Britbike forum Forums Thread Like Summary - Starting a honing thread ...

I searched on "hone" and "honing" because I know this subject has been discussed extensively, but couldn't think of a search that would find "Should the bore be lubed or left dry and degreased after honing and cleaning?", so after reading through a hundred inapplicable posts, I'll ask again, at the risk of starting an "Oil Thread" situation ...

Does break-in on a Brit cylinder work better on dry bores and rings, or lubed with something light that won't prevent bedding in?

Lannis

I leave it dry with the only lube being a dab of oil on the front and back of the piston well under the rings, never had an issue with bedding in rings.

Don't get too enthusiastic with this ?
You are only re-ringing this, so every thou you hone out is pure wear.

I found a bit of emery cloth done by hand was quite good at glaze-busting.
You only want a good pattern of scratches for the new rings to work on ...

"Back in the Day" we used to use 150 grit emery paper and holding the barrels with one hand we would push the emerey paper down the bore with the other hand at the same time twisting the arm holding the emery paper to give the 45 degree approx pattern.
I agree completely with JH about thoroughly cleaning the bores with warm soapy water several times.
However 'back in the day" we would just submerge the whole barrel in gas and work at the bores with an old paint brush.
It worked---and had to work because we couldn't afford to pay anyone to do it and we couldn't afford special tools.

Mark,
If you measure the piston and measure the bore you are generally using two different measurement tools.
Each tool in all probability has not been recently calibrated to national and thence to international standards so you dont really know what their measurements really mean.
You then calculate piston to bore clearance by calculating the relatively small difference between two relatively large numbers.
A metrologist and a statistician would have hebbe jeebies at that process and rightly condemn it as inaccurate and prone to errors as big as the dimension you are trying to measure.
And when I say "you" I mean not only you but also your machinist.
Instead try direct measurements---put the piston in its correct bore and orientation and measure the gaps with feeler gages.
Measure at the top of the bore fore and aft and at the bottom of the bore fore and aft.
Write all the measurements down and you will see what your gaps are and can compare them not only with new clearances but also with wear limit gaps.
Then you have a clear firm set of figures to decide whether you just glaze bust and rering with existing pistons or whether you need to rebore with new pistons.
You will be probably be pleasantly surprised to find out that a glaze bust and rering will suffice.
HTH

Most places that bore cylinders for cars etc will fix the cylinder head side
and bore from the other end if given one of these old cylinders. That's
not really the way to do it, it should be bored from the head end. Then
the last thou or two should be finished with a parallel hone, that's why
you should always provide the pistons to the shop doing the job. If you
ask you can get the guy to then provide a taper at the case end so the
rings will slip in easily making the job easy. As kommando stated, a hone
will follow the bore so if they are bored on the skew the hone will tend to
hour glass the bore.
The finish on these with iron rings should not be the sort of thing that is
used on modern engines either, most of the time shops will use 300 upwards
and that is way too fine, 180 or thereabouts is what's required, you should
be able to file your nails on the bore surface finish. Using running in oil is
good if it's available but primitive old sf/sg for the first few hundred miles
is the standard alternative. Everyone has there own assembly method which
is always the best,,,,,,,, i just use a finger wipe of oil around the bottom of the
bores as i put the pistons in, the bores should be scrubbed with hot soapy water
for at least 10 mins before rinsing then wiped dry and fitted, honing grit will
stick in the finish unless well scrubbed out.
Just my 2c.

Henry -

Thanks, that's the search I was looking for. The info on those threads, plus the information that's been added here on this thread, should give me everything I need.

I notice in reading over it all that there are some slight differences in recommended technique, in break-in oils, and hone grit, but nothing badly in conflict with each other, so I'll take a good average of the advice and go for it ....

Lannis

An actual fitter, rather than a met or stat whatever, can measure the piston with a micrometer, then use the same micrometer on the internal caliper that he used to record the bore diameter. Certainly to a standard exceeding that required for old British bikes.