Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi all..Just received new M90 upgrade hit & miss engine with iron (?) Cylinder liner. Does anyone know what the "mystery" Allen/hex screw vertically located on top rear of clylinder about 1/4 inch from back end  but doesn't seem to penetrate cylinder liner ??. It doesn't seem far enough forward to be useful as a piston skirt oiler. It's a well build engine that usually starts on 1st flip without any prime. Thx for any info or thoughts, Tom.

It's not uncommon for full-size engines to have an oiler in that place.

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Then, too, the screw may be holding the liner in place.

My new engine has the same screw.

I believe this M90 utilizes a top flanged iron cylinder sleeve similar to automotive types which positively locates & retains the sleeve without any lower cylinder hardware or set/grub screw required..If correct, the screw in question could have a different function other than an unnecessary redundant sleeve retention ..

Yes RedRyder...... a truely "Do nothing", ornamental, m3 x 0.180" thread length Button head socket screw (the only one !!, all others are more machine functional Socket head cap screws) casually screwed into the 0.215" thickness aluminum cylinder wall but not touching the 0.065" thick cylinder sleeve....Piston and/or sleeve removal being wa too much work for me,  I'll just "carefully " tiniest drill thru that 0.065"  thickness sleeve & remove any burrs without hitting the piston or rod....The actual oiler device.....are any m3 thread "drip rate adjustable"  oilers available or REALLY liking the diy plastic tube idea, how would I fab up an easy to make variable drip rate oiler ??