I am not gonna repeat the thread I already posted in the Honda section, there are two posts there in which I have included a lot of information that might help someone else looking to cure a hiccup or replace a drive shaft. The subject of that thread was primarily addressing the spline fit from front U-joint yoke to shaft end (http://www.triketalk.com/forum/threa...it-easy-enough).
But it occurred to me that some never got a Lehman build manual with their conversion and some of these GL1500 / Lehman trikes are getting on in years. We love ours, we baby it .... it has it's own room, we've known it since it's birth in 1998 and knew the bike before that. We've loved the looks since she was first seen pulling out of his shop.
But if I hadn't already done some looking and digging .... if on a trip into 3-4 states away .... and the weak link of the whole drivetrain let go pulling out of a gas station two up with trailer as I gassed it .... let's say it could lead to some moments of panic.
I don't know how y'all feel, but as for me, I don't mind the weak link being an easy to replace part. In my reading all over the net, my querries of "Lee H Mann" here who has been doing Lehmans since the late '90s, and my conversations with the original owners who bought our's when it was just a "pupp of a GL1500SE bike" and which we saw later grow into a "full fledged Trike" after the owner went away to school, those who used it as a main ride while they built others for customers into 2004 when we bought it ....
.... consensus seems to be usually a drive shaft failure in these trikes results in damage to the drive shaft or just the Honda front U-joint itself.
Back in the early days, late 90s, early 00s .... Lehman instructions said to cut a stock GL1500 drive shaft to a length of 12.750" long when measured from tip of shaft at splined end to cut line. One also needed a Neapco #N2-28-357 Yoke bored centrally to 0.770" diameter (best done on a lathe). Then the shaft is inserted into the modified yoke so that exactly 11.125" of shaft remains ahead of said yoke. This should be a snug fit. Instructions show the dimension from center of rear U-joint holes to tip to be 13.50" which is not as easy to measure accurately without some thought.
Now is also the time to slip Honda joint on front and check for proper phasing according to instructions ... but I don't know that Honda machined all splines in all yokes to same orientation so I am not sure this step matters .... because next yoke likely will be off half a spline from perfect phasing. If they don't line up perfect, I err to the spline that sets the front drive U-joint a hair ahead of the rear U-joint. There are 21 splines, and odd number and each spline is 17 degrees of arc, you can't get more than half or 8.5 degrees off and if you turn it 180 degrees, you'll find that to be closer to 4 degrees max.
Now it's time to weld. Welding requires preheating the shaft and yoke as a unit to 500 degrees .... I attached instruction below for downloads. I see the instructions say to weld around shaft and to weld inside the yoke the stub. That shaft that served 60-70,000 miles or more from 1998 until last September 2015 is only welded at the shaft at front of yoke, there is no weld at the stub on mine (though I may someday remedy that someday). I guess the person CR had weld it was pretty sure of his weld .... and it is a pretty weld with no undercutting. It has never given indication of weakness even as she has spun a few inside tires when pulling out in a hurry in heavy traffic (and I assure you it was by accident). I have it as spare now that I carry in the trailer but it would be easy to order a Neapco yoke and take a good old drive shaft and make one if desired, fit it with a new joint at back and a good front joint ..... and have "just in case".
I can't help you with a new splined shaft / yoke combo ..... maybe LHM has spares?
Anyway ..... below are some attachments that may help someone else, and I'll take the liberty of quoting LHM's reply to my querries as they are pretty much the same as what my buddy has told me in the past as we talked with he and his wife over a fire pit or some good vittles at Rancho Viejo ....
.... which is partly why I just love riding my Lehman!I have seen failures on both the un-splined and splined versions of the shaft. The welded (un-splined) versions might fail because of initial prep or a bad weld, but mostly from abuse. The original owners were mostly well trained in how they treated their trikes. The second owners were a little more brutal and the third owners are generally worse. The splined shaft failures are usually abuse. Of course proper phasing of the u-joints is imperative.
Failures of the driveshaft, even the front joint rarely cause significant damage such as transmission output shaft.
Driveshaft vibration can be caused by a lot of different things. The splined yoke being loose. It should have a set screw and a groove on the splines for the screw so that the yoke can't move on the shaft. Improper phasing of the u-joints and sometimes just simply rotating the front joint 180 degrees will reduce if not eliminate vibrations. The last thing is front yoke to output shaft. I have seen some that appeared to be good but putting the trike in gear the front yoke would move on the output shaft like the splines inside the yoke were bad. I have never seen an output shaft spline go bad. YET !!
And of course the last thing is balance which I have never seen when using the right parts.