OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 500 series kicks back

Hi... I recently acquired a 2013 Masport with a B&S 500 series motor on it...
It appears that the previous owner may have hit something hard, as the centre of the cutting disc had cracked and allowed the disc to detatch.
Turning the engine over slowly, it makes a chuffing sound... like it was leaking compression. When I gave it a pull on the starter cord it kicked back violently ripping the cord from my hand.
A google search suggested checking the aluminium key on the flywheel... this was found to be intact..
This morning I pulled off the sump expecting to see the camshaft misaligned or had slipped... this also was found to be OK.
What am I missing ?
Ken.

I have one that does exactly the same, I just put it in the corner, maybe get to look at it if you get a result.It didn't kick every time and ran well if it started but every so often it would try and dislocate your fingers. Out of curiosity are you trying to start it with the blade carrier removed, if so this is probably your problem

Lawn mowers that have a alloy flywheel use the blade plate as a flywheel ,I would check the key that locks the blade plate boss to the lower crankshaft.
It's not uncommon for that key to break.

Thank's NormK.
Interesting theory, but cannot see how the blade carrier would make it do what it does..mine does not even run !! It sounds like a timing issue to me.. but.having said that, the flywheel can only be fitted one way, and the cam can only be lined up one way....both are correct.
Obviously we are both missing something !

Hi Ken, they will kick back without a blade carrier fitted and it hurts, 2 strokes will do the same
Max seeing Ken has taken the lower engine case off he has had to remove the boss and I'm sure he would have noticed the key way, but as the blade carrier has suffered sever damage anything could be wrong in there

Most likely.

Due to the light weight of the flywheel only you will get kick back. This because they fire slightly before TDC and they depend on the flywheel effect to get pass TDC as they fire off. They are meant to have the carrier weight to act as the heavier flywheel. Here we use bar blades weight for this. This wouldn't happen if they used a heavy flywheel which they don't.

Once you get the pull rope pull from your hand a few times you learn watch out for it. I have been out action a few times before I learned my lesson. The same thing happens on engines where the ACR fails. While you got it apart go ahead check the cam's ACR mechanism. It has a hair size spring that can fail. (ACR = automatic compression release)

Either way the cutter assembly need to be on the engine while you're trying to start it. Also make sure you torque the flywheel to 55 ft-lbs. Don't guess at it as if you over torque it you risk splitting the flywheel.

Thanks guys .. I will weld and brace the blade carrier ASAP and let you know how it goes... Any ideas on how the blade carrier failed in the first place...?
I would think that this would be the place to install the first line of defence (soft key).
If I wanted to protect an engine, this is where I would place a failsafe !

Ken not the best idea to weld it but if you insist make sure you fit a larger diameter washer that covers the weld area so the area is supported fully. This way you are only relying on the broken center to center up the blade carrier

Yes... that was my intention.. I will be looking to replace the carrier ASAP.
Ken.