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TOPIC: slight backfire problem

slight backfire problem 6 years 1 month ago #56688

Hi Homelite folks, my name is Chris from the Netherlands and I would like to share this disaster. After a few initial succesful startups and some more finetuning of the ignition this happened due to a backfire in combination with dripped fuel and fuel soaked tissues I forgot to remove. How stupid of me to become so careless in this final stage!!
A compression test proved that one of the cylinders has a sticking/bad valve which must have caused the backfire.
I looks worse than it is, but my recently refurbished carburettors are more or less finished due to melted internals. I am glad to have another 2,5 of these engines...

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Re:slight backfire problem 6 years 1 month ago #56704

Chris, I hope your O.K. and no one was hurt. The best one to talk to about this is Billr. He is an expert with the Bearcat/Homelite outboards. He'll be back around the first. He sells rebuilt carbs and kits-very reasonable. I'm sure he'll be happy to help.

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Re:slight backfire problem 6 years 1 month ago #56720

My 62 got hot and back fired and caught fire. We got it out before too much damage it was scary. Checked the water pump it was OK. Must of sucked up a zip lock. Had to replace the fuel lines. They got scorched. I consider myself lucky! B)

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Re:slight backfire problem 6 years 1 month ago #56730

It was scary and I am glad I wasn't hurt. I didn't dare to extinguish it with water as I was scared it would spread al over the place. I felt really helpless!
Yes I hope Bill can help me. I rebuild the carbs partially (couln't figure out all the parts and leather cup) with the kit I bought from him. It seems only the carbs are affected (aparts from the fresh painwork :angry: ), the plastic valve has melted and the float broke when I opened it. I cleaned one of the burned carbs in an ultrasonic bath (great stuff for cleaning things) and other than the melted valve/float it looks new again so maybe they can be reused in the future. I have spare carbs.
The fire was not caused by overheating but there was no water coming out from the control hose, should this happen immediately after startup? There was water flowing through the thermostat so I am sure the waterpump was working.
For now I will finish my 63' which was in much better and running condition when I bought it. I only have to reassemble the lower parts and do the wiring. Hopefully then I can start working on my Glasspar.
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Re:slight backfire problem 6 years 1 month ago #56958

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It should happen soon after startup (telltale stream) if you have a non bypass system, since the block empties at shutdown it has to fill upon startup to start streaming.
I have new carb kits and even new rubber accelerator pump boots now. They are reproductions of the original and are made of gasoline AND ethanol resistant rubber. The die was a lot of money to reproduce these, but I just got the first set from the factory and they're like brand new.
To replace the cup a small vise is handy. You need to compress the spring on acc pump shaft, clamp it, then remove the retaining pin. Remove spring, remove cup, replace, reassemble. Good as new.
Hope this helps.
I'm back from Africa btw.

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Re:slight backfire problem 6 years 1 month ago #57337

Problem solved!!!
The #3 cilinder valve didn't close properly because of an enormous amount of burning deposits.
I heated the valve through the sparkplug hole with a torch and then sprayed a lot of oil in it. Put back in the spark plug and turned on the starter. I don't know exactly how, but after this the valve was totally clean and closed properly. After this I reset the valve clearances. Then I cleaned, partially sprayed and reassembled the engine, put on two spare carburettors and it started fine. It runs very smooth!

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Re:slight backfire problem 6 years 1 month ago #57351

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Very creative problem resolution.
I've seen lots of deposits on engines that sit for years, especially if they are stored horizontally.
Is she going on your boat now?

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Re:slight backfire problem 6 years 1 month ago #57359

Work has yet to begin on the boat, an early 1960's Glasspar.
New floor, new transom etc.

Funny thing: the serial number from the Homelite I purchased recently is only 1 digit up from the engine I bought last september and is now running (with a replaced lower motor pan).

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