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Rear plate gasket for OS46FX

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Rear plate gasket for OS46FX

Old 07-06-2022, 11:30 AM
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voyager_663rd
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Default Rear plate gasket for OS46FX

Out of hobby for a decade and still trying to get back in so I consider myself a newb once again.

My OS46fx got taken apart for a full anti-freeze cleaning in my crock pot. In removing the back plate, the gasket ripped but was still in one piece

Cleaned/dried and re-assembled with the torn gasket. New tubing, new 10% fuel, new #8 plug, glow fully charged but will not fire. Electric starter being used.

Fuel is flowing (even resorted to adding a few drops directly into carb) but no joy. A search here only suggested how to make your own gasket but nothing that I could find about excessive air getting in. It's about .002 mm thick but how relevant is that in trying to source gasket material? Suggestions I found are "folder stock paper" or "photo paper"; even cereal box paper may work. Gaskets for this glow are not available (as expected).

I don't want to take it apart again to make one and find out that's not the issue (although I suspect it is, is why I'm asking).

Question is: is that rear plate split gasket enough to prevent firing (ie too much air being let in)?
Old 07-06-2022, 12:11 PM
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If it has been carefully put back on, and the ripped portion mates up well, then I'd say "no". In general, even with a leak, it should definitely fire, although may not run, or more likely run poorly. But not even a "pop"? then it can only be one of three things:
1. The glow plug is not glowing, or barely glowing. Take it out, and in dimmer lighting, see how it looks when connected to the battery. A bright orange is what you want. Make sure you are using a washer when installing the glow plug.
2. Something preventing fuel flow. Time to check the carb, especially the high speed needle end, seat, passage for any gunk kicked loose from the cleaning method. I'd guess something in the spray bar, blocking the hole/slot in it.
3. Too much fuel, resulting in the engine flooding very quickly. Danger here using a starter, as hydraulic lock can happen, and the starter then bending connecting rods, etc. (almost all of us old guys have done it sometime in our past). Close the high speed needle. 2 to 2 1/2 turns open. Disconnect the fuel line. See if any pours out of the muffler when tipping it and turning the prop by hand. Take plug off, and use the starter to spin the engine (watch out for the spray that may hit you in the face!). Repeat a few times to make sure all excess is out. Put the plug back, reconnect the fuel line. Try to start.

Since you may be taking it out to check the carb, no issue making a gasket out of a business card....
Old 07-06-2022, 12:31 PM
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Originally Posted by tedsander
If it has been carefully put back on, and the ripped portion mates up well, then I'd say "no". In general, even with a leak, it should definitely fire, although may not run, or more likely run poorly. But not even a "pop"? then it can only be one of three things:
1. The glow plug is not glowing, or barely glowing. Take it out, and in dimmer lighting, see how it looks when connected to the battery. A bright orange is what you want. Make sure you are using a washer when installing the glow plug.
2. Something preventing fuel flow. Time to check the carb, especially the high speed needle end, seat, passage for any gunk kicked loose from the cleaning method. I'd guess something in the spray bar, blocking the hole/slot in it.
3. Too much fuel, resulting in the engine flooding very quickly. Danger here using a starter, as hydraulic lock can happen, and the starter then bending connecting rods, etc. (almost all of us old guys have done it sometime in our past). Close the high speed needle. 2 to 2 1/2 turns open. Disconnect the fuel line. See if any pours out of the muffler when tipping it and turning the prop by hand. Take plug off, and use the starter to spin the engine (watch out for the spray that may hit you in the face!). Repeat a few times to make sure all excess is out. Put the plug back, reconnect the fuel line. Try to start.

Since you may be taking it out to check the carb, no issue making a gasket out of a business card....
1)glow plug new right out of the package (and installed with copper ring)
2)remote glow charger may be low (but also tried with a plug-in charger connected to power panel (in the "green" when connected).
3)too much fuel may be an issue but I turned over by hand b4 puttling the elec starter on it so wasn't concerned about fuel lock.

Fuel did pour out of muffler (tank was only 1/3 full when I started this exercise) as I probably over-primed but as said, prop turned freely by hand before putting the elec starter on it.

