1981 XJ750 Seca

Hi guys. It is great being here (in this forum).

I have some questions for you, but first, a little background.

Suffice it to say that I used to ride in the early 80's, and when I faced down wifey some 20+ years later to say, “I am getting a bike to ride for a while before I get to buy a big bike at 50 years...” I was looking for a bike with low miles, low price, etc. Among others I had a Yamaha 450 Special in the early 80's and loved it.

I was patrolling craigslist daily. I found a 1981 XJ 750 Seca. I wanted a Maxim, but I live in the mountains and scheduling my arrival to Denver or another destination always resulted in my missing the good deals. I ended up finding this bike with 16k+ miles that had sat a long time. Never “wrecked,” just abused by sitting.

Paid $700 for it, took it into a small Yamaha shop south of here, paid $500 for complete carb rebuild, oil change and oil parts, but it's not running perfectly. Yet.

It's idling at about 1,500. What is the preferred idle RPM?

I live at 8,000 feet elevation. Although the dealer told me to run it with cheap gasoline, your advice is to run it with premium, which is 91 octane. I will do so soon.

The plugs were recently new but ends are black from prior to carb work. Should I replace or clean?

What is the order of cylinders? The second cylinder from left runs poorly, compression is good, but when I pull spark wire while running, it makes little difference to idle.

Petcock is weird to me. Do I leave it on run always? In PRI it leaks just a little bit. If I put it between run and reserve will it shut off? Where should it be when not running?

I got the luggage off the bike. I am going to put the rear signals back where they belong, wherever that is. The luggage mounts to a frame part that looks unusual. I will sell. I also need a fairing windshield and a grab bar unless anyone has a sissy bar for sale!

When I shift gears, there is a noticeable click. It shifts easy but makes a louder-than-usual sound.

Sorry to tie you up with all of this minutiae, but don't know where to start, so I am starting with everything.

Thanks again!

Paul

 

See pic

 

Nice seca man!

What I can add: Plugs are cheap. If you're unsure of their condition, just buy some new ones. You can clean them, too. They're probably firing fine, though.

I think idle should be around 1050. I just remember reading it somewhere, I'm not too sure and my manual hasn't come in the mail yet. I suggest you get one, too! www.XJCD.org

Also, leave your petcock on run. It is vaccuum operating, so when the engine is off, a diaphragm closes and no gas is running.

As far as your cylinder goes: If the carbs were cleaned, it's getting spark and there's compression in the cylinder, don't worry about it. It has to be firing. You can check for spark by pulling the plug, hooking up the spark plug wire to it, laying it so the threads are touching the engine head, and turning the bike over. You should see a blue-ish spark. If not, get some new plugs.

 

1050 but i'll buy 1200

unless that altitude means something, regular should be fine
i use mid grade just for the heck of it no need to

the shop did all that work but not new plugs??? champion's 1.89$

1234 from the left sitting on the bike

me too, but on prime it should squirt all over, normally leave it on "on" all the time, it's vacuum operated and should shut itself of when the motor stops

not the smoothest trannys at all, normal

 

I've only ever used 87 octane...is the consensus here to use the expensive stuff? (Nice bike, Paul!)

 

I always use high test. Not that everyone will agree, but it makes my bike run much smoother. As far as pulling the plug wire and no difference in idle is heard/felt, could be a bad coil or plug wire. Nice ride though!

 

Thanks for all the great input. As to the altitude, I mentioned it because regular gas is 83 octane which seems kinda low. Add to that the mandatory 10% ethanol and I don't know if this is good or not...

The new air filter is 50% saturated with oil/fuel mixture from when I bought it and it was doing the gas in the oil and all over the floor thing (which is why I had carbs rebuilt). Maybe I'll wait on putting in the new plugs until I get a new air filter.

Later and thanks again!

 

Might be a bad plug CAP, they normally need replacing after a while too.

By the way, the seat on the luggage-box equipped bikes is different from the non-luggage box seats, and the standard rear sissy bar may not fit correctly with that seat (or at all).

You may want to also go through the electrics on the bike, with an eye towards replacing the fusebox and the alternator brushes......these are common problem areas. Checking the condition of the coils and the plug wires and caps is also recommended.

 

+1 on the plug caps.
My '81 Seca devolped a rough idle and started missing after sitting 4weeks.
Ohmed the caps and coils and found my #2 cap at 13 Megs. Hopefuly I'll have my new caps tomorrow.

 

Again thanks. I am now burning 91 octane, and my friend who is also rebuilding a bike poured some sea foam (?) into my tank, the thing is starting to start very quickly and idle. With every run. Better.

I found a loose wire going into my main fuse, I bypassed the fuse and wired the two wires together. Running better. (I will get an inline fuse for the main circuit tomorrow).

I rode the bike to over 12,000 feet altitude today. Ran very well, but not perfect. new plugs, new air cleaner will take care of that. New wires will soon be on the way. Even without that stuff, every run it gets better as the crap gets burned out of the bike. Lots of little stuff to fix, but dang, what a great bike!!!

 

Nice looking bike. I have found that my bike runs better each time I ride it. Used to have trouble with it not idling and now, it will idle like a champ, even if a bit high, (1500) I run the hi octane stuff and leave my fuel in the "on" position also. It's nice seeing the comments left here. What you brought up are some of the same things I've wondered about.

 

That two-tone seat cover pattern makes the bike look a lot better than having a solid color seat.......

 

Thanks Lisa and Chacal.

Hey Chacal, do you know if that two-toned seat was just for the model with luggage, or why they did that? It's a different material than the black vinyl, and it obviously holds stains. Semi-porous. I will be trying to clean up the seat this weekend. Don't exactly know how...

Sorry about the double pic post. Won't happen again. I downloaded a free software that just re-sizes pics. Handy and easy!

 

2-tone seat covers: just for the models that had the hard cases. Don't know why they did it.

 

if it were mine, I think I'd hold on to that hard luggage and fairing and other goodies, they seem to be pretty rare and a nice matching original set on the bike might command a nifty price in the future, especially on a low mileage example as you have there. great looking machine