Re-re-reviving my '81 Seca 750

From the It's Always Something files, she is suddenly idling rough this morning. Dry, garage kept, has a half tank of gas. Was running fine* on last ride on Sunday. Started up fine, but it died out at the first light (after warm up, 5 suburban blocks, removing enrichment along the way, my SOP). Usual idle is a hair above 1k, now sitting about 2 hairs below. Seems fine off-idle - maybe a LITTLE hesitation. Last time I had this, one of the spark plug boots was loose, but messing with them didn't seem to help. I got to work OK and hope to get home without incident and work on it over the weekend.

Only change was a few ounces of Seafoam in the crankcase this morning ahead of a planned oil change over the weekend. Can't imagine that having an impact, but . . . .
Last valve check was Fall 2022, about 2.5k miles ago. At the same time, the carbs had been freshly Churched by Hogfiddles. There's an inline filter on the fuel line and it looks clean.

Only other recent oddness is near the end of my last ride, my right turn signal stopped flashing. Was hoping it was a sign of a bad bulb, but front, back, and Atari all light up (solid). So, something else to track down, but again, just mentioning it. Does NOT seem to be an under-voltage situation - was reading 13.something when running, 12.8v when sitting. AGM battery was also new in 2022.

 

Try new spark plugs

 

Those were renewed in the Great Rebuild of 2022 as well, but I'll take a good look at them for sure.

 

Can seafoam foul the plugs l wonder, never used it.

 

From the crankcase side? I'd think the rings would have to be REALLY bad for there to be a connection there, and it's not like I'm burning through oil. I've never had a problem with it before - neither in the gas tank nor the oil.

 

I have NEVER had seafoam kill plugs. (Crap that the seafoam dislodges might..... )

plugs— a fellow at the Carb Clinic had a bike that had a dead battery..... we got a new battery, and the bike fired up, but minus #4..... then after it ran for a bit #2 started cutting out. Then when trying to run around the lawn a bit #3 went out.
He went home and put new plugs in, it fired right up, and went for a ride.

Try new plugs anyway

 

Gas cap vent blocked?

 

@chacal, was behaving the same on an aux tank. But of course Dave was on to something.

I may or may not have solved it. First, my memory was faulty about the new plugs, which I discovered when I looked back at my notes. I did NOT replace them at the time, I think because I was confused by the whole resistor plug thing or something. Also discovered I'd bought new boots from Len, since #4 had been flaky, but never did install them. So today I replaced all boots, trimming back the leads a bit since #2 and #4 looked SKETCHY. Still have stock coils, so leads JUST BARELY had enough extra without being taut. Afterwards, she smoothed out nicely. Put it all back together, could only go around the block b/c Mom is out for the evening and I've got kids to watch.

Ran great until I got back in the driveway, but then is started acting up again. Had to walk away at that point. I will say THAT 'acting up' felt different and I almost wonder if the engine was overheating at that point (was a hot one today and I'd been idling quite a bit in the garage). We'll see what she does in the morning.

I also discovered the turn signal issue is more than likely due to a bad bulb after all. Went to swap left and right and not only did the left bulb work OK in the right, but the filament fully broke on the flaky one when swapped - so it had been MOSTLY dead.

Pics of the pulled plugs 'for fun.' Qute a difference. 1-4 L to R

 

#4 is looking a bit sooty.......

 

1. What’s the condition of your oil?
2. May want to try a different TCI

 

So, when you're working on a bike you've had for nearly 30 years, it's good to trust your gut. When I said it was good, then then halfway around the block it acted up, maybe overheating? What it really felt like was fuel starvation. BUT I had plenty of gas in the tank and had even tried the Prime setting.

Was still rough this morning. Went to take the tank off to dig back into it only to discover the fuel line was pinched when I'd replaced the tank yesterday. I put the fuel line in the right place, and it fired right up and idled smoothly. Just went for a 50 mile Father's Day ride. Back in business.

And yeah, a fresh bulb fixed the turn signal situation as well.

As for sooty #4, it really was. Again, that was the old one. Interestingly, when I'd first pulled it after getting home from work on Friday, it was a nice tan. That soot was from troubleshooting - or troubleSOOTing, har - at idle. Once things cool off I'll pull the new plugs and see how those look now.

And just to wrap up (for now), the oil looks good as it's only got about 2k miles on it, but time-wise it's overdue and coming out in the next few days - thus the recent Seafoam dosing.

Oh, and I got into some cicadas on today's ride. Dodged all but two, i think - one on the windshield and one on my pant leg. Eech.

 

Glad to hear it was a simple fix

 

Got the oil change in today as well. A good Father's Day.

 

The new plugs after a 50 mile blast yesterday. So clean!

