Dry piston install

[martinfan30]

What are your thoughts? Install a piston dry, or coat it with oil? Does a dry install break in better?

Personally, my thought is to lightly lube a piston, its rings and the bore.

[slow600]

i always do my 4strokes dry. lots o science why its better. not so sure about kx

[Albertan]

I'm a follower of Super Hunky (Rick Siemens) on this.  I lube the wristpin bearing, but not the rings or cylinder wall.  As soon as the bike turns over, it is drawing premix in, and it gets lubed that way.  I think oiling the rings and/or the piston or bore just  sticks the rings, and there is no downside to assembling dry.  I know some will say the bike needs lubrication until it fires, but as I said above, as soon as the induction charge is drawn into the cylinder, the premix contains all the lubrication the bike needs.

[KXcam22]

I may be old school. I lube everything with a nice coat of premix oil and always have.  I have read various theories about "instant glazing" and other bad effects but I am not a believer.  I have seen the effects of "instant galling" with no lube.  Slow600, if you can find any "science" articles to post please do. I am always looking to learn (and maybe change my ways). Cam.

PS. Kind off topic but, the only instant glazing I have ever encountered was a friend adding a teflon oil additive to his not-fully broken in 4-cyl street bike. Engine instantly stopped breaking in. We had to tear it down and deglaze everything.

[BDI]

The very first engine I ever rebuilt in my life was a five horse Briggs. I didn't oil the bore or the piston, the piston stuck on the very first pull start attempt. It stuck so bad it took a two by four and a sledgehammer to get the piston out of the block. My father who had been a machinest and who had built race car engines for years looked at me and said "you didn't oil the piston and bore did you". That cost me a whole summer of go-karting. I think anyone who does not oil the piston and bore needs to have their head checked.

[martinfan30]

I've been a tech for Toyota for the last 14 years and have never assembled a cylinder dry. I am curious as to why some say that it leads to gumming of the rings.

[gwcrim]

Man, dry piston install is news to me.  I started rebuilding engines in the late '70s and I've screwed up my share of times.  I always have lubed the pistons and have never had an issue with that.

[KX500freak]

I'm a follower of Super Hunky (Rick Siemens) on this.  I lube the wristpin bearing, but not the rings or cylinder wall.  As soon as the bike turns over, it is drawing premix in, and it gets lubed that way.  I think oiling the rings and/or the piston or bore just  sticks the rings, and there is no downside to assembling dry.  I know some will say the bike needs lubrication until it fires, but as I said above, as soon as the induction charge is drawn into the cylinder, the premix contains all the lubrication the bike needs.

there,s a down side on installing dry imho

all the movement done for check of piston travel and fitment ,
without adding premix to piston and bore.
will cause small sand/dustparticols (if there)to leave their marks on the bore and piston.
oil makes them less harmfull ,because they get weak and will be tranported down by the oil too.

i like a good amount of premix on everything that needs it ,then i let the piston travel a while ,
with moving the kickstarter by hand ,and if its found to be good i stick plug and start it up .

also bare metal on metal itselfs is not what you should want i believe

[Hillclimb#42]

 I guess the Dry Piston idea came from the same camp that pins the throttle to break it in. No way, I make sure the piston, needle bearrings, cylinder, everything gets a light coat of oil. Warm the bike up at idle then let cool off. Do that a few times, then ride it easy being sure to change throttle position often. Never riding the pipe until letting the bike cool off again. Then its ready to ride. How is 2-stroke oil going to hang a ring before the heat and friction of a dry cylinder? Never had any problems using pre-mix oil as an assembly lube.

[gowen]

In all my years of engine rebuilds (cars, street bikes, and dirtbikes) I've never heard of a dry rebuild and will never try it. Lubing everything works great (for me) and has never let me down.

[muleman]

I only installl them dry when I put them in back wards.

[tharden]

I have mostly built chain saws and they are similar to a dirtbike but overall are built to handle more extreme conditions and run longer in between rebuilds.  I have yet to rebuild one that did not have a thin coat of two cycle oil on the piston,rings, and bearings.  I have seen too many scored pistons from lean running conditions and poor lubrication or no lubrication.

[turtle22]

i can not see how stuffing a dry piston in would not score the cylinder. i have only built automotive(cars&trucks) engines(at this point),i always hone the cylinders(so that oil will flow). i cant see how it would be any differant on a 2stroke

[slow600]

heres a link from tt where eddie sisneros goes into it briefly. he makes more power with the thumpers than anyone, kinda like stewart and the 5hundys. from what i researched most people are just too "yella" to try something different with something so critial. im hope i dont sound like a know-it-all cause im not. when i did my research about dry installs seemed like a lot more evidence supporting than against it whether it was a car, diesel or whatever. i would like to see some evidence supporting oil installs, not just personal preference. oh and im a firm believer in the moto-man break in.


http://www.thumpertalk.com/forum/archive/index.php/t-612236.html

[muleman]

Here is some real good support try and run it with out oil (go boom). It is designed to have oil.  Show me a manual that says not to coat it. All the one I have read say put a light coat on the cylinder and rings.
 I see there point don't get me wrong  There point is a dry ring will file seat faster and have a better seal. But unless you sit there and kick it with the gas off for a while and heat it up with a heat gun your piston will not expaned and seal right any way.
  Good luck on your search.