Bore honing

[Nick]

Hi, ive bought a bore hone, medium grit. One of the bores is a little bit pitted where the piston was seized. i dont care if it smokes a bit, but how much can i hone it? bear with me, ive not done this before

[Tubal Cain]

If you type cylinder bore honing into a search engine there are several sites which explain the process. But bear in mind that in the context of new engines they are talking about expensive honing machines not the simple hone which you have.

Basically in your case your require to hone each cylinder in order to obtain a cross hatched surface, to break the glaze and help the new rings to bed in. If you have a ridge at the top of the liner you will need to remove it to avoid the possibility of breaking the top ring.

Depending on the depth of the pitting it is most unlikey that you will remove it by honing. it may result in loss of compression and possible blow past into the sump, which if the tractor is intended for recreational use shouln't be too much of a problem.

Keep the hone moving up and down the cylinder and use plenty of parrafin or light oil to keep it lubricated and wash away any grit.
Once you have a crosshatch effect you need to use plenty of soap and water to ensure that all traces of grit are removed from the block. Otherwise grit could be picked up in the oil and circulated around the engine.

Gerald

[JC]

I was going to post earlier, but I pinched a nerve in my neck and I can't sit at the computer for very long.

Gerald said almost exactly the same thing that I was going to say. I only have one thing to add. The faster that the hone turns, the faster that you have to move it up and down in the bore. You're trying to get a 60 degree cross-hatch pattern. If you go too slow, the angle will be too flat, and too fast will make it too steep. Don't worry, though, it's not rocket science close will be good enough.

[Nick]

Thanks for your reply guys, the tractor will only be used for messing about on, not properly working. If i put a piston ring down the bore i can see light if i shine a torch behind it, but i can also see high spots (rust) that once worn down will be nice and flat again. What i dont want to do is hone them too much - can you do this?

[Tubal Cain]

As long as you keep the hone moving there shouldn't be a problem, hone until you have an even crosshatch pattern from top to bottom.

If you have highspots of rust I suggest that you remove then by hand, depending how severe they are you could use a scraper to remove the worst and then emery cloth. i suspect that you may well find further pitting under the rust.

Gerald

[Nick]

I was thinking about replacing the liners completely, but would i have to take the block out to do this? ive heard that dexta liners arent made any more, and you have to bore them out to suit, sounds complicated

[Tubal Cain]

If you wish to replace the liners then the engine has to be stripped right down, the liners are a press fit in the block and ideally a large hydraulic press is required to remove and refit them. Replacement liners are available, however as they are a tight fit in the block they are left oversize to allow for machining to remove any distortion caused as a result of being pressed in.

Unless you have access to a press and boring machine I wouldn't advise you to attempt to change the liners. I would suggest that you hone the bores and rebuild the engine with new piston rings and see how she performs. If you are not happy with the way the engine runs after the rebuild you could then plan to have new liners etc. fitted at a later date. The other alternative is to have the liners bored out oversize and fit oversize pistons if they are still available.

Gerald

[Nick]

I have a 50ton press here, but no equipment to bore it out. Also you've answered another question about boreing the existing liners, but im going to clean these bores up as much as i can, and as long as it fires on 3 cylinders i will be happy! As soon as i make any progess i will put up some pictures etc! Thank you for your input everyone!