Yet another carb problem.. I think

[Jaykup]

I've got this Seca 750 and had it running after i bought it. I didnt do anything to it at that time, and it seemed to run OK except for low-end throttle, it seemed as though it was miss firing. As soon as i would give it gas, it would go just fine.

I figured it was carb related, from sitting forever, and I was right, the carbs were extremely dirty.

One of the smaller jets was clogged, and I am guessing that is what made up that low end missfire.

I cleaned out all the jets, everything. Carb cleaner, air-compresser, the works. The floats were still in adjustment (17.5MM) as I measured them all

The floats are also in good shape (did the hot water test to find leaks, nothing). I cant brake free the bottem drainage screws, but everything else was taken apart. (except the mixture screws)

Now the bike wont start. The two far cylinders (1 and 4) are firing, but the middle arnt. All are getting spark, new plugs just installed. The spark to me seems weak, but its there. the main thing is, the plugs arnt wet when im turning it over and over and over. So i thought i messed something up in the carbs.

I took them off, and all the bowls had alot of gas in them. Same amount from what I could tell. I know the jets are cleaned, just double checked them today. For a while, I had it idling, and i could rev it to around 4K or so just fine, even higher, but as soon as I tried to take off, it just died. Like it was running out of gas. Which is why i went to the floats, and the needles.

What would be causing this? What else did I miss? The thing ran great before i tore the carbs apart, so i really dont think its spark

The coils tested 20K and 30K or so, and they were supposed to be around 25K. Also all are sparking.

Where do I start? The petcock also flows great.

Jake

[wildbill]

Check your float needles{valves}.There might be more than one sticking.I had a problem like that with my dirtbike.Would not start but the float bowels would be full and the sparkplug dry.That might be your problem.When you remove them check the tips if there is a ridge formed near the tip just go ahead and replace them{the ridge is what is causing them to stick in the closed position}.My carb was a Dellorto but that should not make a difference-sounds like the same kind of problem just a different bike and carbs.Hope this helps.

[prometheus578]

Go back in and clean the mixture screws/pilot circuit. This circuit meters the air fuel mixture from idle to around one-eighth throttle opening. That would explain your "runs ok, except for low- end throttle" and the miss-firing at idle. Would also explain the plugs not getting wet when cranking. If the carbs still have the factory plugs over the mixture screws, you'll have to take them out. Get a small drill bit and a sheet metal screw or something like that. Carefully drill into the plug. Go slowly, as once the drill bit gets through, the screw is only maybe a 1/4 inch below the plug. (Make sure you're drilling the correct plug, too)
Anyway... drill the hole, screw in the sheet metal screw, and pry the plug out. Take a small screwdriver, and turn the pilot screw gently all the way in, counting the turns. (half... one... half... two... half... etc) Write down the number of turns for each carb. They may not be all at the same setting, and you'll want to reset them back to factory specs when re-assembling. Take the screws out, along with the spring. Then take a dental tool or something similar, and take out the small washer and o-ring. Now, reclean the whole carb again. Spray carb cleaner into the pilot hole, and it should squirt through the hole in the throttle throat, and also out the jet in the bowl area. Replace the pilot screws.... first, the o-ring, then the washer, and then the spring and screw. It's usually easier to put it all together on the screw, and then screw the whole mess in together. Just remember that the function of the washer is to protect the o ring from the spring. Reset the screws to the old factory specs.

[soccer4m]

HI, I have had street bikes and dirt bikes with similiar non start symptons and it is possible that a good long spray of starting fluid can get it running. I usually spray directly into the carb intake opening, make sure plugs are dry first and crank it. If it kicks a bit then you know youre on the right track. Or it could fire up and can clean out whatever is bogging it. Give it a shot, I have had good luck with the same situation, its quick and cheap. Good luck,,,,,,Mike in san diego,,,,xj forever.

[excess11]

I am not an expert on seca 750's but on the xs11 bikes a problem like this would be in the wire harness for the ignition pick ups located under the left side cover. These wires are prone to break down over time and cause problems like yours. Wile removing the carbs you could have disturbed a rotted wire some where causing your trouble. Check for loose connections and tug on wires feeling for the insulation to stretch where there is a break in the wires. This might help! atleast check it out it is worth a shot.

[tab1324]

choke hole clean?

Not familiar with the Seca but my XJ had choke tubes in the carb bodies that dipped into a small opening on the carb float-bowls. Inside this opening was a choke "jet". Mine were plugged. I had the bike running on (3) cylinders for a while but after I cleaned the choke holes, they all fire. This is only when it's cold though, so maybe not the same issue - worth a shot though.

Tom B.

[wildbill]

Sounds like another carb cleaning is in order.Check when you disassemble you might have to replace some carb parts.There is something stopped up some where.