What Causes Piston Slap &/or galled cylinders ?

[harleytoprock]

I have to respectfully disagree with those recommending not using an oil control ring. The practice of not using an oil control ring is old school technology which promotes high carbon build up. Carbon is detrimental to top ends as it is abrasive and creates premature wear on components such as valves, guides, rings, spark plugs etc. A modern harley with oil control rings can go 100k miles and more before needing any top end work. Top end and carbon removal jobs were regularly performed every 4K miles on old bikes in their day. My JD was fitted with Eastern MC aluminum flathead pistons that are cam ground, steel struted and have
.004 piston wall clearance. The pistons use modern thin rings which seal better than antique thick ones. They also use oil control rings and I am not running any crank case baffles. The bike does not burn any oil. The exhaust is clear and the bikes does not overheat. I've ridden with other modern harley riders and have been clocked doing 75 MPH many times. The only problen is that since I am not burning or leaking any oil, I am not loosing any oil on a total loss system. Therefore, I drain the oil daily after a typical 200 mile day so that the crankcase oil does not over accumulate and wet sump. Two fresh pumps of oil into the empty crankcase in the morning and I'm good for the day. With this method, my oil is always fresh clean and the oil doesn't build up in the crankcase. Too much oil in the crank case creates problems. If you are really concerned about valve lubrication some people will add a little 2 cycle oil to the fuel supply. 2 cycle oil burns more clean, carbon free than 4 cycle motor oil leaking past the rings. We have learned a lot in the past 80 years about motor techonolgy, why repeat yesteryears mistakes?

[Randy STL]

I would like to suggest that we continue the oil ring discussion in a post by Tom Lovejoy in the Engine-Transmission Rebuilding section titled "Oil control rings on total loss oil systems, use them or not?"

[SteveAdventure]

We believe the problem was that the pistons were too tight and/or not getting enough oil. We consulted the great folks at Topeka HD and Steve Sackman at the Antique Motorcycle Company in St Louis, Mo. Steve recommends the flat top aluminum cast piston from Competition Distributing and leaving out the thick bottom third ring exposing the ten 1/8” (est) holes. The flat head develops less compression and is easier on the old iron and the holes drilled through the bottom ring position will allow oil to come through. Thanks for all your input; I hope to meet you on the road, hopefully on Fisherman's Wharf! Steve

[Tom Lovejoy]

Steve, good luck with the JD. Hope you have solved the problem and that I get to see ya roar by on the Cannonball.

[Randy STL]

Steve,

The Competition Distributing piston is not a true flat top like the original JD or an 80” UL replacement. The piston on the left is an original JD flat top, the center piston is the Comp Dist mild dome, on the right is a Knucklehead domed piston.

Notice that the sides of the Comp Dist piston is lower the than top of original JD flat top, but the top of the dome is higher. I don’t know what the net difference is, higher or lower compression. Maybe Lonnie can shed light on why they chose this design.

Randy
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