Rebuilding top end "dry"

[GPracer2500]

Does anybody rebuild their top ends "dry"? By dry I mean with zero oil on the cylinder walls, piston, and rings. Cams and everything else get oil and/or assembly lube as normal. I've been reading about this practice and some engine builders swear by it as a method to ensure proper ring seal.

This idea was new to me and I'm wondering if anyone here does it that way...

[2004exrider]

That's pretty interesting. I've always been a firm believer in the motoman way, that just sounds like it would almost cause premature ring wear or scratches in the cylinder wouldnt it? I dont know though, i just couldnt bring myself to do that to a new engine or rebuilt. Where have you heard or seen this at, do you have any links?

Jimmy

[DieselBoy]

For the little bit of oil that will be in there, I don't see how it could cause any significant disadvantage to ring seal. I wouldn't do it personally, I believe the lubrication in that time is quite neccessary.

[plkmonster2]

The crf guys that I have talked to swear by it. They do 50 revolutions with the cylinder dry, but nothing else. It helps to seat the rings in better they say. Those engines only have 2 rings, so they need to seal better.

[GPracer2500]

Originally posted by plkmonster2
The crf guys that I have talked to swear by it. They do 50 revolutions with the cylinder dry, but nothing else. It helps to seat the rings in better they say. Those engines only have 2 rings, so they need to seal better.

I first heard about it in reference to CRF450/250-R/X engines. When I started asking around about it at least one person said they rebuild dry on ALL their engines--plated cylinder or not.

I guess the idea is along the same lines as synthetic oil being a no-no for engine break-in. Any oil on the bearing surface of the ring (especially the top ring [compression ring] that is responsible for much of the sealing) inhibits the burnishing process of the rings during break-in. Synthetic oil really gets in the way of this. But these days, even the cheapest of oils is considerably better than the oils of days gone by. And, modern hones jobs are less "rough" than those of the past reducing the window of opportunity for complete burnishing of the ring faces. That's the theory anyway...

I'm not completely sold on the idea of dry rebuilding--yet. But I'm having a hard time coming up with good reasons to NOT to rebuild dry [shrug]...

[GPracer2500]

Originally posted by 2004exrider
...i just couldnt bring myself to do that to a new engine or rebuilt...

I understand that sentiment. There are products like Total Seal Quickseat Dry Film Powder and Total Seal AL4 Piston Ring Assembly Lube that split the difference, so to speak. Using one or both of those products would still be a "dry" build (no engine oil on the rings) but at least there's something there....

[bansheexcracer2]

I'd do it

[swva400ex]

i was always told lubrication is the key.that holds true to a lot of things in life.lol.


rings dont seem as bad as the cam.especially if it is new and never been installed.

[2004exrider]

I can see in theory that the rings would be wearing a little bit more in a certain spot to help make it seal better, but isnt it supposed to be initially sealing under a good load to where the rings are being pushed out a little more by the cylinder pressure from the compression and power stroke? It could be good i guess, hell it seems that they are finding new and proven ways to break in an engine so it will run stronger and last longer, maybe this is one of those.

Jimmy

[GPracer2500]

Originally posted by 2004exrider
I can see in theory that the rings would be wearing a little bit more in a certain spot to help make it seal better, but isnt it supposed to be initially sealing under a good load to where the rings are being pushed out a little more by the cylinder pressure from the compression and power stroke? It could be good i guess, hell it seems that they are finding new and proven ways to break in an engine so it will run stronger and last longer, maybe this is one of those.

Jimmy

Yes, load and cylinder pressures are important. But I think the idea is that oil on the rings just contaminates the ring face (the bearing surface). Under normal operating conditions there is not suppose to be ANY oil there, so why put it there during assembly?

My suspicion is that the first 20-40 minutes of operation are the most critical for ring sealing no matter what you do. But why not give the rings every chance available to fully seat during that period...

I'm kind of playing devils advocate here--like I said I'm undecided on the merits of this idea. But so far I'm leaning towards "dry"...

[GPracer2500]

I forgot to mention the wrist pin--that should get oil/assembly lube no matter what. Pretty much, the "dry" method just involves the rings, cylinder, and any part that could trasfer oil to those areas (namely, the piston itself). Basically, the idea is to keep oil off the ring faces.

[plkmonster2]

I talked to a guy, and he leaves the head off. The crank is rotated 50 times. There is little oil in the crankcase, and none on just the cylinder, rings and piston. Once the 50 cycles are over, you bring the piston to bdc. Oil the cylinder wall, rotate it a few times, and oil it more. It's a light oiling, just a film. Don't get it all over the piston. Put it together, fill it with oil, spin it over, then start it. If you think about it, the compression rings are normally unoiled during the strokes. The oil wipe is below the compression rings, so there is only a miniscule amount of oil left on the cylinder wall.