Hi-speed was out 1 1/2 turns so that might be it (tried at 2 turns during test but no pop, no nothing either but I'll richen it up more next attempt but AFTER ensuring it is empty of fuel. Then prime normally).

Thanks for the suggestions. Like Arnold said: I'll be back
Old 07-07-2022, 05:14 AM
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Seems to be a classic case of the engine being flooded. Raw fuel hitting the glow plug, and making it too cool to fire. It can be surprising how much is still in there after pouring it out of the muffler. Hence the spinning it without a glow plug in place to clear out the remaining excess. Afterwards, try starting without further priming first.
Just checked my NIB 46FX manual, and correct initial high speed needle is 1 1/2 to 2 turns out, so my previous comment was a little too rich. While not outrageously excessive, still could exacerbate the issue if the engine already has a bit too much fuel in it.
NiStarter meters can be notoriously off - mine is in the green even when nothing is attached! So check the glow on the plug just to verify. Not enough heat can lead to more cranking, which can lead to flooding.
While not as critical for initial starting, check your low speed needle. OS says with the carb fully closed, the needle should initially be exactly 1 turn out.
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Old 07-07-2022, 05:42 AM
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The thickness of the gasket is important with a ripped gasket clean both surfaces and the gasket and let dry. A very light touch of heat resistant rtv on both sides of the rip and reassemble should take care of any leak.

I initially set the needles on those carbs using a 1/16 drill bit. Back the low speed needle out. Put a short piece of fuel tubing on the fuel inlet so you can blow through it into the carb. Insert the 1/16th drill down the throat of the carb and close the barrel until it just holds the drill bit. Do not force. Blow through the fuel line and slowly close the high speed needle until the air stops flowing. Now back the needle out slowly until you can just detect air beginning to flow. Your high speed needle is initialy set a small adjustment is all that should be needed. Now set the low speed needle as per the manufacturer's instructions and your initial carb setup should be complete.

Last edited by Propworn; 07-07-2022 at 06:01 AM.
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Old 07-13-2022, 11:22 AM
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Haven't forgotten.

Checked the hand-held igniter--battery is deader than a door nail. When I plugged in to re-charge, did not notice that the charger light did not come on. Tested battery and I get .2V.

So, looking for replacement battery--rip off city for us Canucks. One amazon site gave me $75 shipped for 1 battery. Cheapest Canuck site so far is $18 shipped for a $3 battery.

persevere and you shall be rewarded--$8 no shipping. Still not as good as US but it is what it is. Be a day or three but I'll be back

Last edited by voyager_663rd; 07-13-2022 at 11:46 AM.
Old 07-14-2022, 03:12 PM
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Stage 2:

Got the igniter battery/charged it and got the engine running at 1 3/4 turns but it won't run without igniter attached. Weak plug?? Tried it in the igniter and no glow so needs to be replaced.

There may be an air leak as well (compression is there BUT not as much as I expect). New plug will be obtained shortly and see what happens before I take the rear plate off for gasket replacement or repair per rtv sealant as above.

I shall return

Last edited by voyager_663rd; 07-14-2022 at 03:18 PM.
Old 07-15-2022, 06:56 AM
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new plug but still a lot of cranking (fuel draw really seems minimal as when I prime (WOT then plug the intake, still takes 7-8 turns to even get fuel to draw). Eventually fires but does flood--runs at 1/2 throttle but dies when igniter removed. Fuel pours out of exhaust when I shut it down (not as much as before but still it should be minimal--it's not).

Getting some new RTV (ya know, the old stuff once opened-but closed tight-still turns into a rock) and some brake cleaner. While apart, I'll check the innards for debris, etc
Old 07-15-2022, 10:35 AM
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I've use regular copy paper before for a gasket with no problems. Also the gasket maker in a tube works.
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Old 07-15-2022, 08:22 PM
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You have a leak and/or shot compression. See if sealing helps. Make sure all screws are tight, especially the head. "ABC" engines have no ring, and depend on critical clearances when at running temp to give correct compression. Turned over slowly they may feel like they only have a little, spun faster and they feel better. Are best after they have been started and are up to temp. BUT, also easy to run too hot, or a myriad of other issues, that scores the piston/liner, in which case they never will have enough compression.

