72 Eldo misfiring (?)

[BrianK]

Looking for suggestions.

72 Guzzi Eldorado, well-maintained albeit all-too-seldom ridden.

Stored without gasoline last winter, drained the tank as best I could, turned off the petcocks, drained the float bowls.

This season, have only ridden a couple times but having issues.

Starts up and runs fine, mostly.  But intermittently it will feel, for a few seconds, like it's running out of gas - and then zooms back as though reserve had been opened.  Neither is the case.

Pulled the plugs and the right looks fine, left is carboned up a bit.

Replaced plugs, same result.

Checked plug wires, fairly new NGKs, they both ohm out nicely to ~5K ohms.

"Feels" like an electrical problem, although I know 95% of electrical problems are in the carbs, or is it vice-versa?

Still trouble-shooting but would welcome any thoughts.  May have the mechanical blinders on.

Thanks as always folks. - BK

[normzone]

I had the exact same bike, and the exact same problem.

It drove me mad as I tried all the logical fixes.

Finally figured out that itsy bitsy teeny tiny rust particles from the tank were getting past the inline fuel filters I'd installed and collecting in the float bowls, where periodically a few of them would jump up into the jet and clog it momentarily.

My solution was creme coating the tank, and it solved all. These days I would probably acid wash it or something, I missed the fuel capacity the creme coat displaced.

I guess your verification of this would be pulling the bowls and looking for tiny hints of rust.

[John A]

Could be a wiring problem. An intermittent open in power to the coil or a short in the points wire.. Could be condenser or coil failing. Intermittent problems are where the fun is . Check for fuzzy fuses , I found with that type of fuse they can grow fuzz on the ends so I just rotate them without taking them out. Could be a float needle sticking . Watch it run in the dark so you can maybe see if spark is escaping from plug wires. Could be a plugged tank vent. You’ll find it….

[eldointheweeds]

I had the exact same bike, and the exact same problem.

It drove me mad as I tried all the logical fixes.

Finally figured out that itsy bitsy teeny tiny rust particles from the tank were getting past the inline fuel filters I'd installed and collecting in the float bowls, where periodically a few of them would jump up into the jet and clog it momentarily.

My solution was creme coating the tank, and it solved all. These days I would probably acid wash it or something, I missed the fuel capacity the creme coat displaced.

I guess your verification of this would be pulling the bowls and looking for tiny hints of rust.

Had the same issue on a long trip in 1984 so my memory may be fuzzy. Fixed it by pulling the bowls and poking a sewing needle though the jets.

[BrianK]

Some good suggestions; thanks folks. 

I can rule out the cap vent - tried that first thing, got gas on my pants and no change in bike behavior!

The rest, I will start working through....   Fun stuff.

[pehayes]

There are pencil-diameter filters inside the fuel tank on top of the petcocks.  Remove and clean.
There are coin-sized disc filters on the side of the carburetor (DelLorto).  Remove and clean.
Blow vigorous air through every carb port.

Patrick Hayes
Fremont CA

[guzzisteve]

Might help to just clean points w/a soaked card. Check off the list. Check off the list----------do a shot, by the time you get done, you'll need a rest.

[BrianK]

Thanks all.  Working my way through the list....  Wish me luck. 

[Tom H]

Thinking about this... Others have mentioned very good starting points.

I would take a close look at the carbs with the bowls off. A dry bowl can get a dried build up on whatever is inside. Could be a float or float needle sticking or a bit of debris going through the jets. As mentioned, carefully using jet cleaning wire tips or a sewing needle or the like I would clean the jets. Heck once the bowl is off, just pull the jets for the cleaning. Then while they are off, take some carb cleaner and squirt it in the holes where the jets go.

Tom

[normzone]

There are pencil-diameter filters inside the fuel tank on top of the petcocks.  Remove and clean.
There are coin-sized disc filters on the side of the carburetor (DelLorto).  Remove and clean.
Blow vigorous air through every carb port.

I remember those - the rust particles I was battling were small enough to get past both of those, AND some aftermarket inlines I installed.

OP's description of the issue sounds as though it may be the petcock/carb filters described. 

[John A]

I remember those - the rust particles I was battling were small enough to get past both of those, AND some aftermarket inlines I installed.

OP's description of the issue sounds as though it may be the petcock/carb filters described. 

The only carbureted bike I have left is a V65 with PHF 30’s. Every so often the tank screens and the inline filters and the screens on the carbs get plugged enough to cause running problems. Mostly at idle but it is something I have to clean once or twice a year, especially because it’s not ridden much.

[Kiwi_Roy]

Could well be rust in the tank plugging the petcock filtersCan you remove the tank swill around the fuel and dump it into a bucket via the fill hole to see if there/s any rust