KX Riders
Maintenance & Technical => KX500 Original => Topic started by: martinfan30 on March 02, 2009, 02:49:32 PM
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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.
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i always do my 4strokes dry. lots o science why its better. not so sure about kx
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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I only installl them dry when I put them in back wards. :-D
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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.
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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
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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.
:-D
http://www.thumpertalk.com/forum/archive/index.php/t-612236.html
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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.
:-D
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no oil go boom is not really a strong argument, ive built dozens of engines with no boom yet. i based my opinion off talking to top engine builders, not just average joes (not intended at muleman). granted they were all 4strokes so the kx might be different. manual does state oil on cylinder wall, however if everyone followed the factory manual there would be no performance builders at all. the rings will have immense heat generated as soon as it starts moving from friction so no heat gun needed. what we are talking about is milli-seconds here so i say do whichever you are comfortable with.
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The only reason you can get away with installing a piston dry is do to the miracle of ceramic coating. I sure hope no one tries this with a cast iron engine. This is kinda like the brake it in like you drive it deal. An engine that is broke in hard will show more ponies on the dyno right off the bat then an engine that is broken in correctly. The engine that is broken in correctly will show the same horse power further down the road and it will sustaine those levels for a longer time. The brake it in like you drive it thing is what you do to motors in race cars that have a very short life expectancy. I'm sure that a motor with a ceramic bore that is put together dry will seat the rings alot faster but their has to be a trade off. I'm sure that a motor put together correctly and busted in correctly will show more peak ponies and sustaine them longer then one done otherwise. So in other words My engine put together wet and broke in correctly will lose to your engine put together dry and broke in how ever you like on the dyno but after a month of running these engines, the dyno will tell a different story. After a year it will be even more apparent. Just my opinion
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I'm with you BDI - I'll always do my top ends with plenty of oil. Lubrication is the key to a happy engine (and bike for that matter). To all of you that put pistons in dry - clean and dry your bearings; I bet they spin super fast - until they don't.
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haha sleeved cylinders get the dry treatment too. like i said earlier, to each his own. voodoo gods say dry engines actually last longer due to less blow-by and oil loss. roller bearings not really a good analogy, kinda like apples and oranges really. i do lube top bearing fyi. im still waiting on proof before i change my mind, i love being proven wrong/learning new things. cheers
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So then would you put a small block chevy 350 together this way too??...
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cant say for sure, i never got into cars. i would prob say yes, but would research first. all honda motors at dealer i work at get dry. (im not honda tech, service advisor)
edit: after quick phone call, small block wet due to high ring tension. always someone smarter than me out there
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Why would you put it together wet do to ring tension? What would happen if you put it together dry?Whats the difference?
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I always use a very light coat of oil and do 2-3 heat cycle it let it cool down in between. Never had any problem.
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With all the engines I have put together, 2T and 4T, I never have had any longevity issues with a decent break in procedure. Including heat/cooling cycles, and most importantly, varying throttle settings.
My break ins will always include light oiling of friction surfaces. I see no reason to worry about gumming up rings when a full dinosaur oil is used. Synthetic oils after break in.
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I did a search last nite on dry cylinder rebuilds (car engines) and came up with about 50/50 dry vs lubed. It would be nice to see some microscope pics of dry/lubed rings after break in to see what the difference in sealing looks like. I couln't find any tech aricles though, only rules of thumb and peoples beliefs, no science. Cam.
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Stewart, oh STEWART!?!?!?!?
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I wonder what the temp of the rings spikes up to when you fire the engine dry. It could go real high and hurt the temper of the rings making them soft but if it got cooled off fast by oil and fuel they could become even harder then they were.
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I've been doing some thinking and I doubt you would find me doing a dry install. Firstly, piston acceleration can be upwards of 100,000 ft/sec.sq at which speed I am sure the rings will be cleaning themselves of any surface oil instantly, therefore the lubed bore would be protecting the piston from galling (a good thing) but not preventing the rings from getting full, almost unlubed contact to seat. Also in a 2-stroke the rings bulge into the ports a tiny bit each stroke. In a new engine, the cylinder lube would be benefitial in helping the rings slowly wear the correct path without gouging or chattering at the port chamfers. Just some ideas. Cam.
PS. the one idea that did show up was to never use regular oil as a cylinder lube. Always use 2-cycle oil. Non 2-cycle oil doesn't burn properly and leaves carburization (sticky carbon) in the ring grooves which can lead to poor long-term ring perfomance.
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So then would you put a small block chevy 350 together this way too??...
I have once.. The total seal brand rings I used specified using a dry-film lubricant that they sell... It was dry powder like substance, very similar to graphite.. It had no issues with ring seal and is still going strong for its 3rd owner.. I cant say I would recommend it for someone else, but it worked fine for me.. The general concensus is that using oil is the way.. But some engine builders swear by dry assembly and it seems to work for them.. I have put 5 or 6 different 2-strokes together dry or with a light coat of WD-40... right or wrong no issues occured.. I think the roundness and finish of the bore are more important than anything else along with giving the engine ample time to wear in before subjecting the engine to heavy loads or high engine speeds... Idk.. just my thoughts, interesting topic for sure