mark kibort

Sorry, i was writing and fighting off my 3 year old when i wrote that. I corrected it. So, no I have never had to cut the rings. and if i did, i wouldnt have been the one doing it!

MK

mark kibort

Adam, thats why i put the Redline assembly lube diluted with oil, on the piston skirts and the very diluted mixture on the cylinders. I knew i would be cycling the engine a bunch of times, in addition to timing it all out ! segway into the last comment, the piston cylinder wall gap is so small, much smaller than the chevy/ford Iron bores. a few cycles of rotation and those rings scrapped the cylinder walls so clean, they seemed like they were right from the pasting machine. i was always squirting oil into the bores before final assembly.

Mk

JHowell37

I've never seen a 2 stroke lawn mower.

mark kibort

obviously brendan has!


by the way, I guess i am not that alone with the use of assembly lube:

http://www.automedia.com/Engine-Rebu...es20021201rp/1

Next, coat the piston skirts and ring package with plenty of assembly lube, place the ring compressor over the rings and tighten until the rings are fully compressed. Rotate the crankshaft so that the rod journal is in the full bottom-dead-center position. Place the piston/rod into the block. After you have made certain that the ring compressor is flush against the block deck, you can tap the piston down into the bore.

mk

Nicholbry

Very well, I won't mess with the cylinders. I just figured it might be ideal to do something for the cylinders if I was using new rings. For curiosity's sake, it would be interesting to know if anyone has attempted it with any success though.

Thanks "atb" for getting me the ring tolerance spec. I must not be doing something right with these Technical CDs I got from Jim M. The PET and WSM are fine, but the others I'm having some trouble with, which explains why I couldn't find it I suppose.

Can someone explain into words how this tool works? I've not seen it in action and the design (of those I've seen) isn't self explanatory. I'm assuming they open the rings up just enough to drop them down over the piston caps and into the lands, right? If so, it seems like that would apply greater stress on the metal by opening it up balanced instead of a slight, offset flexing into the lands by hand. YouTube can be a great place to visually understand the way these tools work (i.e. Piston Ring Compressor), but I haven't found one for the spanner tool yet. Also, any ideas of a particular part no. and website for this tool (aftermarket for cost savings) that will work for these size rings? I wouldn't want to order the wrong thing as green as I am to this.

Brendan, by "edges" are you referring to the cut corners of the rings at the end gap? I don't know so I don't mean to imply doubt in your knowledge, but I would think that by filing the edges (even slightly) that mate to the cylinder wall at the end gap would, essentially, be like increasing the end gap if the ring isn't seated perfectly against the cylinder wall there. But maybe you're talking about grinding more of the edge and less inward of the gap to maintain a straight seal rather than having a "pie" shaped opening by grinding the end gap inappropriately; is that it? I can see where this sharp edge could scratch the cylinders and be a serious threat.

To take your example further, I have seen where some mechanics actually use a fine grit sandpaper and gently dull the leading edge of the rings all the way around before installing to minimize the risk of cylinder scratches. Any thoughts about that; to do or not to do? On new pistons, the mechanic does the same for the piston lands to soften any sharp edge left behind in the manufacturing process. I don't have new pistons so I don't need to be concerned about that, but thought I would put it here for future reference of other Rennlisters.

I can't say it enough; thank you guys for helping me.

Vilhuer

You need to browse folder structure on CD to find all files in it. You probably have autorun on and default internet browser jump on as soon as you put CD in. Just close it and open what ever you normally use to access files on hard drive. Select CD or DVD drive from there and you'll find a lot of documents there.

Normal version of such tools opens up ring by pushing it open from gap. Rest of the curvy tool arms are there just to keep ring straight. This is by far mildest way of widening them enough to fit around piston. I think bending them kills them much more easily.

hacker-pschorr

They exist - I had one, right now my neighbor and another friend use one (cannot remember the name, they are bright green). Not that long ago they were very popular.

Sorry for the hijack.

blown 87

Many of the older "Snapper's" were.

atb

Mark K. wrote:
Hey Mark, wasn't trying to call you out on this. It's just that from what I've seen the rings are really made to exacting tolerances. The reason my stroker isn't built yet is all because of ring tolerances.


Yeah, I must have reloaded my little handheld oil can about four or five times keeping the cylinders wet.

Nicholbry wrote:

I agree, if anyone has had good luck with this definitely pipe up.

A whole new world of easy to access specifications await you in the "Technical Specifications" booklet PDF's.

Here's a pic of the tool, which is available at Harbor Freight for $9.99.



If you were to close the jaws of the ring expander, and look at the tips, you would see something like this: ><
You slide the tips of the tool into the ring gap and when you squeeze the handles together ">" separate from each other and each one catches an end of the ring. The more you squeeze the handle, the more you separate the tips of the tool, and the wider the ring expands.

