I have no fire...checked all the basic options...

A flooded engine will not start even with starter fluid.

You need to get the cylinders dried out and try starter fluid alone by draining the fuel from the carburetor bowl and pinch off the fuel line at the carb inlet. Then remove spark plugs and crank engine for several seconds to dry out the cylinders.

Next, reinstall spark plugs and remove the air filter. Leave fuel line pinched off. Set 3/4 throttle (choke off). Then spray a 1 second burst of starter fluid directly into the carburetor throat. Don't bother with the air filter and promptly start the engine.

Your best option is to start from the beginning as this sounds like it might be a firing order problem.
Assuming yours is a petrol, not a diesel, you'll need to check the correct firing sequence on the engine. Make sure the spark plug leads are in good condition and connected in the correct order AT BOTH ENDS! Next fit new spark plugs as they may be old or faulty. It's also worth checking the silly obvious stuff too like is the battery fully charged and there is fuel in the tank.

Hi Timothy:
Old Dude wisdom..........
- Fire at the plugs and
- Fuel in the jugs

If everything else is OK it should run. Not necessarily well, but it should run.

What to do?
1) Check for hot blue spark at the plug electrodes
2) Check for fuel in the carb.

If you have spark, give it a shot of gas into the carb, and give it a try. If it doesn't start, backfires, or catches fire, you'll need to double check the timing and plug lead firing order.

Not kidding! Don't set fire to it!.

What type of plugs are you trying to use? I had a serious performance issue with the 1999 Dakota after putting platinum plugs in it for a tune up . I found out that with the old-style ignition coil and distributor cap setup that there was not a hot enough spark to fire the platinum plugs properly. Went back to the old copper-core OEM plugs and everything ran fine. High performance plugs on a "low performance" ignition system equals major headaches. Here was one case where better wasn't better.

When you say everything checked, what were the results? For example did you find a strong, regular spark at the lead end?

When you say did the head, what did you do?

Probably after having done so much, maybe it's time to take a step back and get back to basics! Essentially any cylinder that has fuel of roughly the right mixture, a strong enough spark at the right time and compression will fire.

So: Check compression. Check for a spark. Check for fuel.

Is it possible that after so much work something didn't do back properly? Don't get discouraged! It will work, you just need to backwards to find out where the problem is.

What brand of plugs did you use? Nissan engines are very picky, they only like NGK Spark Plugs, if you used a different brand than that your engine will run poorly and misfire.

Use owners manual to see if your spacing on the spark plugs are correct and the torque for each spark plug must be exact to prevent mis-firing. the owners manual will contain all the information you need to know about doing basic maintenance on the car.

The oil around the plug may be a sign that the valve-cover needs a new gasket. Oil on the plugs can cause a misfire but it is important that you check everything over. The misfire could be due to defective wires, boots, coils, spark-plug/s, injector/s, and so much more. Take a look at the cars maintenance history, Maybe it is over due for a complete tune-up or oil change. The car is 11years old, how many miles are on it? How was it running before this?

do a basic test .try starting the bike, then take out a spark plug. is it wet or dry? if its dry, no gas getting into the combustion chamber. if its wet, place the thread of the pluged in spark plug against any engine metal, crank the engine and look for a good blue spark. no spark or an orange spark means ignition problem.

check the cable leading to spark plug and also check whether any blocking in the spark plug