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September 22, 2020, 19:22:31 pm

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OS .40 Fs timing it just won't run !

Started by paulinfrance, January 21, 2020, 15:05:20 pm

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paulinfrance

Well my e-boot OS .40 FS ( old model not surpass ) is giving me nightmares, :banghead: 

 The rockers do balance on TDC, I have stripped the carb, all clear, a piece of silicone tube on the needle valve st stop any air leaks, valve clearances Ok, new OS 'F' plug, 10% nitro mix Fuel tank height Ok, with and without pressurisation no difference, when I first started it, it 'hunted', but no air bubbles and new tank with new silicone tubing, I have an APC 11 x 6 prop on it on the last run it flipped the prop when flat out, all I can think of is the valve timing, and 'maybe it was stripped and the camshaft was installed the wrong way around, when I took the cover off, the bearing has a dob of grease on it, not a good sign, and I can't see any timing marks on it,, so has anyone out there got the timing information,,, pretty please ?.
Mode 2 THE only way to fly

paulinfrance

Another check, the exhaust valve closes only 20° from TDC (balance between admission and  exhaust stroke ) so it looks like that, I won't do anything till some good Samaritan suggests what the timing should be. ^-^
Mode 2 THE only way to fly

paulinfrance

Looking at this it looks like a tooth out,,
Mode 2 THE only way to fly

paulinfrance

It looks like I have now got the timing right, :co  it revs nicely but it is still flipping props, :embarassed:  so two lost props, nuts and washers somewhere in my garage, I have tried different plugs, also with an extra washer, I think that the 'mechanic' also probably left a head gasket out, :banghead:  so tomorrow the head comes off :study:
Mode 2 THE only way to fly

PDR

Those engines were prone to detonating (pinking) and throwing props - mostof the early 4-strokes were. It may also relate to the fuel. IIRC they were menat to have 10% castor-base with no more than 5% nitro. More nitro than this would be a bad idea. If you're using a synthetic oil it may be too volatile and that would probably want some decompression. Similarly if you're using too much oil then it will be running lean and that could make it throw the prop. I think they were also meant to have the shoruded "4-stroke" plugs, although I usually ran mone on a K&B-1L (because I had loads of them).

€0.00008 supplied,

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

firefox

Could it be a bit lean, 4 or 5 clicks of open from max revs might help?

Now you know why the more modern ones have a prop nut with a lock nut!
Nothing is foolproof to a sufficiently talented fool......

paulinfrance

Thanks, but I had 2 of these engines, one I swapped (for a 60 and got conned another story ) and the other my nephew had, and I didn't get any of those problems,, they both ran well on the fuel that I am using.

by the way, it throws props at any speed, but no room for a locknut with a spinner .
Mode 2 THE only way to fly

paulinfrance

I had thought of opening up the inlet valve gap to reduce the air going in,,,
Mode 2 THE only way to fly

firefox

If you get the proper nut it has a recess where the locking nut screws into and uses little length on the shaft.
Nothing is foolproof to a sufficiently talented fool......

paulinfrance

Quote from: firefox on January 21, 2020, 19:42:42 pmIf you get the proper nut it has a recess where the locking nut screws into and uses little length on the shaft.

 Yes I have a spare locknut but no space especially with an APC prop, the protruding prop shaft is only 24mm long.
Mode 2 THE only way to fly

JimG

Try using a Nyloc nut instead of the plain one. I used to do this on my old 48 Surpass which did not come with a locknut.
Jim Gill
Dundee Model Aircraft Club

paulinfrance

Quote from: JimG on January 22, 2020, 11:07:34 amTry using a Nyloc nut instead of the plain one. I used to do this on my old 48 Surpass which did not come with a locknut.

 Not enough room,,
Mode 2 THE only way to fly

paulinfrance

Well that's it  :embarassed:

  I took the head off the gasket ( 0.20mm ) wasn't in properly :''  and it looks like the engine has never been run, I put a thicker one in at 0.3mm it did run much better, but still kicking props, The seller has offered to  refund me it's going back.

I fitted my OS .60 Open rocker in and ran it, my faith in OS is back online, even though the plane will be very overpowered,,  :banghead:
and like me over weight,,  :'' Os .40 head-2048.jpgOs .40 head joint 0.3-2048.jpg

Mode 2 THE only way to fly

firefox

The OS lock nut and nut are made with a taper, one goes a way into the other so they do not take so much space, have a look at one and you will see.

Don't forget it will take time to run the engine in if new before you get a well behaved engine.
Nothing is foolproof to a sufficiently talented fool......

paulinfrance

Sorry 'but' my first 4 stroke was in 1985,,and the first ones didn't have lock nuts,, my OS Open rocker and VT 21 and a few more of my engines don't have them, neither did my OS .40 4 strokes that I swapped and gave away, they both ran really well.

 Running in is another problem, 18% oil, 10% nitro an OS 'F' plug and leave a 1.2v battery on the glow plug while it is running up to 1/2 throttle, when you have run it on the bench ( not over propped ) for around 1/2h on and off making sure that it doesn't get too hot, lean it out till it runs well and back off the needle valve a good 1/4 turn and then fly it,,
Mode 2 THE only way to fly