Misfiring

[Phare Est]

I stored my '81 XS11LH last November and took it out of storage a week ago. The engine almost immediately started misfiring. As soon as the revs pass the 3000 rpm mark, it'll sputter quite noticeably, so acceleration is poor. Also, the bike is difficult to start. I made the following changes, to no avail:

1. Put in new spark plugs.
2. Reflowed the solder the joints in the TCI.
3. Synched the carbs.
4. Replaced the REG/REC with a spare one.

The tach works, so I'm assuming it's not an alternator issue. However, the NEUTRAL light acts strangely. It'll flicker and apparently die, than it'll light back up again. Moreover, it occasionally lights up when the bike is in 1st gear. It did put a new bulb in, but the light still behaves the same.

What could be causing these problems? Ignition coils? Fuel system? Wiring? Thanks for the guidance.

[dansmith65]

What did you do to the fuel system before storage? If you didn't do anything special then I would assume the carbs need to be cleaned.

[MPittma100]

Coils

Check the pickup coil wiring for breaks. Search on this site for how to info.

[Phare Est]

Check the pickup coil wiring for breaks. Search on this site for how to info.

I checked the pick-up coil wires for breaks. They all seemed intact but I replaced all four of them anyway. The engine is still misfiring and sputtering.

I also drained the fuel tank; the petcocks and fuel pump work fine, as far as I can tell. I don't believe the fuel system to be the issue, but I could be wrong. As for the carbs, they were cleaned during the winter and new float bowl gaskets were installed.

It really does seem like some sort of electrical problem. I will be checking the ignition coils with an ohmmeter tomorrow. And even though I reflowed the solder joints in the TCI, it may still be the culprit after all.

Can a torn carb diaphragm cause an engine to misfire ?

[Phare Est]

Ignition coil test

I checked the ignition coils with my ohmmeter. The primaries on both coils give a reading of 2.5 ohms. The secondaries are giving no reading at all (with one probe touching a primary circuit wire and the other probe touching the plug cap contact)... Did I test the secondaries correctly? I'm assuming both ICs need to be changed.

[bikerphil]

The secondary side is tested with one tester lead on each spark plug wire. Unscrew the caps and test without them.

[Phare Est]

The secondary side is tested with one tester lead on each spark plug wire. Unscrew the caps and test without them.

Hi bikerphil,

Thank you! I did as you said and removed the spark plug caps so that the ohmmeter probes could touch the wires. I got a reading of 11.12 ohms (20k setting) on the plug wires leading to cylinders 2 and 3 and no reading at all on the ones leading to cylinders 1 and 4. Does this mean the IC for cylinders 1 and 4 is truly dead?

[bikerphil]

Hard to say, the coil may still operate but something isn't quite right with it. It may or may not be your problem.

[motoman]

I checked the ignition coils with my ohmmeter. The primaries on both coils give a reading of 2.5 ohms. The secondaries are giving no reading at all (with one probe touching a primary circuit wire and the other probe touching the plug cap contact)... Did I test the secondaries correctly? I'm assuming both ICs need to be changed.

81 models use the 3.0ohm coils. With my experience pertaining to these particular secondary ignition systems, 2.7ohms IS the cut-off point of these 3.0hm coils. I'd seriously replace those coils. A good choice and expense saving choice are the Honda VFR 3.0ohm coils. Lots of used ones out there to be had. Just have your ohm meter with you to check the ohm rating, as none of them are marked as such. Reason for checking replacements before purchase is some of them are 1.5ohm coils and some are 3.0ohm coils. These VFR coils bolt EXACTLY in place of the original coils. I did exactly this, keeping the original coil plug-ins by unsoldering wires from original coils and resoldering them onto replacement VFR coils. The VFR coils also use separate plug wires with the plug wire coil retainers. Do NOT use 8mm plug wires, as this WILL split the retaining caps on coils! 7mm high-temp plug wires is what you wanna use, cut to correct length.

[Phare Est]

81 models use the 3.0ohm coils. With my experience pertaining to these particular secondary ignition systems, 2.7ohms IS the cut-off point of these 3.0hm coils. I'd seriously replace those coils. A good choice and expense saving choice are the Honda VFR 3.0ohm coils. Lots of used ones out there to be had. Just have your ohm meter with you to check the ohm rating, as none of them are marked as such. Reason for checking replacements before purchase is some of them are 1.5ohm coils and some are 3.0ohm coils. These VFR coils bolt EXACTLY in place of the original coils. I did exactly this, keeping the original coil plug-ins by unsoldering wires from original coils and resoldering them onto replacement VFR coils. The VFR coils also use separate plug wires with the plug wire coil retainers. Do NOT use 8mm plug wires, as this WILL split the retaining caps on coils! 7mm high-temp plug wires is what you wanna use, cut to correct length.

I will definitely get some new ignition coils and keep you up to date.

[Bonz]

On a bike that ran fine before it was stored, the coils did not go bad sitting there nor did the pick up coil wires. The carburetors are not supplying fuel properly at idle (poor starting) and stutter and stammer when you tell it to go faster. Carbs need cleaned. In the time you’re trying all the rest of the stuff you could have them off and apart and cleaned out, go for it, you will be happy.

[motoman]

On a bike that ran fine before it was stored, the coils did not go bad sitting there nor did the pick up coil wires. The carburetors are not supplying fuel properly at idle (poor starting) and stutter and stammer when you tell it to go faster. Carbs need cleaned. In the time you’re trying all the rest of the stuff you could have them off and apart and cleaned out, go for it, you will be happy.

…..could have, cept' for the existing coils being the primary existing issue.

[skids]

Do NOT use 8mm plug wires, as this WILL split the retaining caps on coils! 7mm high-temp plug wires is what you wanna use, cut to correct length.

I got a set from fleabay and they do work well. There is a lot of crap out there, so buyer beware. Make sure the plugwire caps are included and not damaged. I think mine tested out as 2.7 ohms (not 3.0).

[Bonz]

Maybe I missed something? Sounded like it ran fine before he put it away for the winter?

[Phare Est]

On a bike that ran fine before it was stored, the coils did not go bad sitting there nor did the pick up coil wires. The carburetors are not supplying fuel properly at idle (poor starting) and stutter and stammer when you tell it to go faster. Carbs need cleaned. In the time you’re trying all the rest of the stuff you could have them off and apart and cleaned out, go for it, you will be happy.

The carbs were cleaned during the winter. I tested the primaries on the coils last summer and they both gave a reading of 3.0 Ω. They most likely started to go bad either late last season or while the bike was in storage. The primaries were tested again today : one of the coils is now at 2.4 Ω and the other is still giving a reading of 2.5 Ω. I hope to receive the new coils next week. I will also check those carb diaphragms.