[stalefish_132]

i allways put a good amount of oil on the cylinderwalls/piston and valvetrain. if i'm not mistaken i've heard from a local engine builder that if you don't lube up yout cylinder wall it the rings can scare the cylinder. i dunnoi just feel more save with everthing lubed up.:D

[krt400ex]

Originally posted by swva400ex
i was always told lubrication is the key.that holds true to a lot of things in life.lol.


lol, that's a good one. i agree :devil:

[2004exrider]

Originally posted by stalefish_132
i allways put a good amount of oil on the cylinderwalls/piston and valvetrain. if i'm not mistaken i've heard from a local engine builder that if you don't lube up yout cylinder wall it the rings can scare the cylinder. i dunnoi just feel more save with everthing lubed up.:D

That's what i was thinking at first. But when plkmonster2 said that they turn it over by hand i guess it wouldnt be enough stress on it that it would be able to score/scratch the cylinder walls. The hone would almost act like a file and wear the rings a little more so they are going to seat properly. I guess this is actually sounding like a pretty good idea, have you heard anything else on this yet GP?

Jimmy

[cals400ex]

motoman actually told me he has installed it dry before. he told me what he recommends is just a very very light coat on the cylinder. this is what i have done when i replaced the rings and/or pistons on atv's. however, i have only replaced pistons on 9 atv's....so i have not done this a ton.

[Toadz400]

It's an interesting concept, I'd try it...I think..maybe. As long as it's 50 revolutions just turning it over by hand. I can understand what they mean and how it'd work, but I just don't know if I could bring myself to run the cylinder completely dry for an hour of break-in. During normal operation the cylinder wall does have a small amount of oil on it, but it makes sense to not have any at first to ensure the rings wear properly. I guess I'm torn between the two, I guess I just don't like the idea of trying something "new" like that with an expensive high-tech machine. Maybe if someone wants to try it on their 400ex?:p

[GPracer2500]

Originally posted by Toadz400
...but I just don't know if I could bring myself to run the cylinder completely dry for an hour of break-in...

It wouldn't be. During actual operation, the engine's cylinder would be oiled as normal--the oil control rings doing their job of keeping oil away from where it shouldn't be (namely, the compression rings). Part of the idea behind a "dry" build is to keep oil away from the areas that oil should never be getting to anyway.

[Toadz400]

Originally posted by GPracer2500
It wouldn't be. During actual operation, the engine's cylinder would be oiled as normal--the oil control rings doing their job of keeping oil away from where it shouldn't be (namely, the compression rings). Part of the idea behind a "dry" build is to keep oil away from the areas that oil should never be getting to anyway.

Alright, I see what you're saying now. Makes complete sense, maybe I should try this method out if I ever rebuild the YFZ.

[Mx_523]

It seems like it would work. But wouldn't oil get into the cylnder anyway when the pistion hits TDC? Then the oil ring will clear the bore when going to BDC. When the pistion going back up to TDC the oil would lube up the cylnder and so on and so forth. I would think only the first few strokes would actually be dry.

[bwamos]

Originally posted by GPracer2500
Does anybody rebuild their top ends "dry"? By dry I mean with zero oil on the cylinder walls, piston, and rings. Cams and everything else get oil and/or assembly lube as normal. I've been reading about this practice and some engine builders swear by it as a method to ensure proper ring seal.

This idea was new to me and I'm wondering if anyone here does it that way...

That's how I installed my 330ex piston several years ago. Never had any problems with it.

And, yea I'd imagine you'd only get 3-4 strokes tops before you got fully lubed.

[GPracer2500]

Originally posted by Mx_523
It seems like it would work. But wouldn't oil get into the cylnder anyway when the pistion hits TDC? Then the oil ring will clear the bore when going to BDC. When the pistion going back up to TDC the oil would lube up the cylnder and so on and so forth. I would think only the first few strokes would actually be dry.

You're correct but the point is to keep the oil below the oil control rings at all times. The oil control rings (the bottom set) are suppose to keep all the oil below them. It doesn't matter where in the stroke the piston is located. The cylinder gets oiled, yes--but the oil control rings continually wipe the oil away so no oil ever gets above that point onto the compression rings or into the combustion chamber (two places oil should never be).

The hand cycling is suppose to be done with no oil (or very little oil) in the crankcase. That does keep the cylinder dry until you actually start the engine (after you've added the proper quantity of oil of course).

A two stroke is a little different. Two stroke pistons don't have oil control rings (only compression rings) and oil IS suppose to be in the combustion chamber. However, I believe the "dry" method is applicable on a 2 stroke because you still want to keep oil away from the bearing surface of the rings (that's the surface that actually touches the cylinder). I imagine the "dry" method has somewhat less of an impact on a two stroke but the theory behind building "dry" still holds AFAIK.

