OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Reed Valve 160

Motor wont start .Hi Imay be thick but what stops the back flow on a old 160 ,when piston goes down ,well ok on the old iron horse motors there where a reed valve flap to stop back flow,yes i under stand on the compression stroke it fires ,does the piston position in barrel cover over the intake port to cut the flow from going out the carb ,just remebered the vaccum stop valve opens to let air come in for the commpression stroke it closes for the firing stroke,perhaps the valve is stuck or spring in it shot causing the motor to have less commpression when requird for the firing stroke ,motor wont start any other ideas

There are three main ways low-cost two strokes can control the induction process: a piston-controlled intake port at the bottom of the cylinder bore, to let gas into the crankcase, a reed valve controlling an intake port permanently connected to the crankcase, or a rotary valve controlling an intake port into the crankcase. Rotary valves are fairly expensive and are mainly found on relatively high speed two strokes, such as motorcycle engines. Reed valves cost slightly more than piston-controlled ports. The lowest-cost two strokes usually use piston-controlled ports.
A piston-controlled intake port is opened and closed by the skirt of the piston, not the top edge above the rings, and it only opens briefly at the top of the piston's stroke. At that point there is a vacuum in the crankcase because the piston has moved up to the top of its stroke with the crankcase sealed, thus increasing the internal volume of the crankcase. As soon as the piston begins to descend down the bore the intake port is shut off by the piston skirt, and the gas in the crankcase starts to be compressed due to the crankcase volume decreasing. At the bottom of the stroke the top edge of the piston opens the transfer port which connects to the crankcase. The transfer port allows the compressed gas in the crankcase to be transferred into the cylinder, ready to be compressed as the piston moves upward.
If your engine won't start there are some basic checks to make: is there spark, is there good fuel in the tank, does the fuel flow readily into the carburetor, does the compression feel normal. Before assaulting the carburetor and possibly making things worse, it pays to identify the general cause of the problem. If you have spark, fuel is entering the carburetor, and you are confident that compression is normal, you could try squirting some fuel into the engine (through the spark plug hole or the carburetor air intake) and see if it starts then. If it starts but then stops, it's time to take a look at the carburetor. If it still doesn't start, you most likely have loss of compression, or less likely, a problem with the speed control or governor. If it has spark and priming the engine with fuel as described does not make it start, checking the decompressor might be a good idea - they seem to give a fair amount of trouble.

Hey all, FYI,
Some of the old Kirby Tecumseh 2 strokes were fitted with a reed valve intake system, through the bottom end of the engine..... (I'd like to find one??)

After thought, hard starting on an old two stroke engine usually means hard leaking crankshaft seals (if all else tests good) and from my exp. if the engine runs ok cold then dies when hot and wont re-start till cold again, it needs an ignition condenser.

I'm sure Moderator Bruce will be able to sort you out a new set of parts plus gaskets if need be.

if the decompresser is ruled as the problem a standard spark plug fits strait in the hole and does not impede the operation at all. the terminal on the end is the exact right size for the rubber hose to slip over the decompresser in victas are of poor quality because the diaphragms often perish and eventually do not open and close the valve as it should because of vacuum loss.
i have had a few old Tecumseh engines with crankcase mounted reed valve assemble and some weren't to bad. the difference between the good and bad ones were one had a totally flat assembly with all the valve on one plain but the other had a triangular shaped assembly that meant it had about twice the surface area and therefor more valves so it sucked freely and closed quicker because the valves were physically smaller. the smaller valves allowed sharper acceleration and response, and also let more fuel in easier when cold starting. i might take a pic of the two different types if you like.
regards jay

Hey Jay,

Yeah mate please do send a pick or two. I'll get my camera happening on a few of the beasties I have.
I do have a kirby tecumseh reed valve motor on an old back pack yard blower, ( a freebie saved from a Govt. skip, still has cross hatching in the bore!) but the motor is quite a bit smaller than what I'm looking for that has the single plane reed petals....

What did you have the old motors on?


John