Need help with timing.

[Luke M]

I need some help setting the timing on a 78 XS400 guys. I followed the instructions in the manual but the timing seems to be still completely off. I loosened points A and attached a test light to point B. I spun the motor over so that it is aligned at the "LF" mark. Before"LF" and after the line the light still stays on. I cannot rotate the plate enough to make the light go off before the "LF". Any ideas on what can be done to set the timing? I went ahead and removed the screws at point "A" and removed the plate and spun the motor to see if I can get the light to stay off before the line after "LF" but still no dice. Help would be greatly appreciated please. I'm a complete XS newbie so please bear with me.

 

[HoughMade]

Have you seen this:

 

[Drewcifer]

Jesus. This is way too complicated!!!!!!!

Rotate your crank until the left side is at the top of the compression stroke (will push air out on your thumb if you cover the hole) That means it should fire at the top at LF. If you put a drink straw in the plug hole it will move upwards with the piston... Make sure it's when the PISTON is up, and the valves are closed (pushes air on your thumb over the plug hole)

You put a plastic wrapper made out of cellophane between the points. Tug gently on the plastic. When it gets to LF, the plastic should suddenly be released, and your spark should fire between the point gap.

I rotate until I get to TDC left side, then rotate backwards until I can't see the LF mark. Then I put cellophane between the points. While tugging gently on the cellophane, i roll the crank forward until I see the LF again, and the cellophane should be released when LF is below the arrow. That's all there is to it. Do the same on the Right side. You're done.

You can gap them easily. If they aren't opening at the right time nothing will matter.

Ride safe.

Drewcifer

 

[Luke M]

Have you seen this:

Yes I followed this. The timing is still way off, there doesn't seem to be enough adjustment in order to set it correctly.

 

[HoughMade]

Are you sure that the plug or coil wires aren't switched?

 

[Drewcifer]

Are they OPENING at the correct time? that's what the cellophane test verifies.

Luke, hang in there, it's maddening trouble shooting ignition because it's a primal need to feel the bike START at least. mine was off a bit two weeks ago. I did my carbs and found an issue inside. So it's going to take searching, but if you do the due diligence, we've got your back.

 

[Luke M]

Are you sure that the plug or coil wires aren't switched?

I plugged them into the same exact place they were plugged into when the bike ran. I don't think I switched them.

Are they OPENING at the correct time? that's what the cellophane test verifies.

Luke, hang in there, it's maddening trouble shooting ignition because it's a primal need to feel the bike START at least. mine was off a bit two weeks ago. I did my carbs and found an issue inside. So it's going to take searching, but if you do the due diligence, we've got your back.

I got the video link you PM'ed me, helped but it still didn't solve the issue. The bulb goes off when the line for LF is crossed. For RF the bulb goes on when the RF line is crossed. I followed the manual verbatim. What is killing me is that the bike ran before, and now I cannot start it with the timing set to what the manual says to set it.

 

[drewpy]

What is killing me is that the bike ran before, and now I cannot start it with the timing set to what the manual says to set it.

are you sure the engine is in compression when they do that or 180' out?

 

[Drewcifer]

yeah, make sure piston is on it's way up and air is pushed out the hole if you cover it with your thumb. That's the compression stroke.

Now if its NOT the timing then, as my dear old bro says, "What's the last thing you fucked with before it stopped running?"

Think analytically. you might have removed a battery retaining nut...loosened a fuse, or disconnected a connector...

 

[Luke M]

I used the thumb trick over the spark plug hole to make sure I'm on the compression stroke. I haven't changed anything prior to doing the timing.

 

[Drewcifer]

Okay, then eliminating that will be easier. If you kickstart it in the dark, and you have a spark plug removed from the engine, but attached to the plug wire, and the electrode tip still touches the engine case, there should be a visible spark on each side when you try to start the bike.

Verify that you are getting
air
spark
and gas.

Also check your fuses.

