Stihl 038 Mag keeps jumping time.

[Okie294life]

I put this thing back together and it sheared the key on the flywheel when it started. I tried a second time making sure to clean the connection and put a little more azz into it, by blocking the flywheel. It ran good for a little but, erratic now nothing, so I would bet it’s jumped time again. Any secrets to doing this once and for all. I don’t have an impact wrench, but I do have a 3/8 torque wrench.

 

[Tobystihl]

I put this thing back together and it sheared the key on the flywheel when it started. I tried a second time making sure to clean the connection and put a little more azz into it, by blocking the flywheel. It ran good for a little but, erratic now nothing, so I would bet it’s jumped time again. Any secrets to doing this once and for all. I don’t have an impact wrench, but I do have a 3/8 torque wrench.

It could be that the flywheel has a crack in the taper, if the crank and flywheel is dry and clean on assembly it shouldn't move at all, in fact it's such an interference fit that the woodruff key is only there to align the timing correctly.

 

[HarleyT]

Put up some pics of it.

 

[drf255]

Use some rope in the cylinder as a piston stop. Clean crank and flywheel snout with acetone.

Torque the nut to 27 ft/lbs.

 

[Okie294life]

Use some rope in the cylinder as a piston stop. Clean crank and flywheel snout with acetone.

Torque the nut to 27 ft/lbs.

I’ll try the rope trick on this and thanks for the torque. I keep thinking I may be putting the key in wrong. I put the flat side against the crank, line the flywheel up and whack away with a rubber hammer to get it to seat.

 

[cus_deluxe]

Sounds silly, but ive used toothpaste and abrasive hand soap after shearing a fw key. Put it on the taper, put fw on, get comfy and push down and spin that fw about a million times. Clean it up and stuck on there fine. As said, the nut does very little to retain the flywheel, the taper is what does it, amd it must be clean and perfectly matched to the taper in the fw.

 

[Chainsaw Jim]

Use some rope in the cylinder as a piston stop. Clean crank and flywheel snout with acetone.

Torque the nut to 27 ft/lbs.

This ^^^


Make sure to turn the piston just above the exhaust port roof and then stuff as much rope in the hole as you can fit.

 

[drf255]

I’ll try the rope trick on this and thanks for the torque. I keep thinking I may be putting the key in wrong. I put the flat side against the crank, line the flywheel up and whack away with a rubber hammer to get it to seat.

The round side sits in the crank. That would explain things. You’re not seating your flywheel.