Well, I agree with most all of the points presented for sure. Honing is actually “boring” to some degree, a bit of metal is being removed. I agree that many people “overdo” the honing procedure in order to get a nice looking cross hatch and not see any cylinder surface untouched by the hone. Using the rigid hones on these two stroke engines usually leads to this condition. Don’t get me wrong, rigid hones (if they are good quality and have the correct grit stone in new condition) do a great job, but you really have to avoid the natural tendency to clean up every bit of the metal cylinder surface…Doing this will probably lead to honing/boring a bit oversize. This is why I usually use the flex/ball hones to “clean up” a used two stroke cylinder, these hones will hit all the cylinder surfaces while cleaning up any burrs on the ports. Two strokes tend to have more wear in the port area for obvious reasons, especially the loop scavenged models.
So, I guess the best place to start is an accurate measurement of cylinder oversize and taper in a few different areas. Needless to say, a nice looking hone job (with flex/ball hone) on a cylinder that is oversize and tapered isn’t worth much, just “looks good”. The tough decision is deciding how much wear is acceptable in terms of how it will affect the engine’s running quality/compression, etc. Needless to say, if the oversize and taper is out of spec, the cylinder needs to be bored oversize. But, like we always say, these engines never get many hours on them, so aren’t really worn out very often. Folks are often fooled by seeing the “original hone” marks still in the cylinder, then assuming there isn’t much wear. But, they have failed to take overheating into account…The overheat condition may have warped the cylinder and caused it to be out of round.
In this case, we are talking about an old 7.5hp that probably does not have many hours on it, but it was overheated. I’m betting measurements will show the cylinders to be within spec for oversize and taper. We will never make this powerhead absolutely “new” again, unless you replace the crankcase with a NOS piece. Brent has purchased NOS standard pistons and rings, and I’m sure the rebuilt unit will have great compression and run like new…These old engines are pretty tolerant to alot of things, and we are not rebuilding the space shuttle or high performace car engine for sure.
I’m surprised reading about someone using my 50 cent emery hone job on a chevy 350 though. Don’t get me wrong, I use this procedure on most OMCs that I pull the head off for an inspection without tearing the powerhead down. The powerhead is apart and will benefit from a light honing job after it has been measured. Give me a call, I have a flex/ball hone for the 7.5hps….D
Correction/addition… The cylinder bores should be lightly honed with a decent hone on any powerhead that is pulled apart/pistons/crank out of crankcase. In Brent’s case, his 7.5hp is all apart, I agree that it should be honed properly/lightly with a decent hone tool. The 50 cent hone job is not appropriate here….
