Points open way too early

[kevith]

Hi everybody.

This is my first post here after enjoying all the knowledge gathered here as a reader only.

I´m 56, live in Denmark EU, and rode an XS 25 years ago. Now I´ve picked up one again, a ´77, and has done an intake rubber and cam chain change. I´ve put it all back together, and all I need to do now is adjust valves and ignition.

And here´s my problem: When I try to set the ignition timing, everything is WAY off. I´ve set both points to open 0,35 mm. So now I´m to set the timing with the backplates. I use a piece of Rizla cigarette paper to determine when the points opens. In the old days that used to be fine to get it running, and then fine adjust with a timing light.

But when I try to set the timing, I can see, that the points for the right cylinder opens half a revolution before they should, when the timing mark on the rotor is opposite to the F-mark...!

I really can´t see or figure out what I did wrong. Is there any one here, that can?

Thankas

 

[TwoManyXS1Bs]

Welcome to the forum, kevith.

What you're describing would indicate a camshaft 90° out of time.

Did you use the correct cam sprocket indicator notch during camchain install?

 

[XSLeo]

Are you sure you are timing the right set of points?
The right set of points is the upper set. The ones on the full breaker plate.
The left are the lower and on a half breaker plate.
Leo

 

[kevith]

Welcome to the forum, kevith.

What you're describing would indicate a camshaft 90° out of time.

Did you use the correct cam sprocket indicator notch during camchain install?

Thanks, 2M. Yes, I would say so, I used the long, deep groove, put the shaft on so the groove is on the LHS and set it vertical with the timing mark on the rotor aligned with the T-mark on the stator.

I know, that you can put the advancer unit wrongly on, but the line on the advancer itself and the line on the advancer backplate lign up just fine.

 

[kevith]

Are you sure you are timing the right set of points?
The right set of points is the upper set. The ones on the full breaker plate.
The left are the lower and on a half breaker plate.
Leo

Hi Leo. Yes , I´m aware of that. After I set the points gap, I started working on the upper - RH - set of points. The ones on the big plate.

 

[retiredgentleman]

Quote:
"But when I try to set the timing, I can see, that the points for the right cylinder opens half a revolution before they should, when the timing mark on the rotor is opposite to the F-mark...!"

I think you are mistaken. The points close (not open) about half a revolution before the
F mark. 93 degrees dwell = 186 degrees of crankshaft rotation.

If its really happening as you say, then maybe you have the advancer rod pins reversed with respect to the slotted disk.

 

[kevith]

Quote:
"But when I try to set the timing, I can see, that the points for the right cylinder opens half a revolution before they should, when the timing mark on the rotor is opposite to the F-mark...!"

I think you are mistaken. The points close (not open) about half a revolution before the
F mark. 93 degrees dwell = 186 degrees of crankshaft rotation.

If its really happening as you say, then maybe you have the advancer rod pins reversed with respect to the slotted disk.

Could look as 186 degrees, a tad more than half a revolution. But they do in fact open at that point, not close.

If I look at that advancer side, there is a mark on the backplate, that - as far as my knowledge goes - should line up with a mark on the advance unit itself, which it does.

But as far as I can see, IF I were to turn the advance unit 180 degrees, it would seem to solve the problem. I´m just a little hesitant to do so, as I think it´s wrong according to the Haynes manual.

 

[5twins]

Check the locating pins on the advance rod for the advance disc and the points cam. They should point in the same direction. If they point 180° from one another, your timing will be 180° off .....

You don't need to remove the advance unit to fix this, just the advance disc or points cam on the advance rod. Remove one of those and change it's pin location so it matches the one on the other end. The holes in the advance rod ends for the locating pins go all the way through. That means the pins can be installed sticking out either side of the rod. I usually make my changes on the advance disc end.

 

[kevith]

Check the locating pins on the advance rod for the advance disc and the points cam. They should point in the same direction. If they point 180° from one another, your timing will be 180° off .....

You don't need to remove the advance unit to fix this, just the advance disc or points cam on the advance rod. Remove one of those and change it's pin location so it matches the one on the other end. The holes in the advance rod ends for the locating pins go all the way through. That means the pins can be installed sticking out either side of the rod. I usually make my changes on the advance disc end.

I will check that. I think you might be on to my error. I actually did try to reverse the points cam, as that would solve the problem, but the little guide pin can only be inserted from one side, there is a small recess in the one end, that acts as a "stop", so the pin won´t fall through.

But I will look into the advance side and et you all know how it went.

It´s 6 p.m. here now, so it´s probably going to be tomorrow.

Thanks so far all of you.

 

[TwoManyXS1Bs]

It's also possible to install the points cam backwards, with its shoulder outboard. The shoulder should be inboard...

 

[grizld1]

OK, folks, let's cut to the chase. The points should open near the "F" mark, that's when the ignition fires. The question is whether the ignition is firing on the piston that's on the exhaust/intake cycle (valves open) or the piston that's on the compression/power cycle (valves closed). Just trace the ignition wires to the coils so you know which point set fires which cylinder, pull a valve cover, line up the timing marks, and inspect the valve lash on the cylinder with the points that are opening. Wiggle a rocker; if the ignition is out of phase, both valves will be open, with no rocker movement detectable. If the ignition is correctly assembled both valves will be closed, and the rocker will have a bit of movement. If the ignition is out of phase, the quick fix is to switch the plug leads from one side to the other.

 

[kevith]

Hi again.

So, it seems I´ve got it right this time. I took it all apart, and reassembled it, considering all the very informational inputs here from all of you.

As 2M suggested, I had put the cam on backwards. I put it on correctly and made sure it was the right stroke I was working on, by checking the rockers, and now everything is just the way it should be.

You have all contributed with very helpful information and even drawings, thank you very much!

B.r.

Kent