Running Issue

Hello all.......
I've have a 1983 KZ1000P which has developed a glitch. She starts on three cyclinders and after 10 seconds or so the fourth joins in. She'll run sweet and powerful for 10-15 miles, then will drop down to three cyclinders or sometimes cuts out. A coffee in a McDonald's and off she goes again. She's had new coils, leads and carbs cleaned and an in-line fuel filter added. Any ideas??????
Cheers.

If not already done, would check:
Valve clearances (perhaps one or more is/are too tight);
Spark quality (need fat blue, not weak orange);
Fuel levels in carb float bowls (clear tube test);
Fresh unobstructed air filter;
Pilot circuit fuel mixture (is perhaps too rich).

Good Fortune!

Cheers for those ideas. She had an engine rebuild 1500 minute miles ago, so it won't be a bad idea to check the shims

Intake leak.

Would also assure having a good fully charged battery installed.

Good Fortune!

Plugs all removed, cleaned and gaps checked. Started on the button!!! Went for a quick blast and she spluttered, farted and dropped cyclinders. I got home and noticed the inline fuel filter was empty of any fuel, I turned the fuel from main tank to reserve and even on prime nothing happened. After about five minutes, put the tap from main and onto prime again and the fuel immediately filled the filter and she started perfect. So it seems like fuel starvation. What the hell is causing the fuel not to flow?

It looks like you have a vacuum in your tank cause by a clogged vent in tank cap.
clogged = vacuum = insufficient fuel flow

Do a short ride with open cap to test

www.kzrider.com/forum/3-carburetor/60430...a-bigger-tank#747435

JTTMF wrote: Plugs all removed, cleaned and gaps checked. Started on the button!!! Went for a quick blast and she spluttered, farted and dropped cyclinders. I got home and noticed the inline fuel filter was empty of any fuel, I turned the fuel from main tank to reserve and even on prime nothing happened. After about five minutes, put the tap from main and onto prime again and the fuel immediately filled the filter and she started perfect. So it seems like fuel starvation. What the hell is causing the fuel not to flow?

Patton wrote: Okay -- moving to possible fuel starvation, which could result from several different reasons.

Is there ample fuel supply in the tank?
Tank vent clogged? (Try running with cap ajar which allows for ample venting).
Any crud inside the tank, possibly suspended in the fuel and collecting around the petcock pick-up screens so as to obstruct flow?
Petcock malfunction, or dirt inside?
Fuel line kinked or obstructed?
In-line fuel filter dirty?

If the petcock is vacuum-operated, is it receiving vacuum and opening to permit flow as it's supposed to?
Could test run with petcock in PRI position (which allows fuel flow absent any vacuum).

What sometimes happens is that an obstructed fuel flow (for whatever reason) dribbles enough fuel into the float bowls while the engine isn't running to permit starting and running normally until fuel level in the bowls gets too low, where the bike "runs out of gas." Going through the progressively leaner mixture while "running out of gas" could account for the heating before stalling as noted in the topic title.

Could test run with ample fuel in the tank, tank cap ajar, and petcock on PRI, to see whether the same symptoms persist. And if so, could disconnect fuel line at the carb intake tee to assure that ample fuel flow is available at the carb intake.

Is the stock air-box still fitted? Is the air filter fresh and clean? And unobstructed?

Sometimes a tank needs flushing to rid it of unwanted stuff floating around in there. Imo, the "fast dump" method is best, where the tank is removed so that it can be emptied quickly by turning it upside down and dumping contents out the filler hole. Add a little fresh gasoline -- or some common household rubbing alcohol -- slosh it around inside the tank, and you know -- re-dump it.

May also be a good time to remove the petcock from the tank in order to clean the petcock pick-up tube screens that stick up inside the tank.

Rusty tank interiors may require more aggressive measures.

Good Fortune!

It's very possible for matter in suspension in the fuel inside the fuel tank to collect around and obstruct the petcock pickup tube screens that protrude up inside the tank.
In such situation, a fresh refueling might temporarily relieve the clogging, until fuel level again gets lower and the clogging repeats itself.

For example, a repainted fuel tank could have paint over-spray residue suspended in the fuel, which residue can and will clog the pickup screens.

Good Fortune!

Nice one fellas.
Tank removed and rinsed out, fuel tap removed and dismantled and cleaned and all working well (vacuum on main and reserve and straight through on prime). The fuel filter was full of shit, so that's removed. Tomorrow will be a new fuel filter, fuel line and fuel. Stand by!!!