not running properly

ok so i bought my first bike a 1981 xj750 seca II and it ran great was riding all over on it. but i was looking it over and it had no fuse box, the wires were taped together, my license plate light,gauge lights,tail lights were not working.and i heard from someone on here that i needed to upgrade my fuse panel and change the fuse in the headlight bucket.so i did all that changed to blade fuses,and replaced the fuse in the headlight bucket and it all started working except my plate light. but now my bike is not running right it doesnt want to idle sometimes and when it does idle when u rev it up to about 2500rpm its starts backfireing alot. i tried to ride it and it didnt want to go. i put in gear and it wont go past 1000rpm. should i put everything back the way it was b4?, should i just shoot it?sell it? im at a loss and mechanically challenged. some1 please help me out thanks.

 

here is a good guide for troubleshooting ignition problems:

Ignition Troubleshooting

 

First off, it's a Seca not a Seca II. The Seca II was a later-model restyled 600.

Secondly, the problem you are describing most likely has nothing to do with your electrical repairs, unless removing and replacing the fuel tank shook loose some crud that is now lodged in your carburetors.

You can't just buy a quarter-century old bike and start riding it, you WILL have problems, as you're finding out.

First off: Did you pull the rear wheel and check the brake shoes for delamination? If not, STOP RIDING IT right now, and do that. You don't want a sudden unexpected rear wheel lockup at the wrong time, you could die. Read: http://xjbikes.com/Forums/viewtopic/t=15874.html

Then, as I mentioned above, you have some carburetor work to do. What you're describing are classic symptoms of carbs in need of attention.

Install an inline fuel filter.

BUY A MANUAL.

Read: http://xjbikes.com/Forums/viewtopic/t=24010.html
Read: http://xjbikes.com/Forums/viewtopic/t=14581.html

How you proceed from here is up to you.

 

jeez man u dont have to be so sarcastic about it. if u didnt mean to come off that way i apologize but thats the way it seemed to me. thats a great way to treat new people!!! ive never owned a motorcycle b4 so i dont know what to look for to be wrong with a bike but i would greatly appriciate any help i can get since i dont know what im doing. so carb work? can i just clean them or do i have to sync them which alot of people on here seem 2 dred?also what is delamination on the rear brakes so i know what i'm looking for? one of my side panel emblems says seca II thats why i thought it was ok sry 4 the insult to the bike!!!

 

Jaymckn, don't worry about the tone so much as the advice. Heed the words of Bigfitz. His advice is based upon experience and your life isn't something to be treated lightly. I don't know of a single person here who doesn't get the hairs on the back of their head up hearing about one person after another reporting they had their brake fail/lockup on them while tooling down the road. A serious topic indeed.
The first and best tool you can ever own for any vehicle you work on is the maintenance manual. The Factory Manual, although expensive, is the bee's knees in maintaining these museum pieces. I've used the less expensive Haynes manual for decades without problems although it is known to contain some jetting errors. Given your admission of being mechanically declined, I'd suggest the factory manual.
Moving right along, I think you will be pleasantly disgusted with the crud I'm certain you are going to find clogging up your carbs. It will run soooooo much better after you've cleaned them out. It may look like a daunting task but is rather straight forward, no magic involved. The inline filter Fitz mentioned is a great investment to keep this from happening again.
Sadly, you are fighting an uphill battle with these older bikes due to age and neglect. The best defense against this is a complete baseline of the bike (oil/fluid changes) and REGULAR maintenance. In this way, you will be aware of changes of the machine and can act appropriately in a timely fashion to head off costly damage and repairs.
I hope you find these words of use, let us know how we may be of further assistance and good luck to you!

 

well thank u robert,i will heed fitz's, and ur advice.where can i pick up a manual?is it somethin i can pdf online or do i have to buy it? im going to start with an oil change,plugs&wires, then i will check out those brakes. is my bike air cooled or does it take fluid?how can i get to my air filter so i can change that as well?thanks 4 all the help and to fitz sry i thought u was just being a douche.is there a forum link with pic by pic on cleaning the carbs? once again thanks guys.

 

Apologies if I came off sarcastic.

Robert is correct though; I wasn't being sarcastic I was being SERIOUS.
I was trying to impart some of that to you.

I was also trying to get you to understand that putting an old bike back on the road, if not done properly, can be very dangerous.

What is rear brake delamination? Brake linings peeling off the shoes. Read the post I linked to. A LOT of responses, with pictures. It happens a lot and can lock your rear wheel.

Another "gotcha:" How old are the tires? Not worn, OLD? You have tubeless tires, anything over 6 years old is dangerous. (Think blowout at speed.) Do a forum search on tires and see what you find.

Then you need to read the other two articles I posted links to so that you understand what needs to be done if you are ever "to figure this thing out" in your words.

Your bike is air-cooled; the air filter is in the airbox which is accessed by opening the seat and taking out the tool tray, the cover is held on with (captive, I believe) phillips screws.

You can't replace the plug wires like you can on a car. They're molded into the coils, it can be done but it's not a "maintenance" item.

Once again, this is an OLD motorcycle. Do this right, and it can be very rewarding. Otherwise you will be fiddling and fighting with it long-term, rather than enjoying it.

All the assistance you will ever need is here, but there are things YOU need to do, like get a manual. Factory reprints are available through various sources (including our resident parts guy, chacal) and I've had really good luck on eBay. The Haynes book is readily available.

Yes there are forum links, look in "FAQ suggestions" or do a search on "Old school carb cleaning."

But as I said above, and I was being serious not sarcastic: How you proceed from here is up to you. (Do it right or do it forever.)