I need help with my 1978 G5 regarding a misfire

[FISSELtheMISSILE]

Hello all-

THE HISTORY: I've got a 1978 Guzzi V1000G5 that I got with just over 2400 miles on it about 6 years ago. It had sat for a very, very long time in a NYC garage, then for a short time in NE Pennsylvania before I got it. Upon receiving it I rebuilt the carbs & all the hydraulics, changed all the fluids, installed new air/oil filters, new battery, new cables, tires & a couple other little things. Then I rode the hell out of. It's been on lotsa long trips like up to Montreal for the F1 race on four separate occasions. It now has nearly 14,000 miles and prior to the current issue has been rock solid. About two years ago I removed the factory airbox in favor of a K&N and rejetted (this mod made a tremendous difference in power, almost unbelievably so) but otherwise have only done regular maintenance.

THE PROBLEM: Last Fall I was heading down to Richmond VA when I developed a misfire which at first cut in & out then got progressively worse (more constant) all over the course of about 40 miles. I barely made it to my destination & had to have a family member truck the bike & I back to Delaware. I looked over everything and one coil was testing pretty erratically (they were the original oil filled units called "Klitz" I think) So I ordered new coils, plugs, wires & caps & installed everything- still missing. Checked the points (which only had perhaps a 1000 miles on them & found them to be a little out of adjustment so I adjusted them & confirmed static timing was perfect- still missing. Double checked compression, 168# on the left and 172# on the right (bike was just under 175# on both cylinders when I got it with 2400 miles) & installed new condensors- still missing. Removed the carbs to find no problems, everything was clean, reassembled- still missing. Went totally crazy inspecting and ohming out the entire wiring circuit, found lotsa carbon on the ignition switch, installed new ignition switch- still missing.

Anyone got any ideas? Most of the inquiries of this nature in the forum stem from Dyna Ignition issues with some people removing the electronic ignition in favor of points- BUT I ALREADY HAVE POINTS, so that's not my issue.

Any help is much appreciated,

Fissel

[oldbike54]

 Sorry if I missed it . Is it missing under load , or all of the time ?

  Dusty

[FISSELtheMISSILE]

Sorry if I missed it . Is it missing under load , or all of the time ?

  Dusty

All the time. At first it was sporadic (loaded or not) now its all the time, totally unrideable.

[oldbike54]

 Do the plugs look the alright ? Both the same ?

  Dusty

[FISSELtheMISSILE]

Do the plugs look the alright ? Both the same ?

  Dusty

When plugs were removed they looked pretty similar. I installed new plugs with the coils and it hasn't run enough since then to show any difference.

[oldbike54]

When plugs were removed they looked pretty similar. I installed new plugs with the coils and it hasn't run enough since then to show any difference.

 Were the plugs that you removed a nice tan color ? Have you tested the new condensors ?Two new replacement condensors on my old beemer were bad . I'm guessing the carbon buildup on the ignition switch is an indication of the root cause .

  Dusty

[fotoguzzi]

 you have a sidestand switch?

[lucian]

Does it have a kill switch that could be shorting. Sounds like an ignition short somewhere.

[nunzio]

Charlie M. lives near you...He's really good!!!

I live in Texas so "near" is relative..

[mtiberio]

One or both cylinders missing? Interested because my convert does same. Its in an eldo, so I have other distributor option. But I like the stock advance curve better

[Groover]

+ 1 on checking the new condensers. I also got a bad new one. Easy way to check them is to look at the points while the bike is running; If there is one sparking out, then that's the circuit with the bad cap.

[chuck peterson]

Try running it in a dark garage looking for misguided sparks...

Too much anti sneeze?

[FISSELtheMISSILE]

you have a sidestand switch?

No, side stand switch failed a couple years ago, I removed & bypassed it. Sorry I failed to mention that.

[FISSELtheMISSILE]

+ 1 on checking the new condensers. I also got a bad new one. Easy way to check them is to look at the points while the bike is running; If there is one sparking out, then that's the circuit with the bad cap.

Just did this, the right cylinder points seemed to be sparking a touch more than the left cylinder. Disconnected the condenser & it sparked about the same as with it. Could be condenser then? Whats the chances the old condenser was bad & the new one is too?

Maybe the brains of this forum could help me make a laundry list of everything I should order to try to get it sorted & I'll order everything Monday morning.

[FISSELtheMISSILE]

Were the plugs that you removed a nice tan color ? Have you tested the new condensors ?Two new replacement condensors on my old beemer were bad . I'm guessing the carbon buildup on the ignition switch is an indication of the root cause .

  Dusty

Plugs I removed looked pretty decent, not super black or anything.

Carbon build up on the switch really wasn't that bad, in hind site it was probably wishful thinking that it could've been the problem. I think I kept it, I'll see if I can find it and snap a pic.

[nunzio]

You could rewire it for a total loss system with new wires.

This eliminates all possibilities but the basics.

It consists of only a few wires.

