Cylinder Troubles

Cylinder Troubles

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Cylinder trouble after rebuild

As  I reached a milestone of  49.8 hours on the new Franklin! I had decided to do an oil change every 25 Hrs. and so I proceeded to drain and change the oil, adding a 12 oz. can of “Avblend”, that I have used from day one.

As a habit I cut the filter can, and flush the element in gas, just to see what is going on inside the engine.  This time, it paid off. I found what appeared to be very fine, bright, shiny metal shavings, perhaps best described as in length and thickness the same as what an eyebrow hair. Mixed in with these shavings was a darker gray, fine metal. During the preceding month or so a couple of times when I had tried to start the engine, the starter had failed to completely engage, due I found later, to a few smoothed edges on the starter ring. Could this be the cause?

Next day I had to go do the other favorite thing I do every month, getting back from work in time on the weekend to go down to the hangar. Examination of the starter bendix assembly found nothing. So I ran a compression check; cylinder #1 was 78/80, #2; 33/80, #3; 78/80, all were 77 or 78 psi., so old #2 came off.

This was one of two cylinders that I had had relined in San José by AeroTech, and that Little Red Arrow had re-valved.

The cylinder was clean and smooth, the valves looked great! Examination of the piston showed a small groove, about 1/8”wide by 1/8”long between the skirt and the wristpin orifice. The wristpin plug from that side had a strange wear pattern that radiated from the center of the part; these marks were very obviously where the fine bright shiny metal shaving had come from. What caused this? The inside of the case was nice and clean, no wear or scraped metal could be seen.

Closer examination of the cylinder showed that the liner had rotated 180°, the pin that holds the liner in place had broken, gotten caught in the piston, marked the wristpin plug, gouged the groove, and fallen into the oilpan. The aluminum shavings cycling through the Oil Filter.

It takes 630°F to remove the liner, and I’m told it is no easy task, yet the liner had rotated at normal cylinder operating temperature. John Godwin at Aerotech agreed to reline the cylinder at no charge, and Good ‘ole Goodman, bless his black little heart had all the other parts “In the Mail”, I expected total cost to be about $200 and felt most fortunate at that.

When I fitted the newly re-sleeved cylinder, and pulled the engine through by hand the prop froze solid!

Removal and inspection showed that the cylinder was tapered and has a ridge at about the sparkplug orifice. Again Pat Goodman came to the rescue with a PZL cylinder. These cylinders are machined just a little differently at the intake port and a spacer of .125” with a gasket either side works fine. The #2 cylinder is the only “Franklinski” in the engine and at 7.4 hours after installation is doing fine.

Moral: Nickson’s Machine Shop Inc., (805.925.2525 ask for Heinz,) in Santa Maria does a fine job and I rue the day I gave them 4 cylinders and had the other two done by the other shop.