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OS FX 61 - 5/29/2008 11:59:25 PM   
Glenn111


 

Posts: 15
Joined: 9/16/2007
From: Auckland, NEW ZEALAND
Status: offline 		I have a reasonably new FX 61 that I have in my Intruder 90R airplane with about 80 mins run time. During the last couple of runs I have noticed a knocking noise occuring at half throttle. The knock disappears at full RPM. It happens on the ground and in the air so is quite loud. I have checked for movement in the crankshaft and found there is slight forwards/backwards play which I believe is the cause of the knocking. There is no sideways play. The engine still runs well but I will not run again until I sort it out. Has any one else had this problem or could suggest any reasons for this problem? Should there be any crankshaft play? Any suggestions on parts likely to be required would be appreciated. Thanks. Glenn
       Post #: 1

RE: OS FX 61 - 5/30/2008 12:17:44 AM   
Flyboy Dave



Posts: 13375
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		Glenn....what prop are you running on there, what fuel ?

....your engine may be complaining.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to Glenn111)
       Post #: 2

RE: OS FX 61 - 5/30/2008 12:29:09 AM   
Glenn111


 

Posts: 15
Joined: 9/16/2007
From: Auckland, NEW ZEALAND
Status: offline 		Running a 12 x 6 APC with 10% nitro. My other engines run fine on this. do you think there should be any play in the c case?

(in reply to Flyboy Dave)
       Post #: 3

RE: OS FX 61 - 5/30/2008 12:44:30 AM   
mike109



Posts: 124
Joined: 7/25/2004
From: DubboNew South Wales, AUSTRALIA
Status: offline 		G'day I have a Leo 46 that was making a similar noise. I suspected (and it was confirmed here) that what I have is an engine with slightly too much compression for the 10% nitro fuel I was using. What I was getting was pre-ignition - knocking - or pinging. What plug are you using? If the plug is too hot it can cause this problem. So can too much compression or a lean midrange. The solutions suggested to me was to replace the OS A3 plug I had used (it was the only one I had) with an Number 8 and to either use less nitro or to add an extra head gasket under the head. I have not yet managed to do the tests as the engine is in a friend's plane and he is away but I will report once I get a chance.

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If it''s not right on the ground - it won''t get better in the air. Club Saito # 597

(in reply to Glenn111)
       Post #: 4

RE: OS FX 61 - 5/30/2008 12:18:47 PM   
BlackB12


 

Posts: 374
Joined: 9/22/2004
From: lancaster, PA, USA
Status: offline 		I noticed that sound on several OS glow engines, lately my os55ax and my buddies 120 ax. In our case it was normal sound from a slightly rich, burbly midrange but the stock muffler really made it sound metallic. Unless the sound is different I'd say it's normal. There will probably a lot of posts below of how you should completely tear apart your new engine or that it will blow up from detonation, but I don't think this is the case. You don't have a video of it doing this do you?

Mike

(in reply to mike109)
       Post #: 5

RE: OS FX 61 - 5/30/2008 3:49:50 PM   
bob27s



Posts: 4737
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		without going into the engine construction ..... its just something the engine does. Tends to be normal. I'd not worry about it.

Just a precaution ensure that all of the engine fasteners and the glow plug remain snug in place.

If the engine gets suddenly starts getting hot, runs oddly, starts blowing plugs, or you see black crud in the exhaust...... then something is coming apart.

< Message edited by bob27s -- 5/30/2008 3:51:33 PM >


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Jett Engineering - Engine Mfg Support Forum Host

(in reply to Glenn111)
       Post #: 6

RE: OS FX 61 - 5/30/2008 8:59:26 PM   
Glenn111


 

Posts: 15
Joined: 9/16/2007
From: Auckland, NEW ZEALAND
Status: offline 		Guys thanks for the reply. I am concerned with this rattle (loud knock really) as I have not heard it before. My other OS engines do not have this. Does any one elses crankshaft have any lateral play? When I push on the crankcase (CC) and turn I can feel it rubbing on the backplate. When I dont push it doesnt rub and is smooth. Is that normal? I reckon that it is this freeplay that is causing the rattling at lower revs and when it is full rpm the prop pulls the CC away from the backplate and the rattle goes away. I am still running the engine slightly rich as it is still quite new and will lean it up next run and see. Are running a 12 x 6 APC prop, no. 8 OS plug and 10% nitro fuel with 17% syn oil content.

I have attached the reply I got back from the New Zealand OS distrib re this problem. What do you think of the 3% castor oil suggestion? OS doesnt reccommend on their web site but will mix some in at 5% and see if that helps.

I couldnt help myself and stripped the engine down to check bearings and all seems ok. Only noticed some scuffing on the CC backplate and a couple of vertical scuffmarks at top of piston.

As I said in my first posting the engine runs fine other wise and is not running hot, blowing plugs or has an off coloured exhaust.
Anyway thanks for your help and keen to get any more thoughts you may have. I purchased from Tower Hobbies in the US and with the postage @ US$22 each way I would like to try and sort it myself. Thanks again. Glenn

Hi Glenn

I have been repairing OS motors for around 20 years and would suspect your rattle is crankshaft movement. If the correct fuel is being used which should contains at least 3% of caster oil in with the normal oil content of around 20% the rattle will go away. The rattle is most probably due to not enough oil around the bearings, and crank.. The motor does not need repair, only the correct fuel. Also check muffler and mounting screws.



Regards

Lloyd



(in reply to bob27s)
       Post #: 7

RE: OS FX 61 - 5/30/2008 11:09:46 PM   
Flyboy Dave



Posts: 13375
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		....I would recommend a lot more castor than 3%. I use 33% castor
in my fuels, and sometimes add more castor.

Add 4 or 5 ounces of castor to that fuel and see if the noises go away.
You can get castor at the motorcycle or go-kart shop.

FBD.

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to Glenn111)
       Post #: 8

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