Checked Timing,one side advances more than other?

XS650D

XS650 Junkie
Messages
925
Reaction score
397
Points
63
Location
Ont,Canada
Not sure if this is related but my left side cylinder has approx 10 lbs lower compression than right.
I checked timing with a timing light (I have electronic ignition and mechanical advance)
left side full advance is aprox 2 mil past full advance mark and right side is approx 1 mil before full advance mark.
I have always used the right side to set timing as I thought both should be the same unless I have points which I dont. Plug readings look the same.Should I just ride it ! Compression drop may not be related
to this ,not sure. Could the Electronic advance be the cause. If I set the left side to read correctly the right side will retard to much and the motor is not responsive. Any ideas Thx
 
Does your ignition use one or two coils?
If it uses one coil then both plugs fire at the same time. If two then they should be able to be adjusted separately.
A timing light reads the spark pulse as it passes through the plug wire. On a single coil ignition, one plug gets a positive pulse, the other a negative pulse. Some timing lights read differently depending on which pulse it reads.
The check to see if your is sensitive hook the light on the plug wire shoot timing. Flip the over, shoot again. You may see a difference.
If so I would mark one side of the clamp. That way on one side I could have the mark toward the plug and when I shoot the other side have the mark away from the plug.
This should get the light to read the same on both sides.
If you have to coils then on the sensor plate the pickups should be adjustable. Try making a slight adjustment and recheck timing. Play with it till they read the same.
You use the term "mils' when describing how far off the mark your timing is. What do you means by "mils"?
Timing is in degrees, If the difference is less than a couple degrees I wouldn't worry much. The stock points variation was about 3 degrees.
Leo
 
Hi Leo, I have 1 coil (mikes xs the one that comes with the Electronic Ignition kit) Mil means measurement as in Milimeter.
Yes I know its degrees but I have no way of measuring degrees that I currently know. I just know the marks on the rotor and
stator. At idle (1200 rpm) the mark on the rotor is on the right mark of the F on the stator for right cylinder. Change timing light to left cylinder and mark on rotor
is now on the left mark of the F on the stator. There is an arrow on the Timing light pointing to spark plug. I make sure that
it is pointing correctly. Have to flip it upside down to check timing on left cylinder.
If I rev the motor to 3500 rpm the mark on the rotor for right cylinder will line up exactly with full advance mark on stator.Other side it goes approx 2 millimetres past advance mark maybe 3 ml
past (not sure how many degrees)
 
I would do as Leo suggests, flip the timing light pick-up over and re-check that left side.
 
I did flip it over to check other side as I have to or arrow to plug on timing light will be going wrong way.
I have always timed the right cylinder only as the timing light does not bounce around as much and its easier to read.
If I flip it so arrow points away from plug it will read much closer.So essencially I have 4 possible ways of testing or 2 for each cylinder.
Theres a big difference between each and I just needed to know which was the correct reading I guess. Which cylinder is the pos and which is neg and is either the correct one to have a base setting?
 
I'm going to guess that your left cylinder reading is correct because if you change the timing so the right cylinder matches, the bike runs bad.
 
Instead of what I had here I'll approach it from another direction. In my Clymer book under adjusting the points it gives a spec on how far off the mark you can be.
After you set the points timing you check the full advance. You do this by blocking the advance fully open. Now check the timing on the left cylinder. It should be right on the mark. Switch over to the right side. Check timing. "A tolerance of 0,12(3mm) is allowed I either direction from the mark."
Now if I was checking full advance timing on both cylinders to compare them, If the left was right on the mark I would assume it would be ok if the right side was no more than 3 mm ahead of or behind the other.
Now if one side did go past the full mark I might set the idle timing back a bit so the more advanced cylinder didn't go past the mark.
You have a Mike's ignition. Perhaps the rotor is of center a bit or the magnets are off a bit. Perhaps the advance rod is bent. Perhaps one or all of these things are present. Would this move the magnets away from the pick ups for one side to not get a signal as soon as the other?
This is jut a guess on my part. Perhaps someone with more knowledge on this can add a few words of wisdom.
Leo
 
Last edited:
...You have a Mike's ignition. Perhaps the rotor is of center a bit or the magnets are off a bit...

I agree with XSLeo on this. The ignition rotor has 2 pairs of trigger magnets that *must* be precisely placed 180° from each other, and have their magnetic poles in alignment/agreement.

XSChargeIgn-20181017c.jpg

I suspect a manufacturing error...
 
I think u are on to something. Mikes (xs650 direct) sent me an email while ago regarding bad batch of Ignitions and rotors from ignition.
When they sent me the replacement ,I wonder if the new unit was bad also. I have the old original rotor from my first ordered ignition that
fried from a wiring issue I had but solved. Will swipe out the Ignition rotor for my old unit and see if that solves the issue.Thx for the
information guys.
 
FYI, Twomany u nailed it, changed the rotor and bang on ,same reading both sides. The rotor was defective.
Visually looks the same, i dont see any difference or wear pattern but theres definitely something out of spec.
Mikes never did say what the issues were, just that there was a bad batch of ignitions and rotors.
 
If the two magnets weren't the same strength, one might affect the sensor sooner than the other would.
 
