Cylinder Honing

[FuzzyDriver]

I'm going to hone at least two of my F-engines (I have at least six to mess with). Looks like a flex-hone is the way to go. I can't find a spec for what grit to use, though. Any of you guys have experience with different grits and what worked the best? BRM has flex-hones in 120, 180, 240, and 320 grit. Looking to get a good cross hatch, but don't want to remove more material than necessary to accomplish that.

 

[Rivets]

Grit size will depend on condition of the cylinder and how much material you want to remove. Are you resizing the cylinder or just have a cylinder within specs and just trying to put a good crosshatch in it? This will dictate type of hone (rigid or flex) and grit size. Hone a closed 2-cycle cylinder needs to accept stones which will extend past the end. If you are trying to resize the cylinder, I would recommend starting with 120 grit and finish with 240 grit using a rigid hone. For simple crosshatching I would use a 180 grit ball hone. Some other things to remember when you are doing this is. You will need the proper size telescoping gage and vernier caliper. Hope you have the time to learn how to use telescoping gage and how to measure a cylinder. I would also recommend you use a drill press and not a portable drill, plus fasten the block down properly. Use the proper lubricant for the type of hone you use. Just my opinion. If you have more questions please feel free to ask.

 

[FuzzyDriver]

Thanks, Rivets. I'm not trying to resize either of the cylinders I've got laying on the bench right now, just wanting to clean them up and put a nice cross-hatch on them to go with new rings. Looks like I'll go with a 180 grit 2-1/2" BRM Flex-Hone. My micrometer didn't reach in very far (F-engine), but I got 2.378 on the first one I checked. That's .002 over new bore (??), but I don't know how accurate my reading was anyway. The 2-1/2" hone looks like the best size. BTW, this engine was only 62 psi so I was surprised how good it looked.

 

[bertsmobile1]

BE very careful using rigid hones in 2 stroke cylinders as they are very easy to catch on the edge of the transfer ports which will usually smash the stones .

 

[Rivets]

If you have a local machine shop or old fashion auto shop, you might want to see if they have a set of telescoping gages and a vernier you can borrow. Will make your job a lot easier. I like your choice of hones and would use mineral spirits as a lubricant. Remember you must measure at top, middle and bottom of the cylinder and make two measurements 90 degrees apart.

 

[FuzzyDriver]

Bert: Yup, that's why I'm going with the flex-hone. I have a stone hone with long stones, but still the flex hone is safer.

Rivets: Checking at several stroke positions and radial positions seems like good advice. They sell special honing oil, I don't have any, but I do have several different kinds of light machine oil that's probably all that "honing" oil is anyway. But you think mineral spirits is better, eh? Thanks.

 

[Rivets]

I taught my students to use very light lubricant to eliminate as much stone clogging as possible. The heavier the lub the more it will grab any particles, plus I over use my lube. This does get messy, as I do get it everywhere, but to me it’s worth a good job. Most people do not agree with me on this, but since it works for me, I‘ve seen no reason to change anything but my clothes. I have a large rubber apron which works great.

 

[bertsmobile1]

I have always used kerrosene ( parrafin or lamp oil to some ) because it is thin as Rivets said, has good thermal qualities and is itself abrasive

 

[FuzzyDriver]

For those in the future looking for advice on this:

Following Bert's advice on grit, I got a180 Grit Silicon Carbide Flex-Hone, Part No: BC21218. This was the perfect size for a Lawn-Boy cylinder (2-3/8"). I spun it at ~400 RPM. After a couple of iterations (sorry, I didn't time them), the cylinder had a beautiful cross-hatch. Good luck!