'76 Yellow Wing - Winter '24/5 Project is On

[NotSoLilCrippseys]

Leonard: I hope your bike is out and about soon enough. I was sure you'd have yours on the road first, especially given my delays as spring gave way to summer.

My bike's strange behavior is explained by Occam's Razor: The simplest explanation is the right one.

I was getting power pulses through each of the wires - as measured by my clip-on tach. Plugs are 200 miles old NGKs; failure was unlikely.

I opted to swap in the old fuel pump before digging deeper, since that's all I changed before noticing the issue.

AND problem solved - for now.

I had tested the replacement pump, which was clearly moving fuel. (I didn't measure flow rates.) My guess is that it was not moving enough of it. It could fill the bowls at idle and/or keep things mostly full. As I called for more and more fuel, starvation ensued.

I'm riding with the old pump. It doesn't leak much - yet. I'll need to scavenge another pump but should have at least one more laying around.

Here's a question for the real experts: Could I have installed the replacement pump such that it bolted up cleanly but was NOT making a good mechanical contact with the cam?

I don't think it's possible given the was the pump lever hangs. But I found myself having to separate the top portion of the pump from the "lever" portion to get my old pump back on. I've installed a few of these and don't recall having that much trouble. I know I got this one on correctly, but it left me wondering if I could have done a "semi" installation of that replacement pump.

I'll need to source another pump soon enough, but I think I have at least one more laying around.

I can also report that the bike wants to go fast - and that the speedo is loosening up and coming closer to keeping pace with the actual accel/decel curve.

[CYBORG]

Could be a bad install. I once sold a pump to a guy, installed it, and it sat and idled for at least half an hour. He left and got about ten miles down the road, and the bike dies. I went out and pulled the pump. It looked good, and I knew it was. I re-installed it, making sure everything was in the right place. (as I thought it was before), and it worked fine. And still is to this day. The level of fuel in the tank may have been a factor.

[NotSoLilCrippseys]

Thanks, Cyborg. I'll reinstall.

Given the finicky fit to the head, I'll unbolt the top portion of the replacement pump and affix it to the bottom "lever" portion. That way I won't mess with the cam-driven mechanical end.

If that doesn't address the flow level, it's on to another pump.

[NotSoLilCrippseys]

I have successfully mated the top portion of the '75 fuel pump to the bottom (head-attached) portion of the leaky '76 pump.

I can report that a good hard run at 4-7.5k rpm for 6-8 miles produced no fuel starvation, hesitation, etc.

I think I had a faulty installation of the mechanical fuel pump.

Whew! (I don't enjoy chasing ignition issues.)

After a couple weeks on this girl, I'm starting to think that I may want to source those jets to address the off-idle stumble. I find myself with too much throttle, too little and a stall at the light, or a nice clean launch.

[NotSoLilCrippseys]

It seems that I'll be sorting out a series of issues over the next few hundred miles, which isn't all that surprising.

I set out this afternoon for a good 50+ mile run with the old girl and headed to the station to fill 'er up. As I approached the turn off, the bike signaled that I needed to flip the petcock (tripmeter, fuel gauge, and then near empty bowls). I made the mistake (or maybe not?) of rolling in with the bowls draining. I figured I'd crank her a few times after filling up and head off for a nice hour on the bike.

After filling up, she started then died - over and over. She needed more fuel in the bowls. OK.

Then she stopped turning over. Press button. Nothing. I had lights on the dash. I pulled the side panel. Dogbone fuse was good. A fellow rider offered to push me for a pop start, and that worked immediately.

With my plans for a nice ride on hold, I tucked my tail between my legs and headed back home mulling over the issue: solenoid, start button, starter?

• I tried jumping the solenoid with a screwdriver, which didn't bring the starter to life. I thought starter.

• I ran a line straight from the battery to the starter, and she cranked the bike. OK. Starter works, which had me scratching my head about the fact that jumping the solenoid didn't work.

• Dogbone fuse is fine.

• I dug out another old solenoid and tried that. Push the button, no workie. I can hear the solenoid clicking with either unit.

• I jumped the terminals on the solenoid. Bike cranks. OK.

Conclusion right now: Get another solenoid.

[Rat]

Beware the cheap solenoids …

Gord

[NotSoLilCrippseys]

Gord.

