Preparing a new piston for install?

[blakester122]

So I'm about to start putting my bike back together. I have a new piston that I'm putting in and I have been told in the past to soak the new piston for 24 before install in oil.

Has anyone heard of this being done. Does anyone have suggestions around these lines?

[OTD]

Never heard of soaking a piston, do they think it's going to absorb the oil?. I always put a thin coat of oil on the piston and cylinder walls making sure to oil the ring grooves.
We were having some ring adhesion problems on our race bikes and a Kawasaki mechanic recommended putting it together dry only lubing the pin, I was skeptical but it worked and we didn't suffer anymore wear than we had previously.

[markk53]

For the past decade or so, from my friends at the bike shop, the pistons and rings are installed dry. No oil, no tricks. It's no big deal, after all, the whole thing is going to seat together anyway and oil will be everywhere in the engine in about a second. They don't oil things up or put on any other special goo. It's gonna get oil baked on soon enough and oiling things up will get oil in the compression rings where it can turn to goo and sticky crap. The oil ring scrapes off excess oil that is below the piston, but isn't supposed to be scraping oil up toward the combustion chamber. Build it dry.

Even two strokes are done dry now.

[MeadowHobbit]

In the inside of the piston, where it doesn't contact
anything, engrave the date installed and mileage.

[robow]

I have always just coated the cylinder wall in a thin coat of oil to make things a little easier to slide together; never heard of soaking a piston in oil, sounds like a waste of 24 hours.

[OTD]

For the past decade or so, from my friends at the bike shop, the pistons and rings are installed dry. No oil, no tricks. It's no big deal, after all, the whole thing is going to seat together anyway and oil will be everywhere in the engine in about a second. They don't oil things up or put on any other special goo. It's gonna get oil baked on soon enough and oiling things up will get oil in the compression rings where it can turn to goo and sticky crap. The oil ring scrapes off excess oil that is below the piston, but isn't supposed to be scraping oil up toward the combustion chamber. Build it dry.

Even two strokes are done dry now.

Kind of strange you are the only person I've ever seen on a forum that has heard of that. I was called a nut on a MX forum for recommending that to someone.

[Blaine]

Before installing piston check your end gap on your rings and make sure they are within specs. Also did you check the taper in your cylinder walls. I always put pistons in wet, meaning I dip them in oil before installing. However I know there are two schools of thought on that. Any excess oil in the combustion chamber is burnt off right away. Need not worry about any oil trapped between rings, it won’t turn to goo.

I simple way of checking for excessive cylinder wear is measure ring end gap at the top of the cylinder then at the bottom, the difference is the taper in the cylinder walls. Most engine builders use a dial indicator for an exact measurement. Also be sure to check your rod alignment. Good luck on your rebuild.

[blakester122]

Thanks everyone for the advice. The last one I did I just used the red engine assembly lube. everything worked great! I had the cylinder bored with the piston there with them so everything should be just fine as far as clearances. I also have no rode play either. The motor was rebuilt several years ago but sat for about 10 or 12 I think before I bought it. Lets put it this way there were rust spots from where the rings sat in the same spot for so long. Now everything looks new thanks to the bore.

Thanks again! also what about break in periods? Which would you use? The slow take it easy or this method?

http://www.mototuneusa.com/break_in_secrets.htm

[markk53]

Kind of strange you are the only person I've ever seen on a forum that has heard of that. I was called a nut on a MX forum for recommending that to someone.

I guess that's because I asked people who did it for a living back before the internet was a big source of advice - right or wrong advice. Thus I quite frequently recommend people do exactly the same. Find a good reputable mechanic and simply ask. They'll tell you.

Besides if you ever notice on those hot rod TV shows they never show the piston being gunked down with anything or mention it for that matter. When they tap in a piston there's no puddle of junk on the deck from the piston or rings. But that's not where I got my information - I asked the guys who did the engine work at the shop where I sold bikes.

And the old school thought for the back yard mechanics back years ago was to pour oil on the pistons and rings. Key words - back yard. Again, I learned to put the assembly together dry. After all, the premix or oil injection will have oil in the fuel and coated down the necessary surfaces virtually immediately with the right light layer of oil. Again, per mechanics who build them.

