Engine kick backs - Cord Pulls Out Of Your Hand

[Jocke90]

Hi!
I have a Briggs & Stratton 5HP that I recently bought second hand. The problem is that the cord is being pulled back really hard quite often when I try to start it. My father is quite good with engines and have disassemble it and we still don't know what the problem is.

The flywheel key is not broken and the 2 vents seems to be good so we are planning on grinding the vents and put everything back. We also thought if the ignition coil has moved so it ignite to early but that didn't seem to be the case.

Does any of you have any ideas of what the problem could be?

Thanks!

 

[slomo]

Is there a blade on it?
What 2 vents are you talking about?
Post up model and serial numbers for the engine. Pictures are great too.

slomo

 

[Hammermechanicman]

Check your valve lash. The engine has a bump on the cam that acts as compression release. If lash is too wide it can cause kickback. If you pull the rope hard enough does the engine start and run?

 

[Jocke90]

Is there a blade on it?
What 2 vents are you talking about?
Post up model and serial numbers for the engine. Pictures are great too.

slomo

Sorry, I meant the intake valve and exhaust valve.
It's an old Stiga vertical cutter.
I have attached an image of the model and serial number.

 

[Fish]

You need to see if your flywheel is heavy enough. If the engine came off of a mower, the blade added weight and so the engines have a lighter flywheel.

 

[Jocke90]

Check your valve lash. The engine has a bump on the cam that acts as compression release. If lash is too wide it can cause kickback. If you pull the rope hard enough does the engine start and run?

Do you mean the valve clearance? This engine does not compression release, it's quite old. Yes it does start but it kick backs very hard often when you pull it.

 

[Jocke90]

You need to see if your flywheel is heavy enough. If the engine came off of a mower, the blade added weight and so the engines have a lighter flywheel.

The engine is for a Stiga vertical cutter and it's been like this since we bought it.

 

[Born2Mow]

Advanced ignition timing will have that effect at starting RPM. The ignition occurs before TDC, so the piston is pushed backwards. The pull cord ratchets are designed for one direction of rotation, so when the engine turns the opposite direction the cord gets abruptly yanked back.

 

[Hammermechanicman]

You need to see if your flywheel is heavy enough. If the engine came off of a mower, the blade added weight and so the engines have a lighter flywheel.

130202 briggs will have a cast iron flywheel.

 

[Hammermechanicman]

Do you mean the valve clearance? This engine does not compression release, it's quite old. Yes it does start but it kick backs very hard often when you pull it.

The engine does have compression release. On the cam there is a the "easy spin" bump on the intake lobe. If the valve clearance is too wide it defeats it. Also, remove and decarbon the head. If it has heave deposits it can cause it to have higher compression. You can also check the intake valve operation to see if it stays just slightly open by a few thousandths on most of the compression stroke