[wilkin250r]

Interesting concept, but I'm not sure I buy into it fully.

First off, I can't imagine hand-turning with a dry cylinder would seal better than actual combustion with a wet cylinder. The combustion pressures will force the rings against the cylinder wall with much more force.

Second, how in the world do you get your cylinder completely dry? You couldn't just wipe all the oil off with a cloth or rag, you would still have a residual amount. That residue wouldn't hold up long to combustion temps and pressures, but it certainly holds up to hand cycling. Whether dripping wet, or the residual amount left after wiping, I imagine it's all the same when you're hand-cycling. You still have a small barrier film between the rings and wall.

To get it completely dry, you would need to clean it with a solvent. And now, without oil, you don't have any barrier against rust. Better assemble it quickly. On contact with moisture, you cylinder walls can literally develop rust within minutes. Now, you probably won't be getting your cylinder wet while you're assembling, but if it DOES rust that quickly, I imagine just normal humidity in the air can cause imperfections within a few hours.

Plus, heat changes things. Pistons expand, as do cylinder walls and rings. I want to break in my motor AT TEMPERATURE, or as close to it as I can get.

Interesting concept, but I'll stick with the tried and true.

[Mx_523]

I see what you mean GPracer2500.
Good point also wilkin250r.

[GPracer2500]

Wilkin,

--I think the hand turning is only designed to just begin the seating process. Full seating still demands actual engine operation. If there's any part of the idea that I'm the least sure of it's the hand cycling part. My suspicion is that the hand cycling is an extra step that is only a small contributor to the theoretical benefits of buliding dry.

--Yes, solevents would be needed to get the cylinder completely clean and dry.

--Never thought about rust. I can see that being something to consider with a iron sleeve. No worries though with a coated aluminum cylinder.

[krt400ex]

Originally posted by wilkin250r


Second, how in the world do you get your cylinder completely dry? You couldn't just wipe all the oil off with a cloth or rag, you would still have a residual amount. That residue wouldn't hold up long to combustion temps and pressures, but it certainly holds up to hand cycling. Whether dripping wet, or the residual amount left after wiping, I imagine it's all the same when you're hand-cycling. You still have a small barrier film between the rings and wall.

well usually if u hone the cylinder, there won't be any oil left after u do it because it's not just getting cleaned, it's actually shaving a slight amount of the cylinder out. not enough to need to get a larger piston, but enough

[cals400ex]

yeah the cylinders do rust quick. i always wash the cylinders out several times with soap and water whether they are brand new, were honed, or were bored. cleaning everything down is pretty important. i do this to all new cams and pistons as well. i dont' wash the cams in soap and water but i do spray them off with a cleaner such as carb cleaner or something along those lines. then i quickly lube it up with assembly lube and/or oil. the cam and piston manufactures don't always necessarily clean them off good after they have been machined/grinded.

[Toadz400]

Originally posted by krt400ex
well usually if u hone the cylinder, there won't be any oil left after u do it because it's not just getting cleaned, it's actually shaving a slight amount of the cylinder out. not enough to need to get a larger piston, but enough

You use honing oil when honing your cylinder, I've never done it dry.

[bwamos]

Originally posted by Toadz400
You use honing oil when honing your cylinder, I've never done it dry.

^^^ what he said. ;)

I'm sure my cylinder also had some oil when I installed it. But, I didn't make any extra efforts to lube it. I just intalled the piston, and everyhting else.. and started her up. no hand cycling, or extra lube in the cylinder. (I did use assembly lube in the head on the cam and rockers though, I also used it on the piston's wrist pin.)

Whether that's the correct way or not I can't say. Odds are it's not. I'm not a professional engine builder by any stretch of the imagination, but it worked without any problems form me to date. ;) Of course, I'm not running 50+ hp either.. lol.

[dork]

atf in the cylinder, marvel mystery oil on the ring lands. thats what joe mondello recommends, hes been building engines for 40 years and is into cryogenics for stress relieving, cutting edge stuff. i've done 4 engines like that, no problems and good ring seal. bottom line is you don't need a lot of lube. then for break in, warm it up thouroughly, then get into 4th or 5th and give it WFO. load the engine, don't just rev it.

[strapped9]

I'm myself a dry break in believer. My father taught me that it gives the rings a chance to "wear" down into the smallest of grooves before the oil has a chance to take their place. has always seemed odd to me but I've always had a great seal on all of my machines. both 2-4 strokes alike. hand crank is the key. dont think i'd ever start it up dry. always nice to lube the crank bearings a bit as well as the head assembly. might be worth a try yourselves. may cost a bore and a set of rings at the worst.