 

Bike still needs a little tweak. May e due to the plugs being at full bang potential, the RPMs were floating a bit on shifting and coming to lights on the commute today. Hadn't noticed it on yesterday's ride, but that was pretty continuous blasting. Did think throttle was not as snappy. A carb sync should solve it, I'd think. Always something.

 

Plugs may be a bit lean yet, too. Double-check for vacuum leaks at the intake boots.

 

Never circled back to this, but some VERY minor tweaking of the carb sync brought everything back in line and purring nicely.

 

Ok, just in the last 2 days, my oil light is REALLY annoying the hell out of me, so pulling the sensor for manual cleaning will likely happen sooner than I'd wanted (planned to do it this winter). Oil level is confirmed good, have tried 2 Seafoam treatments, and it still acts a fool with little rhyme or reason. It comes on with some hard accelerations, but not all. Sometimes a gentle rise in the road, or a seam in the pavement can turn it on OR off. Occasionally it's on for a flash or two, but lately it's more likely to stay on for a minute or more. Just long enough for me to get annoyed, cancel the warning, have it clear and then re-activate. Yesterday morning, it didn't come on once in 26 miles. Today, at least a half dozen times.

Aside from needing to replace the seal (which seems to be leaking anyway), my big concern is going to be dropping the exhaust, which, to my knowledge, has never been done. Do I need to mess with the header bolts, or can I just (try) to separate the header pipes from the collector (and how much damage will I do to the already-rattling collector when I do?)? I did have the megaphones off in late 2022, so hopefully those come back off fairly easily, but any tips appreciated.

 

Exhaust bolts suck, no matter the vehicle. Start spraying everything on it with penetrating fluid days or weeks ahead of time. Spray it, ride it to get some heat in it, spray again, rinse and repeat.

 

Many times, the collector rattle is actually due to the heatshield on one side or the other.... they’re welded on across the top and bottom, by there is a welded-on ring clamp at the front and back. Often one of THOSE rust through and then make an awful rattle. I just wedged a thick piece of leather in there, and I’ve also just carefully bent the heat shield out just a bit so the vibration does cause metal contact anymore.

Sometimes, the rattle is inside the collect itself, as it gets a loose rusty part, and I’ve also had rattled that are actually inside the muffler as the baffles get loose.

 

I cleared all the crap out of the mufflers and checked the heat shields when I messed with it all 2 years ago.

 

Of course, on yesterday's ride home from work, even with two HARD pulls up to 50 and 70 MPH, no oil light at all.

Make it make sense . . . .

 

They joy of an old bike. Oil level indicator is wonky, and you’re waking it back up..... or, you may have a loose wire somewhere——

 

The saying is with the Vmax - if you're not making the oil light come on you aint riding it right...

 

I have wondered about a loose or grounding wire, but ran out of time to run that down this weekend.

 

A new gremlin has appeared - not sure yet if mechanical or electrical.

When I de-mothballed the bike late 2022, I'd noticed the turn signal switch felt a bit . . . gummy. Turning it on was fin, but cancelling in the middle took more effort than I remembered. When I got back on the road this spring, I finally decided to try to degunk the switch. I didn't want to go too aggressive with contact cleaner, so I just spritzed some IPA (not the beer) in the switch and it was immediately better.

Yesterday, a new behavior was observed after months of reliability. The turn signal would only stay on if I held the switch left or right. As soon as I released it, it went off. After about half an hour, it was back to working properly for the rest of that ride. Then, on the way home, it was fine again, until about 15 minutes in when it stopped working correctly for about 5 minutes and then was fine.



Have not had a chance to take the switch apart yet, and I also wondered if it might be a fault with the auto-cancel unit. It was pretty hot when it first acted up and I wondered if that heat would prematurely cancel the signal. But when I rode home, it had cooled off considerably - upper 60s, so not putting a lot in that theory now.

Anyone seen this? It will probably be a couple weekends before I can get into the control body.

 

What happens if you disconnect the auto cancelling unit?

 

I would have used kroil, rather than an IPA.... you may have intoxicated the switch.

 

The turn signal thing, like the oil light, is VERY intermittent and very frustrating. LOL

 

Heh, I forgot the actual point of my post - what are y'all using for fuel line? I feel like I'm always wrestling with it - have tried various things from the auto parts store and I'm not sure what's on there now, but the OD seems too big for the standard clamps and the ID seems a TOUCH too tight to be able to get fully on the barb of the petcock.

 

Warm it up just a tad with a heatgun and it’ll slide right on—- unless you heat it too much, then it’ll just mush into a pile.
Put the ring clamp on anyway.

 

A different OD will require a different clamp.

 

Ring clamps are adjustable