Intermittent Problem

[OhmsLaw43]

So, bike started running bad (front cylinder popping and backfiring with no power). Took it to a good shop where he ran the valves and checked my carbs/sync. Bike runs great except for one issue. After running 65 on the freeway, the bike starts to miss and pop again only after about 20-30 miles. If I pull over and sit for about 5 minutes I can restart and go on my way for another 20-30 miles. I’ve replaced all the fuel lines, plugs and cleaned the fuel cap vent all to no avail. Really at wits end on this one. Even changed all the bulbs to led in case this is a voltage issue. At idle fuel pump “clicks” approximately every 3 seconds. My FI bike clicks way more rapidly however don’t know if this is wrong. BTW it’s a 1995 VS800gl with 40k miles

[navigator]

Many times this type of problem (sputtering / backfiring) appears to be fuel related, when it is actually an electrical issue.
Clean your battery cable connections with sand paper and apply star washers to ensure a tight connection.
Don't forget the negative cable connection at the frame near your oil fill cap.

[OhmsLaw43]

I will try those when I get home. Just seems weird that it runs fine for miles and then starts acting up. All when running steady freeway speeds

[navigator]

I suspect vibration at the terminals since you said it was intermittent, it won't hurt to check them.
Let me know what you find.

[OhmsLaw43]

I’m still going to do all the ground connections however I have a different thought as well. Would it be possible for the signal generator windings to be failing when they get hot? I had a bike mech ask me if they might be causing the issue. I’m assuming that they are integral with the stator since I can’t find them anywhere

[hillsy]

Have you checked the fuel pump flow rate? Sounds like it might be a fuel starvation issue if it happens after sustained high speed but then comes good after a "rest".

[OhmsLaw43]

I’ve checked it several times. Almost new fuel pump and when it’s idling I can hear it pumping (1 click ~every 3 seconds). Tightened the negative battery terminal before leaving work and it ran flawless on the way home. There was heavy traffic so maybe not a true test

[Lechy]

One odd-ball fault often overlooked is the resistivity of the earth cable. Remove the cable and flex it especially near the battery side, if you find any stiff or swollen areas replace the cable.
Did you clean out the small filter screen behind the float valve?
The 3 phase wire (yellow) connector between the alternator and regulator should be checked as it tends to heat up and burn. Always best to eliminate the connector and solder the wires together.

[emoji41]

[OhmsLaw43]

Checked all the grounds, replaced the float needle and seat and added star washers to all grounds. Weird thing is that it seems to do it more into a head wind. Could K&Ns cause that? I haven’t cleaned them yet so they are still factory oiled and almost new (less than 300 miles on them). My commute is about 42 miles each way that’s why so many miles so quick

[Lechy]

These bikes were not designed to use the K&N style filters. If you didn't do a re-jet your bike will not run optimally. If you didn't remove the air boxes and still have the OEM filters and boots. try re-installing them to see if there is an improvement.
[emoji41]

[OhmsLaw43]

I didn’t go to pods. Just the reusable K&N filters inside the air box. Bike ran fine with them until this last month. Not saying they couldn’t cause it just adding info

[Lechy]

Re-check the path of the fuel line from rear to front, could be getting nipped when you put the tank on.
[emoji41]

[OhmsLaw43]

It’s nice and loose. I replaced all the fuel lines with factory grade 1/3” od/1/4”id line.

[WintrSol]

Weird thing is that it seems to do it more into a head wind.

This comment goes back to a fuel delivery problem, since it takes more fuel to push against a headwind. Since the front carb fills after the rear, it would be the first to be starved. A clog or sticking ball in the vent of the cap, if a non-Cali model, or an issue with the canister in the Cali model, could cause a vacuum in the tank, restricting the flow. A clogged in-tank screen can also restrict the flow. Either may be tested by running the fuel pump for an extended period with the fuel cap on, to see if the flow begins to drop off.

[hillsy]

I know you said you cleaned the tank vent, but to double check this is working....when the bike starts to splutter....pull over....turn the bike off...listen carefully.....and SLOWLY open the tank cap. If you hear any sort of hiss or pressure relief you might still have a problem.

[OhmsLaw43]

I’ve tried that. Unfortunately when it does it I’m on the freeway. Couldn’t hear it if I tried. Another question, is the signal generator part of the stator on these bikes? I can’t find the coils in any parts store however, I heard they were built into the stator. Anyone?

[OhmsLaw43]

Ok, so went back thru the grounds (all good) and checked voltage at idle. 14.2 vdc however it didn’t go up any when revved. I’m not thinking that’s bad though since my book says 13.7 to 14.2 vdc. I checked the gas cap again and can actually see the little valve moving and it rattles loosely when I shake it. This is getting very frustrating to say the least

[WintrSol]

Ok, so went back thru the grounds (all good) and checked voltage at idle. 14.2 vdc however it didn’t go up any when revved. I’m not thinking that’s bad though since my book says 13.7 to 14.2 vdc. I checked the gas cap again and can actually see the little valve moving and it rattles loosely when I shake it. This is getting very frustrating to say the least

What your meter shows depends a lot on the design of the meter, as much as the regulator in the bike; some show the Voltage actually drop with increasing rpm, after a small rise. Your measurements look typical, to me.

The signal generator is attached next to the stator, and has a two contact connector, with a blue and green wire. The service manual says you should measure between 50 and 200 Ohms between those two contacts. If you have a copy of the service manual, page 3-53 shows two signal generators (the original had two) in the case. Yours should have one, but I can't tell you which position it is, since I never removed that part of the engine,

[Lechy]

[emoji41]

[OhmsLaw43]

It’s funny how the factory manual only shows two while my Hanes manual actually shows both. Anyway, cold I get 125 ohms across the blue/green connector. I’m using an upper end Craftsman multimeter as the wife stole my Fluke. Here is another mystery. Rode in at 60 mph vice 65 and bike went about 5 miles further before acting up. Headwinds still seem to affect it however if I give it throttle it seems to clear up for awhile. Doesn’t act up at all slow speeds. I’m pretty stumped on this one