Screwed up cylinders?

Jim Thu Dec 24, 2020 2:26 pm

After using the cox tool to remove the cylinders from my 4 Baby Bees the pistons will no longer pass thru the bore. Very little force was needed to remove the cylinders. These are 50 year old Baby Bees with open exhaust and I really want to save at least one of them.
Any suggestions?

emanuel Thu Dec 24, 2020 2:39 pm

Clean both well, put the piston in the refrigirator and warm up the zylinder with a hairdryer and try again.

Ken Cook Thu Dec 24, 2020 2:55 pm

To fix it, acquire a piece of 5/16" tubing about 4" long. Wrap tape on the top of the tubing and drop the rod into the center of the tubing and push the skirt of the piston onto the tape. Make certain the piston fits tight on the tubing. If needed wrap more tape on the tube and force the piston onto it. You need to pass the tubing into the cylinder the piston will be upside down on the tubing.Using the tubing as a handle, pull the piston skirt up to the point where the piston won't pass through. Use chrome polish or brass polish, liquid polish works best for light removal. Twirl the brass tubing in up and down motion until you wear the burr. It shouldn't take long. Remove the piston and tubing and re insert with the piston orientated into the cylinder correctly and do the same thing. DON"T bring the piston high up in the bore keep it low in the cylinder. Wash with hot soapy water and dry and reassemble.

Jim Thu Dec 24, 2020 3:08 pm

Just to clarify these engines turned freely before I removed the cylinders.

crankbndr Thu Dec 24, 2020 3:20 pm

The wrench probably put a small burr by the port common problem. Get a looking glass a see if you can see it. Many here have been able to remove them with exato blade as cylinder is fairly soft steel

rsv1cox Thu Dec 24, 2020 3:26 pm

Ken, if I'm reading you right you mean something like this:

with enough tape inside the cylinders skirt to create friction when you twist it.

I have had luck using the same method only with fine steel wool only coming up far enough to remove the burr without touching the top half of the cylinder.

I would also suggest to Jim that he buffer the Cox tool with masking tape and insert the tool fully after applying a little heat. Also, doing multiple cylinders/ pistons, keep cylinder and piston together and don't mix them up. I put the case in a buffered vice, just snugged down and bump the tool with the palm of my hand, gives much better control.

Oldenginerod Thu Dec 24, 2020 3:37 pm

I'm not sure what Jim might have done here, but I suspect that he may have inserted the wrench incorrectly, placing it through the port rather than across the port. It's an easy mistake to make, and can burr the port in short order. I have used the wrench as intended (across the ports) many times and have not had this problem. For it to happen to four engines with little force used, there must be a problem in the execution. Extreme care needed in cleaning up the burr. Lots of good advice already.

crankbndr Thu Dec 24, 2020 3:42 pm

Doesn’t sound like enough force to twist the cylinder that can happen on the thin walled Then they are toast

OhBee Thu Dec 24, 2020 4:03 pm

Burred up the exhuast ports! Dosn't take much...probably unnoticeable without magnification.

Ken Cook Thu Dec 24, 2020 4:32 pm

Bob, your correct . I use brass tubing and I've posted it on here multiple times so somewhere are pictures of it. Brasso is a good polish to use but I like to use rottenstone. I mix a little rottenstone with oil and make a slurry which I drip into the exhaust port. I finish with a finer polish with the piston in the bore correctly. After that I use a Davis Diesel brush and apply the fine crosshatch marks. I never had a cylinder that I recall in which I couldn't repair from this damage.

**Cribbs74** Thu Dec 24, 2020 4:34 pm

I have to wonder how this happens. I’ve disassembled more engines than I can count and the only one I have ever burred was a .020 cylinder. That was because it was super tight and the wrench slipped. This was before I figured out about heat.

Not knocking anyone or the OP it’s just it happens more than it should. The cylinders were designed to be removed this way before the cylinders were modified in later production.

Anyway, the knife method worked for me with that .020 cylinder. Ken’s method will work as well and will make a better running engine in the process.

Jim Thu Dec 24, 2020 5:58 pm

I made a replay that somehow got lost.
I clamped the crankcase in my vice using what you call "buffers" and tighten just enough to prevent it from slipping out. I then used the cox tool as it was intended not thru the exhaust ports.very little force was required to loosen the cylinder. I used the same procedure 50 years age, when I last had the engines out, with no problems. Maybe I haven grow stronger with my advanced age. I will try the exact knife method.
Although I can see no burr under magnifation.
Thanks for all the advice and I will keep you informed as to my results.

