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Is this flywheel key bad enough to cause rough running?

#1

P

PeteAU

Hi LawnWorld,

The title says it all really. Is this bad enough to cause rough running, e.g. some pops/crackles in the exhaust, hunting idle and sometimes kickback in the starter cord?

I've already cleaned the carby and tried 3 different (used) spark plugs, so I guess this is it. The flywheel ain't budging though (can't get it off yet)...

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#2

I

ILENGINE

Very minor offset results in major timing changes. I wouldn't be surprised if that amount of offset advances the timing 5 degrees. So instead of firing at 13 degrees BTDC it is now firing at 18-20 degrees BTDC


#3

Fish

Fish

What is your problem removing it? What method are you using?


#4

Fish

Fish

Is the crankshaft bent on the other side?


#5

P

PeteAU

ILENGINE said:
Very minor offset results in major timing changes. I wouldn't be surprised if that amount of offset advances the timing 5 degrees. So instead of firing at 13 degrees BTDC it is now firing at 18-20 degrees BTDC
Click to expand...
Perfect, thanks. Now I know this needs fixing to get it running right.

Fish said:
What is your problem removing it? What method are you using?
Click to expand...
I've tried prying while hitting the nut/shaft with a hammer. Tried gentle hitting from underneath. Tried heating it with a heat-gun (paint stripper). Reluctant to really hit it hard, I realize it's aluminium.
Next I might try tapping M8 threads into the two little holes and home-made puller plate.

Fish said:
Is the crankshaft bent on the other side?
Click to expand...
Spinning the blade around, it looks pretty straight.


#6

StarTech

StarTech

What I use most the flywheels I pull is a harmonic balancer puller. I tighten it up good and tight then smack the forcing screw with a two brass hammer. Shocks it off after a few tighten rounds of the forcing screw.


#7

I

ILENGINE

I've tried prying while hitting the nut/shaft with a hammer. Tried gentle hitting from underneath. Tried heating it with a heat-gun (paint stripper). Reluctant to really hit it hard, I realize it's aluminium.
Next I might try tapping M8 threads into the two little holes and home-made puller plate.


the standard Briggs puller uses 1/4-20 self tapping bolts at least in the USA.


#8

T

Tinkerer200

PeteAU said:
Next I might try tapping M8 threads into the two little holes and home-made puller plate.
Click to expand...

You have the right idea, put tension on it then a solid rap over the crankshaft end with a hammer.
Walt Conner


#9

P

PeteAU

OK, I got the flywheel off. But now, is this flywheel key way too far damaged? Maybe make/file a custom key that's slightly oversized. What is your experience?

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#10

I

ILENGINE

Yes the key is too far damaged. I think i would put a standard key in there and properly torque it and see what happens. The key doesn't keep the flywheel in place it is just for timing alignment, and the proper torque on the flywheel holds it in that location until you hit something that causes the flywheel to not stop when the engine does.


#11

P

PeteAU

ILENGINE said:
Yes the key is too far damaged. I think i would put a standard key in there and properly torque it and see what happens. The key doesn't keep the flywheel in place it is just for timing alignment, and the proper torque on the flywheel holds it in that location until you hit something that causes the flywheel to not stop when the engine does.
Click to expand...
I will get a new key. I was referring to the damage to the key-way (slot) in the flywheel. Maybe it won't matter if I can tighten the nut without it moving, but then you can't see if it did.


#12

K

keakar

PeteAU said:
I've tried prying while hitting the nut/shaft with a hammer. Tried gentle hitting from underneath. Tried heating it with a heat-gun (paint stripper). Reluctant to really hit it hard, I realize it's aluminium.
Click to expand...
what works best is to hit the flywheel itself, not the shaft, never hit the shaft because all you are doing is beating against the bottom bearing.

give the flywheel a good hard whack while pulling up hard with your hand and it will pop right off, but sometimes it takes 5-6 whacks to let go

with aluminum flywheel be a bit gentle with the hard whacks and only go as hard as needed to release it

in your case yes, replace that flywheel, the key way is deformed and will no longer hold in place correct timing, it will slip on you again unless you can only keep the key way down on the still undamaged area (unlikely)


#13

Mower King

Mower King

keakar said:
what works best is to hit the flywheel itself, not the shaft, never hit the shaft because all you are doing is beating against the bottom bearing.

give the flywheel a good hard whack while pulling up hard with your hand and it will pop right off, but sometimes it takes 5-6 whacks to let go

with aluminum flywheel be a bit gentle with the hard whacks and only go as hard as needed to release it

in your case yes, replace that flywheel, the key way is deformed and will no longer hold in place correct timing, it will slip on you again unless you can only keep the key way down on the still undamaged area (unlikely)
Click to expand...
I'm curious as to where you learned this method of removing a flywheel ? " what works best is to hit the flywheel itself, not the shaft, never hit the shaft because all you are doing is beating against the bottom bearing"

Experience, school, youtube ?


