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intake push rod cover is partially out of place

Old 12-30-2007, 04:48 PM
  #1  
selnekav
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Default intake push rod cover is partially out of place

Hi Troy,
few weeks ago my YS-110 engine returned from repair, and for the last 10-15 flights it was running very well ( high speed, smoote transition, stable idle ) but then few days ago when i arrived to the field i tried to start the engine ( i want to mention that i didnt change any of the needls setting HS , LS , regulator ) , but instead of reving 2200 rpm at idle , now the engine rev at 4000 rpm !!

i tried immidieatly to close the throttle by using the transmitter offset ( like i do when i want to shut down the engine ) but although the thorolle was fully closed there was no affect on the rpm so i needed to cut the fuel supply..
i visually checked the engine, and noticed that one of the two buttom backplate screws was missing
so i screw new one instead, and thought that i solved the problem.. but again after starting the engine it was acting the same so i needed to cut the fuel supply again ( lucky me it was not on high revs like 8K, 9K )

after i returend home i remove the engine from the plane, and i was thinking of checking the throttle barrel seal but then i noticed that the top side of the intake push rod cover is partially out of place so there is small hole which allow air to flow into the valve cover or in the opposite direction into the cum gear.

is that can cause the problem that i facing ?

Thanks,
Old 12-30-2007, 05:00 PM
  #2  
Troy Newman
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Default RE: intake push rod cover is partially out of place

Yes that can be a big air leak.

If you are vibrating carb bolts and such out of the engine you need to look at balancing your prop, and making sure the engine mount is secure in the airplane.

For those pushrod tubes to be off the had had to come loose or something had to hit the pushrod tubes. Since you said nothing happened to the engine and bolts were coming loose, I suspect the head bolts are loose as well.

Troy Newman
Team YS
Old 12-30-2007, 05:27 PM
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selnekav
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Default RE: intake push rod cover is partially out of place

Hi Troy
Thanks for your quick reply, it's very helpfull to have such great support.
the engine mount is secure ( i have checked it before removing the engine from the mount and it was tighten ), also the prop is balanced, and the posh rod cover wasn't get any hit.

my suspicion is that during the engine assembly in Japan ( the ring was replaced ) when the cylinder was tighten, the posh rod was not in the right place, and then by the vibration or the air flow caused by the prop revs the posh rod was moving slowly slowly till the point when it started to affect the engine setting but this is only only my guess..

also is there passage between the engine buttom backplate thread to the engine ( because even when there was missing screw the backplate was still tighten )

anyhow do you see any point to disassemble the carburator to check the throttle barrel seal or the fact that i found the posh rod cover probelm will be enough to explaine that beaviour ? ( i really don't want to mess with it unless i must to, i belive that it can cause new problems )

Best Regards
Shlomo.
Old 12-30-2007, 08:34 PM
  #4  
Troy Newman
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Default RE: intake push rod cover is partially out of place

No I would not pull the throttle barrel, you could actually damage the seal taking it in and out. If it was leaking at the pushrod tube...that was your problem.

As for missing carb or backplate bolts. YS engines are very highly tuned to the pressure inside the engine. The rear disc valve and the pistons stroke both up and down create the pressures that run the engine. If you have a leak any leak, missing bolt is just that.....will cause problems. Even if the carb or backplate appears tight it is probably leaking at some point.

See the bottom of the engine is not always in vaccum...when the piston is moving down it is in compression...this higher positive pressure can leak out if its not sealed properly...

If the prop is balanced and its still shaking things loose perhaps the crankshaft is bent even slightly can be a problem.

Troy Newman
Team YS
Old 12-31-2007, 12:26 AM
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selnekav
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Default RE: intake push rod cover is partially out of place

Thanks Troy
Last question.. do you think that locktite can help for the backplate screws ? i am planning to put soft mount soon

Shlo0mo.
Old 12-31-2007, 12:40 AM
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Troy Newman
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Default RE: intake push rod cover is partially out of place

No lock-tite needed...if you need locktight then the prop is out of balance. The crank is bent or something similar. They should not shake their own bolts out of the case.

Happy New Year

Troy

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