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Author Topic: MARZ 2.5 D strange noise  (Read 638 times)
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Fourfingers
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« on: November 13, 2016, 01:17:17 PM »

Another dumb qwestion from a beginner ...
Just acquired a new MARZ 2.5 D, so tight I cant turn it over without fear of breaking something.  But did just that and no damage, I think ...
However, on flicking, now reasonably free, and has run a couple of minutes, there is an odd click - more prononced on 'bounce back' (clockwise).  Im thinking its the rotary valve at rear engaging a bit loosely in the crankpin.
Any thoughts out there?
Thanks
Two and a half fingers
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Fourfingers
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« Reply #1 on: November 13, 2016, 01:19:34 PM »

PS
Theres a video about the problem on youTube.  Search "john chadwick MARZ"
Oh no, Ive revealed my true self ....
One finger.
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old4570
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« Reply #2 on: November 15, 2016, 07:07:52 AM »

Remove the rear back plate / assembly ..
Is the noise gone ?

 What happens with rear inductions is ...
If the slot for the crank pin is a little over sized , then the crank pin will bounce of one side of the drum slot to the other as you flick the prop .
Once the engine is running , the crank pin will drive the drum on one face and not bounce from one side to the other ( flicking )
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Fourfingers
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« Reply #3 on: November 15, 2016, 09:43:16 AM »

Yep, old4570, I reckon this is the cause ..... will give ti a few more runs to bed it in, then take the back off.  Will let you know.
Thanks
john
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old4570
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« Reply #4 on: November 16, 2016, 04:26:39 PM »

I would highly recommend an inspection before running the engine ...

 Pull of the back plate , remove the head , pull out the piston ( noting which way things go - back )

   Check for any debris in the engine , or anything that may cause issue ..

Get some WD40 or RP7 or such like and clean the internals ..

Re assemble , and run the motor ... 

I never ever run a motor out of the box , I don't think I have done it even once . And I never fail to remove debris from a fresh engine , and used engines too often . 
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Fourfingers
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« Reply #5 on: November 17, 2016, 03:32:46 AM »

Good advice, thanks.  In fact did take to bits, clean, oil and reaasemble before running.  Surprisingly clean, and I dont think it had been run, either.  Head screws mangled though!  Going to replace with cap screws.
Seems the Delphic Oracle out there reckons the noise is the play between rear disc and crank pin.  Some slap acceptable, appRently!
john
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old4570
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« Reply #6 on: November 19, 2016, 07:16:49 AM »

Yeah , when the engine is running the crank pin will be driving the rear induction drum on one face ...( Constant pressure )
The clicking sound is there because of the hand flicking .. Crank shaft is bouncing back and forth .. 

 All rear induction engines suffer from this to some extent ..
Set things up too tight and you may cause more problems than you think you might fix ...

  A lot of people destroyed rear induction engines when they set up the rear disc overly tight .
And others were destroyed from the rear disc being overly loose ( too much play )
Good thing about drums is they are hard to kill ... 

One of these days I hope I can build some drum rear inductions for my Rossi 15's  ( Do away with the fragile disc induction ) ( If I ever get another lathe )
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