Correct me if I'm wrong, but........

nhsteve

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Basic info: 1978 XS650E, standard. Has 33k on it, but it has evidently been pretty well cared for, as evidenced by clean oil(s), nice grease in the head bearings, good rear brake shoes, etc. (front caliper was buggered- how I got it). About 130/135 PSI compression each side.

What I did: Front brakes sorted, swingarm bushings replaced, tapers installed, new sump filter(s), tires/tubes, etc. Timed up (very close to spec), cleaned carbs. Actually got the bike started sufficient to check the charge rate (13.5 VDC, thanks for that), synch the carbs, & get all lights working sufficient to pass inspection, and put maybe 80 miles total on it. Always started a bit hinky, but it ran ok once going. Had EMGO aftermarket automotive-type coils on it that for some reason I was suspicious of, and decided to swap out with EMGO OEM-type. Before I started that swap (on a now running bike, I want to be clear on this point), I saw that the points leads at the coils were swapped left to right.

New OEM coils installed, swap leads so left is left,etc.

Hmmmm...........

Things went downhill after that. Could not get it to run, backfires only. More Hmmmm............ Timing light sez fire is all over the place, sometimes ok, then not.

Investigating the timing more closely, and removing the advance unit and rod, to check if the locating pins are A.) there, and B) in the correct orientation, this is what I see: When I put the motor at top dead center on the compression stroke of the left cylinder (left intake valve has opened and closed, and piston is now at TDC). The locating pin for the advance unit is at 6 o'clock, and not 12 o'clock, as expected.

I believe I am looking at pulling the motor to remove the head top cover, and am expecting to find that the camshaft is 180' out.

Am I correct? Is there something else I am missing? If I rotate the motor another full 360' then the locating pin (and therefore camshaft) appear to be correct, but am I not then on the exhaust stroke at TDC?

Appreciate comments. Am not afraid of the work at all, but at 70 pulling the motor is a pain (I can still do though!). Pic is of the advance unit end of the cam at Left TDC.
at LTDC on compression.JPG
at LTDC on compression.JPG
 
Here's my guess. Coil leads were swapped because the cam is indeed 180 out. Swap the leads back to where they were and see if it runs... since it ran before like that. If that is the case... and just speaking for myself, I'd just let it be. On a 360° twin, it doesn't matter if the left or right fires first, as long as they both fire... and apparently they were before you swapped the coil leads.
 
I think you're OK on the cam install. That's the way it is, at one cylinder's TDC on it's compression stroke, the pin points up, on the other cylinder's TDC compression stroke, it points down. I think your issue is the advance rod is installed 180° off. That's why your points to coils wires were switched originally I'm guessing, to compensate for that. Now, you changed the wiring back but didn't change the advance rod install, so the timing is 180° off again.

Put the advance unit back on. Now, you have to align the advance rod when installing it. It can go in one of two ways, and one will throw the timing off 180°. The locating pin for the points cam on the advance rod, and the one for the little disc on the advance side must point in the same direction .....

LhHXTz4.jpg


There are some alignment slash marks on the advance unit and the little disc to help you with this. They should point to one another, or very nearly so (yellow arrows) .....

Abg8svm.jpg
 
5twins, just so I'm clear... you're saying it's possible to install the advance 180° out? My bike's got the TCI iggy, so I'm not well versed on the mechanical advance. I didn't know that was possible.
 
Well, not the advance unit itself, it can only go onto it's locating pin in the cam in one position. But the little disc that ties the weights to the rod, that can be installed in two positions. One is correct, the other throws the timing off 180°. The hole for the alignment pin in the advance rod goes all the way through. That means the pin can stick out either side. It needs to stick out the same side that the pin for the points cam does. If you don't do that, the little disc will lock onto it and be 180° off from where it should be. That throws the timing off 180°. Cylinder firing points are reversed, left cylinder firing when right should, right firing when left should. The "farm boy" fix is to change which coil the points wires run to. But now your top set of points that are supposed to be firing the right cylinder (labeled "R") are firing the left cylinder, bottom "left cylinder" set of points (labeled "L") are now firing the right cylinder. It works but it's not right, not as Yamaha intended, and can get confusing. The correct "fix" isn't hard but you have to understand what's going on to figure it out.

0dOr3wg.jpg
 
Yup swap, wires, or pin position, be happy.
Get the neon timing light out and get BOTH sides properly in time. Remember that full advance timing matters most. If you can't get both exactly timed, don't be afraid to change one point's gap a bit to bring it in. .012 to .016 or so is fine for points gap.
 
Thanks very much for shedding light on all this. I did actually see your drawing of the advance rod and pin explanation before I dug into this 5twins, and did find that both locating pins were correct. I'm thinking the small disc may have been out of position, and my "farm boy" PO switched the leads at the coils to compensate. Looking at the disc and the advance assembly, I can see that my disc and unit are out of phase.

To compound my confusion, the points leads colors are swapped also, at the points themselves. He has/had the grey lead going to the left set of points and the orange going to the right, not as your photo shows. Sometimes I wonder why someone would go to so much trouble swapping things like this around, instead of just fixing the problem at the source (which perhaps he/they did not realize I guess).

We must go away this weekend, but I will endeavor to get on this when we get back, and get things back to 'standard', and report back the results. Appreciate the help very much, the drawing, photos, and write-up. Kudos!!

Pic is of my advance unit, showing how the lines are not lining up, and evidently the start point of my issue (?).
advance unit.JPG

This pic shows how it should NOT look.
 
Yes, change everything back to the stock configuration. Change the wires at the points sets, then they will match the wiring diagram. It will all be less confusing this way.

Yes, your advance rod install is incorrect, 180° off. Installing the advance rod correctly so the timing is locked in right is a two step affair. First step is to insure the alignment pins match side to side, stick out the same side of the rod. You say that's done correctly so the P.O. apparently got step one right. Second step is to install the rod so the alignment slash marks on the advance unit line up. That's where the problem occurred. Should be an easy fix now that you understand what needs doing.
 
Follow up to all this: advance unit and disc are now assembled correctly, with the disc mark and advance unit mark aligned. Rod pins were ok (and tight- no need to remove them), swapped the grey and orange leads so they are correct and agree with OEM schematic, and coil leads corrected at the coils. Static timed initially then checked with timing light, needed only a minor tweak on the left. Bike started up much better, although it wants to start on just one cylinder for the first minute or so (when cold), have to play with the throttle a bit, but overall sounds ok. Mercury stick check showed me the levels were still as I had them last summer, quite even at 3000, maybe a bit off at idle.

All this was with the EMGO automotive-type coils. As I had gotten OEM type, which I could never get to work, I put them on, just to see if they would. They did indeed and bike seemed ok with them also. So maybe I didn't really need them. Oh well.

My plan is to take it over to a friend next week to do a leak-down test on it, as I don't have the needed tools to do that. My compression test showed about 135 psi each side when I started all this last summer, but we may do that test over again also. Goal is to decide if I need to go into the top end and freshen things, or leave it all alone (for now?)

Thanks all for the help, it is appreciated!
 
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