[markk53]

Before installing piston check your end gap on your rings and make sure they are within specs. Also did you check the taper in your cylinder walls. I always put pistons in wet, meaning I dip them in oil before installing. However I know there are two schools of thought on that. Any excess oil in the combustion chamber is burnt off right away. Need not worry about any oil trapped between rings, it won’t turn to goo.

I simple way of checking for excessive cylinder wear is measure ring end gap at the top of the cylinder then at the bottom, the difference is the taper in the cylinder walls. Most engine builders use a dial indicator for an exact measurement. Also be sure to check your rod alignment. Good luck on your rebuild.

Did you ever see what oil in confined spaces does under high heat? Remember the old Mobil1 ad with the frying pans. Sure oil in the combustion chamber will eventually burn out, the stuff on top the piston, but oil behind and between the rings will very likely not burn out. I've seen two stroke rings with oil baked into in the ring lands when too rich an oil mixture is used. It doesn't have time to burn back behind rings, only to bake. That was why I was told they assembled dry. That from factory trained mechanics who also raced, so the experience is there.

Of course maybe the oil won't be a big deal, but why have the mess if you don't need it?

[markk53]

Thanks everyone for the advice. The last one I did I just used the red engine assembly lube. everything worked great! I had the cylinder bored with the piston there with them so everything should be just fine as far as clearances. I also have no rode play either. The motor was rebuilt several years ago but sat for about 10 or 12 I think before I bought it. Lets put it this way there were rust spots from where the rings sat in the same spot for so long. Now everything looks new thanks to the bore.

Thanks again! also what about break in periods? Which would you use? The slow take it easy or this method?

http://www.mototuneusa.com/break_in_secrets.htm

Rust spots. So are you rebuilding to run or to sit?

My bet is that engine was run after rebuild, so everything had gotten lubed as needed originally, so the rust is just what happens over time. That would happen if any fourstroke sat long enough if the rings did a good job of scraping the cylinder walls and seal up (after all, that's what they do). It is no proof that any cylinder or piston lubing in assembly is needed.

It is often recommended that a very tiny amount of oil be sprayed or put in a cylinder and the pistons cycled through (not run) a few rotations to oil the walls if a bike is to sit for a length of time. This may or may not stop rusting as some have found when finding stuck pistons in two strokes, which actually run oil in their gas, after sitting for years.

The only good argument for assembly lubing of pistons and rings is if the engine will sit for a length of time before being run. If that's the case I'd be doing the research to see what lube would be used for that. I'd be in touch with some engine builder who may have tens or hundreds of engines on the shelf to sell - aka NASCAR builders and the like.

But hey, it's the internet. Why talk to verifiable engine builders when you're not quite sure.

As for that break in. It's almost exactly what we used to tell customers to do. You may notice he never said "run it at redline" or "run it to redline" at any point that I saw. You may notice he mentioned acceleration and deceleration. The idea is to get pressure behind the rings to push them out to seat - but this causes heavy friction which creates heat. The deceleration time allows for some release of combustion pressure on the rings and time for some heat transfer (aka cool down).

We used to tell customers to just go out and ride the bike as they normally would, but only use up to about 80% of redline range. We also said DO NOT LUG the engine, do not short shift and use heavy throttle. You see, running a bike hard as described in that article isn't really loading down the engine that much. If it was all about load you'd be hammering the throttle at about 1000 rpm creating tremendous cylinder pressure as it tries to accelerate, but can't and will just generate a lot of heat that can damage rings or even cause piston siezure. It is about running the engine working in it's power band and using on and off throttle with some harder acceleration for sure. That is for longevity, but emember his race engines only cover a few thousand miles too, so getting too extreme may not be the best. Err to the middle - see if you can get a look at a general dyno print out for your model bike and use the midrange.

Ie. my Zephyr had a dyno print in Cycle back in 90, it showed the power generation to start relativey strong at about 3000 rpm and continue up to 10,000. If I broke in the engine I'd be using the range from about 4000-8000 for my hard acceleration - perfect back road range. In town light cruising would be in the 2500-3500 range without lugging the engine, but with the actual "stop light to stop light" reving up around 4500 or so (the beauty of a small engine in town - you can rev it more with less speed). But I'd be out of town as much as possible on some back roads using that 4000-8000 range a lot. Another: I did a top end on the KLX, I knew the power range to be about 3000-7500, so I did the break in as described in that article to an extent, using 3500-5000 most of the time and a lot of harder on/off throttle on the secondary highways and county roads of eastern Ohio - hilly winding roads which work perfect for break in, hard up the hills off down the hills and so on. The engine still has virtually all it started with 27,000 miles later with no burning of oil.

