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Old 03-03-2008, 07:03 PM
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jimcork1
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Default Quadra 52 won't run under 3500 HELP

I have a new Quadra 52. It is very difficult to start even with electric starter. At first I though it was ignition so I have installed a CH ignition jump start system which provides a strong at zero rpm, just moving the prop.

With the jump start on and using 24 v electric starter spinning over it is very difficult to start and will not start at low throttle.
I have a prime bottle I use to prime the carb and with the throttle 1/2 open if my batteries arent down in the starter it will start. When running it won't go below 3500 rpm without dying. This is with the CH ignition on. The plug is clean/gapped and dry when removed. I am thinking low speed on the carb preventing fuel below 3500 rpm. The engine is strong turning a 20 x 6/10 prop and has about 18# of thrust. There is no issue from 3500 rpm to full throttle. I have pulled both needles, cleaned the carm (remember this is a new out of the box I bought when Q52 were the biggest you could find). The engine sat new in the box for 7 years until I had a plane for it.

The carb:

The carb is a ZAMA and I have opened it up.
The filters are clean,, needle and seat free to move.
The ports from the L needle through the very tiny ports in the throttle barrel are open and flow easily.
All the internal porting is clean and free.
There is NO damage to the metal parts of this carb.

I have attemped to adjust the needles to get good starting. I used the reco. settings from the Q manual and they don't work. They do work for the high speed, but nothing below 3500 rpm. I have attempted everysetting I can think of on the L needle and no idle. The compression is strong and the engine is almost run in from the higher running.

I really think this is fuel delivery and have ordered the "rubber" carb parts from a Huskavara chainsaw part supplier. I found a H chain saw that uses the same ZAMA body and the diaphrams appear to be the same.


Fuel,, spark air it has to run, There is air,, I know there is spark,, just can't get the fuel. Also is there a substitute carb I can use on this engine.

My current plan is to replace the "rubber" parts and if this doesn't work to adjust the lever arm from the needle to allow more fuel to enter the carb.

Is there any help out there in R/C land that can tame the starting idle on this beast. I am about at wits end as the wife would say.
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