Thanx for letting me join the forums.
I have a general question about rapid piston ring wear in aluminum cylinder small engines. I can not seem to get more than 2 seasons use of any mower or tiller engine I overhauled. Air filters kept clean and sealed, and ran fine for first year, but both now have lost significant compression and appears the rings are shot.
Can not understand why the aluminum cylinder can wear the cast iron piston rings so fast. Seems like the other way around.
One engine was a 130202 horizontal on a tiller and I can not recall the other model but 3.5 hp vertical on a push mower.
Tom S. in Tn.
#2
Boobala
The bore of an ALUMINUM cylinder has a STEEL sleeve in it, an ALL aluminum cylinder would wear-out in short order and would be a real mess to hone, loss of compression is usually from worn rings, blown head-gasket, valve problems.
Not all aluminum cylinders have sleeves, in fact the vast majority do not. Wearing a cast ring on an aluminum cylinder that fast means you have other problems. Dirt ingestion is number one, followed by out of round or over sided cylinder, non OEM rings, wrong oil, etc. How do you know the rings are bad? Have you measured the cylinder and checked against standard size? Have you checked ring end gap against standard size? Are you sure you installed the rings in the proper order and right direction? Don't blame rings until you rule out other possibilities.
#4
Boudreaux In Eunice La.
Rivets is correct not all cylinders have sleeves, only the I/C types have a cast iron sleeve.
As for as the rings go you need to put the OEM Chrome rings in there......
Yes an out of round cylinder can cause that.. If the engine is dear to you, a place that does boring can bore it 10 thousands over., but you will have to buy a new piston and rings. Not cheap.........
Will an overhaul with rering usually last on small aluminum engines?
I can see minimal wear when mic-ing the cylinder and piston, and yes the rings are shot again with much end gap.
Valves and faces still very good. I 'think' the air filters are working, and never gave much thought to the oil other than 30 wt. detergent, sometimes the B&S container kind. Sometimes the house brand.
I just light hone with 600 grit paper so as not to remove additional cylinder material.
I'm beginning to think Chrome faced rings are the answer, and yes, these were inexpensive.
Where is a good source for these?
Never had much problem with motors with liners. How long should I be able to expect a rering to last on one of these aluminum engines?
Thanx; Tom S. in Tn.
Tom, Many knowledgeable people contribute to this forum. The dimensions necessary on piston-ring-bore are not easy to obtain but there seems to be widespread belief that anyone can fix problems. That is difficult for a home based mechanic because most lack the required tools and experience using them. This is not to be critical of anyone. On worn cylinders a very careful measurement is required . A telescoping gage can be used, but a 3 point dial indicating gauge is best and the latter is expensive. Properly used, taper, out of round and remaining usable cylinder thickness can be determined. Overboring has its dangers: reduced cylinder stiffness , holding a dimension for piston fitting, wrong finish. Once a cylinder head is torqued bore distortion can occur especially of thinned cylinders. Failure to hold desired diameter with boring tools is common and can cost much heartburn. Unfortunately, taking a machinist's word that the bore is "clearanced" for the new piston skirt is a risky business without proper verification. That dimension is so critical less than .001" error can result in blowby and oil consumtion. Again, not critical of any machinist, just to be cautious (don't ask how I know).
Rings: As noted these things are little understood. For instance they do not hold compression through spring tension alone. The sealing depends upon them being proper diameter, end gap that can open and close across the temps and being free in the lands (slots). The land dimensions must be held. Gas pressure forces them to seal against the lubricated cylinder walls. It is amazing that this process works as reliably as it does.
As usual too much talk and not meant critical but hopefully helpful to the home mechanic.:2cents:
I'll bet if you give us the measurement you got on your units, we will be telling you that the cost to repair will be more than it is worth. If you have been taking 600 grit paper to the cylinder and using non OEM rings, the cylinder will probably need to be bored and oversized piston and rings installed. Once you add up all costs, with no warranty, not worth it.
Without proper crosshatching the rings will skip on the cylinder walls, and if you are not getting the block surgically clean, the grit from the honing process will stick to the rings and cylinder walls, and continue to act like sandpaper leading to quick wear and engine failure.
All right, I'll rethink scrubbing in Kerosene and simple soap & water bath. Other fellow stressed 'hot water' and lots of scrubbing also, then use paper towel to check for residual grit until it wipes clean.
I'll admit I've not been that diligent. One wash and I usually let it go.
What about using the dishwasher prior to assembly?
Forget the Kerro.
Hot soapy water, degreaser that is what you use on bores.
Rinse in hot water then get a white cotton rag, press it hard against the cylinder wall and run it through the bore in one direction then look at the rag.
If it ain't clean wash again. If it is clean run the rag through in the opposite direction and check again.
I use white cotton conservators gloves ( not coarse garden gloves ) to do the testing.
Also make sure the ring grooves & lands are clean.
