few searches without any luck.

I might have left this out, when I pulled my cylinder last winter the connecting rod bushing had rotated 1/8" in the bore and moved to the left over 1/8". That side is where the piston got really mashed. The keeper spit out on the opposite side. I fit a new oversize bushing and honed to spec before adding the new .040 piston and having the rebore done.

[flatman]

So this is the same cylinder with problems 2nd time around?

[montuckymatt]

So this is the same cylinder with problems 2nd time around?

That it is. I pull off the head every winter to de carbon them. It also gives me a chance to inspect things.

There is no square groove for the spiralock. Just one round groove for a keeper. I didn't notice any asymmetrical wear on the piston. The pin sides actually look good. I wonder if my engine builder installed a std diameter rod bushing years ago and that's why it moved two summers ago.. I also wonder if that is what caused the keeper to pop out. Maybe having the bushing sticking out on that side 1/8" contributed to the piston slamming that side?

The new bushing I installed was .002 oversize

[flatman]

Since rods have been mentioned, a question. Is the female rod in the front cylinder (1940 and back?) or rear cylinder? is the problem cylinder the front or back and is the rod in that cylinder male or female? Just thinking back to the rod lower end rocking that was brought up, thinking male rocks more than female , female being wider less side to side rocking? The mystery continues.

[TriNortchopz]

There is no square groove for the spiralock. Just one round groove for a keeper.

I believe you need to have the round wire c-clip pin retainers to match the round groove in the piston boss, and the pins need to have chamfered ends so when the pin does move sideways, it forces the c-clip into the round groove, not out the end into the side of the cylinder. Spirolox need a square groove to sit in inside the piston boss, same as the sometimes used Tru-Arc snap rings - the ones you need to use snapring pliers for install/remove.
To confirm cylinder base square to the bore, I would mount it in a 4-jaw chuck on a lathe, align the bore to be exactly centered using a dial gauge, then moving the dial gauge to the base and turn it to check for squareness of the base to the bore...if not, a thin cut while in the lathe and you make it square. You could do the top of the cylinder too while the cylinder is at the lathe, using the same technique.

[CDeeZ]

Just did my annual routine of pulling off my head on my flatty. It has low miles on new bore and rings. I had a keeper let loose and the connecting rod bushing move 1/8"out of the rod two summers ago. Left a nice finger nail gouge and I had to tear the motor apart. Here's a pic of the old damageAttachment 109814Attachment 109815
Here's what I found tonight. Engine has under 1000 miles on new bore,piston,rings,and connecting rod bushing +.002...I think
Attachment 109816Attachment 109818
No ridges or Knicks that I can feel. Just the lines in the cylinder. Thoughts? I have my pistons set loose at .002-.003 since I do lots of high speed riding. It does slap a little in this cylinder when running.

Matt! Are these the same jugs you got from Friebus like I'm running?

I really don't see any problem here other than what Dragstews pointed out. My first inclination is that even if some scoring or wear marks are present, if a fingernail doesn't catch it, I'd just run it. Maybe a closer look at the piston, ring and ringland in that area circled in red by Dragstews would be a good idea though.

Me and some buddies just finished buttoning up a Shovelhead that belongs to one of them. We had to redo the heads, the valves needed lapped and one of the valve guides was fucked up. We pulled the jugs just to inspect them since we were in there. This isn't a great picture, but you can see some wear/scuffing on the cylinder walls. Pistons looked about the same. We just broke the glaze off with one of those springy 3 arm hones and slapped it back together. It's rippin again.




You might already know this, but you can re-use the copper head gaskets on these flattys a few times if you anneal them between reuses. That's what I did with mine last time around.



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M,

Did you align the rods with the case decks after replacing the wristpin bushings? In my experience, you will NEVER be able to ream them exactly straight when doing them in place, and tweaking the rods is just part of the job. That's the first thing that came to mind when I saw the pic.

Jim

I bought the tool and aligned the rod with case deck using the paper pull trick. Felt good and looked good.

I checked mine the same way as you, which as far as I can tell, is exactly what the service manual says. I'm a glutton for punishment so I made my own squaring plate tool out of like some 3/8" plate.









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Attachment 109889

There's where the piece of crap got stuck ...

Looks to be. Good eye




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seems like 2 to 3 clearance is not enough?

Even with pistons that say to fit tighter I've never had any luck fitting a flat head tighter than .004. The way I ride .005 seems to be minimum. Fit the front .0005 or so looser than the rear.
Dusty

I agree. Mahle specs .0025 - .0033 for pistons in a SBC. I feel like an air cooled engine should be looser, flathead or otherwise.





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I find the 45s with loose fit cast pistons do go "tink tink tink" when they are running. It's a very distinctive sound. I don't have any experience of the big flatties.

My 80" BTSV makes that tink noise. I love it





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13 fin big flatty cylinders are getting hard to find.

Next set of jugs I buy I'll get them from Brandon @ HillTop Twins. I bought my cylinder heads from him and he is great to deal with. He's the closest distributor of Flathead Power stuff that I know of. Also, check out the Flathead Power website below. Anders built a flathead on what looks to be an EVO Sporty set of cases. Pretty trick.

https://www.hilltoptwins.com/product...head-cylinders

https://www.flatheadpoverty.com/






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To confirm cylinder base square to the bore, I would mount it in a 4-jaw chuck on a lathe, align the bore to be exactly centered using a dial gauge, then moving the dial gauge to the base and turn it to check for squareness of the base to the bore...if not, a thin cut while in the lathe and you make it square. You could do the top of the cylinder too while the cylinder is at the lathe, using the same technique.

Pretty cool idea. I would think that the play in the connecting rods would be enough to compensate for anything that was only minutely out of square.


-Chase