For 99% he's right. He just seems to miss the part of avoiding lugging the engine down below the power band and maybe not enough emphasis on not reving too high for too long/often, where heat generation can affect rings. The former is probably because he's talking toward sport riders, not so much toward cruisers. The latter is because he's got more focus on racing, but he still somewhat notes that you should avoid continuous high rpm. Another example: I had a friend who broke in his Kaw 900 Z1 with the "ride it like you stole it" attitude - ring blowby in 10,000 miles - he damaged the rings with too much heat in break in. He just overdid it. I've also seen engines broken in by the manual where rings didn't seat in properly. Where there was carbon build up back in the leaded gas days in a few cases,that had the pistons crudded up pretty bad. Heck Kawasaki had us two stroke triple owners on that same break in - don't exceed 4000 for the first 600 miles and 6000 up to 1500 miles I think. Per my friend the trained Kawasaki mechanic and fellow racer - the cylinders were broken in within the first 100 miles, using the range of power up to about 7000 rpm on and off and from there it was pretty much run it as you like. Seems if you tried to follow Kaw's break in the cylinders would load with oil since the true powerband of the two stroke wasn't reached until around 5000 rpm. The engines would load up and smoke like mad. He'd have a customer come in whining about power, he'd go out and ride it off nearly hitting redline in each gear, cleaning out the engine, come back and tell them to run it like they want to ride it, but not to hit redline for several hundred miles. Kaw would rather replace fouled spark plugs than engine parts under warranty - and probably not warranty spark plugs then.

So, go out and ride it like you plan to, but don't run over about 80% of redline for a few thou, use the engine's power range thoroughly. The hard bursts are good, constant drone bad. Stay off the freeway unless your freeway has curves like West Virginia and you can run triple digits. Hilly back roads are perfect. Constant throttle variation is the ticket. That and reving the engine in the power range. I know a perfect break-in for any of my bikes is simply a few weekends of riding like we always ride on the back roads of eastern Ohio. I like to ride aggressively including my engines, but I don't particularly like to flirt with redline all day long. It's about using the middle and using it aggressively. My break ins are exactly how I regularly ride.

[OTD]

I guess that's because I asked people who did it for a living back before the internet was a big source of advice - right or wrong advice. Thus I quite frequently recommend people do exactly the same. Find a good reputable mechanic and simply ask. They'll tell you.

Besides if you ever notice on those hot rod TV shows they never show the piston being gunked down with anything or mention it for that matter. When they tap in a piston there's no puddle of junk on the deck from the piston or rings. But that's not where I got my information - I asked the guys who did the engine work at the shop where I sold bikes.

And the old school thought for the back yard mechanics back years ago was to pour oil on the pistons and rings. Key words - back yard. Again, I learned to put the assembly together dry. After all, the premix or oil injection will have oil in the fuel and coated down the necessary surfaces virtually immediately with the right light layer of oil. Again, per mechanics who build them.

Don't watch those Hot Rod shows I've been an Auto tech for over 25 years and have no interest in watching people work on cars on TV. I built my first engine using a book titled "How to rebuild a small block chevy" when I was 16. I still Believe as I was taught that a thin film of oil is likely to more good than harm. I was told that dry install promoted quicker ring seating, that is why I did it on our MX motors. We were doing Top ends every 15 hrs. and you don't want to use much if any of that time breaking in a top end.

[Blaine]

And the old school thought for the back yard mechanics back years ago was to pour oil on the pistons and rings. Key words - back yard.

Calling someone a back yard mechanic because they use a different technique than you is down right stupid. You have no idea of the experience level of the individual.

