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    Soloed in Hi-Max!

    After 3 years of preparing the Max, and 10-12hrs preparing me to fly it, We did the deed! The weather was good and the 503, with 8 hours total time, was running well, and this 82 year old pushed the throttle up and away we went. Wheels got light at about 35 mph, and up we went...
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    Landing Gear Replacement on a High-Max

    My Hi-Max suffered some damage to the main wood landing gear struts with a hard landing. Nose wheel unn affected. The hinge connection on both sides deformed and the braces put a Bend in the axle. Would like to replace with new gear of 6061 aluminum with either spring or bunji cord shock...
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    Exhaust spring failures - ROTAX 503

    In less then 8 hours of running time, 4 out of 6 springs have failed. These are the stock, CS, 66mm springs. Piping is strait forward, one 90deg elbow and strait pipe to muffler. clips on elbow to muffler are almost 3 inches so springs are stretched pretty far, so 66mm springs are too...
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    High Idle RPM - 503DCDI

    Engine idle after 4 hours of run-in, runs 2,300-2,500 RPM no mater where the slides are set. can't get it down to 2000. In addition, if running at 4000 and pull back the throttle to idle, the RPM drops below 2000, the engine vibrates and shales as it dies. The idle jets, needle jet, main...
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    503UL DCDI, Static RPM Expectations

    Anyone, Need some advice! Engine is new for all practical purposes, 2:40 time on the ground, plane not yet flown. Dual Bing 54 carbs, manually sync'd; Std complement of jets, needle jets, etc, per ROTAX; Jet needle at #2 position; Auto gas, 1:50 oil, Ultra-prop(three blade) with 12 deg...
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    Balancing two Bing 54 Carbs on a Rotax 503

    As a alternate to using a manometer to balance the two Bing 54's, is is possible to use a Dwyer, diff. pressure ga, 10 inches of water max rating, to do the fine tuning on the balance. Can't find the manifold suction pressure rating for the 503, but I suspect it is in line with the impulse...
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    Leaking exhaust joint!

    Need some suggestions. The first flexible joint out from the exhaust manifold does not seal properly, resulting in oil spray on the side of the engine, firewall and under side of the fuse. Makes a mess! Thanks, Johnc
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    Safety Wire on Ultra-Prop

    The Rotax 503 prop hub has 6 threaded holes for 5/16" prop bolts. Should locking nuts be used behind the hub , or should castle nuts be used with holes on the bolts for safety wire? Thanks
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    Orientation of ROTAX Fuel Pump

    Just mounted the ROTAX diaphram fuel pump in the horizontal position with the impulse line out the bottom. While watching an EAA video, a review of an installation pointed out that the fuel pump was improperly mounted, in the vertical position. I also have been told that the impulse line must...
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    Alternate Rectifier/Regulator for a Rotax 503 DUCATI

    The ROTAX user manual and installation manual don't say much about the chatacteristics of the output voltage for instr's, battery charging, lights other then that it is an a/c voltage that increases with RPM. Does anyone know what the a/c voltage out of the generator is thru the operating RPM...
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    Primer vs Choke - ROTAX 503, dual Carb.

    For operation in the sunny south, Is a choke really needed, or is a primer to both carbs sufficient? Is it possible to siphon fuel from one carb to the other thru the primer tubing? Will balancing the carbs prevent this from happening? Are check valves available to insert in the 1/8" tubing...
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    ROTAX 503ul DUCATI

    Can some one tell me how to tell the year of Manufacture from the serial NO. on the engine. I have an engine that has never been run, plastic plugs still in place, with no identifying sales information. Have no idea what shelf life is! Thanks, Johnc
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    Gearbox oil , pre-mix oil for ROTAX 503UL

    Came across a ROTAX 503UL w/DUCATI ignition that has never been run, probably bought just before the 503 was discontinued. Unfortunately, no operating instructions. 1. Can anyone tell me what type/manuf oil should be put in the gearbox. Also, what is the recommended oil to mix with the...
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    wanted provision 8 lower case with gearbox for ROTAX 377

    I have a working ROTAX 377 with drive shaft designed for strait drive shaft to remote belt drive PRU i.e. powering a Quicksilver UL. Would like to convert to gearbox - PRU for direct connect to prop. I understand that the 377 is physically same as the 477 so would consider similar unit from a...
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    Post Conversion - Crank Rotation Tight

    Completed the conversion process. Engine is 69mm std. crank, 92mm case re-bore with new jugs; AS-41 type 1 case align bored, oversize bearings; new dished, std cam size zero; #4 thrust bearing moved to #3 position, #3 to #2 position (no split bearings installed); cut end of crank has end play...
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    Oil Pressure control

    On a full case 1/2VW, the oil cooler is removed and in my case, the interface plate over the ports on the case is 1/2" alum that has a channel routed between the two case ports. In this configuration, the relief valve is almost non functioning since the oil gets to the main gallery in either...
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    Rotax 377?

    What can you do with a Rotax 377 that was intended to be used on an ultralight with a belt redrive remote from the engine? The crankshaft has a coupler for an extension shaft. Evidently, the engine was not designed to be fitted with a standard gearbox like most Rotax engines, at least there...
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    Mikuni carb size and Jet size

    Need some help with sizing the jets for my 32mm, carbs. Engine is a 1/2 VW, std. crank, 92mm cylinders, set up for 2 carbs. Intent is to derive about 32hp @ 3500RPM. My two carbs come from different sources, and the jets under the plug below the bowl have different numbers on them, 250 and...
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    Valve Seats

    I am installing new valves on a 1/2 VW build, and the exhaust valve seats re-used heads)are not clean and shiney as are the intake valve seats. The seats have been lapped with the old valves to clean up the seats, but the coating of carbon or corrosion and discoloration did not come off. The...