Assembling top end dry

[SharkB8]

Group K told me they lightly oil a top end upon reassembly if the motor is going to sit for a while before starting, because some rust my develop.

I didn't ask them to do that with the motor they assembled for me in January, so they put it together dry (which I prefer... for proper ring seating, etc).

Unfortunately I am STILL waiting for parts from some well-known PWC service companies who for some reason get rave reviews on the PWC web sites but for seem to be very slow for the past couple months and can't return emails or voice mails. (Not that I'm bitter about it or anything.)

Anyway, 4 months later my motor is still sitting on my work bench out in my garage. This spring, as with any other, the outside temperature is warm-cold-warm-cold, and that causes condensation. I should have taken it in the house months ago, but I kept expecting my parts to arrive in the mail 'any day now'.

So I am giving up and putting everything back together now, using whatever parts I have here, old or new.

Should I tear into it and give the cylinders a little rub? Or just fire it up...

 

[Shifty]

I would try to swab the cylinder through the sparkplug hole with a long Q-Tip or something to check if there is any surface rust developing. If the head is O-ringed removing it would be easy enough to warrant pulling the head for a good view.

 

[750SX]

i doubt they put it together completely "dry". Spray some fogger or a little oil down the plug hole and turn it over by hand. That should lube it up.

 

[sflsurfrider]

Group K told me they lightly oil a top end upon reassembly if the motor is going to sit for a while before starting, because some rust my develop.

I didn't ask them to do that with the motor they assembled for me in January, so they put it together dry (which I prefer... for proper ring seating, etc).

why would you want your brand new top end completely un-lubricated on its initial fire-up????

'proper ring seating'?

not too sure about that one....

 

[SharkB8]

Excess oil causes glazing and the rings don't seal well.

If you have primed the engine at all, there will be premix in the cylinders within just a couple revolutions anyway.

 

[SharkB8]

i doubt they put it together completely "dry"

Yup, completely dry. They do oil the lower end bearings and rod bearings. This is what I used to do with my race bikes, as advised by Dirt Bike magazine... pistons in cylinders completely dry and you'll get a great ring seal. I usually dumped s shot of premix in the spark plug hole just so there's a tiny amount of oil in there, but most dry-assembly advocates don't even do that.

 

[Waternut]

Well I know the whole concept of "dry" cylinder break in is still a heavily debated topic and for the sake of preventing a flame fest and keeping on topic, I won't get into that.

However, the idea of assemblying an engine with slight corrosion on the sleeves, crank, etc isn't debated at all...it's just down right stupid. I don't agree with dry assembly but I think the real question is, are you willing to risk a potentially catastropic failure in your engine due to corrosion just for a marginal increase in ring seating? Or are you willing to bite the bullet on the lubrication and break it in the old fasioned way?

 

[SharkB8]

Well... I don't think the choice is lubrication or no lubrication... this motor is going together dry, I'm not breaking it in the old fashion way. I think the choice is whether or not to waste a head gasket by pulling the head off to check for rust. It also means postponing the rebuild for another week while a new gasket arrives in the mail. (I should have had the foresight to have a spare.)

I was just hoping someone would say something like, "I've left freshly rebuilt motors sitting for 6 months with no rust showing up".

But now that you have used the word "catastrophic", and since I'm going to try breaking this motor in "hard", I guess I have no choice but to disassemble and check. If something goes wrong during my "hard" break in, I want to be fully confident that corrosion did not cause the problem.

I will post a message here re: how it looks (rust or no rust) for the benefit of people who search for this topic in the future.

 

[Waternut]

I was just hoping someone would say something like, "I've left freshly rebuilt motors sitting for 6 months with no rust showing up".

Well I just checked my used lubricated pistons that have been sitting in the garage for 3 months and they've got light surface rust that leaves marks on the pistons when you wipe it off. A new piston would be more resilient than used when both are perfectly dry but mine weren't perfectly dry either.

I'm trying to remain fairly nuetral on the topic since ultimately the decision is yours but I highly recommend not letting your engine sit unlubricated for months or even weeks. Do keep in mind, we're in the rainy season here...don't know about there though.

 

[SharkB8]

ooooooh, now I understand what you were saying before about lubrication.. you meant I shouldn't have left it sitting around with no oil on it. Yes, I agree. But now that the damage is (possibly) done, I'm gonna tear it apart to check. Thanks for checking your pistons.

 

[750SX]

Well I just checked my used lubricated pistons that have been sitting in the garage for 3 months and they've got light surface rust that leaves marks on the pistons when you wipe it off. A new piston would be more resilient than used when both are perfectly dry but mine weren't perfectly dry either.

I'm trying to remain fairly nuetral on the topic since ultimately the decision is yours but I highly recommend not letting your engine sit unlubricated for months or even weeks. Do keep in mind, we're in the rainy season here...don't know about there though.

Steel pistons?

 

[SUPERTUNE]

Try mixing a bit of premix @ 20:1 and squirt down the sparkplug hole, then turn the engine by hand from the coupler, if smooth when turning, you'll be fine. If it's tight, then take it apart, just lift off the top end at the base bolts. Base gasket is a lot cheaper than a headgasket...

 

[Waternut]

Steel pistons?

Very good point... Perhaps it was just steel dust from something I was grinding in the garage that stuck to the oil and rusted. Sorry for the confusion. :dunce:

 

[kevbo]

Dry and Lubbed are relative terms when you are talking to motorsports enthusiast. If the cylinder was truly free of oil it would begin rusting immediately in most areas. Yet if you tell a jetskier to lube the cylinder they will always overdo it. The safest bet is to dilute premix with gas to 5-10% and coat all metal parts.

 

[SharkB8]

I was able to find a long flexible flashlight and I "snaked" it in through the exhaust manifold and into the cylinders and it lit it up very well. I could see clearly through the spark plug hole. There was no rust whatsoever.