Hopefully the gasket will resolve the issue, then you can have a more dependable needle setting to resolve the too rich/flooding issue. And running leaner may help with the plug issue - may be a bad plug, or it may be just too much fuel putting the fire out. But the needle won't adjust right until any possible leaks/compression issues are resolved.
Old 07-16-2022, 05:02 AM
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Originally Posted by tedsander
You have a leak and/or shot compression. See if sealing helps. Make sure all screws are tight, especially the head. "ABC" engines have no ring, and depend on critical clearances when at running temp to give correct compression. Turned over slowly they may feel like they only have a little, spun faster and they feel better. Are best after they have been started and are up to temp. BUT, also easy to run too hot, or a myriad of other issues, that scores the piston/liner, in which case they never will have enough compression.

Hopefully the gasket will resolve the issue, then you can have a more dependable needle setting to resolve the too rich/flooding issue. And running leaner may help with the plug issue - may be a bad plug, or it may be just too much fuel putting the fire out. But the needle won't adjust right until any possible leaks/compression issues are resolved.
Don't think the head is the issue here. Maybe.

When I did the anti-freeze clean, I removed the back plate, gasket (that's when it tore but only one rip) and carb. Can't remember if there's a carb gasket/o-ring or not. The plug I'm using is fresh out of the package.

I did not remove the head. I don't believe that warm anti-freeze would damage the head gasket. OR would it? OTOH, reading elsewhere on "another forum: , there is no need for a head gasket on air cooled engine (such as this 46). So I dunno

Last edited by voyager_663rd; 07-16-2022 at 06:11 AM.
Old 07-16-2022, 07:21 AM
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https://www.ebay.com/itm/16421653252...cAAOSwXspeyUqr
Comes in an envelope, decent price tag.

Did you insert the sleeve backwards? Show a photos of the exhaust port. I've bought improperly assembled engines in the past, it's pretty common.
Best to take photos as you take something apart to get it back together again right, if all the above fails. Not firing at all, not even spitting, that's what I'd check to rule out next.
Old 07-16-2022, 07:38 AM
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As said, I only removed the back plate and carb, not the head.

BUT watching an unrelated dissassembly vid, I note that there is also carb O-ring. Now, I really don't remember if/what I did with it. Hopefully I put it back in place? Dunno. I really have to remove the engine and partially disassemble it again and see what's what. If it is missing, it's probably where my leak is and not the rear gasket.

Thanks for the tips but I have some work to do so until next time ........
Old 07-16-2022, 09:42 AM
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Originally Posted by voyager_663rd
As said, I only removed the back plate and carb, not the head.

BUT watching an unrelated dissassembly vid, I note that there is also carb O-ring. Now, I really don't remember if/what I did with it. Hopefully I put it back in place? Dunno. I really have to remove the engine and partially disassemble it again and see what's what. If it is missing, it's probably where my leak is and not the rear gasket.

Thanks for the tips but I have some work to do so until next time ........
Just checked one of my New-In-Box, and yes there is an o-ring. Not super critical as to size, as long as you can compress the new enough to get the retaining screws back in. Your local hardware store may have "close enough". Since you have to remove the engine, take it all with to the hardware store, so you can try out different sizes. Not having one would surely cause the issues you have seen with poor ability to draw fuel and set the needle. Good to hear you didn't disturb the head/liner, so unlikely you have any issue there. Just check the head bolts for tightness. If there is a shim/gasket for the head (I haven't torn mine down to check), it will be metal and not bothered at all by the cleaning method.
Old 07-18-2022, 10:26 AM
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Well good news and well, not sure now.

Carb o-ring in place so that's not the issue. Took the back plate off and hmm the gasket is not ripped BUT is every so slightly deformed (ie bent over on one side by a mm or so. MIght be enough to let air in at that point.

In any case, I've flattened it back as flat as I can get it. Both mating surfaces and gasket have been cleaned and just awaiting drying now (probably is now as brake cleaner evaps really quickly).

Will try once again (without RTV for 1st attempt) to start. I'll be back.

