Changing ignitions from TCI to points

I have an 81' xs currently set up with a stock TCI ignition. I've gone thruough everything in the carbs, swapped TCI's and coils and adjusted every idea that has been thrown at me and still can't get past the "bucking" when I get to high RPMs. The bike will not go over 60mph. The left cylindar is burning up the plug while the right side burns perfect.
I believe it is an ignition issue and I have a 72' sitting in my garage with everything I should need to switch to a points set up. I guess I'll trust 70's mechanics over an early 80's electrical system.
If anyone knows of a link or two that will help me set this up on my 81' I would appreciate it.

Both cylinders fire @ the same time I'd put $ on your carbs being screwed up seen it too many times to talk about owners try doing carbs themselves screw them up then after they got the thing so tuned up it won't even run it ends up @ the shop for them to be gone thru and synced

MatRat88,

I'm with sreimer. Both spark plugs are fired at the same time by the same coil, so it is unlikely that you have an ignition problem. (not impossible, just unlikely)

SO, before I would go through all the trouble to install a set of points, I would just swap the spark plug wires and see if the problem stays the same.

If it is ignition related, then it would be something simple, like a bad spark plug or a wire that is not making contact in the coil, or an open plug cap, all of which can be easily fixed.

So, do these steps after you have done the swap wires thing:
1. Install new plugs.
2. Measure the resistance from plug cap to plug cap to ensure continuity and that both plug wires are making contact in the coil.
3. Replace the plug caps anyway because they are all crap after all these years and they can act up when they get hot.

In any event, if you decide to use the points ignition from your other bike, you will have to get the brass bushings and steel Labyrinths from MikesXS because it is almost impossible to remove the bushings without damaging them. You will also have to fab up some brackets to mount the coils.

Thanks for the input fellas. My carbs are synced and were rebuilt by my friend who has done hundreds of these carbs. Not saying his work may not have flaws, but to make sure I threw on a known good set from my buddy's 80xs that is running perfect. I also changed out the coil last night to try and eliminate that out of the equation and it actually ran worse.

So if I am reading your recommendation properly the answer may lie in a new coil? I switched wires from one side to another at idle and nothing changed, maybe switch wires and run down the road? Does any 12 volt coil work with these bikes and how do I test the resistance in my current set? Both sets of coils I have are stock and definitely show their age.

30 year old coils are always suspect. A coil that works okay at idle might break down at speed.

Something I forgot the other day is the hose that covers the spark plug wires. I put new high output coils on and my XS started acting up. I took the rubber hoses off my old spark plug wires and put them on my new wires. Problem solved.

Mad Rat 88,

Well, here is a list of things that can cause porblems at higher speeds or RPM's. They all may not apply in oyur case, but it's a good check list.

One item not on the list is a weak trigger magnet that is inteferied with by the strong magnetic field of the rotor. To test for this condition, unplug the Reg/Rect and see if the problem goes away.

1. Low battery / charging system. A low battery will produce a low ignition voltage at the plugs which is most evident at higher RPM's.
2. Timing. Did you use a timing light to check the timing?
3. N/A
4. N/A
5. Fouled plugs. Did you install new plugs? Check them after you got it running?
6. Plug wire not making contact in the coil. Measure the resistance from plug cap to plug cap to ensure that both plug wires are making contact in the coil.
7. Brakes dragging.
8. Speedo out of calibration. You are actually going faster than 60 MPH! Use your GPS to check the speedo.
9. Tire pressure. Pump up to 32 PSI for high speed.
10. Drive chain too tight. That will rob you of power to the wheels.
11. Enricher plunger stuck partially on.
12. Enricher (choke) left on or partially on.
13. Weak or loose advance springs. Weak or loose advance springs cause the advance to use up some of the available movement because you have to essentially retard the advance to get it on the idle advance mark, so there is less movement available at higher RPM's.
14. Timing chain needs adjustment.
15. Cheap or bad gas.
16. Low octane gas.
17. Water in the gas.
18. Partially blocked pet cock or fuel filter.
19. Paper filter that has low flow when the tank is not full.
20. Try a run with a full tank of high octane, fresh, expensive gas.
21. Blocked fuel cap vent.
22. Incorrect sprockets. What RPM are you getting at 60 MPH.
23. Rear tire rubbing on brake rod or swing arm.
24. High wind resistance. Are you a large person?
25. Throttle cable not fully opening the throttles.
26. Blockage in the muffler(s)
27. Dirty or blocked air filters
28. High altitude
29. Very hot air, like 95+F
30. Very cold air, like 32F
31. Low oil
32. Really dirty oil
33. Gas in the oil

What about running down the road, slowly, on just one cylinder? Then swap the wires to the same cylinder and see if the problem is the same or worse. Now switch cylinders and repeat the test. Should only take you 10 minutes.

hotrdd said:

What about running down the road, slowly, on just one cylinder? Then swap the wires to the same cylinder and see if the problem is the same or worse. Now switch cylinders and repeat the test. Should only take you 10 minutes.

