XJ650 Seca 1980 Not working right part 2

I tested the fuel passages with compressed air and they all seem to be clear.
My biggest doubt is to know why I don't have any kind of alteration in the operation of the engine when I remove the spark cap or close the entire mixture screw.

 

Sorry if I missed anything but can you check compression? I’d be interested in the reading and valve clearance.

 

I'll chuck in my two penneth worth.
You say you've blown through the passageways with compressed air, but what about the passageway for the pilot jet, that's the one down at the bottom of the tunnel at the side of the main jet.
That passageway can get a partial blockage and i had this problem on a set of 34mm Mikuni's fitted to a XJ1100. I was positive it was totally clear.

 

And from me - you have to squirt carb cleaner through these, and check you get the same "squirt" out of all four of them - kind of an easy comparison check if you like?
Blowing them doesn't tell you anything or at least everything.

 

With you there mate, i didn't want to say but i put through nearly two tins of aerosol to clear it.

 

Thank you all.
I will try to check everything again on carburetor 4. And as soon as I have the tool to test the compression I will put the results here.
Thank you again

 

With the bike running and the carb to air box boots off, see if you can block off the back of the carb with your hand. This will more or less force gas to be sucked up into the carb. It might, just might unblock anything that could be holding back the fuel. While doing this test and all fuel related testing, make sure you have the bike on the center stand. You said you were using a AUX gas source, but if the bike is still leaning on the side stand the carbs will not be flat and level. Having it placed on the center stand will help trouble shoot the carbs (imho).

You have checked the #4 spark plug by pulling it out of the cylinder and make sure it is sparking as the bike is running? The bike will run on the other three cylinder as you do this.

Keep us posted on how you are doing and what steps you are taking. Carbs are no joke, when they are out, do a really good job on them the first time. I have pulled carbs as many as six times before I got the right. Now I really am careful and take my time to do them right. Using thin wire, carb cleaner ( I use chem tool B12) and compressed air.

 

Lots of good suggestion above - one other possibility is a large vacuum leak from the intake manifold boot because of large cracks or a defective gasket.

 

My XJ would not start, I thought I had cleaned the carburettors properly but at the time I didn't know about the float bowl jets. Once cleaned the bike started. It was on this site I found out about those hidden jets.

 

Well,when I asked if there is fuel in the bowl, and you said there is fuel in the bowl, then there is not a fuel shortage. You need to determine if fuel is getting into the cylinder. Then you need to find out if you are getting spark.

 

This is what I already checked:
I have a good spark in all cylinders;
Fuel reaches all carburetors;
The jets are all open;
When I close the air intake of carburetor 4 by hand, fuel comes out;
The mixing screw was removed and the orifice cleaned;

What I haven't done yet:

Compression test;
And checking the valves

Thank you all

 

Put a direct line of current to the starter so you can spin the engine with no spark. Then Remove spark plug number four To see if the spark plug is wet. If it is wet, you have fuel to the cylinder. If it is not wet, you have no fuel getting into the cylinder

 

I have a similar problem with mine. Cylinder 1 just never fired no matter where the mixture screw was. I think it turned out to be a clogged jet (even after poking wire through all of them to make sure they were clean). There are (I believe) 4 of them and one of them was clogged. I have the carb sitting in my ultrasonic cleaner, and I am making sure all the jets are clean this time. If it still doesn't work, you've got more troubleshooting ahead. I would make sure the electrical system is still in spec and no parts have too much or too little resistance. Then check the valves before compression. Bad clearances can lead to compression tests with false values. Valves will change a lot on the bike, and it feels, pulls, and sounds 100x better with the clearances fixed.

 

NOT A GOOD IDEA!!!

while many of us DO that, it’s very dangerous. If the gas is getting into the cylinder, you are now blowing it (atomized) out of the spark plug hole—- hope the spark from the plug you’re checking doesn’t ignite it!!!!! You won’t have enough time to say “UH-[insert big explosion here]-OH”.

 

Fair enough...sorry for giving advice that could be potentially dangerous. In my defense I was hoping that some common sense would prevail.

 

No prob...... like I said — a lot of us DO do it that way and, yes, common sense SHOULD prevail. But sometimes the desire to get something working, coupled with the frustration of it NOT working can lead to impulsive action. That can blind some common sense at times.

 

Hello everyone.
I come to make an update.
The problem of cylinder 4 seems to be solved (I cleaned the carburetor again) however, although cylinder 4 already works, it seems to be only 80%.
When I turn off the motorcycle, some smoke continues to escape from the exhaust on the
right
side of the motorcycle. Does this mean a possible problem with the exhaust valve on cylinder 4?
Thanks

 

Sounds like either it’s loading up with fuel or excessive oil in the exhaust pipe.

1. Did you do a compression test yet?
2. Did you check valve clearances yet?
3. Did you sync the carbs yet?

 

No,No and No
I don't have the pressure test yet.
Thanks

 

Can someone help me on the wiring please