Gasket, seal, skim or bin?

[chunterjam]

So I have some scuff marks on the top of my liners. I can actually only feel one of the scuffs.

Do I just put the gasket back on, put some gasket seal, get it skimmed or F it in the bin and get a good one?

Thanks in advance.


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[Trigger]

Looks like it needs just a few rounds on a lapping block.

[ka-ja]

In place of a lapping block, we used to use a piece of 3/8th plate glass and grinding paste and use circular movements and regular paste changes. work your way from rough paste to smooth, just wash very well before refitting.

[jimv50]

My Grandad used to own a bike shop in Bristol many years ago and my dad had to take apart all the fine example of british bikes straight from the factory and lapp all the crankcases in so they didn't leak oil (as much anyway).
He had to use a slab of plate glass and lots of elbow grease.
On another note, him and his brothers had the run of the shop and could have any bike they wanted, his favourite bike? Norton Dominator 500SS with Brooklands exhaust, can you imagine the noise!

[Bryanj]

Fine wet and dry used with oil and thoroughly washed off then new gasket

[chunterjam]

Thanks folks...plate glass and wet & dry bought. Grinding paste to be ordered. Any recommendations for a grinding paste?


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[ka-ja]

Hi,
    Everyone has their favourite grinding paste, but for what you are doing and the amount required ( valves take very little) it does not really matter,start with rough, and when the marks have almost gone, change to smooth to finish off, but don't use downward force, let the weight of the cylinder do the work on a good bed of paste in small circular movements.

[chunterjam]

So I double side taped some wet and dry to plate glass...used drop of oil and a lot of elbow grease.

That got 99% of the scrapes out. The. I did something that maybe naughty and did some localised rubbing down. Worked a treat on the liner but a bit of over rubbing left an ever so slight dip in a small part of the surrounding aluminium.

I think the gasket should fill the dip but am happy to be told otherwise




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[chunterjam]

Dip at 12.7 likely to cause me an issue?


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[ka-ja]

I've seen worse, the gasket will seal on the liners and oilways usually have "o" rings, usually too much pressure on the wet and dry causes the the wet and dry to "balloon" outside of the area of metal. The reason for glass plate is the fact it is very flat, industrially, we always used grinding compounds as it tends to "suction" the two together while working them, you could almost feel the drag when something was flat!

[Trigger]

I would start again, without any localised rubbing.

[chunterjam]

Thanks folks.

@Ka-ja...The wet and dry was stuck down well with double sided tape. I was so surprised it held but it worked perfectly.

The general consensus from this and other forums is that it should be fine - the gasket seals on the steel liners and that some gasket sealant should sort the low spot. I've been recommended Hylomar blue.


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[Bryanj]

NOT HYLOMAR if any gets in an oil jet it blocks it

[Alex jb]

industrially, we always used grinding compounds as it tends to "suction" the two together while working them, you could almost feel the drag when something was flat!

Completely agree, I remember finding this and writing it up in my work book as an apprentice when my head fitter said well done for spotting it.
I was always told 'figure 8' pattern though, we'd get something thrown at us for circling while lapping bronze pistons slippers for hydraulic pumps.

Sorry OP, not much of use for you in my reply!
I would move away from paper if you have paste.
The glass is just a flat lapping block, just much cheaper than an industrial one, it is tough enough to take paste as long as you keep using as much of the surface as you can, try figure 8's