In a related question: anyone get glow plugs that are dead right out of the blister pack (or really soon thereafter)? My original won't light up so that's not a biggie but when I try to light up the new one (just in the igniter, it won't). I did get the engine to fire up when it was in place but engine died when igniter removed. Hence my question.
Old 07-18-2022, 11:24 AM
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It's possible, but unlikely to get a DOA glow plug. What voltage do you get out of the ignitor? Was it charged enough? I just replaced the NiCad in my old one (800ma) with a 3600 ma NiMh. Took a good 12+ hrs for the NiCad to charge using the included wall wart charger. The new would take at least 2 full days, if not longer, if ever. Since NiMh is much more forgiving for fast charging, I now use the multi-charger I use for my electric planes. Does the trick in 1 hr, even if it may be hard on the battery. Given my usage, I expect it to not need a recharge for the rest of the summer.
Just testing, you can use any old dry cell (AA, C, D) and hunks of wire to the glow plug. Being a bit higher in voltage (1.5) you should see a nice glow. Plugs are made for that voltage, most people went with NiCad or NiMh for the rechargeability, and the lower voltage still worked. So will be no harm to the plug.
Dyeing when the ignitor removed is a classic sign of a bad plug, although being way overly rich can sometimes mimic that.
Old 07-18-2022, 11:30 AM
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igniter tested at 1.3 but hey, that's just on a tester. I've put it back on the charger for longer as it's also 3300mah so it may take longer. All is put back together (no RTV at this stage) so we'll try again tomorrow.

Thanks for the insight
Old 07-18-2022, 01:45 PM
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Originally Posted by voyager_663rd
igniter tested at 1.3 but hey, that's just on a tester. I've put it back on the charger for longer as it's also 3300mah so it may take longer. All is put back together (no RTV at this stage) so we'll try again tomorrow.

Thanks for the insight
If it's NiCad/NiMh, it appears to be charged enough, even if not at full capacity. So you should get a glow....Check in reduced lighting - can be hard to see in full sun.
Old 07-18-2022, 02:40 PM
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I think it's the igniter itself. Original plug doesn't light/new out of the blister pack won't light either but battery is fully charged. When i plug it in on the wall wart, the red light flickers / full depending on how the igniter is plugged in. It may very well not be making solid contact with the plug when installed.

Gonna have to wait till I get to the field and have another member check it on their bird.

Later.

Last edited by voyager_663rd; 07-18-2022 at 03:11 PM.
Old 07-18-2022, 04:31 PM
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Based on what you've told me and what I'm actually experiencing, I have a theory:

The ignitor "wobbles" on the plug (both when I attach it and when I tried to charge it on the wall wart (light on plug flickers at times). When I start rotating the prop, the plug is not hot enough (due to poor contact) and the fuel keeps flowing as the cranking continues. When the plug eventually gets hot (because I adjust the igniter) and starts to fire, the engine is already flooded and can't continue when the igniter is removed.

The igniter needs to be able maintain constant contact with the plug so it fires before the engine floods.

Sound plausible?
Old 07-18-2022, 07:48 PM
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Sounds like a very likely theory. You can see if cleaning up the center and edge contacts helps. There can be quite a bit of gunk that builds up where the plug inserts into it. May need some fine grit sandpaper to clean the buildup off. If this is the kind with a spring plunger to lock it on, the grippers that open/close to grab onto the side of the plug sometimes bend outward a bit, making the grip less dependable. Careful work bending them back in a little with a needle nose can temporarily make the connections tighter. But the metal does fatigue, so it will loosen after a while again. Something to try while you wait for Amazon to send a new one! My Dynamite's have seen many years of service, and still going strong. McDaniel has been around for a long, long time but the cell is not easily replaceable, and the brass versions are a lot less long lived than the stainless ones. I'd avoid most others, especially Chinese clones.
Old 07-18-2022, 07:57 PM
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Other alternatives: There are clip ons that look like cloths pins. Require wires from the clip to the battery. Or really old school - lamp wire and alligator clips. One clip to the post of the plug, the other clip to any handy spot on the engine. For either, you need to source a holder for the battery to run the wires from, or solder the wires directly to the battery. Just take care in soldering, as heat applied too long can be detrimental - a higher wattage iron with a big tip helps you minimize the total amount of heat you subject the battery to.
Old 07-19-2022, 06:47 AM
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It is pretty black in there (at contact point) so I'll try some brake cleaner (with battery removed) and wipe it out with a clean cloth. Worked well on removing the gunk from the back plate so.........

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