Cylinders, Pistons, and Rings oh My

[mcgovern61]

I've had the heads off two engines and the ridge at the top of the cylinders on the '81 engine (169k miles) was minimal at best. Didn't go so far as split the case, but was suprised that everything else seemed to be in really good shape considering mileage and knocking. Aluminum skirts worn.....makes sense to me.

 

[dan filipi]

I'm doing this rebuild to locate and eliminate the knock.

Gerry, did your knocker engine have piston slap on cold startup anything like mine does?

 

[dan filipi]

So metricpartsoutlet says standard pistons and .25 over are discontinued, wah!

Its looking like my only options are using the best used pistons I have from my collection, knurling skirts if needed.

I once had a Chinese company contact me saying they can manufacture any piston for dirt cheap.
I'd send them one piston with my required finished specs.

What do you think of this option?

 

[slabghost]

Check with your machine shop about knurling. If they can and what would the advantages or drawbacks be along with cost. It's possible it may be the cheapest option as well as a lower friction piston with a better fit than stock.

 

[mcgovern61]

I'm doing this rebuild to locate and eliminate the knock.

Gerry, did your knocker engine have piston slap on cold startup anything like mine does?

No...nothing like your bell ring( :smilie_happy: ). Just noisy start up and the knock you hear in the videos.

 

[mcgovern61]

So metricpartsoutlet says standard pistons and .25 over are discontinued, wah!

Its looking like my only options are using the best used pistons I have from my collection, knurling skirts if needed.

I once had a Chinese company contact me saying they can manufacture any piston for dirt cheap.
I'd send them one piston with my required finished specs.

What do you think of this option?

My experience in the maritime industry as that Chinese companies will do anything to try to copy a product, but there are no materials standards that are followed and quality control is only worth the paper it is written on. IMHO, I would not spend my money to try it.

 

[jdegase]

material standards are very high when it comes to pistons they need be very close.
I would choose the best four used you have... make sure they are closest in size to the bores your putting them in... next go over them and make sure there are no grooves that can cause a high spot at the end of the groove... any high spots can be LIGHTY filed but only to make them even with the surrounding area ....
defiantly install new rings, maybe look into a better ring than stock(high performance or longer life)
metallurgy has come a long ways in 30 years.. improvements in rings defiantly have improved longevity in engines..
chromalloy may be available. ring manufacturers have guild-lines to the honing process follow them!
note about chrome they may take longer to seat in... but seal excellent.

basically if your pistons and bore are within serviceable limits the only "comsumable" is the rings...

 

[dan filipi]

Question on piston measuring,

At what point on the skirt do I measure?

I know 90 degrees from pin but how far up the skirt?
Since the piston is tapered I get a measurement larger than new spec at the end of the skirt.

Google searches say it varies with manufacture.

Next question,

At what measurement in a cylinder would the "serviceable limit" be referring to? The largest point or the smallest point?

 

[scdmarx]

Question on piston measuring,

At what point on the skirt do I measure?

I know 90 degrees from pin but how far up the skirt?

90* from the pin, about the same height as the pin.

Since the piston is tapered I get a measurement larger than new spec at the end of the skirt.

Google searches say it varies with manufacture.

Hmmm..... don't know what to think of that. I don't remember ever crossing that bridge.

Next question,

At what measurement in a cylinder would the "serviceable limit" be referring to? The largest point or the smallest point?

Since the cylinder wears "bigger" the serviceable limit would be the largerst point.
Since the piston wears down smaller, the serviceable limit would be the smallest point.

 

[Piper]

Just put all the measuring stuff aside for a second and put the piston in the cylinder dry without rings. See what it feels like at the bottom and top of the cylinder. It'll be obvious to you if you have a problem or not. If it seems too loose, try a different piston. Kind of a feel thing. Remember .006" is the uppper limit.

 

[dan filipi]

That's sort of the problem. Since I don't have any experience doing this I don't have a "feel" for it so I have to use the gauges.

 

[Piper]

I checked into it with the experts and some still do knurl pistons. Whether you can do it 1100 pistons, I don't know. After they are knurled you have to hand fit the pistons by running a wide flat file lightly over the knurling until you get the "feel" right in the cylinder. I'm sure scdmarx and the other auto mechanics on the forum are familiar with this technique. The knurling is actually beneficial because it holds oil in the cylinder. Years ago it was done all the time on overhauls.
Also, on opposed cylinder engines like these, the rod/piston assemblys should be balanced with each other if you want a really smooth engine. I like to shoot for 3 grams maximum but it's tough to do.

 

[joedrum]

this is a great tectnic for oldwings when you cant get parts ....like we cant for oldwings :mrgreen:

 

[scdmarx]

Years ago it was done all the time on overhauls.

I've never used knurled pistons. I do remember hearing about it years ago, but for some reason just always ended up with new pistons. Maybe because 90% of the time I went oversize anyhow. Looks like a worthwhile alternative for obsolete parts. I have knurled valve guides, but found that new guides lasted longer. But guides are different than pistons.

Another alternative for obsolete parts, if you were forced to do some research, we have a burned up Honda car motor sitting in the shop right now and I noticed the cylinder bore seems to be nearly the same size as the 1100 bore. If the dementions of the pistons were the same, like wrist pin location, etc. the motor wouldn't care if it was a car piston. Even if you had to shave off a bit from the skirt length to make it fit. Just make sure it will have the needed valve clearance and stuff like that. There's a better chance that pistons are still available for the car motor.

 

[jdegase]

cylinders usually wear 90 deg. from the wrist pin..
usually the cylinders will wear into a oval kinda shape.
same with pistons really.. only they will become smaller across the worn area. so either should be measured 90 deg. from wrist pin

also one addition to the "car piston" thought would eb to NOT mix car pistons and bike pistons... and if you need to trim them make sure and match the weight on all 4.

 

[Omega Man]

Saber's rings are NPR, Nippon Piston Ring Co., Ltd.

Are these ok?

I'll be checking around, not saying I'll be buying them but it gives me a basis for comparison.

WOW, Honda OEM is $54 per piston ring set!

surprised? isn't an OEM air filter like $30?

~O~