You may have read one of my posts, but I can explain the timing of the magneto to the starting engine, it's relatively simple, maybe not so at first. RD6 should be a 3 cylinder diesel D6600 with the vertical cylinder starting engine, the older and common type used on the RD6, RD7/D7's RD8/D8, the earlier Diesel Forty and other tractors I may have forgotten.
Take the side inspection cover off the starting engine's flywheel/clutch compartment and look at the flywheel for a hash mark that has been punched into it. Pull the number one piston spark plug, use a cork in the hole,(it will pop out on the compression stroke) then spin that flywheel until the marks align and #1 piston is at top dead center on the compression stroke. Use the hand crank to spin the motor and move the piston,(mag is off engine, fuel shut off etc.)
The magneto needs to align to fire a spark at this same time for the engine to run. I am assuming the magneto is rebuilt and is ready for installation, it should be firing a nice blue spark, make sure the plug wires are solid wire, never use carbon filament. I don't know the inner workings of the magneto like a rebuilder would. Figured I'd best mention that.
You can turn the magneto by hand while you hold it and determine which of the 2 will fire a spark. (you can be 180 out on this when installed via the plug wires). I went through this exercise years ago, and actually turned the thing over in my hand and took the electrical discharge into my hand, from the wire. I don't recommend it for safety reasons, but honestly it was not that much, and at the time was the only way for me to understand the magneto cycle.Maybe a test light or something you can arc it off to will work, I just used my hand. So it basically builds up tension, snaps over/sends a spark and repeats. I think it skips in between but I'd have to go pull one off the shelf and do this again, been a long time now, so I don't recall, but know that it worked by timing or aligning from the beginning of the tension cycle to fire from the left plug wire if you hold the mag in your hand, with the cap facing you. The next paragraph is the key to all of it. The SRB (book) does not tell you what cylinder is #1 and it is the one closest to the radiator.
The magneto should tension up, then snap over and fire a spark, it should be building up tension just before those marks line up I mentioned above, and it should fire just as #1 piston reaches T.D.C. You have to fool with the magneto a little to get it to align and couple properly to the motor and have it building tension to fire the spark as the #1 piston is rising to top dead center. If it does not want to mount, spin it over to the next tension cycle, this will move that big tab on the back that fits in the groove on the engine coupler, you may be close or it will fit right in, if not, its off. I went through this, finally it became clear as to what needs to be done, and in actuality, its very simple. I am not sure how the spark advance/retard works on these, there is a small switch/lever with a clicking surface on the engine for that.
This starting engine needs a hot, nice blue spark, and clean fuel to the carb, to run correctly. The old steel fuel tanks get coffee grind rust in them and plug sediment bowls and the carburetor fuel line screen easily. You can clean these with crushed stone, nuts/bolts, a length of some chain or whatever makes sense, while you spin it when mounted on the wheel of something, in a mortar mixer or by hand like I have done with crushed stone, flush clean then reinstall, I have even raised the internal screen in the tank to keep fuel flowing.
Crankcase oil in these starting engines is important to monitor for level and contamination, they can get thinned from gasoline and a leaking carburetor. Its best to shut off the petcock on the sediment bowl, run it out, or like I do, install a petcock on the carb bowl, do the above, and use a small hose off the barbed end of the petcock to drain into a container, then you know the carb is dry. Most just run it out of fuel after shutting the fuel off to it. I took it one step further because I wanted the bowl drained and know nothing can get into the crankcase/sump as on my D7 the drains are a real pain to get to, I actually take the side inspection cover off, clean the area surrounding prior, then suck the oil out with a drill pump, napa had one with a reducer, for a small line, it has garden hose fittings on each side.
I believe you need to spin the diesel on this engine to allow coolant to circulate, so don't run the starting engine long without having the diesel spin, it will overheat.
Another thing to watch for is when the diesel fires, the starting engine pinion should disengage at a particular rpm by centrifugal force, so that the diesel does not over speed the starting engine. When I start one of these, I have my hand on the throttle linkage, and as soon as the diesel fires, I make sure to shut down or slow the starting engine, they will easily over speed one of these if you are not careful or lets say attentive by ear, to anyone familiar with older engines, it won't sound right, too fast etc. The pinion can be adjusted via the adjustment screw and each turn of it relates to R.P.M.s, the serviceman's reference book would describe that adjustment procedure, again if necessary. Mine was starting to need adjustment, so I made sure to keep this in check by having a hand on that linkage as the diesel fired, you can also just close the carb choke butterfly, the L shaped lever on the carb.
The one reason I mention all of the above relative to the care of using one of these starting engines is because you or others may be new to these, and it is easy to screw one up if you don't know about these things. Besides that, they are reliable and work well when properly cared for, kept in good mechanical condition. You can't beat them for cold weather starts.
The books on this tractor are as follows, Operators Instructions, Serviceman's Reference Book, Parts Catalog, and there may be one specific to the engine in addition to the SRB, if it was used for stationary applications, there is usually a little more information on the engines in these, though the SRB for the tractor should cover it, I did notice this for the D8800 in the D7 which was used on generator sets, marine applications, compressors etc. The D6600 I am not sure about, that 3 cylinder motor was in at least 2 tractor models before they put the six cylinder in the later D6's. I don't believe there are a lot of 3 cylinder/D6600's around, not rare either, but the production was certainly less and ended in the 2H series D6 or the 5R series.
Who would steal books on these? That is sad, whomever probably does not have one of these tractors or never will, and the books are useless to anyone who does not have the tractor, except maybe a model maker or someone doing similar work.
CAT legendary literature will likely be able to provide you with good reprints. You can check ebay for good used originals, I don't recommend Jensales or other reprints out there, you may be disappointed in the print quality, photos especially. Also ACMOC and ACME antique caterpillar forums will be very helpful.
For the books, you need to match the serial number production range of the tractor, make sure yours is within it. Being an RD, not a high production series, you may not find a lot of these books on ebay like other tractors, so CAT legendary literature may be your best bet. I attached a link to an ebay search, and I see Jensales, a really way overpriced original, and one or 2 others. NO way I'd pay $200 for that well used original, reprints by CAT will be a lot less and you'll get all of them for less than that one book listed for $200.
ebay
