driesbabe

Morning Guys,

I have again got a question concerning one of my engines. I have a 26cc rear reed induction engine, that is running quite nicely.....but, it spits back huge amounts of fuel out the carb when running?
I am familiar with this on side port induction engines, and there it's nothing strange, but a reed induction engine should not do this as far as I am concerned.
Should the reeds not close off on the down stroke and keep the fuel charge inside the crank?

The engine runs very nicely, but it dose tend to run rich especially in the midrange, if I lean the L needle more, the transition suffers?
I not sure what to do.

Could it be the reeds are to stiff? And cannot react fast enough? These are metal reeds, and I have not yet opened the engine to take a look at them.

Regards
Andreas

rc bugman

My Feedback: (30)

Hi,

It sounds like the reeds are not sealing. If this was a 3W engine with fiber reeds, I would say they are warped and need to be flipped over. I also had an engine which sucked a piece of metal through the reed and damaged the reed. Engine ran fine but spitted back fuel badly.

Elson

driesbabe

Thanks bugman,

Do you think that if I turn the reeds over, that I would get some more performance?

rmh

reeds----------
properly done, the reeds " just" seat perfectly when firmly attached- NO seating pressure.
the material to use - -- can be anything - we one used .010 Mylar on a tiny four petal bank - fast response and no danger from swallowing a broken reed.
reeds have least blow back of any induction design -if properly done.

pe reivers

Reeds may be open a little without interfering with the function. They also should not be tightened too tight (if glass or carbon reeds)
The other day I repaired an engine, where the reeds were warped by excessive torque. I re-fitted them, only loosely tightened, and the engine ran and started like a champ.
When the reed is damaged, the engine will spit back, sure sign of the need for reed replacement.

altavillan

My Feedback: (1)

If the metal reed is laying on a fiber impregnated plastic housing or carb base you can apply a thin coat of epoxy where the reed lays then lightly touch the reed down and let it cure. Makes a perfect seal and your engine will idle very low.

driesbabe

Thanks for all the replies.
Now here is another question. The reeds opening point to the pistons skirt, letting the discharge right into the port, this makes sense, but In my opinion, the piston moving downwards inside the cylinder would force the reed open a little, or am completely of track here? Would it matter if I turn the reed around, so the discharge would go inside the crank first?

pe reivers

Every engine is different. The proof of the pudding is in the eating.
Consideration should be, will the conrod bearing get hit by the flow to keep it cool?

rmh

The reeds open/close -only by pressure changes in crankcase - so how the reeds point means nothing -in this case
the size of the reed bank - the stiffiness of the reeds - the resonant peak of the reeds, DO make differences .
All the why's and wherefore about reeds could fill a dumpster .
The designers and aftermarket people all have their own ideas as to "best setups -BUT they all operate the same way -The reed setup in your engine is a compromise of best strength and best operation.