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BF20D Flame Trap issue

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Wizaro2000

New member
I have a Honda BF20D (saltwater use) and when I took the engine cover off to spray some CorrosionX on it, I found the flame trap screen sitting loose in a random location near the front of the engine. I know this is part of the muffler assembly and keeps backfires from igniting fumes.
Question: If I take the engine in to my certified Honda mechanic, will they be able to just pop it back in? Or is it likely there's another piece that held it on that broke off also?

Thanks for any help or advice.
 
Hi,

That flame trap screen is supposed to be held in place by small "tabs" molded into the plastic of the muffler box.

Over time, the combination of the acid and/or other chemicals in the crankcase vapors plus vibrations causes the metal of the screen frame to erode those little tabs down causing the screen to come completely loose.

I used to secure the screen with a tiny sheet metal screw installed in the plastic at a slight angle to the screen to wedge it in there. And, while I've never known one of those "bush fixes" to fail, I have since decided that it isn't a good idea.

Because, if the screw were to ever work loose, there is a high probability that it could be injested by the engine. If that were to happen, some major engine damage would likely occur. Not worth the risk.

Therefore, the only safe way that I know to repair that failure would be to replace the engine side half of the muffler cover. Item 2 in the link. About $40 plus shipping from boats.net


I have thought about finding a reliable glue to hold it in there but haven't tried that. You would need to "rough up" the surface of the plastic to give some tooth for adhesion but there's usually enough of the tabs left to hold the screen in place while the glue cured.

If the tabs are too far gone to hold the screen, you could still use my little screw trick to hold the screen while the glue dried but remove the screw prior to reassembly.

If the glue were to fail, it wouldn't hurt anything as the screen would simply fall to the bottom of the box just as you found yours.

Just an idea.

Please let us know if you come up with a better way.

Good luck
 
SaltTime said:
Can you post a picture
Click to expand...
I've attached a photo of the flame trap screen I found floating around in the front upper part of the engine. I'm not even sure where the engine muffler it came from is located, much less how to get to it.
 

Attachments

  • Screenshot 2024-12-02 195321.jpg
    Screenshot 2024-12-02 195321.jpg
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Referring back to item 2 in the link above, if you decide to remove that to replace or work on it, know that you would also be unbolting the carburetor as well.

Not a huge or difficult job but not for everyone.
 
jgmo said:
Hi,

That flame trap screen is supposed to be held in place by small "tabs" molded into the plastic of the muffler box.

Over time, the combination of the acid and/or other chemicals in the crankcase vapors plus vibrations causes the metal of the screen frame to erode those little tabs down causing the screen to come completely loose.

I used to secure the screen with a tiny sheet metal screw installed in the plastic at a slight angle to the screen to wedge it in there. And, while I've never known one of those "bush fixes" to fail, I have since decided that it isn't a good idea.

Because, if the screw were to ever work loose, there is a high probability that it could be injested by the engine. If that were to happen, some major engine damage would likely occur. Not worth the risk.

Therefore, the only safe way that I know to repair that failure would be to replace the engine side half of the muffler cover. Item 2 in the link. About $40 plus shipping from boats.net


I have thought about finding a reliable glue to hold it in there but haven't tried that. You would need to "rough up" the surface of the plastic to give some tooth for adhesion but there's usually enough of the tabs left to hold the screen in place while the glue cured.

If the tabs are too far gone to hold the screen, you could still use my little screw trick to hold the screen while the glue dried but remove the screw prior to reassembly.

If the glue were to fail, it wouldn't hurt anything as the screen would simply fall to the bottom of the box just as you found yours.

Just an idea.

Please let us know if you come up with a better way.

Good luck
Click to expand...

This is incredibly helpful info and advice, thank you. I just found this response from a 2012 thread in these same forums:

These "flame traps" tend to fall out of their mount because of vibration. They get loose and then "walk" around and eat at the little plastic ears that hold them in.

My solution on a fleet of 40 small Hondas is to use a #4 wood screw. I put it in to the plastic at the bottom of the trap and screw it in at a 45 degree down angle. This allows the countersunk head of the screw to contact the trap and "wedge" it in place. In five years I have not had one come loose after this treatment.

If you don't want to risk a screw in there, the entire housing is available from boats.net for around $25. It is item #2 on the parts page link below. This "muffler plate" is also the source of aggravation when you try and remove the bolts that hold the cover on. They can seize in the bronze nuts and cause the nuts to rotate and break their moorings in the plastic. Not the best in Honda engineering for sure. Be sure to use anti seize when re-assembling.

HTHY
jimmyd
 
Ha ha! A blast from the past.

I DID use wood screws but I found sheet metal screws that worked better. Now?..
....
DON'T DO THAT!
 
I don't know. I'm not familiar with that sealant. But, I would recommend NOT putting a bead around the screen. I would try small "dabs" at the tab locations and maybe a couple more spots.

Because, don't like the possibility of a bead coming loose and going into the carb. The engine would probably tolerate a small dab of a non-hardening sealant or adhesive but keeping it to a minimum would be the safest way to go.

I still have my old 20D and, when I think about spending $40 as opposed to taking a chance of harming the old gal, I believe I will choose to just buy a new muffler plate if the screen falls out.
 
How this ended just in case others have the same issue. The flame trap screen metal wires actually broke (not very noticable) not the plastic tabs that hold it on the muffler assembly. If you look closely at the photo I posted above, you can see where it broke in two places. The mechanic popped on a new screen and all is well again.
 
Wow! That's a new one on me! But, it does illustrate how vibrations can wear on things.
Thanks for the update.
 
On second thought, I wonder if it was simply air flow causing the screen to flex...sorta like the old coat hanger bending trick?
 
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