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Flathead 45 cylinder baffles

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  • Flathead 45 cylinder baffles

    I am assembling a 1942 flathead 45 engine for a friend that was brought to me in boxes. It has been boxed up for 30 years. The cylinder baffle remains on the front cylinder but the rear baffle has been cut out. I was going to remove the front baffle as well. What is the purpose of these baffles? I believe these baffles keep splash oil off of the cylinders. Saying this w/o the baffles do the pistons require oil control rings. The pistons he supplied have just 3 cast rings on the pistons no oil control ring.
    Thanks
    Pete:::::::::;;;;;;;;;;;

  • #2
    I would leave the existing baffles in there. I believe they help with oil retention in this area. Must be somewhat beneficial because my 36 VLD has them (so they've been around for many model years) and the factory wouldn't put them in there unecessarily. The rear may not be as important due to the natural splashing up of the oil from the crankshaft rotation. As with many things, there are many opinions on this subject but this is mine. Hope this helps........Smitty

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    • #3
      Thanks Smitty. Another friend of mine has a 1946 Indian chief that has the baffles and he left them in as well.
      Pete:::::::::;;;;;

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      • #4
        They also stiffen the castings, Pete!

        Any oiling concerns are eliminated with modern oil-control rings.

        ...Cotten
        AMCA #776
        Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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        • #5
          Thanks Cotten are these oil control rings readily available?
          Pete::::::::::;;;;;

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          • #6
            Shop Dope 218 of 04 April 1941 shows how the baffles were changed for the recirculating oil pump models. For 1940 up the 45s had a full baffle at the front and none at the rear, with the plain connecting rod rather than the forked rod at the front. The idea of the baffle was probably to put more suction on the front cylinder to draw up oil mist, as the flywheels turn clockwise seen from the right hand side, and so splash oil preferentially into the rear cylinder.

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            • #7
              Originally posted by Pete Engelman View Post
              Thanks Cotten are these oil control rings readily available?
              Pete::::::::::;;;;;
              I haven't shopped for pistons for decades, Pete,...

              But modern pistons will most likely use modern three-piece oil rings.

              And Steve!

              When the rods were reversed, the forked rod was also enclosed with a web on the bottom side to catch and throw oil to the front.

              ....Cotten
              AMCA #776
              Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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              • #8
                Let me ask this about baffles. I've had my '41 Big Twin Sidevalve since 1973. It came with baffles removed. The N.O.S. pistons that I have for these models come with 3 compression rings. These pistons are the -30 ones that were for VL's, then used on ULH's. Also am I correct in assuming that without the baffles that you use an oil control ring on the non baffled cylinders ? This is how I've run this motor since I got it running. It has never smoked or prematurely wore out the cylinders.

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                • #9
                  Golly Craig!

                  If it works, please don't fix it.

                  ,,,,Cotten
                  AMCA #776
                  Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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                  • #10
                    The VLs ran with no scraper oil rings and I don't know when Harley started using them. Was it with the 1938 strutted skirt pistons? And why run 1936-40 recirculating oil machines with the earlier one through oiling baffle and conrod set-up? An oil ring on the back cylinder sounds like a sensible way to go today.

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                    • #11
                      Thanks Cotten and Steve. I'll keep running the oil control rings.

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                      • #12
                        The 45 pistons with oil control rings did not appear until the '50s with the advent of the K series (the pistons are different between the models, but the rings became common due to sharing bore size.). They also went to a 1/16th compression rings. The early pistons including all wartime production used the 3/32 rings with an oil ring that was just the same but with a groove machined in the center of it.
                        Robbie Knight Amca #2736

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                        • #13
                          I haven't looked at his pistons too close yet. I just noticed his rings all looked the same. Thanks for the tip about the forked connecting going to the front instead Steve. The owner has a shop dope manual and some other schematic diagrams with tolerances etc. we are going to use for assembly.
                          Thanks Pete::::::;;;;;;;;

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                          • #14
                            Dear Pete, after 1940 it's the plain rod that goes at the front.

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                            • #15
                              Although a useful method of lubricating the front piston in 1940-73 45 engines, the baffle is a serious pumping loss. Moving 375cc of air in & out of the rod clearance slot in both directions takes power away from the crank, aerates oil droplets, and increases case air temperature.
                              If you run skirt oilers the baffle can be removed (the K/KH with oilers never had them; 1953-* OHV big twins used drain oil to the skirt).
                              I suggest cleanly removing any trace of the baffle where it joins the bottom of the spigot mouth (including the rear spigot mouth), and radiusing that opening from the bottom where it opens into the case interior.
                              The Linkert Book

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