IN NEED OF HELP, made a stupid mistake, XJ500 Now Won’t start :(

Hello, i went thru a nicotine withdraw and with bad concentration made a really stupid mistake. I am very embarrassed about it…(especially because i am an Mechanical engeneer by education…)

I have recently rebuild the YAMAHA XJ500 1981 (bassically a rare European version of XJ550, seca, etc.), picture bellow:

The rebuild took time, my battery died (before rebuild and during it motocycle ran like a dream).

I connected electricity to start it up from a running car and without battery in the motorcycle…it didn’t start, then i connected cables from a car backwards (switched +/-)to the motorcycle (still without the battery on the motorcycle)…
BEFORE I REALISED WHAT I HAVE DONE, IT WAS TOO LATE..

I then changed regulator, ignition coils, CDI , FUSES all 5, starter relay solanoid.
now it cranks up, has spark but will not run or start. If a crank it for a really long time it fires on a cilinder or two, wont rev and then dies. I suspect missfiring?!

I tried to find solution for 2 months now..but couldn’t
IF SOMEBODY HAD THE SAME ISSUE PLEASE HELP ME, I AM DESPERATE…(and extremely embarrassed)

 

was the T.C.I. the correct one for the bike, if not the firing curve ,(advance /retard) could be wrong for your bike

 

can you please be more specific, what do you mean with the firing curve? and what does the "(advance /retard)" mean? I am really bad with electrical parts..
i changed the TCI with an aftermarket copy, so it is not original. I can try with the original one-hoping it wasn't damaged..

 

when you are riding the bike ,as you increase speed the point at which the spark plugs fire, moves closer towards top dead centre,
with these XJs this is done automatically in the TCI
as different XJs are not all the same "point of firing" when at full advance (i.e. firing nearer to top dead centre)
then you have to have the correct TCI for the bike, if not then the "timing" will not be correct
you say you changed the TCI for an aftermarket copy, was it for your specific bike,
only true test of a TCI is to swop it for a known good one, not easy to find i know


then again are you sure you are getting fuel into the cylinders, try squirting some starter fluid into the carbs as you crank

 

Check that the coils haven't been reversed.

 

Do you maybe know what are the resistances for checking electrical components for this bike?

 

That i am pretty sure about it is ok, as i wrote on each one where it was, but i will anyway check that, just to be sure, thank you for advice.

 

One of the aftermarket TCIs I purchased was wired for the 900 and I had a 750 and the plugs were on the wrong wires for that.

It had a harness coming out of the TCI. The wire colours were correct so I just moved the spade terminals to the right spot in the plugs. Hopefully not your issue but it's worth having a good look.

 

Well, "increasing speed moving the spark closer to tdc" is not technically right. Ignoring engine load (which the XJ does), the idle spark will be somewhere around 5deg btdc. (someone here now will have the exact number, but humour me for now). As the engine speed increases the spark actually advances, which means it moves away from tdc, to be earlier, by around 25 crankshaft degrees, giving 30 degrees or so maximum advance.
It's a small point, and not really relevant to the issue, but if testing with a strobe this is what you should be seeing. Anyone got the exact timing at rpm intervals for different models?

 

I believe the manuals on xjcd.org had all the timing curve diagrams, but apparently before the site went down I only managed to save the docs for my 1100, which of course has the additional vacuum switch absent on most other models. To call them a "timing curve" is polite, as they are a pretty crude linear function, and all models look similar. A tunable aftermarket chip would be fun to experiment with.

 

Minimutley, you are of cource correct, my bad, the spark moves further away as you said

 

35/36 degrees is a lot of advance, I'm surprised the XJ needs that much. Defo a future project on electronically mapped ignition is called for, but the list is getting longer rather than shorter..