Old Lesson Re-learned

[CTYank]

Subject: 2-stroke plug "whiskering".
My antique Echo SRM-200, still alive and kicking ess, had a fun week. OEM point-set failed gradually while out in the woods clearing trail. Replaced with new points- working great again.
After an hour or so whacking multiflora rose/privet I let it rest & cool while I ran my 26 cc Tanaka. On returning to the echo it ran fine for 10-15 minutes, and then ceased to run. Period. Not a peep.

Finally, looking at the plug to see if it was fouled, sunlight was right to see TWO whiskers of debris bridging the spark gap. Pop them out and it fired on the first pull.

Take-away: change of operating conditions of a two-stroke can generate chamber deposits which can then be shaken loose and magically attracted to the spark-gap, causing stream of invective.

Mind the gap.

 

[bigbadbob]

The ceramic parts slides up and down the tip, was still running, but very strange, and the first thing we do is look at a plug tip pointed up, so it looked ok.

 

[CTYank]

The ceramic parts slides up and down the tip, was still running, but very strange, and the first thing we do is look at a plug tip pointed up, so it looked ok.

Don't you love those sneaky little probs? With the ignition stuff, I was focused on the magneto innards and didn't pay too much attention to the plug for a bit, just checked that it was dry. Duh. Little demon worked hard Sat. for at least 3-hours in multiflora & privet. Got more carbide blades on order.

Note to self: hey, dummy remember also to see that plug insulator's not floating if the engine's running inconsistently.

How'd you manage to spot the prob. Bob? Rattling ceramic?

 

[bigbadbob]

Don't you love those sneaky little probs? With the ignition stuff, I was focused on the magneto innards and didn't pay too much attention to the plug for a bit, just checked that it was dry. Duh. Little demon worked hard Sat. for at least 3-hours in multiflora & privet. Got more carbide blades on order.

Note to self: hey, dummy remember also to see that plug insulator's not floating if the engine's running inconsistently.

How'd you manage to spot the prob. Bob? Rattling ceramic?

Bad idle and only run wide open,, even did a carb kit B4 the plug as the saw was a few years old.
I guess the wide open made the bit jump back into place,,, or bounce very good,,I did check the plug a few times,,,
BBB

 

[67L36Driver]

I've come across a few plugs like that. Drive you knits. One broke off nose ceramic and dinged up the piston.
Two Bosch and one Champ.