Backfiring : Honda 5.5 HP Craftsman

[Drosselmier]

Very nice u-tube. The follow -up u-tubes were also nice to see. Very informative.
I don't have the special tools to get at the flywheel key so if that is the problem there is a hobbyist in the neighbourhood I can take it to. I will try a new spark plug and see what I can do with gas.
Thanks for your help.

 

[Jake54]

yoy're welcome, did you pull it hard and have it snap back out of your hand?

 

[Jake54]

+1, good advice!
Originally Posted By: Skittles
Originally Posted By: Drosselmier
Is there an additive I could clean the carb with ?


Most likely the carb will need to be pulled and cleaned if it is starting to gum up. Wire needs to be run through all the small passages. I do this on 100's of mowers, snowblowers, atvs, and motorcycles every year. This fixes 99.9% of the starting and running issues I deal with on carbed equipment.

But again, I get the occasional sheared flywheel key too. I have had keys that didn't actually shear either but just bend the aluminum enough that it is off 1/8". This will cause a slight miss and popping while running.

 

[Drosselmier]

No it did not pull beck hard.
I found the blade is bent a little . Not as badly as the one in the u-tube. I ordered a new one and I bought a new Spark Plug just in case.

 

[Jake54]

Ooh, so the flywheel key might be the issue, could someone else have used it and accidentally bent the blade?
have you inspected the flywheel key?
also have you cleaned the carb?

 

[old1]

If the blade was bent, even slightly, SOMEBODY hit something, and probably at least partially sheared the flywheel key. The blades don't bend mowing grass.

 

[philipp10]

Generally speaking, a backfire is caused by a lean condition. Look no further than that first. Use the KISS principal first before looking for the unlikely causes as has been mentioned by others.

 

[philipp10]

Originally Posted By: Drosselmier
No it did not pull beck hard.
I found the blade is bent a little . Not as badly as the one in the u-tube. I ordered a new one and I bought a new Spark Plug just in case.


and for Gods sakes....its NOT the spark plug. If the plug was bad you wouldn't be getting any fire, much less a backfire.

 

[Drosselmier]

No one else uses it. I must have hit something with it. I'll have to have a look around the yard for something I hit. Hard to find in the grass.
It only Pops on hot starts and not every time .
The spark plug has had about 4 seasons of use. About 100 hours or so. Still starts well. I think it is OK. I squirted some carb cleaner in the air intake. A little almost stalls the engine. I ordered a new blade for it.

 

[meep]

backfiring is often caused by lean condition. Those of us that lived with older vehicles with carbs could diagnose lean/rich based on how an engine behaved.

Hondas are thrifty on fuel. As such, their carbs have very tiny, very precise passages, much smaller than the briggs and tecumsehs from the previous millenium.

It is quite possible that a tiny bit of dirt got into the tank during refueling and made its way to the carb, restricting the main jet. This happened to me 5 times before I figured it out and installed an inline fuel filter in the fuel line.

You have to remove the carb, drop the bowl, wear safety glasses, and try to clean it out with spray carb cleaner, or run an impossibly fine wire through the jets.

The hardest part is just carefully pulling the carb clear of the engine. It's easier after the 1st time.... I know.

Good luck.

 

[Quest]

Originally Posted By: meep
backfiring is often caused by lean condition.....


Bingo!

Clean yer carb and then try again.

Q.

 

[yeehaw1960]

Speaking of bent blades, I just realized the other day that blades are made so cheaply now they can be straightened out by clamping them in a vice and using a little muscle (NO HEAT).

By the way, I've also found an alternative to dragging out my micro drill bits to clear very, very small passages on Tecumseh and Honda carbs. Take your wire brush and clip off one of the bristles. Lock it into a pair of vice grips (as a makeshift handle) and go to town. Been sitting there in front of my eyes for years, but I never noticed just how small those bristles are. Now I don't have to buy a torch tip cleaner every year just to wear out the smallest wire (file) and throw it away.

 

[Clevy]

Originally Posted By: yeehaw1960
Speaking of bent blades, I just realized the other day that blades are made so cheaply now they can be straightened out by clamping them in a vice and using a little muscle (NO HEAT).

By the way, I've also found an alternative to dragging out my micro drill bits to clear very, very small passages on Tecumseh and Honda carbs. Take your wire brush and clip off one of the bristles. Lock it into a pair of vice grips (as a makeshift handle) and go to town. Been sitting there in front of my eyes for years, but I never noticed just how small those bristles are. Now I don't have to buy a torch tip cleaner every year just to wear out the smallest wire (file) and throw it away.



Hardened blades shatter when you catch a rock,so using them for a lawnmower is beyond dumb and extremely dangerous for the operator and anyone nearby.
And if they were tempered to begin with heating it would nullify the hardening process anyway.


Op

As already mentioned running lean is the usual cause for pre-ignition however you claim it only happens on hot restarts which tells me it's pre-ignition due to inadequate octane.
Basically there's hot spots in the combustion chamber. As soon as the fuel comes in contact it explodes before the spark event.
Before playing around with any settings or drilling or doing anything that requires tools and modifying parts try higher octane.
Combustion chamber may have deposits that are increasing compression and those deposits hold heat creating hot spots.
I've got 16 Honda 5.5hp gx motors that power air compressors. I've got 2 thT are easily in excess of 15000 hours without so much as an oil drip. Never had anything for service other than oil changes every 100 hours,mos2 every second interval and tc-w3 mixed in to every fuel tank.
Combustion chambers are so clean I can see the piston crown clearly without any residue.
Try high octane first. While using high test use an additive to clean out the combustion chamber. There are YouTube vids where a guy used a product like seafoam to do a piston soak and the before and after pics are very telling in my opinion.
Mmo works very well as a piston soak in my experience as well. Look up the YouTube vids and judge for yourself.
It's pre-ignition due to deposits that are creating hot spots so the fuel explodes before the spark event.
We have a member here. I forget his username offhand but he is well versed when it comes to Honda engines. Once I remember I'll pm you. Then you can pick his experienced brain.
Forget drilling until you confirm the combustion chambers are clean.

 

[Clevy]

Originally Posted By: philipp10
Originally Posted By: Drosselmier
No it did not pull beck hard.
I found the blade is bent a little . Not as badly as the one in the u-tube. I ordered a new one and I bought a new Spark Plug just in case.


and for Gods sakes....its NOT the spark plug. If the plug was bad you wouldn't be getting any fire, much less a backfire.
Originally Posted By: philipp10
Originally Posted By: Drosselmier
No it did not pull beck hard.
I found the blade is bent a little . Not as badly as the one in the u-tube. I ordered a new one and I bought a new Spark Plug just in case.


and for Gods sakes....its NOT the spark plug. If the plug was bad you wouldn't be getting any fire, much less a backfire.



Says who. If there are deposits on the plug that end up glowing red hot during use it certainly can cause ignition.
If the electrode is clean and not worn then this certainly isn't likely.

I'm still saying deposits and octane. Only costs pennies to try premium and if the condition no longer presents itself you've saved yourself a possible headache putting parts back together.

Having used a generator and compressor every day of my working life I can say with all honesty how hard you pull over the engine has no bearing on whether it starts. That's hilarious.
In fact the faster it turns on start up the better.

 

[yeehaw1960]

You are, obviously, the smartest man alive... I wish I weren't beyond dumb.

 

[meep]

nice compliment.

Guys like Clevy, always level-headed on this board, and several others I also see here regularly make this a much nicer, useful, practical, and grown-up forum than many countless others that can't see beyond the tip of their nose.