Right. I think that's especially true of starters!

My two "failed" ones are OEM.

I plucked an known-good aftermarket solenoid from one of my other bikes to confirm a solenoid failure.

The yellow lady fired right up. I'm taking this issue as an opportunity to replace the dogbone with a 30-amp blade fuse. Tidier, less fragile, and easily sourced. (I'll toss ye 'ole dogbone holder in the tool tray, just to keep things period correct-ish.)

It occurred to me last night that she needs a name. Hmm. Blondie? (as in "Call Me" or "One Way or Another"). Probably not.

And in other news...
I have had a couple interested potential buyers, one of whom has been talking with me for about a week. My neighbor is also interested in the bike, with a thought of adding a sidecar rig to it. Funny. I would have sold it on the spot last week. Now that I'm having fun riding her, I'm not so sure I'm ready to hand over the keys. I probably won't have the opportunity to ride another yellow '76.

[leonardhcross]

Great update. Thanks for sharing all the trials and errors.

[NotSoLilCrippseys]

I'm on the third fuel pump in 400 miles. It sounds worse than it actually is.

Pump 1 - Original to the bike as it came to me, it had heavy old gas staining that ran onto the engine block. It was probably leaking long before I noticed anything. It dribbled a tiny bit - pinhole most likely.

Pump 2 - Scavenged from a very neglected '75. Worked for about 40 miles before leaking way worse than Pump 1.

Pump 3 - I'm in a good week of riding (200 miles?) on one from an '81 that I tore down a few weeks back.

With two bad pumps, my inventory of good ones is nearly (but not quite!) exhausted.

I'm now eyeballing NGWClub tutorials on replacing the pump diaphragm on my failed units. A suitable replacement seems to be at the bottom of this Chevy repro parts vendor's site: https://www.marxparts.com/repro%20chevy_fuel.htm NGWClub has several reports from members that this part lasts for years.

[Fred Camper]

Let us know how it works. Switched mine to a Bosch electric pump using a GL1200 mount and it works great. No more diaphragm and faster starts.

[Lucien Harpress]

Electric fuel pumps are actually real nice. Had one on my 1000 before swapping it to keep it stock. Super simple- turn the key, wait to hear the tone on the pump change when the bowls are full, press the start button, and away you go.

[CYBORG]

I agree. Completely stock bikes are good for bragging rights and show trophies, but upgrades are the best answer for riding performance, and reliability.

[NotSoLilCrippseys]

Thanks.

I'm not seeking to brag or score a trophy (maybe a participation trophy?), but I don't think I'll go electric pump with this bike.

[NotSoLilCrippseys]

I swapped out the air jets for smaller ones (110s from a '75 rack). If there's a notable improvement in the off-idle stumble it feels close to a placebo effect. Maybe there's a little improvement. Not sure.

In more fun news...

I've now had the opportunity to do a little side-by-side (week-by-week) comparison between my yellow '76 and my '79 mild custom (Ginger Lynn).

Of course, I've read about the hot-cams on the '75 and '76, with rougher manners at low RPM but a real kick up high. This yellow girl hits another torque band above 5k that is very noticeable at WOT. She pulls hard, and then pulls harder. It's not something one needs in day-to-day riding, but it's fun to know it's there.

My '79 goes pretty darned good right from idle to redline, so I wasn't thinking there'd be a noticeable difference. But I hadn't ridden the '79 in more than a month owing to my need to replace fork seals, which I prioritized late last week.

When I got on Ginger this past weekend, I decided to see if I noticed that surge above 5k that I've been getting with the '76.

It's not really there. She pulls really hard all the way to redline, for sure. But it's more hard and steady.

[Lucien Harpress]

Of course, I've read about the hot-cams on the '75 and '76, with rougher manners at low RPM but a real kick up high. This yellow girl hits another torque band above 5k that is very noticeable at WOT. She pulls hard, and then pulls harder. It's not something one needs in day-to-day riding, but it's fun to know it's there.

I think that's my favorite part about my '76. It's this sedate little slug most of the time, but that kick at 5k combined with a slightly stiff throttle (long cables plus a strong return spring will do that) turns it into a bike you kinda gotta manhandle, but will wake up and sing if you do. And there's a LOT of real estate between that 5k and the 8.5k redline to play with.