OhBee Thu Dec 24, 2020 7:05 pm

I don't believe I've ever had a reason to remove a cylinder. We just ran the hell out of them for years! If one sat around and gummed up we had heat and lots of penetrating oil. Used to set them on an
electric stove burner on low. Have never even used a pliers on a prop driver...as you see so often. Had one neighbor kid that liked to tear EVERYTHING apart! Constantly buggered cylinders and he wondered why the piston would no longer go up and down. His solution....sand on the piston until it did! His motors cranked easier than an electric. Took him all day to get one started......if at all. My dad was a Machinists mate in the Navy during the war. I learned at a very early age how to properly work on an engine. By age 8 I had overhauled our old monkey wards gas lawnmower. Piston,rings valve job,new points. And that was where it all started. ......and has never ended!

davidll1984 Thu Dec 24, 2020 8:28 pm

Tink u need laping tool look its one defect tool wit two correct mabe its wat u have use Not the way m'y self dont like To use exaust port y use strap lether wit vise grip

Jim Fri Dec 25, 2020 12:25 pm

With furtherwork three cylinders were just carboned up clean up and they are now fine. The forth does have a burr at one corner of the exhaust port. I have not had any luck removing it using the excox method. I need to find some 5/16 brass tubing , I don"t know if lapping will remove the burr.
Thanks again for the advice.

davidll1984 Fri Dec 25, 2020 12:39 pm

Laping after work the burr wit the 5\16brass tube take of al the fine scratch left

rsv1cox Fri Dec 25, 2020 12:56 pm

I tried to find some brass tubing coming up empty. Turned to my fuel tubing cutoffs and was surprised how nicely it fit over the connecting rod. Don't think it will ever have an application though. I never was a fan of the knife approach, no way I could pull that off. But steel wool wrapped around a dowel for me does the job lubricated with a little Remoil.

Ken Cook Fri Dec 25, 2020 1:07 pm

Lapping will remove the burr and it will do it better than any freehand method suggested. Your using a ground hardened surface. As I mentioned, I've never had a cylinder I couldn't fix. I use the same method on new Sure Starts prior to running them in. It works excellent and using polishes which are liquid prevents one from removing too much. The cylinders are dead soft which is why the wrench burred it in the first place.

roddie Fri Dec 25, 2020 2:15 pm

Ken Cook wrote: To fix it, acquire a piece of 5/16" tubing about 4" long. Wrap tape on the top of the tubing and drop the rod into the center of the tubing and push the skirt of the piston onto the tape. Make certain the piston fits tight on the tubing. If needed wrap more tape on the tube and force the piston onto it. You need to pass the tubing into the cylinder the piston will be upside down on the tubing.Using the tubing as a handle, pull the piston skirt up to the point where the piston won't pass through. Use chrome polish or brass polish, liquid polish works best for light removal. Twirl the brass tubing in up and down motion until you wear the burr. It shouldn't take long. Remove the piston and tubing and re insert with the piston orientated into the cylinder correctly and do the same thing. DON"T bring the piston high up in the bore keep it low in the cylinder. Wash with hot soapy water and dry and reassemble.

I followed Ken's method (above) for a couple of my Cox .049 cylinders with great results. I actually made a holder for the piston, using the outer tube of a ball-point pen (BIC Round-Stick) after removing the inner ink-tube. The outer tube has a .318" outer diameter and just a few wraps of masking tape around one end makes the fixture that you need for holding the piston.

I wiped the cylinder-bore using a facial tissue afterward.. and washed both parts with warm soapy water as Ken recommended.

A light coat of air-tool oil on the parts after washing, will prevent oxidation until you're ready to reassemble your engine(s)

bakergw Sat Dec 26, 2020 2:53 pm

many good ideas in here on how to fix it if it happens to you. And at times this type of stuff happens to all of us if we are mucking around with enough engines, big or small. I feel the cross hatching the bore as suggested by Ken with a Davis Diesel brush as the last part before final cleaning is very important. Although it will work without it, but cross hatching barrels is beneficial. Very careful cross hatching of glazed pistons is also useful, but the pistons are soo small it may defeat the purpose. Cross hatching bores and pistons on two stroke race bikes after each meeting was a common thing to maintain performance, but then again, I am the sort of person that owns and uses bearing blue still Laughing

Keep the piston and barrel matched run the buggery out of it and it will probably end up being your fastest engine. Laughing

Cheers,
Gary

Oldenginerod Sat Dec 26, 2020 6:45 pm

I'm not really sure that cross-hatching is of much use when we're not dealing with ringed pistons. I suppose there might be the advantage of the "scratches" holding a little more oil.

davidll1984 Sat Dec 26, 2020 7:42 pm

M'y self doubt that cross hatching cylinder help performance wit tiny engines use castor oil for compression castors varnish serve as protection on very hi rpm and heat exesive varnish build up Not Good old goo stuf dry nead cleaning other than that its no nead Most of m'y Good tuning engine tend To keap piston kleen like polish finish compression is Good in Most of m'y engine if turn prop 1\4 turn than let prop it return back To its position if rest stay in position Not Good in som engine without glow plug just crank casse compression is felt and it work litle those engine performe like no other so y tink very soft brush in Most case Good for cylinder no métal copper or abrasive brush remember like the .010 is so smal just tiny scratch can make them run bad lost compression tru exaust port y use straw brush made of nilon tink come wit silicone straws

**Cribbs74** Sat Dec 26, 2020 8:11 pm

David brings up a valid point. Rod too for that matter. The reason cylinders are honed is so the rings can seat properly and wear into the bore.

Depending on the fuel you use any crosshatching will eventually varnish over. That’s not to say that a new cylinder and piston couldn’t benefit from it though.

balogh Sun Dec 27, 2020 12:45 am

This " varnishing over" also helps fill unwanted scratches ploughed by the piston in the cylinder wall if some debris gets into it somehow..that is another blessed function of castor oil.

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