[robow]

Don't watch those Hot Rod shows I've been an Auto tech for over 25 years and have no interest in watching people work on cars on TV. I built my first engine using a book titled "How to rebuild a small block chevy" when I was 16. I still Believe as I was taught that a thin film of oil is likely to more good than harm. I was told that dry install promoted quicker ring seating, that is why I did it on our MX motors. We were doing Top ends every 15 hrs. and you don't want to use much if any of that time breaking in a top end.

I have never understood the point of watching someone do there job, imagine a show about a UPS driver delivering packages, just seems pointless.:biggrin:

I just looked through several repair manuals; Haynes for my bike, Chilton and Haynes for 3rd generation Camaro, and a Chilton Chevy small block rebuild; all said to lube the rings, piston, and cylinder wall before installation.

[OTD]

I have never understood the point of watching someone do there job, imagine a show about a UPS driver delivering packages, just seems pointless.:biggrin:

I just looked through several repair manuals; Haynes for my bike, Chilton and Haynes for 3rd generation Camaro, and a Chilton Chevy small block rebuild; all said to lube the rings, piston, and cylinder wall before installation.


Yeah but people have a lot of passion for cars that's why they watch those shows. I'm not saying dry doesn't work I'm just not going to use it on anything that I am not positive is going together right away. Let's say you're assembling your old Honda 750 4 and you get the piston and cylinder on it and notice an overlooked problem with one of the cams. You don't have the money to buy it right away so you wrap it and store it in the garage for a few months till you have the money. Now it's been sitting on the shelf w/o anything to protect it from corrosion. The engines I was putting together dry were going out immediately. I used to do performance rebuilds but these days it doesn't pay. So if I rebuild an engine it's pretty much always for me and I'm going to coat all moving parts. He!! I rebuilt my golf cart motor 2 months ago and still haven't had time to put it in. Imagine if I hadn't coated those parts.:thumbsup:

[65sky]

Calling someone a back yard mechanic because they use a different technique than you is down right stupid. You have no idea of the experience level of the individual.

Very true!
Someone on here with zero real world experience himself :rolleyes:, is giving advice that simply is not right. :frown:
I just hope that those listening can tell the difference between GOOD ADVICE and misconceptions based on what his neanderthalistic buddies tell him is the way to do it.
I get paid (for the last 30+ years) to build engines and as a matter of FACT the pistons go in oiled.
Along with the cylinder walls.
Some people, actually build engines to last! :thumbsup:

Sky...

[cbdallas]

Coming from someone who has never built an engine from the pistons-up, I have to say that I think I'd want mine oiled if it were my engine. Even at startup, an engine that's already been run has SOME amount of oil on the rings and cylinder walls, so calling it a dry startup isn't completely accurate. A truly dry startup would be starting a brand new engine for the first time with dry pistons and cylinders. Yes, I know the oil will start circulating quickly, but it's possible for a piston to complete quite a few cycles before the oil gets there. Sounds like a bad way for an engine to start its life.

[markk53]

Calling someone a back yard mechanic because they use a different technique than you is down right stupid. You have no idea of the experience level of the individual.

Okay, so I'm stupid. I'm stupid enough to actually go ask people who do the work for a living in a shop that I know who have been trained by three different manufacturers (one by the military too), not to mention their own experience with the bikes they rode and raced. But for some reason I don't particularly think that sort of stupidity is all bad.

By the way, here's a couple of definitions of "Backyard mechanic":

From Termwiki (http://www.termwiki.com/EN:Backyard_mechanic) : A person who repairs cars on his own property, and is very often unqualified

From Autozone (http://www.autozone.com/autozone/repairinfo/common/repairInfoMain.jsp?leftNavPage=glossary&startLetter=b&targetPage=glossarySelected) : An amateur mechanic or one with little training. Often called a shade-tree mechanic.

There are times when I consider myself a backyard mechanic and others where I am a knowledgeable mechanic. After working in a bike shop full and part time I can tell you there is a difference - and the service department usually gets to straighten out what the former may mess up.

Of course you have to start somewhere if you don't get training. I screwed up a lot of stuff on my bicycle and early on with my first motorcycle because I was the typical backyard mechanic. I took my lumps, learned, and also learned when to either ask for information or have a mechanic do the work. I still do on some things - especially electrical wiring stuff (partial colorblind).

