Bon Ami 'Trick'

[e3steve]

Oh dear, here we go.....

INSTEAD OF LISTENING TO "EXPERIENCED" MECHANICS, TRY TO FIGURE OUT WHAT HAPPENS IN THE ENGINE.

My anecdote wasn't from a "mechanic's" perspective (and it was just and anecdote), but it was based upon experience. Read it again; I was 17! And it did the job. On an old engine and I had little to lose.

SO, DON'T DO THIS, THERE IS NO BETTER WAY TO DESTROY YOUR ENGINE. THE POSITIVE EFFECT ON THE RINGS IS MINIMAL, BUT THE (NEGATIVE) ABRASION EFFECT ON THE BEARINGS IS MAXIMAL. (YOU MAY INTERPRET THIS AS SHOUTING)

If you insist upon shouting I, for one, shall dismiss my respect for your posts.

[jensen]

Hi steve,

Point taken, no shouting. I wasn't referring to your mail at all, but in general. I can really getting angry when reading these fairy-tales, and I was carried away (a little) when writing, sorry for that.

There're many "experienced" mechanics, with many so cold "quick" tricks, saving you a lot of money.

Problem is that these mechanics are not responsible for any damage on your bike, nor for time , nor by money. Ask a hand written guaranty, signed by his manager, that a abrasive trick A : works, and solving the glazing, and B, doesn't harm the engine.

My bet that he doesn't do this.

My point is that when there's an official statement from, for example, Honda, Yamaha, Suzuki or Kawasaki, it wasn't so bad, but there aren't any.

When glazing appears, there's only one trick, re-bore and re-hone, or only re-hone when the amount of glazing is low.

Jensen

[e3steve]

Apology graciously accepted.

I am compelled to agree with your final sentence

When glazing appears, there's only one trick, re-bore and re-hone, or only re-hone when the amount of glazing is low.

and your quite-correct comment

The only real answer is to abrade the bores in a CIRCUMFERENTIAL direction, using either honing stones or abrasive papers.

, but when one has little to lose from a short-term solution, why not try it?

Short cuts are not something I would normally countenance; I'll repeat my personal work discipline: "do it right, do it once".

Happy New Year back, J-man!

[jensen]

Hi Steve,

Quick tricks are used by commercial mechanics, not by people with a heart for there property.
I know a few as well, but these quick tricks always have a short live and short time effect, and that's not what you're looking for when you have to depend on your bike.

Rebuilding one of these engines is costly, a proper rebuild will vary between 750 to 2500 USD and above. I don't see the point of risking bearing damage, transmission problems because of the very delicate bearing on the counter shaft, and disintegrating your valuable clutch bearing by an abrasive. grinding your oil pump with an abrasive is also not a good idea either. And yes, it will be in your oil because one of the problems with glazed cylinders is blow-by.

Every serious mechanic knows that you have to work clean when rebuilding an engine. You don't take all the effort to do this and then afterwards putting some abrasive in it after a few hundred miles.

No, break it in carefully, which doesn't mean riding slow (see my previous mail), and ride it as you suppose to ride it, remember, this engine is build to deliver, not only for gently touring. It's a supersports, and that's what it is. To gentle will glaze the cylinders and too wild either.

So make sure your carbs are in good condition, make the fuel mixing a little richer, and break it in as explained in my previous mail.

Jensen

[brewsky]

I always use this procedure described below, it works.

Jensen

Somwhat similar to the "Motoman" method outlined here:
http://www.mototuneusa.com/break_in_secrets.htm

Interesting tidbits:
When I bought my new CB77 in 1968, the mechanic filled it up with gas, added a couple ounces of oil to the gas tank, and said to break it in exactly like I was going to ride it.

When I toured the Honda Manufacturing plant in Ohio, I watched the VTX 1800 assembly in progress. After the last piece was bolted on and a splash of gas added, the next thing done was fire the engine and ride them straight onto the dyno for a wide open run!!

I would be very skeptical of adding abrasive powder to a running engine unless I had plans to rebuild it anyway.

[Nick]

I worked in a Triumph shop in the seventies, and the guys there also said they used the Bon Ami trick. Never tried it myself.
Don't think it would hurt the engine too much. Most of it would get blown out the exhaust port, and an oil change would take care of most of the rest.
As far as the effect of abrasives on the bearings, I know racers who lap in their bearings using fine abrasives to clearance them and reduce their operating friction.

Re. break-ins: It's important NOT to use a detergent oil such as typical automotive oils, as they will prevent rings from sealing. Use a non-detergent oil during break-in and for assembly. It is also very important to use the right grade of honing stone to suit the rings. Chrome rings use a different hone than cast iron rings.

[jensen]

Hi Nick,

Thanks for your input. I do not agree with all your points, and I shall try to explain why.

It is known that the tolerances on British machines are bigger then on Japanese machines, therefore glazing of the cylinders and piston rings where more common then on Japanese machines if bored and honed to specs. Next to that, British engines where not known for there reliability either. In the seventies people also thought smoking would not hurt you.

A race engine is rebuild more often then a standard engine, these engines are not build to last miles and miles. The breaking in process of a racer is different then street bikes. Normally rings and sometimes pistons where changed after every race.

The breaking in oil is holding enough abrasive material to lap the bearings, not need to put in extra abrasive.

The use of a non detergent oil for the breaking in process on these engines is not bad and will not heart the engine, make sure to change the oil directly after the first 50 to 75 miles or so. Using a detergent oil together with the breaking in process I described is working also, at least I didn't have any problems during the breaking in process. Make sure you don't use a synthetic ore a half synthetic, and make sure to change the oil quickly after breaking in.

Yes, that's correct, a good shop knows this. I always ask something in between for the process because a Honda CB72 / 77 have one chrome ring (top ring) and one cast iron ring (second ring).

The smoother the honing surface after machining, the faster and reliable the breaking in process goes. Plateau honing is my favorite, not too smooth, but smooth enough to have a short breaking in time.

Plateau honing, see this link :

http://www.digitalmetrology.com/Papers/ ... NoBkgd.pdf

Also for deglazing :

http://www.goodson.com/technical_suppor ... Honing.php

I know, it's a little scientific, but take the time to understand, or ask questions,

Jensen