I'm not an expert and have only rebuilt a couple of engines myself. My suggestion was based on the fact that you are unlikely to be able to remove the rust pits full stop but I think the engine will still run fine even with them present. My concern about the emery paper was that it would destroy the honing pattern. A sweep of the piston would remove any rust on the surface of the cylinder wall whilst not affecting the honing.
Non ST - 2.5T S Max Engine Rebuild it’s in that thread somewhere bud
I knew there was something lol
Cheers bud 👍
I did think that too lol I used that method to unseize an rd125 twin when I was a kid haven’t heard anyone else say that for yearsIt looks bad but does it feel as bad or feel smooth? Turn it more and see if its getting better.
I feel a strong urge to fill that engine with CocaCola
Nah, the pits feel a little rough. I'm wishing myself into believing otherwise but it doesn't feel right.It looks bad but does it feel as bad or feel smooth? Turn it more and see if its getting better.
I feel a strong urge to fill that engine with CocaCola
Thats far worse! The rust will likely be dragged up and down causing vertical scoring and damage to rings and pistons. The only course of action is a light hone or carful diagonal rub down with fine abrasive medium. Trouble is you cannot see or get to lower bores. But once rusting has caused pitting, the bore is really none serviceable. I would not be happy using those bores anymore, Will likely have blowby issues.
If it was heavily rusted up such as having had pools of coolant left in cast iron lined cylinders for months then you might be right, but the rust in the photos is really no different to what forms in any engine that is left for some time without running. Provided there isn’t any significant damage these engines will almost always start up and run fine, and at a much higher speed than turning over by hand.
Cylinders do not normally rust when the engine is standing, not for a bloody long time after the oil film has eroded. I’ve opened engines stood for 40 years without any sign of rusting. Any rusting is pitting, the longer it stands the deeper the pitting will get. You do not want any pitting on bores and certainly none you can feel or easily see. Yes it will run, that means nothing, but the combustion gases will leak past the rings in that pitting eroding it further and in extreme cases able to blow by the rings and cause flutter, that can destroy the piston in seconds. You certainly never want to force pistons over a rusty bore! I have rebuilt many dozens of motorcycle engines and a number of car engines and learned the hard way that bore quality is critical especially on high performance engines. It’s not just rust and pitting, clearance, ovality and taper are also critical and should be measured accurately whenever you think of fitting new rings or continued use of old bores. New rings in an old worn bore is usually a very bad idea.