[markk53]

Very true!
Someone on here with zero real world experience himself :rolleyes:, is giving advice that simply is not right. :frown:
I just hope that those listening can tell the difference between GOOD ADVICE and misconceptions based on what his neanderthalistic buddies tell him is the way to do it.
I get paid (for the last 30+ years) to build engines and as a matter of FACT the pistons go in oiled.
Along with the cylinder walls.
Some people, actually build engines to last! :thumbsup:

Sky...

Looks like both YOU AND I are wrong according to Wiseco (http://www.wiseco.com/PDFs/Manuals/MSeries.pdf). I decided there had to be a place to learn the facts since it had been several years since I'd done my last top end and as noted in an earlier post - I'm stupid - I hadn't called and talked with the guys before making my statement. Here is direct from their instructions with the bold highlight by me:

IMPORTANT: After honing, the cylinder must be washed with warm soapy water to remove all honing grit. Be sure to wash away any grit that may have traveled into the transfer and exhaust ports during honing. The cylinder is NOT clean until you can wipe the cylinder wall with a clean, oil dampened cloth, and it does not pick up any honing grit. Lightly oil the cylinder bore to prevent oxidation and assist with piston installation.

There you go - a light oiling of the cylinder wall, only to prevent rust and help with piston installation. That isn't some slathering of oil, it's simply wiping the cylinder with a bit of oil to prevent rust. Piston goes in dry. Now if you can find fault with Wiseco, one of the largest piston manufacturers, have at it.

[Blaine]

Okay, so I'm stupid.

Mark did they explane to you why they wanted to install the pistons dry. The idea is to seat the rings faster, and I can understand the thinking behind that. However it can also cause scoring on if the engine isn’t run in properly, here again there are different thoughts on that procedure as well. I know and work with some excellent technicians and we all have different ways of doing things. Not saying that I’m right and they are wrong it is just procedures that each of us have developed over the years.
I’m not saying you are stupid, what I’m saying is your comment was. One of the technical schools put on by Caterpillar I caught the instructor giving wrong information to the class, once pointed out to him he corrected himself. None of us know it all, and we as humans all make mistakes but that doesn’t make us shade tree, back yard, or misfits in what we do. I’m a truck technician, and have been for way too many years. I run a shop with several other technicians and we have some lively debates on how certain things should be done, however I respect the talent and abilities of each one of my guys. However I’m the boss in the shop so of course I’m always right LOL

[mattness]

honestly i dont think it matters whether you oil it or not, cuz every night you park the bike the oil drains to the bottom anyway. any oil that settled up top will swish around once the engine is started anyway.

i mean theres benefits to both.

why would you want to gunk up your combustion chamber with burnt oil? but at the same time why wouldnt you want to do everything possible to protect your engine?

decisions decisions..

[soxOZ]

OK I haven’t read all these posts, but putting pistons/rings in dry isn’t a really good idea and soaking them in oil can possible cause other problems.
What I’ve been doing for the last 30 years building engines for street, performance and race cars is to just spray the rings and bores with WD40.

This will give them enough lubrication prior to starting, after all how many time will you turn the engine before starting and even when you do, there’s minimum to no load on them.
And the second the engine starts the cylinder walls will get enough lubrication from the crank/rod oil spray/mist.

Also by using WD40 or similar it will help the rings to start bedding in the second the engine fires up, after all, you want the rings to have minimum oil around them for this to happen.
As one of the main reasons oil is misted up into the cylinders is not only to help lubricate the pistons but to aid in cooling the rings.

Now whether you agree, disagree or don’t like this idea, that’s OK, as I’m not telling you that this is the only way to do it. As every engine builder will have their preferred method, but what I am saying is that I’ve built well over a thousand engines from Street Performance to Fuel Funny cars and have not had one problem with the pistons or rings using this procedure, and this is the way I will continue to do it.

[Blaine]

As every engine builder will have their preferred method,

You are so right, and I wouldn't say your method is any worse or better than mine. If something works for you, don't fix it.

[OTD]

You are so right, and I wouldn't say your method is any worse or better than mine. If something works for you, don't fix it.

Yep, and why mess with what works? I would have never tried dry if I wasn't having blow-by issues. But that was on a extremely high compression engine with a nikasil plated cylinder that your not supposed to hone. Anything else I oil.