Will XJ650 TCI work on a '82 XJ550 ?

A Guy I'm helping stupidly tossed his original '82 XJ550 TCI (probably still good) when he bought a used TCI for a XJ650. Are they interchangable ?
It appears someone actually stole his side stand switch and harness extension. We're not getting any spark, though the starter turns over well. If we replace or jumper the side stand switch circuit, should it start?
What other causes could there be for no apparent spark?
It ran when he rode it to work, but would not start hours later (after sitting in the rain all day). When he got it home & called me I found the side stand switch was gone.
Any ideas?

 

if you remove the sidestand relay under the seat it will bypass the sidestand switch circuit. bike will start if that was the issue

bike should start with 650 tci but will not run well.

 

Thank for the answers. Went ahead and got a new (used) blue (XJ 550) TCI, with code matching the code on the pickup coil mounting plate.
STILL NO SPARK ?? after fixing sidestand switch, wiring and relay. Ign. coils checked good. Three bad Plug caps were replaced. The old, shot main fuse box was replaced with new ATC style. I've got 9.5 v. when cranking, and the pickup coils have the right resistance (650 Ohms). I there any way a Regulator/Rectifier problem, or a Stator problem could cause a no spark condition? All other electricals, lights, etc. work fine.
I'm totally stumped on this.

 

Cranking voltage needs to be 10v or more, else the TCI won't play ball.
Can you jump it from a car (not-running) battery?

 

What he said, use your car/truck 12V.....

 

the 550 will not start with voltage that low even tough to start with 10 volts

 

I think MOST of the XJ's are very...weak' electrically, not the most robust charging/electrical system even when newer...add in > 38 years of 'abuse'...I find you need a VERY strong battery, to obtain multiple successful ( non slip) starts.....IF ever a bike needed the old XS series kickstart, it's STILL the XJ!! As an aside, if you've ever push started one warm, they DO fire surprisingly easily (ask me how I know...out couriering, manic day, could not quit, but my XJ 650's starter motor did....I push started her about 35 times, that day!! Was fitter......and more tired than a butchers dog when I got home!!!)

 

a starter in need of cleaning and rebuild can drag down the voltage when cranking.

for no cost
you would want to start is cleaning the cables of the starter.
battery connection ground cable at battery and motor , would be a good time to clean wire to frame from motor under the battery.
positive terminal and cable, connections on both solinoid posts
then down at starter