Fire Extinguisher Fallout

Scout63 · Dec 20, 2020

I had a backfire when starting my 72 Combat with stock 932 Amals and factory airbox setup in late October. Luckily I noticed that the filter was on fire and shot a quick puff from my fire extinguisher into each side of the air cleaner. I hosed the extinguisher dust from the bike and put it away for about three weeks while I ordered a new air filter element.

In those several weeks the carb slides corroded solidly into the carb bodies. Yesterday I removed the carbs and put them into an ultrasonic cleaner for an hour in order to free the slides. I’ll vapor hone them before reassembly and hope they fit and work properly. The extinguisher media also corroded the rear filter plate and the filter screen fairly significantly in that short time.

The lesson I’ve learned is to immediately disassemble and thoroughly clean any part of the bike that is touched by the extinguisher powder. It gets into everything and appears very corrosive.

Ben

Peter R · Dec 20, 2020

Powder type fire extinguishers contain a salt that is very corrosive indeed, I feel sorry for the damage it caused to your bike. I have two foam type extinguishers in my workshop, but fortunately never had to use them.

cyclegeezer · Dec 20, 2020

That's a good reminder for all of us that a CO2 extinguisher may be more expensive up front, but cheaper in the long run. When I worked with electric fork lifts, the maintenance guys always said in case of a fire, if possible, use a CO2 extinguisher.

baz · Dec 20, 2020

Scout63 said:
I had a backfire when starting my 72 Combat with stock 932 Amals and factory airbox setup in late October. Luckily I noticed that the filter was on fire and shot a quick puff from my fire extinguisher into each side of the air cleaner. I hosed the extinguisher dust from the bike and put it away for about three weeks while I ordered a new air filter element.

In those several weeks the carb slides corroded solidly into the carb bodies. Yesterday I removed the carbs and put them into an ultrasonic cleaner for an hour in order to free the slides. I’ll vapor hone them before reassembly and hope they fit and work properly. The extinguisher media also corroded the rear filter plate and the filter screen fairly significantly in that short time.

The lesson I’ve learned is to immediately disassemble and thoroughly clean any part of the bike that is touched by the extinguisher powder. It gets into everything and appears very corrosive.

Ben

It probably wouldn't have helped you I don't think because your filter was alight
But very often kicking the bike over will suck the flames into the engine and extinguish them

Scout63 · Dec 20, 2020

baz said:
It probably wouldn't have helped you I don't think because your filter was alight
But very often kicking the bike over will suck the flames into the engine and extinguish them

I wonder. It backfired, then started and then I idled it for a few minutes. I think the airflow kept the fire going. The filter was glowing red after I shut it off, then it turned into a flame. I’m surprised that a stock setup would do this. I’ve heard about open intakes flaming backwards. It was a colder day and I was using the airslides, which I never do. This will give me a chance to remove them and install that gorgeous Don Pender carb linkage that is sitting on the shelf.

lazyeye6 · Dec 20, 2020

Peter R said:
Powder type fire extinguishers contain a salt that is very corrosive indeed, I feel sorry for the damage it caused to your bike. I have two foam type extinguishers in my workshop, but fortunately never had to use them.

Ammonium Phosphate is the base material in that type of fire extinguisher. I would be scrubbing those alloy engine parts very carefully with a weak
sodium hydroxide solution and then rinse well.

Tornado · Dec 20, 2020

Scout63 said:
I had a backfire when starting my 72 Combat with stock 932 Amals and factory airbox setup in late October. Luckily I noticed that the filter was on fire and shot a quick puff from my fire extinguisher into each side of the air cleaner. I hosed the extinguisher dust from the bike and put it away for about three weeks while I ordered a new air filter element.

In those several weeks the carb slides corroded solidly into the carb bodies. Yesterday I removed the carbs and put them into an ultrasonic cleaner for an hour in order to free the slides. I’ll vapor hone them before reassembly and hope they fit and work properly. The extinguisher media also corroded the rear filter plate and the filter screen fairly significantly in that short time.

The lesson I’ve learned is to immediately disassemble and thoroughly clean any part of the bike that is touched by the extinguisher powder. It gets into everything and appears very corrosive.

Ben

Might be needing a resleeve on those carbs. Several places offer this service. Got my original Amals done by B. Chessell in Ontario for a very reasonable price. Here's a thread on sleeving:

Amal Sleeve photos

I sent my carb bodies to Andy Hardan at Lund Machine Co., a source I found on this site. They do good work. Mr. Hardan told me he was surprised at how much "slop" there was between the body walls and the new slides I had installed. I'll post results when I put some time on them but this is what...

accessnorton.com

Scout63 · Dec 20, 2020

I’m going to give them a good vapor blasting and see if there is any noticeable play or they don’t work well. I really hope not as they are the original carbs and really were spot on. I did rinse them thoroughly. Thanks Tornado for the link.

Onder · Dec 21, 2020

CO2 safest and best. Besides, how else can you 1. use it to freeze bearings before insertion and 2. defend yourself during fire extinguisher wars?

Beezer Josh · Dec 21, 2020

I sent my carbs to Lund for sleeving close to a decade ago. Top notch job. Just be sure you have the correct slides. Best of luck getting them working again!

Scout63 · Dec 21, 2020

Thanks Josh. I’m going to send them to Lund. Ben

Fire Extinguisher Fallout

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