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MVVS 45 IRS/MG - spark plug getting loose

Old 06-11-2006, 05:39 PM
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Default MVVS 45 IRS/MG - spark plug getting loose

Hi all,

i have a brand new MVVS 45 IRS/MG in breake-in phase. The engine is horizontally mounted, in a 81" Phoenix CAP232.
The engines has enormuous power, but there is a big problem: the spark plug get loose at every 2-3 minutes. I have
tightened it with the included tool, the plug cable is attached with the standard VLACH hardware. I have noticed that
the prop I use is a little bit unbalanced. Can this unbalanced prob cause such a vibration that leads to loosening the plug
from itself??? I don't want to ruine the thread in the cylinder head...
Thanks in advance

mrsad
Old 06-12-2006, 08:50 AM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

Balance the prop first. Track and mass balance. The 43cc engine has very low vibration levels, so any excess vibration is from prop unbalance.
The included tool in it's original form was for centering the plug only, and has a soft steel bar, which is too small to proper torque the plug. Replace with a slightly thicker (6mm or 1/4" ) and longer piano wire bar. A standard socket or pipe wrenchwill need to be turned down in Outer Diameter, but that would another solution allowing for stable rod inserts.
A properly tightened plug will not loosen.

Added in edit:
Proper tightening for conical seat plugs without washer is 1/16th of a turn after the plug seats well.
I tighten mine about 1/12 th, because the plug boot is clamped between plug seat and plug taper, so it adds another element, and 1/12th is easy to guess with the hexagon flats of the wrench.
I took the original soft bar out of the wrench, and insert a philips screw driver to use the original factory tool.
Old 06-12-2006, 05:11 PM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

Thanks for your quick reply. Could you tell me please what is the tightening torque for the plug in the 43cc engine?
I have heard some info about 15 Nm. Is this correct? It seems a little bit too much for the aluminium cylinder head.
Thanks in advance.

mrsad

Old 06-13-2006, 03:51 AM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

15 Nm would not be too much (clever guess). The bar I inserted is 7" long, which is about right for manual operation.
Never torque the plug into a hot head.
Old 06-13-2006, 04:10 AM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

Thanks for your help.

mrsad
Old 07-10-2006, 06:52 AM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

Same hapened to me ... but in interval of 2 or 3 flights.

I have huge problems with engine operation since last incident. It does not run smoothly when warmed up. What is your guess - burned ignition or sth else?

I would apreciate your hint ....
Old 07-10-2006, 03:48 PM
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Default RE: MVVS 45 IRS/MG - spark plug getting loose

Late information:
Brisk prescribes 1/16 th turn tightening after the plug seats with light figer pressure. I tighten mine about 1/12th turn, probably because the extra inserted lower plug boot adds some extra deformation.
ZDZ specifies a torque of 30 Nm. This is more than the supplied tool is capable of.
Remove the plug tool's bar, drill the hole to about 5/16" (8mm) and insert a suitable 6" piece of piano wire or phillips screw driver.
Old 09-23-2013, 07:06 AM
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Put a 14mm to 10mm cm6 adaptor in your engine. Replace the death cap with a cm6 cap! And all problems solved!!

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