500 Two-Stroke Tech

aaronmvrider

questioning the life span of the inner tube the needle slides in and out of......
i am having trouble on 1 cylinder, it keeps fouling the plug, could i have a worn needle or slide / emulsion tube on the 1 carby.....upper cylinder throttle side

any thoughts as to what else could be attributing to this

have checked enricher is closing
no fuel leaks / overflows
float levels have been set at 23mm
new pilot and main jets all round
balanced and synched carbs according to manual set at 1mm then backed off to .75mm
changed plug leads to other cylinder
aligned oil pump marks according to manual
throttle movement activates both sets of carbs at the same time
fresh oil lines clear and all have oil in them

paranoid as this is the same cylinder that pinched a ring prior to rebore, fresh bore, pistons etc run in and no visible oil leaks on gaskets, has good compression (not measured as yet), with fresh plugs runs excellent other plugs are all dry and nice brown tan in color

the only thing i havent checked is the needles are clipped evenly all round ???? i would assume they are evenly set but you never know !!!!!
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my rides
rz 500 1984
rz 350 1984
mv agusta f4 1000 2004

smurph · Posted: Mon Feb 08, 2010 4:25 am Post subject:

Check your fuel level, not your float height. If one float is heavy, it will go rich. But possibly not so much as to overflow the bowl vents. Just enough to kill your plug.

I doubt it is the needle jet. These bike never get enough miles on them to seriously wear carb internals like that. But... have you checked your needle jet numbers in all 4 carbs to make sure they are the same? Pilots too? One guy brought me a bike that had a #20 in one carb and a #25 in the other. He pulled his hair out trying to get it straight. I pulled the pilots out and showed him and then I had to keep him from beating his head against the wall.

Steve
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Fuel Injected RZ350

aaronmvrider · Posted: Mon Feb 08, 2010 5:08 am Post subject:

fuel level ???
how do i set up a measure for this, run an over flow hose up the side of the bowl somehow ???
or is there a special piece of equipment for this

all pilots are matching but will double check numbers stamped they are all new

i havent checked any detail re: needles yet !!!!!
_________________
my rides
rz 500 1984
rz 350 1984
mv agusta f4 1000 2004

rzatch · Posted: Mon Feb 08, 2010 10:55 am Post subject:

Yes just attach a clear piece of tubing to the drain open the screw and hold it up to the side of the carb..

Jeff B · Joined: 18 Nov 2005 Posts: 290 Location: Wisconsin

Which cylinder is it? The reason I ask is the check valves on the oil pump can leak oil into the cylinder when it's not running. It seems to be worst on the lower left cylinder.

aaronmvrider · Posted: Mon Feb 08, 2010 9:45 pm Post subject:

upper right cylinder
_________________
my rides
rz 500 1984
rz 350 1984
mv agusta f4 1000 2004

aaronmvrider · Posted: Mon Feb 08, 2010 9:54 pm Post subject:

cleaned oily plug, rotated plugs into different cylinders and switched leads, just been for a ride, bike is running well, (wheelstands under power over slight rise, pulls cleanly through revs) plugs all look similar in colour, and all pipe ends look to be running the same, no excess oil spitting out of 1 of the pipes ???

might try a set of hotter plugs and see how they go for lasting or dealing with this condition ???
will also check fuel level in the carby bowl

does that sound like a bandaid fix ???

thanks to all for advise, keep it coming

Aaron
_________________
my rides
rz 500 1984
rz 350 1984
mv agusta f4 1000 2004

smurph · Posted: Mon Feb 08, 2010 10:48 pm Post subject:

A hotter plug is a band-aid. It might cure your problem cylinder, but if you also put the hotter plugs on all the other cylinders, you may end up with a whole new problem. Best to get to the root of the original problem and correct it that way.

I'd just about bet it is a fuel level problem from a heavy float or a float valve starting to go bad. It's very common for these carbs.

But check your plug wires and caps too. There is a procedure in the manual for this. Don't look to hit the resistance numbers dead on. What you are looking for is a consistent reading for all for pots.

Also check your cylinder pressures. Again, you are looking for a consistent pressure across all cylinders. A 5 PSI variance is not going to hurt anything. But if you have one at 110 PSI and the problem cylinder is at 80 or the like, then there's your sign.

Once you get it running right on all four cylinders, you will really see a difference. If one cylinder is dragging, it really kills the power. Even if the cylinder is just rich and not a dead miss. Wheel stands over slight rises may become full on power wheelies!

Steve
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Fuel Injected RZ350