 

[RevrdMark]

I had a similar problem with the points after i took the top end off for repairs. It ran fine before then nothing after. Two things that were a problem for me: 1st, i put the cam in 180 degrees backwards so it was firing at the exact opposite time it should. I fixed that. 2nd, when i took the points off, i moved the gap between them so that even when the timing was close the gap was so messed up they never separated. I re-gapped the points then reset the timing per the manual and it worked fine, but it was a long few days tracking those issues down. Hope it helps. I posted a couple things about it in my build log might look through it and see if it helps (Click here)

 

[Drewcifer]

Rvrd Mark is absolutely right.

First, you spin the WHOLE circular points plate until the LF line to the right of the LF letters is when the points open. You can do the cellophane test or the light test. You will have two major steps for each point. 1. Getting the point plate in the right rotation. two, getting the gaps in the right gap.

I do my points the same way each time. I roll them to where they close as the piston is rising. They close to build voltage like a slingshot being pulled back. At the top of the stroke, they open just a speck, an almost invisible amount. You will hear the spark "crack" if you do it correctly. The bike as to be keyed on for this test.

KEEP YOUR BATTERY ON THE TENDER DURING THE TESTING so you don't lower it's charge.

After the left side is dialed in to your satisfaction, now you LOOSEN the screws that rotate the right points plate. On mine counter clockwise made it late, clockwise made it early. When it's close to right, you go around again until it's the compression stroke and move the gap until it sparks as the RF line crosses. This isn't EXACT! The worse that can happen if you're a tiny bit off is the bike loses a few psi of compression at normal speeds and might be less peppy above 6k.

Until I get my timing light I can't get my timing perfect. So keep at it. Even badly timed correctly gapped points will run.

perfectly timed poorly gapped points will not! LOL

Good luck

Drewcifer

 

[drewpy]

or use a dwell meter and a strobe lamp, its important to ensure both points have the same gap and timing.

 

[Luke M]

Ok guys, I ended up changing the worn points with a new set and the bike starts on the first kick now. The only problem I'm experiencing is that the bike dies when any throttle is applied. It idles fine and runs fine without the choke, but when throttle is given it dies. The carbs are clean, and the bike ran fine prior to replacing the points. The left exhaust pipe is also way hotter than the right after a minute of idle. The right pipe and right side of the motor is warm while the left pipe and side of the motor is extremely hot in comparison. Any ideas?

 

[Drewcifer]

Yes, you might have an issue with having accidentally advancing the timing on that side.

Your bike might, like mine, be so old that you need to remove some metal to allow it to rotate in the timing chamber for the left setting. Mine was too tight fitting to really turn, and I had to make sure the replacement screws didn't prevent the right timing from moving around because they were too long. If you pull apart the timing plates you'll see what I mean. JUST MARK EVERYTHING AND I MEAN EVERYTHING FIRST! Make marks for where everything overlaps EVERYTHING.

good luck

 

[ondrej91]

Hello guys, I have same problem like LukeM, but I can't solve it.. My bike runs fine on left cylinder, but right cylinder is misfiring into exhaust when i start the bike.

so I check timing, set the left cylinder first, was little bit late, now is ok, but i can't set right cylinder properly, it's firing somewhere after RT mark, i think the plate need to be rotate more into right, but there is bolt for left cylinder and it blocking the rotation..

should be the problem in gap setting..?

 

[hypnogen]

I was setting the ignition timing yesterday on my 79 XS400 using 12V bat + 5W bulb circuit that I connected to the relevant spots (1st - ground, 2nd contact breaker plate exacly like it is at the picture above)... but the bulb was on even the contact points were separated! just at half power ... when contacts connected, it was shining at full power. It was doing so for L and R as well. I took the change between half and full shine of the bulb as the (dis)engaging point relevant to LF/RF setting. Bike is running well, but what it's suppose to mean? Is the condenser dying or the coil(s)? Thanks for help.

 

[Jester401]

Could be a bad coil on the right side. Not that I don't believe you but are you sure your carbs are clean? Is the arm for the points on that side loose? From experience here...its probably something you touched...lol