#14

P

PeteAU

keakar said:
in your case yes, replace that flywheel, the key way is deformed and will no longer hold in place correct timing, it will slip on you again unless you can only keep the key way down on the still undamaged area (unlikely)
Click to expand...

That's a pity, it was a free throw-out mower, but it looks nice, nothing else broken, no rust, year 2010. I'm just tinkering with it while there's nothing to do during lockdown 2.
I'll try a new key and see if it holds. Maybe move the coils 2-3 mm to the left to compensate?

It's a 450 series 148cc 9T502-0152 B1.


#15

Scrubcadet10

Scrubcadet10

What's the engine model and type numbers?
Sometimes you can get lucky and find a flywheel used on ebay for cheap,.


#16

Mower King

Mower King

PeteAU said:
That's a pity, it was a free throw-out mower, but it looks nice, nothing else broken, no rust, year 2010. I'm just tinkering with it while there's nothing to do during lockdown 2.
I'll try a new key and see if it holds. Maybe move the coils 2-3 mm to the left to compensate?

It's a 450 series 148cc 9T502-0152 B1.
Click to expand...
"Maybe move the coils 2-3 mm to the left to compensate?" 2mm = .080 - 3mm = .120 I don't think the coils will move that far.....and they won't need too!


#17

P

PeteAU

Just for a laugh I put the bent key back in but rotated 180 degrees (left-to-right), it felt tight in there. Put everything back together and tried running it.
It's smoother, but not 100%. Then I undid the nut again to see if it has shifted, surprizingly it's straight as an arrow (photo is after the engine ran).

So, I suppose this motor has more issues. It runs well enough to mow my little grassy area, I'll take it for $0.

I also tried two used spark plugs (cleaned, de-carboned, gaped, multimeter tested) and that didn't help. What else could it be:
- Get a brand new spark plug
- Intermittent coil
- Intermittent cable to spark plug
- Deeper motor issues like the valves
(I already ruled out the carby, because I have two of them and one has a new gasket/diaphragm).

What's the most likely/common with these Briggs 148cc classics?

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#18

Mower King

Mower King

PeteAU said:
Just for a laugh I put the bent key back in but rotated 180 degrees (left-to-right), it felt tight in there. Put everything back together and tried running it.
It's smoother, but not 100%. Then I undid the nut again to see if it has shifted, surprizingly it's straight as an arrow (photo is after the engine ran).

So, I suppose this motor has more issues. It runs well enough to mow my little grassy area, I'll take it for $0.

I also tried two used spark plugs (cleaned, de-carboned, gaped, multimeter tested) and that didn't help. What else could it be:
- Get a brand new spark plug
- Intermittent coil
- Intermittent cable to spark plug
- Deeper motor issues like the valves
(I already ruled out the carby, because I have two of them and one has a new gasket/diaphragm).

What's the most likely/common with these Briggs 148cc classics?
Click to expand...
The key itself is only for timing, it's the taper that holds it on !


#19

P

PeteAU

mower king said:
The key itself is only for timing, it's the taper that holds it on !
Click to expand...
Right, so I don't need a new flywheel, as long as it holds the correct timing after being tightened (which it is, for now).

What the hell is this little hole near the exhaust? It looks like the head-bolt threads go right through. Normal?

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#20

Mower King

Mower King

PeteAU said:
Right, so I don't need a new flywheel, as long as it holds the correct timing after being tightened (which it is, for now).

What the hell is this little hole near the exhaust? It looks like the head-bolt threads go right through. Normal?
Click to expand...
Yep, looks like head bolt threads, I wouldn't worry about that!


#21

P

PeteAU

All right, I've got this mower running at about 80% now. There's something still a-miss and I don't know what it could be.
So while measuring the coil resistance, I realized the boot (Briggs logo on it) measures 4.7kOhm by itself! Is that normal that the boot has a built-in resistor?

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#22

Mower King

Mower King

PeteAU said:
All right, I've got this mower running at about 80% now. There's something still a-miss and I don't know what it could be.
So while measuring the coil resistance, I realized the boot (Briggs logo on it) measures 4.7kOhm by itself! Is that normal that the boot has a built-in resistor?
Click to expand...
Yes, some caps have a resistor in them, some don't.


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