Putting Cylinders on Pistons - Oil or No Oil?

[sharpy]

See that's what I figured, which is why I couldn't understand the whole assemble it dry thing, but probably 99% of posters on here know more than I about this sort of thing, so I must ask...

If its a new top end overhaul DONT baby it. Worse thing you can do it putt putt around glazing the bores. Gor for a ride thru the mountains is best, just a casual ride thruthe Gap, Nebo to woodford, peachchester and back again will be perfect.

[pete]

Cheers for the tip Sharpy, I was going to ask how I should be running it in a little further down the track as I believe what I know to be wrong... which is to baby it the first 1000km's or so.

It'll be interesting to do that as I'll have some tuning to do with the carbs/pods/exhaust when I get there and I haven't ridden it for 9 years so I'll just be doing the on/off throttle thing in straight lines to start with until my confidence is up again I think.

[Nessism]

I've seen engines being assembled in an OE automotive plant and the pistons/rings/cylinders were assembled basically dry. All parts went though a special cleaning chamber before assembly, and the solution may have had anti corrosion and/or lubrication characteristics, but other than this there was no lubrication used on these parts. Does this mean you have to assemble dry? No.

[tkent02]

I have always used oil, but I have heard some engines recently are assembled with no oil at all around the cylinders and pistons. I can't figure out any reason why this would be a good idea but it is apparently done sometimes.

[pete]

Thanks Tom... just 5 years late

[tatu]

Loads of oil, start up check no leaks and ride the arse off it change the oil after fifty miles and ride it normally, the theory is that it is the first few miles beds the rings in and makes the best matching, bearings just go round and round so nothing to see there.

[JamesWhut?]

I love the smell of the puff of raw engine oil that comes out of a newly built engine.

[John Park]

I have always used oil, but I have heard some engines recently are assembled with no oil at all around the cylinders and pistons. I can't figure out any reason why this would be a good idea but it is apparently done sometimes.

The best leak down I ever got was on a new piston and rings fitted to a new bore dead dry. The few passes it makes at low rpm as it starts up take off the high spots and there isn't enough time or heat to do any damage to anything other than the high spots. The motor ran tight and fast and raised eyebrows at the track; sold it with 12k miles on it still running perfectly. I also used to assemble VW motors dry and had no problems, long life, and great seal.

That said, there isn't much point in bothering to assemble a dry hole unless you have a perfectly honed and bored surface and new rings. And with the oil jets on the plain bearing rods it's only going to make a few passes before it gets showered anyway. But I have never heard of a problem ascribed to not having oiled the bores and rings.

It does feel kinda hinckey though, stuffing the rings in the hole dry. I don't like the idea but it works.

[tkent02]

The best leak down I ever got was on a new piston and rings fitted to a new bore dead dry. The few passes it makes at low rpm as it starts up take off the high spots and there isn't enough time or heat to do any damage to anything other than the high spots. The motor ran tight and fast and raised eyebrows at the track; sold it with 12k miles on it still running perfectly. I also used to assemble VW motors dry and had no problems, long life, and great seal.

That said, there isn't much point in bothering to assemble a dry hole unless you have a perfectly honed and bored surface and new rings. And with the oil jets on the plain bearing rods it's only going to make a few passes before it gets showered anyway. But I have never heard of a problem ascribed to not having oiled the bores and rings.

It does feel kinda hinckey though, stuffing the rings in the hole dry. I don't like the idea but it works.

Hmmmm, I might try it on the next 550/699 engine, since it will have new pistons in a new bore, but it sure seems wrong. At least I have a lot of time to do some reading about it.

[tkent02]

Thanks Tom... just 5 years late

Oops, didn't see the date.

How are your pistons holding up?

[pete]

Hahaha all good

They seem to be just fine... getting close to 50,000km's since the rebuild and been back on the road nearly 4 and a half years now...

[Grimly]

See that's what I figured, which is why I couldn't understand the whole assemble it dry thing, but probably 99% of posters on here know more than I about this sort of thing, so I must ask...

Dry assembly is meant to hasten sealing of rings to bore, but it only works if done right.
You turn the engine over relatively slowly for three or four turns, kickstart or starter motor - dry.
Put oil down the bores and do the same.
Then start it up.
I had success with a few engines doing that, and I explained the procedure to a friend.
Next time I met him he complained that the piston rings on his newly-assembled XL500 were like corkscrews after he'd STARTED AND RAN IT UP bone dry.

Hardly surprising, really.

[John Park]

I think you would get a lot more pressure on the rings with the thing firing; turning it over with the plugs out would be rather useless as the spring pressure of the rings is so feeble. Compression pressure is probably the safest method.

You also don't want to 'run it up' for maybe a minute. I always like to turn it over on the starter until the oil light goes out if it's been sitting or assembled. Your method - especially on a roller bearing engine that has far less pressure and flow to the rods - is safe and easy. The tendency for dirt riders to be throttle blippers seems to be either congenital or a leftover from the two stroke era.

I think the theory is that the cross hatch honing presents a pattern of ridges which are scraped down to a level surface; the remaining valleys are lateral and don't leak, but act as a reservoir for oil droplets. A perfect mirror surface doesn't work as well.