Regarding the comments on adjusting the ring gap. I'm no expert on rings, but it seems that only some types of ring sets can be ground or filed to size. I have a piston ring end gap file , it's one of the old style hand crank models. It works great on rings that come over sized and are meant to be ground to spec, but it takes a long time, and it is a lot more time intensive to get a nice and square end compared to having the rings professionally cut. The piston set on the RMT engine used these kinds of rings. The tool does create a build up material on the inside edge of the ring that need to be removed with a hand file to prevent it from interfering with the ring back spacing.

Two stroke mowers? I've never seen one but my neighbors probably think I have one. Every spring I empty the old premix out of the dirt bike and run it in the mower. Smokes like crazy, and coats the neighborhood with the unmistakable scent of "Golden Spectro"

BC

Did I say grind the rings? No. I said taking the outer edge down where the gap is.

BC

Think of the rings as a spring circlip that pushes out, so technically they are perfectly round when they are a circle, but when under free spring, they are kind of an oval. So would take a file the the OUTSIDE edge of the each end of the ring where they nearly meet, and take it down JUST a bit. Just to make it not sharp.


I wouldn't file or sand anywhere else on the ring other than real ring grinding, but as ATB mentioned, they normally do not need this in this engine. There is something to be said about opening up the ring end gap under high boost though, because of the heat expansion. A. Graham Bell, in his "Four stroke Performance tuning" series of books, mentions how if the ring expands too much, the ends could meet... And break.

BC

I don't even know why this has to be said, but I think its because mark doesn't want to focus on his actual mistake.

All I ever used was two stroke motors when I cut lawns a long time ago. The four stroke stuff was too new for me to afford at 13.

mark kibort

Im sure they exsist, as do 2 stroke diesel chain saws (just small in number)

However, i posted this becasue the article that Brendan was referencing was for 4 stroke briggs and stratton engines, not two strokes, even though when this reference discussion talked about using assembly lube on the piston skirts, he tryied to discount it by saying "forget about the lawnmowers. those are two stroke engines anyway". I then find two other articles that talk about using assembly lube on the pistons skirts as well as a manufacturer that suggests using it on pistons as well.

The insults were flying as my suggestion was supposed to cause some listener to loose his new engine buy putting a light coating of Assembly lube on a piston skirt! Then, he equates the break in process of our engines on a 928 with a chevy, saying its all the same. Most of the experts say there really is no break in process. and even if there was, the assembly lube, especially the stuff from Redline would be completely gone in a few cranks. In a iron block bore, the hash marks allow for wear patters on initial start up that is required for ring seating. If assembly lube was used, it could trapped in those microscopic areas that are not really present in the Alusil bores of a 928. It could cause a problem.

mk

BC

Like I said originally - EVERYONE ELSE BUT MARK don't put anything but a conventional oil on your pistons and rings and bores at assembly, and have a happy break in. Mark is now discussing microscopic areas in iron bores that do not exist supposedly in a crystalline structure of aluminum and silicon where the aluminum is worn back to show the 14% or more of silicon. Right. No extra space there at all.

We have already accomplished what was important - the OP will not be using assembly lube on or near the pistons and bores. Thats fine. Everyone else who actually has an ability to learn instead of spout static info has also gotten some info as well.

And no one will "loose" (lose) their engine with lube on the pistons. It won't break in properly (the rings or bore depending on the engine type) and probably glaze the rings, causing them to have to redo that step. Meaning removing the engine and all that again.

mark kibort

I know im not much younger, but all i ever saw was the old briggs a stratton 1hp engines! we used to scrap them and take the motors out and make mini bikes with them! I think when we rebuilt them we used Cheese Whiz for assembly lube

Hey, we are arguing over something that really is not a big deal on a 928 engine. the one time i didnt use the assembly lube on the piston skirts, we ended up with an engine that grenaded. i was only the witness here! the shop kept on trying to start the engine, while the coil wires were reversed. the bores ran out of lube and locked up.

Dont get frazzled, but how may 928 engines have you built? you sound like you are trying to come across as one of the experts.
By some of the articles i posted, there are some that suggest using assembly lube on piston skirts. I used the redline stuff and highly diluted with engine oil. again, anyone that knows 928 engines knows this is not a big deal, and probably a good thing if your motor doesnt start right away!

Below are pics of scots original 4.7 euro that grenaded after the rebuild (the mistery engine the grenaded originally due to #2/6 bearing) and the cylinder walls were lapped with the Silicon paste process.
This one was started by the shop unitl dry. the pistons just got toasted. We bored this block and i put it together in my garage. ran a full season this year, no issues 290rwhp. burns no oil, and i used assembly lube on the piston skirts. The pics show what happens when you start an engine with no oil for too long. also the bores before we started.

mk