OS 70II - RCCanada - Canada Radio Controlled Hobby Forum
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Old 10-06-2003, 06:27 PM   #1
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I have been running a OS 70II in a float plane with a 12/6 prop. I have run about a gallon of fuel through the engine, and have broken two valvle lifter springs. Can anyone explain why these springs are failing, and has anyone else had this problem
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Old 10-06-2003, 08:56 PM   #2
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I think that a 12 x 6 is possibly too little prop for a .70 4C, allowing the engine to over rev. I use a 13 x 6 on the original .70 without any problems.

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Old 10-06-2003, 09:16 PM   #3
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I always used 13x8 on my OS 70. 15% coolpower Green stuff, runs like a charm.
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Old 10-07-2003, 07:17 PM   #4
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I've the older one

I have a OS 70 Surpass. It's older than yours,, however most of the specs are the same. I currently use it in my UCD 3d with a 12x6. I would check to make sure your not over reving it but also make sure that your not running so rich on the bottom end that it is delaying the timing. I had this problem and the motor made a sharp knocking sound at idle. It could be firing as the piston is already on it's downward stroke.
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Old 10-07-2003, 10:14 PM   #5
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I run a 14-6 on my 70.....
In the absence of any other info, I would guess that it might be high RPM related...

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