Timing impossible, acceleration impossible.

[BSomerfield]

I've been fighting with this bike for 3 months now and it's still running like crap.
I cannot set the timing. Trying to move the white line to the F marker cannot happen. If I try to adjust while running using a timing light, the line can only move further from F no matter which direction I go.
I also keep popping my carbs off the engine somehow. The mixture is somehow both too rich and not enough because I cannot get acceleration. I have it full throttle and it didn't go above 1500 rpm. The times it does throttle up are random and usually after holding the accelerator fully open but with no control of when it'll end.
At this point I don't even know what question I'm supposed to ask to get an answer. Just tell me what to do.

 

[Its been a long time]

What exactly is the bike and what is the ignition system please?

 

[BSomerfield]

73 tx650 with points ignition

What exactly is the bike and what is the ignition system please?

 

[Its been a long time]

73 tx650 with points ignition

At what engine RPM are you trying to use the timing light? F is the retarded timing marker and anything faster than tick over could be advancing the ignition. So you would never be able to set to the F marker.

Is the auto advance unit in good condition? Are the springs pulling the bob weights back properly? Are the points gaps set correctly?

 

[BSomerfield]

I think the auto advance is in good condition and the points gap is set to just above .3 mm

I am attempting to set the timing at the lowest possible idle which is 1000 but the bike constantly dies at that rpm. That's when the right carb pops off the bike.

 

[BSomerfield]

These are the carbs I have.

 

[Wingedwheel]

What condition is your cam chain in?

 

[Its been a long time]

I think the auto advance is in good condition and the points gap is set to just above .3 mm

I am attempting to set the timing at the lowest possible idle which is 1000 but the bike constantly dies at that rpm. That's when the right carb pops off the bike.

Can you set the timing to the F mark statically with the bike not running. Using a multimeter or a test bulb?

 

[gggGary]

start with static timing using a small 12 volt bulb
synch carbs by eyeball. with idle screws matched and idle speed screws matched throttle cables should both start pulling at the same time.

 

[WideAWAKE]

All of my XSs have likes to idle at 1200-1500rpm

Also make sure your timing light doesn’t have an adjustable knob that will advance the timing mark. If it does, make sure it’s set to zero.

 

[BSomerfield]

At the moment, idle is a fully open throttle and anything less than that the bike dies.

 

[BSomerfield]

So I guess I don't care about timing anymore, I just need to know why my carbs can only deliver fuel when the throttle is completely open

 

[WideAWAKE]

What happens when you put the choke on?

 

[WideAWAKE]

Carbs need to be synched as stated

Diaphragms in good working order.

 

[BSomerfield]

The choke doesn't do anything.

I've been working at syncing the carbs but I don't know what that means. Am I just setting the idle screws to a slight open position? Am I just setting them to sync acceleration? Does setting the jets require syncing as well? Do the floats need to be adjusted somehow? Is there any hope I can do that without a rod connection the two carbs?

 

[Its been a long time]

So I guess I don't care about timing anymore, I just need to know why my carbs can only deliver fuel when the throttle is completely open

You need to care very much about the ignition timing or nothing else can work properly. My suggestion is to go right back to basics. Check the auto advance is working properly and the springs are fully retarding the bob weights. Check the advance rod is lubricated and free to move. Then set the top set of points statically to the F mark. Then the other set too. Check the points gap is OK. It's really essential to get this right before you use a timing strobe light.

By doing this you should have no problems timing at the F mark. Only then should you worry about the carburettors. Hope that helps you.

Let us know when you've done this.

 

[Wingedwheel]

The reason I asked about the chain is because if it’s too stretched you won’t get it timed. Set the pin on the advance at
12 o’clock and see where the timing mark is. Pretty easy to do and might save some frustration.
Also here’s how to bench sync your carbs.

 

[BSomerfield]

You need to care very much about the ignition timing or nothing else can work properly. My suggestion is to go right back to basics. Check the auto advance is working properly and the springs are fully retarding the bob weights. Check the advance rod is lubricated and free to move. Then set the top set of points statically to the F mark. Then the other set too. Check the points gap is OK. It's really essential to get this right before you use a timing strobe light.

By doing this you should have no problems timing at the F mark. Only then should you worry about the carburettors. Hope that helps you.

Let us know when you've done this.

The points cannot be set statically to the recommended "just getting ready to open" position. Either one is open or the other is and the opposite one is closed. I've moved the points, half plate, and the full plate to every conceivable combination of positions and it cannot be set at the F mark. So the next best thing I've been able to do is set the gaps, then set the timing as close to F as possible. It's still very far from F but there's nothing I can do about that.

If the timing is off can it cause the issue I've described where turning the throttle all the way open only gives the engine barely an idle? I really want to know what's causing that issue.

 

[BSomerfield]

The reason I asked about the chain is because if it’s too stretched you won’t get it timed. Set the pin on the advance at
12 o’clock and see where the timing mark is. Pretty easy to do and might save some frustration.
Also here’s how to bench sync your carbs.

"Set the pin on the advance at 12 o’clock and see where the timing mark is."

I don't know what this sentence means. Also, this method of carb tuning in the video doesn't work with mine because there's nothing connecting the two carbs together. I have to tune them individually while they are attached fully to the bike.

 

[Its been a long time]

The points cannot be set statically to the recommended "just getting ready to open" position. Either one is open or the other is and the opposite one is closed. I've moved the points, half plate, and the full plate to every conceivable combination of positions and it cannot be set at the F mark. So the next best thing I've been able to do is set the gaps, then set the timing as close to F as possible. It's still very far from F but there's nothing I can do about that.

If the timing is off can it cause the issue I've described where turning the throttle all the way open only gives the engine barely an idle? I really want to know what's causing that issue.

Personally, I'd not do anything until I had understood the cause of what you describe. Nothing else will work properly until you can set the static timing properly. There's any number of reasons why the static timing can't be set. It's a case of working methodically through checking everything as you go until you understand what the problem is. My own opinion is that until you do this, it's pointless worrying about anything else.

Good luck with it, you'll get terrific support here. I had great help from members when I was checking and fixing the points ignition system on my 77 XS650D. The main problem I had was a too stretched auto advance spring and the advance rod being timed 180 incorrectly.