Cylinder Honing Questions

[Erik Frank]

I'm contemplating purchasing a Sunnen Portable Hone (most likely a JN-95 model) to hone cylinders on some old DAP T-80 reed and T-81 rotary engines that I have sitting on the workbench collecting dust. In the past, I have run these engines in a bracket class at the local sprint track. These rebuilds are just for fun and amusement, and to resurrect my inventory of 100cc engines.

What stone sets would I need to purchase with the hone itself in order to properly hone the cylinder for the next oversize, as well as to achive the proper surface finish?

Is it worth my while to machine a torque plate for the cylinder to simulate the distortions caused by torquing down the head?

Is there a kart specific tech document somewhere that discusses the honing process? I found one small writeup on Sunnen's own site: http://www.sunnen.com

Any advice or insight is greatly appreciated.

-erik

[Jimmy Moore]

What's the price on the Sunnen? You might want to go with an Amco. You don't need torque plates for a fun engine, just give it a little more clearance. The stones I use are about a 240 grit.

[Pete Muller]

Erik,

If you can afford a few extra bucks, I'd highly recommend a Sunnen honing machine.

Here's the deal... Sunnen has been building honing machines for many, many years... and they used to build a "bench model" machine, which was basically the head from a floor model machine (without the base, which is a cast iron thing that contains the oiling system). Usually, the bench model machines go for a lot less money than the floor models, even though it's essentially the same machine, just without a stand and an oiling system!

If you can find a bench model, you can fabricate the oiling system (nothing more than a pan to catch the oil, a tank/bucket for the oil to drain into, and a pump to get the oil back up and onto the mandrel). You may have to fab another part or two... but the end result is well worth it.

The control you have with a Sunnen machine is far beyond what you can do with a portable. The beauty of the Sunnen system is that you could literally use a 40 year old bench model "head"... and you can hone as accurately with it as you would with a new MBB 1660 floor model machine. The new stuff has a few more bells and whistles... but the system of how it works is still pretty much the same as it has been for decades.

If you keep your eyes open, you can sometimes find these things at garage sales, or at an auto parts store going out of business, or maybe even a swap meet.

You will, of course, still need a mandrel, but once you have the machine, it will never lose value.

Pete

[ August 19, 2001: Message edited by: Pete Muller ]

[Guy Barrett]

Pete is right,a couple of years ago I picked up a 197? vintage Sunnen floor model at a government surplus auction for $600.00 Canadian ($375.00 U.S.) that included over 50 mandrels and hundreds of stones, these machines are so nice even a six year old could hone a perfectly round and parallel cylinder.My portable hone has been sitting on a shelf ever since.Check with all your local automotive machine shops because there is a chance that they may have an old honing machine sitting out back that they just may want to unload for cheap.

[ August 19, 2001: Message edited by: Guy Barrett ]

[fatoldman7]

Hey Pete, I Know you recomend using a keyway mandrel for honing, but what kind of stones do you use...grit/hardness? Also what do you use to relieve the exaust port bridge...hand stones or sand paper?

[Erik Frank]

Pete,

Thanks for the advice. I've seen a few of those Sunnen machines on Ebay, and I know of a couple in the DFW area as well. I'll put one of those on my "treasure finder wish list".

Of course, one would have to assume that your advice is also applicable to a good Series II Bridgeport Mill, a Clausing Lathe, Miller Synchro Wave 250 welder, etc, etc. Right?

Uh oh...the project just got more expensive!

-erik