The idea started when I looked at the Ausralian 270 crank pin and thought to myself, "I could make one of those." The problem with that design is that you need to cannibalize a second crank to get a splined crank web. That splined shaft is the weakest part of the crank, so why add a second one? A big straight pin is stronger, doesn't require parts from a second crank, and can be phased for any conceivable firing order. With that kind of freedom, why not try something a little different?
with the 144mm rods and 74mm stroke the "offset" is 76 degrees for one piston to be at rest and the other at max acceleration .
Max velocity, not max acceleration. I understand the Phil Irving concept but all that does is make improvements in one segment of the cycle while hurting others. The net result is the same.
This chart shows the instantaneous torque of the two combos.
The improvement from the re-phase can be seen immediately after the 360° mark. The burning mixture is only having to accelerate one piston so the output is much higher. However, look at the trend just before the the 360° mark. There is a large dip on the re-phase motor since there is only the inertia of one piston pushing against the burning fuel mixture. When you integrate the trends you find that the mean torque values are the same. No matter how you rearrange it, the same work is required to move the pistons up and down.
315/45 would give the same firing "cycle" as my common crank pin 45 degree V-Twins
I wondered if anyone would catch that. Yep, It'll say, "potato."
Ah So your building a Sportster out of your XS. Leo
75 XS650B with 79 forks and dual disc, braided lines, disc brake on back, Pamco ignition, Pamcopete's reg/rec mods, kill switch relay, home made harness, all LED turn, brake and tail lights, tapered head bearings, bronze bushes in swing arm, soon to get shock and fork upgrades
Ah So your building a Sportster out of your XS. Leo
Nah, if I wanted a Sportster then it would be a hell of a lot cheaper to just buy a Sportster.
I liked the sound of my 277° motor but didn't like the buzzy vibes. The 360° has more pleasing vibes but sounds bland. I'm hoping to split the difference and get the best of both. Of course, it could end up worse than both but you never know until you try.
I had a bit of a setback when I cracked the pins while trying to heat treat them. Started over with 4130 instead of 1045. The chromoly pins should have the same strength as the heat treated 1045 pins, but not require heat treating.
I'm just about back to where I was before and [hopefully] will be assembling a crank soon.
I got one pin done but haven't had time to build up a crank yet. There is always something more important that needs my attention. I may be losing my shop so this could be one project that never gets done.
I assembled and trued the center section a few weeks ago.
Unfortunately, I made an error in measurement [or calculation] when determining the width of the flanges on either side of the sprocket, and the crank assembly is 1mm too short at this point. I had to order a couple 1.5mm connecting rod thrust washers to use on the inside of each rod. That should put the rods and outer webs where they need to be.
While I was waiting for the backordered washers, I started on the ignition system. Sure, I could have simply made a new 315° reluctor for my HEI ignition but I've already been-there-done-that. This project is about pushing it to the next level so I designed a digital ignition that will work with the odd firing order. In fact, it will work with ANY firing order! With two DIP switches it can be set for 360°, 270°, 277°, or 315°. All done without changing the pickup or reluctor.
r80rt: :)This is a splendid write up, THANK YOU!!!!
Dec 26, 2015 16:54:05 GMT -5
mashermoto: What the what is this shoutbox for? Or should I shout, WHAT THE WHAT IS THIS SHOUTBOX FOR!
May 12, 2016 22:22:21 GMT -5
motormike: Good Day ...just a FYI.. Wild Cat is this Labor Day weekend. Still go'n on. A few 650's still make the scene. Various rides at different skill levels each day.. awards dinner sunday eve. BS in the park'n lot after dinner.
Aug 23, 2016 7:57:01 GMT -5
lsettle: First post in over 6 years!
Aug 28, 2016 19:45:17 GMT -5
kardon: Wow quiet here, where did they all go.
Oct 7, 2016 2:18:13 GMT -5
gggGary: XS650.com LOL
Feb 16, 2017 20:49:02 GMT -5
buell88: Anybody have any idea who built the xs650 tracker used in the Draggin Jeans Ad on Pipeburn?
May 16, 2017 16:24:09 GMT -5
joshua: The regulator/rectifier unit I got from Mikes PMA has closer hole spacing than original. Are we supposed to mill the holes to fit?
Jun 7, 2017 19:25:58 GMT -5
joshua: My bad. I found the bracket they supplied to mount the rectifier/regulator... Uh oh. How is this meant to work? Which way is it meant to mount? Looks like I have to use some spacers or something. Good instructions would be nice.
Jun 7, 2017 22:09:52 GMT -5
craig8johnson: Not sure if this is the right spot or not but oh well...
Jul 11, 2017 18:04:15 GMT -5
craig8johnson: I'm checking the charging system. I'm afraid I might have fried the last battery. With the solid state regulator (after market) what should it be charging at. The book says, I think, 15 volts. I'm hitting 17 when revved. Is that too high?
Jul 11, 2017 18:06:19 GMT -5
gggGary: Yes 17 volts is too high, about 14 volts is max, sounds like you don't have the right regulator or it's wired wrong.
Jul 13, 2017 6:54:33 GMT -5
dean: Just saying Hello, new member who is going to fix up a 79 XS650 that has seen its better days. I will definitely have lots of questions coming up.
Jun 23, 2018 16:45:32 GMT -5
tt650: Trying to breathe life into a 1980 that's been stored (indoors) for 25 yrs. Air filters are dry rotted. Have cleaned carbs but she only runs briefly on choke then stops. Need jet setting info and other ideas that might help her idle and rev.
Jul 3, 2018 19:15:19 GMT -5
trix13: Hey everyone! New to the forum and am fighting those gremlins!! New charging system, ignition switch, coil and fuse box. Resistance is higher than normal on the ignition pick up so I'm trying to find one. No such luck yet.
Aug 16, 2018 8:50:48 GMT -5
trix13: Also, even though all of my connections are clean, I cannot seem to find out why , when at higher rpms, I hit the signals and the rpms pulse with the signals...hahah. same with the brake light. I appreciate all input!!
Aug 16, 2018 8:55:08 GMT -5
bob99: how do I post a question. I am new to the forum
Jun 6, 2019 10:52:10 GMT -5
adlpc: Hello all! Been enjoying your edifying posts and discussions - and as a fan of the XS650 since my early teenage years happy that I now own a 1980 Special which I plan to turn into a vintage half faired racer. Thank you all for being here!
Oct 1, 2019 0:58:56 GMT -5
jimothyj: Hello everyone, I just joined & wish would have known about this site in 2014 when I brought my 1974 TX650A back from the grave. I have spent a good deal of $$ and alot of time on it. Just painted it and working on electrical, I will post pics soon,
Apr 10, 2021 2:14:13 GMT -5
louisvan: trix13 - I had a problem with my 1975 SX650. When I got to highway speeds, the engine lost power. The problem was in the connectors. At a certain vibration and the wind pushing on the wiring loom, the connector lost continuity. A bad crimp to the wire.
May 20, 2021 1:19:09 GMT -5