ZDZ 50
10-10-2005, 03:40 PM
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ZDZ 50
Thanks for your response on the rpm loss, I tried your ideas and all of these runs were one at time with the aircraft tied down, not flying. First run I changed the fuel to 32:1 and the rpm increased to 6900 but began to decrease to 6750 after about 1 minute of running, engine cowl was on and cht next to the spark plug was 310 degrees about 10 seconds after engine shutdown after a full throttle run. I cut away some of the cowl to expose most of the cylinder and ran again with the same results. I ran with the cowl removed with the same results, I removed the engine so I could clean the carb filter and found that the filter was dirty, cleaned and ran the engine with the same results as the first time. Changed nicad battery, no change. The engine will respond to a needle change while running at full throttle, it takes less than 1/4 turn either way to see a difference. Idle is a very solid 1600-1700 rpm with great response while rapidly advancing the throttle. While running at full throttle the rpm will vary by 150 rpm with no throttle change. When the propeller is "flipped" for starting the compression seems great but when the propeller is turned over slow I don't detect much compression.
10-11-2005, 09:33 AM
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RE: ZDZ 50
Huey-Pilot:
Sounds to me like it isn't broke in yet. I have a ZDZ50RV and it took a very long time to break in. Mine also didn't develop a lot of compression, hard to start when hot etc. Once it broke in it has lots of power, compression, starts easily when hot etc. I am beginning to think 40:1 is not enough oil for these engines. I increased the ratio on ZDZ80RV from 40:1 to 32:1 and it ran much better. You may want to consider a baffle in the cowl for cooling. I followed the example on RC Showcase website. I really didn't think it would make any difference. But, I tried on my ZDZ80 and IT DID make a difference. Mike Dooley is right on this one.
FWIW, Brian......
Sounds to me like it isn't broke in yet. I have a ZDZ50RV and it took a very long time to break in. Mine also didn't develop a lot of compression, hard to start when hot etc. Once it broke in it has lots of power, compression, starts easily when hot etc. I am beginning to think 40:1 is not enough oil for these engines. I increased the ratio on ZDZ80RV from 40:1 to 32:1 and it ran much better. You may want to consider a baffle in the cowl for cooling. I followed the example on RC Showcase website. I really didn't think it would make any difference. But, I tried on my ZDZ80 and IT DID make a difference. Mike Dooley is right on this one.
FWIW, Brian......
10-11-2005, 10:02 AM
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RE: ZDZ 50
YIKES! Please do not run the engine at full power on the ground until it starts to sag!
You are overheating the engine!
Yes, It is normal for the engine to fall off especially running at full power for almost a minute on the ground!
Please, just fly the engine and be very easy on the throttle.
Give the engine a chance to break-in. It will love you for it!
You are overheating the engine!
Yes, It is normal for the engine to fall off especially running at full power for almost a minute on the ground!
Please, just fly the engine and be very easy on the throttle.
Give the engine a chance to break-in. It will love you for it!