Thats a possibility xj. I dont think I ever would have figured this one out if xs650 direct had not responded
to an email I sent that I was having issues with there Electronic Ignition kit. They responded to my email
with this info regarding a bad batch. Im not sure if this was a squeaky wheel gets the oil scenario but
if I had not questioned the issues I was having I may never have figured out what exactly was the problem.
Something strange happened out of this that was an added bonus. I noticed that my left side was down on compression
maybe 10 lbs compared to the right side . 142 Right. 132 Left. My left carb has never run correctly (ran rich) since ive owned the bike
maybe 7-8 years. I finally found a used carb from a 77 and replaced it this spring. Both sides running same now. BUT I think I must have
carboned up the valves on the left side and they werent closing properly therefore compression was down somewhat when I tested.
This is just a theory but with the ignition timing running very advanced on the left side only for the last few weeks and not being aware
I may have burnt of the carbon with the added heat as my compression has now returned and is an exact match to the right cylinder. Fluke,maybe,maybe not, just a theory.But I tested comp more than a few times previously and tday and theres no doubt, its back to normal. Pretty happy about that.
I thought I had wore the cylinder or rings some with all the electrical issues ect I had previously but apparently not!!
 
I believe you guys are really over-thinking this whole thing. That double ended coil fires both plugs every revolution at the same time. If those trigger magnets were unevenly spaced the coil would fire at a different spot every other revolution. Since you're not seeing two timing marks in the light the magnets are properly aligned. Both cylinders are the same, timing-wise, the accuracy of the strobe is being affected by the different polarity between the sides. Are you using the motorcycle battery as the power source for the light? It's recommended by most manufacturers to use a separate, car-sized battery to power the light since the bike battery is smaller and more susceptible to voltage variations while the bike is running.
 
... That double ended coil fires both plugs every revolution at the same time. If those trigger magnets were unevenly spaced the coil would fire at a different spot every other revolution. Since you're not seeing two timing marks in the light the magnets are properly aligned. Both cylinders are the same, timing-wise, the accuracy of the strobe is being affected by the different polarity between the sides...

Excellent points, and correct, Mike.

But, his new rotor corrected the situation.

Opens the door to more overthinking.

The only thing different between left cylinder firing and right cylinder firing is the effective resistances presented by the spark plugs.

Left cylinder on overlap, Right cylinder on compression. The Left plug see about 1 atmosphere pressure, Right plug see several atmospheres pressure. The Left plug will present a lower resistance than the Right plug. This scenario reverses on the next firing.

How can this influence the timing light? Depends on its probe design and the timing light's circuitry.

In both firing scenarios, the currents are equal in both plug wires. But, the relative voltages to ground are not.

An inductive pickup senses the passage of current. Both cylinders will be the same.

A capacitive pickup senses voltage swings. The plug wire on the higher resistance plug will present a greater voltage differential to ground. The plug wire on the other plug may not present enuff voltage to trigger the strobe. Maybe an intentional design feature.

An inductive pickup also has the capacitive feature. It's possible to use an inductive pickup for a capacitive/voltage triggered timing light.

With all that gobbledygook in mind, it's possible to have a timing light that flashes on only the "firing" cylinder, giving the Left/Right distinction.

Ok, that's my "overthink" for today...
 
Mike, thx for your input, yes I do use the bike battery with the strobe. The strange thing was that with the other
Rotor the Timing was not only off by a large degree but it was also unstable and bouncing around a lot,especially on the
left side. So essentially you are correct, the timing was bouncing back and forth. With the replaced rotor the timing is steady, easy to read and exactly the same on both sides. I cant explain it
but something was defective on the unit.I made no other changes other than removing ,replacing and resetting the Timing to 5T specs.
I prefer that setting, bike runs smoother but still responsive. But thats another topic!
 
Last edited:
142 Right. 132 Left. .... Both sides running same now. BUT I think I must have
carboned up the valves on the left side
142 isn't bad. I assume you tested with the engine warmed up and the throttle fully open. If sealing the rings with a squirt of oil doesn;t bring it up you might try de-carbonizing by shooting a spray bottle of water into the carbs w/ the engine running. I think I've read XSLeo's suggesting that.
 
mike in Idaho, You are correct on the coil firing at the same time.
On the rotor there are two sets of magnets. When the left cylinder comes up on compression, one set of magnets trigger the coil, The left side fires, the right don't.
Now when the right side is coming up on compression the other set of magnets trip the coil. Now if these magnets are consistent with the left the timing light will be the same, If they are off, the timing light will show it.
XS650D, I'm not sure you understood what I meant about turning the timing light clamp one way on one plug and turning it over for the other.
On your timing light, you say it has an arrow that should point to the plug. That works when the plug fires with the proper polarity. I'm not sure if it's set for a positive or negative polarity.
Some timing lights can be polarity sensitive. If the arrow is set to read a positive polarity it reads well when the clamp is on a positive polarized plug. . If put on a negative polarity it may not read well.
On a dual out put coil one plug gets fired with a positive polarity the other a negative.
So on one side you need the arrow to the plug, the other away from the plug.
There are ways to determine if your plugs fires positive or negative. Hold the plug wire about a 1/4 inch away from plug, hold the tip of a pencil between the tip of the plug and plug wire, Might have to remove the plug cap to get better access to the wire.
Crank engine watching the spark. It will jump from the wire to the pencil then to the plug.
As the spark jumps from the pencil tip it will be a shower of sparks instead of a solid arc.
I don't recall which way is which but if the shower of sparks is on the plug side it is one way. If the shower of the wire side it's the other.
A bit of a search on goggle will probably find a better description of this process.
Leo
 
Back
Top