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Old 11-25-2004, 05:42 AM   #1
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Default Something burning in the back of my mind...

Something just occurred to me, what stops the conrod moving and rubbing on the backplate of a non pullstart engine??
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Old 11-25-2004, 06:04 AM   #2
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Default Re: Something burning in the back of my mind...

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Originally posted by jamiekulhanek
Something just occurred to me, what stops the conrod moving and rubbing on the backplate of a non pullstart engine??
Taper on cranckpin and vertical ballance of piston/conrod
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Old 11-25-2004, 11:25 AM   #3
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Default Re: Re: Something burning in the back of my mind...

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Originally posted by Top Gun 777
Taper on cranckpin and vertical ballance of piston/conrod
Hey Ed, are you referring to the Wristpin is wearing out? not in perfect round?
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Old 11-25-2004, 11:43 AM   #4
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the pin boss on the piston (look underneath piston) stops the rod from moving too far and contacting the backplate.

this is why it's sometimes hard to remove the piston/rod assembly from the crank on a fresh engine. the rod does not always move real freely on the pin in a fresh engine. there is just enough room for the rod to slide on the wrist pin and remove it from the crank.
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Old 11-25-2004, 08:27 PM   #5
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Default Re: Re: Re: Something burning in the back of my mind...

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Originally posted by Ah10
Hey Ed, are you referring to the Wristpin is wearing out? not in perfect round?
Hey Tony. Actualy I am refering to cranckshaft pin.
Initaly there is negative taper-very small. This is why conrod is not sliding out. Ones it is wearing out-you can see results on back plate.
Corey you are absolutly right about some engines is very dificult to take on parts and it is due t the tolerances on cranpin and wrist pin. In airmodeling all high end engines for speed and pilon even procedure is very special to take piston/conrod is complaceted, First we taking out sleeve, tehn G-clip from exhaust windows, then frist pin, next piston and conrod. Assembling is opposit way-put conrod, put piston, put wrist pin etc. To put G-clip we made specila tool-it is pretty dificult to put that clip through the exhuast, but it is done and with exprience it is done within a second. BTW, I do use this tool for regular assembling too.
Tool look like very thin wall tubing. OD is 0.02 mm smaller then wrist pin and wall thickness is 0.03. I put G-clip inside that tubing and then slide that tool inside piston's wrist pin hole and pushing G-clip out side by the pin ( which is close size to ID of tubing)-G-clip is on it's palce. Very fast and never fail.
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Old 11-26-2004, 08:34 AM   #6
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thanks guys...


One other question, i am fairly new i guess to nitro engines, and bought an engine to replace my old one...

I pulled it down completely and cleaned and oiled it, but unlike my crappy GX 15 engine the O.S. has a hole or "window" in the piston, i was a little unsure of how to orientate the piston. It can either be installed with the window on the exhaust port side or on the booster port side, i reassembled the engine with the window on the booster port side. I hope i did the right thing...

I wasnt totally sure if the window was a port or weight balancing...

Please help
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Old 11-26-2004, 10:37 AM   #7
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Quote:
Originally posted by jamiekulhanek
thanks guys...


One other question, i am fairly new i guess to nitro engines, and bought an engine to replace my old one...

I pulled it down completely and cleaned and oiled it, but unlike my crappy GX 15 engine the O.S. has a hole or "window" in the piston, i was a little unsure of how to orientate the piston. It can either be installed with the window on the exhaust port side or on the booster port side, i reassembled the engine with the window on the booster port side. I hope i did the right thing...

I wasnt totally sure if the window was a port or weight balancing...

Please help
Window on piston must to look on booster, not on exhaust.
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