Mr. Greg Bender could help you with this....Alan

[oldbike54]

Just did this, the right cylinder points seemed to be sparking a touch more than the left cylinder. Disconnected the condenser & it sparked about the same as with it. Could be condenser then? Whats the chances the old condenser was bad & the new one is too?

Maybe the brains of this forum could help me make a laundry list of everything I should order to try to get it sorted & I'll order everything Monday morning.

 I would simply go to a parts house and buy a couple of condensors and make the appropriate wiring changes . Start there .

  Dusty

[FISSELtheMISSILE]

Does it have a kill switch that could be shorting. Sounds like an ignition short somewhere.

I checked out the kill switch when I checked the rest of the wiring. Seemed a-ok. I seem to be getting a reliable 11-11.5 volts measuring at the coil which should be more than adequate.

[FISSELtheMISSILE]

I would simply go to a parts house and buy a couple of condensors and make the appropriate wiring changes . Start there .

  Dusty

I'd rather just order stock condensers, unless someone knows a readily available suitable sub with the same microfarad rating and comparable cable arrangement.

[oldbike54]

I'd rather just order stock condensers, unless someone knows a readily available suitable sub with the same microfarad rating and comparable cable arrangement.

 The problem there , you have already tried new stock ones . I have had much better luck with the comdensors available at auto parts houses . Easy enough to change out the ends .

  Dusty

[nunzio]

I checked out the kill switch when I checked the rest of the wiring. Seemed a-ok. I seem to be getting a reliable 11-11.5 volts measuring at the coil which should be more than adequate.

A voltage drop could be so quick you would NOT catch it with a volt meter...unless you have an oscilloscope.

[FISSELtheMISSILE]

A voltage drop could be so quick you would NOT catch it with a volt meter...unless you have an oscilloscope.

I'll hard wire the coils straight from the battery tomorrow to be certain, but I really don't think this is the problem.

Good to be 100% sure though......

[oldbike54]

I'll hard wire the coils straight from the battery tomorrow to be certain, but I really don't think this is the problem.

Good to be 100% sure though......

 A philosophical point here . Since you don't know what is wrong , keep an open mind .

  Dusty

[Toystoretom]

You might take a fuel sample to see if you got some water or diesel mixed in at your last fuel stop. Also check the fuel flow at the carbs, possibly there is a blockage starving your carbs.

I don't think you ever did tell us if it is just one side or both sides.

[Groover]

If you still have the old caps, one of them should still be good from what you described. If so, you can clamp the old caps to ground, and then screw the terminal/wire to the right side points. At this point, you'll have two caps in parallel (so temporarily disconnect the one on there now) and if the old cap is still good, then the sparking should be gone (or drastically reduced) at the right side cylinder points. If one doesn't change things, then try the other old one that same way. (In case the 1st one you try ends up being the also bad one).

I had a similar issue when I first got my bike. It was cutting out, so I replaced points and condensers. Still kept cutting out and then I started changing the coils, then this and that, but the problem was that I installed a bad/new cap so of course I keep going, but it was just a bad cap and would have been done right away if the cap I bought had not been defective.

Hard to find, but if you dig a little you may be able to find some old stock OEM Magneti Marelli caps. Even if used, I'd take them over some cheap ones out there.

When you unplugged the cap during your test, did the engine cut out more or was it the same? If the same, then it definitely sounds like that is where the problem is to me. Try the left side too. A tiny bit of sparking at the points is normal especially at higher RPMs.. Hard to quantify it, but when the caps are good you'll see a tiny spark say every 30 revolutions of that cylinder, whereas it will be at almost every revolution of that cylinder when a cap is bad.

Hope that helps.

[FISSELtheMISSILE]

You might take a fuel sample to see if you got some water or diesel mixed in at your last fuel stop. Also check the fuel flow at the carbs, possibly there is a blockage starving your carbs.

I don't think you ever did tell us if it is just one side or both sides.

Ah, two more things I failed to mention, after removing and checking the carbs I drained the old gas into my mower and refilled with fresh VP Vintage racing fuel that I use for my Gilera & race bike. Gas ins't the problem.

Also, the miss is coming from the right cylinder.

Sorry I missed those two tidbits.

[lucian]

When you replace the capacitors I would also slap in some new points as the old ones will likely have developed a carbon track to earth.

[FISSELtheMISSILE]

When you replace the capacitors I would also slap in some new points as the old ones will likely have developed a carbon track to earth.

I took them out & checked them over when I adjusted them & checked the timing. They look very clean, as new.

[acogoff]

     You could string a new wire from the dizzy to the right coil and eliminate a wonky crimped end or corroded wire. Easy enough. A timing light on the right spark plug wire would tell you if you have a spark at least as far as to the spark plug. If that checks out, next would be a valve train look see, I guess.

[atavar]

This might be way off base but check compression.  Symptoms sound a LOT like what happened to my G5 when a head bolt stretched.  Are you getting any oil in the fins?