Click to expand...

Just make sure the unused plug wire is grounded. If it isn't then the ignition will get fried.

MadRat 88 said:

I have an 81' xs currently set up with a stock TCI ignition. I've gone thruough everything in the carbs, swapped TCI's and coils and adjusted every idea that has been thrown at me and still can't get past the "bucking" when I get to high RPMs. The bike will not go over 60mph. The left cylindar is burning up the plug while the right side burns perfect.
I believe it is an ignition issue and I have a 72' sitting in my garage with everything I should need to switch to a points set up. I guess I'll trust 70's mechanics over an early 80's electrical system.
If anyone knows of a link or two that will help me set this up on my 81' I would appreciate it.

Click to expand...

I love the points set up, I also love the TCI setup, BUT until you nail down the original problem, you are likely to introduce a second layer of issues in addition to what you already have. Read my tag line below and every time you approach your bike repeat this mantra.

I tested both coils that I ran on my bike. Coil 1 tested at 3.5 ohms through primary winding and didn't move the needle on the secondary. Coil 2 also tested 3.5 through primary and barely made the needle move on the secondary. From what I read on testing coils, the secondary should be somewhere between 10K and 15K ohms...
sound about right???

MadRat 88 said:

I tested both coils that I ran on my bike. Coil 1 tested at 3.5 ohms through primary winding and didn't move the needle on the secondary. Coil 2 also tested 3.5 through primary and barely made the needle move on the secondary. From what I read on testing coils, the secondary should be somewhere between 10K and 15K ohms...
sound about right???

Click to expand...

Wait a minute, something is wrong here. IF this machine has TCI then it should have only ONE ignition coil and this coil will have TWO high voltage wires, one to each spark plug. It would not have two coils.

You're right, it is a single coil with two plug wires. I just had 2 different sets that I tried on the bike.

MadRat 88 said:

You're right, it is a single coil with two plug wires. I just had 2 different sets that I tried on the bike.

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OK, that's better. Back to basics, TCI coils, the primary resistance (low voltage side) is from around 3.5 to 6 ohms. This is measured with the VOM set to Rx1 scale (Mine measured 5 ohms). The secondary resistance (high voltage side) I think is around 15,000 (15K) ohms. This is measured with the VOM set to Rx the highest scale your meter has. I'm not 100% certain that 15K is the number but it's somewhere in that area. If anyone has the exact number, jump in here. Basically with TCI systems, because one coil fires both spark plugs at the same time, if one cylinder runs, the coil is good.
In a earlier msg you said one cylinder (spark plug) runs OK but the other (spark plug) burned up. Is this really what is happening? Because this implies the burnt cylinder(spark plug) is running extremely lean.

Yeah, that's the deal. The one time I actually ran wide open with no problems the plug on the right was burning a brown color and the left side black and a hint of oil. The left side is also consistently back firing, more as the bike gets hotter but not at all on the right. I have new carb holders and exhaust gaskets in the bike, no idea where its sucking air if that's the deal.

MadRat 88 said:

Yeah, that's the deal. The one time I actually ran wide open with no problems the plug on the right was burning a brown color and the left side black and a hint of oil. The left side is also consistently back firing, more as the bike gets hotter but not at all on the right. I have new carb holders and exhaust gaskets in the bike, no idea where its sucking air if that's the deal.

Click to expand...

No, wrong colors. If one side was burning up the porcelain insulator would be white/light gray (some times silver) with tiny metal bits melted into it. There would be signs of melting on the ground and on the electrode. Light tan is the ideal color. Brown/chocolate is rich. Black (soot) is extremely rich/flooding, black (shiny) extremely rich/flooding again and/or burning oil.

On the TCI coils the primary side is 2.5 ohms. The Secondary side 10.5K to 15.5K ohms. Infinity between the primary and secondary.
Leo

Did you do a compression test on both cylinders?

plus 1 on the compression test. especially because you said "one plug had a hint of oil". if the carbs are assumed good (and you've tried a different set with same results) and switching the plug leads doesn't move the problem, it's engine related, not spark or fuel.