I've had several and I think it was to keep impacted sawdust from building up around the decomp valve.
My experiences with the 394/395s-
394 Cons-
cracked intake blocks
throttle cable wears through insulation where it rubs against airbox
low-top filter needs cleaning more frequently
parts unavailability
394 Pros-
wider torque range
earlier muffler has larger exit and bolt-on deflector
WJ-39 carb the best in the 394/395 series
395 Cons-
more prone to ignition failures
choked down muffler
needs porting for the engine to really come alive
peakier HP range
395 Pros-
better anti-vibe for intake channel
intake boot (more reliable, takes more abuse)
when ported, turns into a monster
parts currently available
I'll add some more.
394 Cons-
Prone to hot start problems, most think it's from the solid intake heat soaking the carb. In my experience they don't like Bosch plugs, I switched to NGK's and the problem went away.
395 Cons-
Small flywheel snout easy to strip threads.
Cast in flywheel key easy to shear.
Both Cons-
Throwing chains or getting tossed seems to break the rear PTO side of the chase exposing the fuel tank to harms way.
Front AV bumpers often get loose and fall out allowing the saw to wiggle side to side excessively.
LF AV bumper mount easy to break off.
Wing of case over front vertical AV mount prone to chipping, just cosmetic.
Top cover screws always seem to rattle loose and mess up the threads. It's never happened to me but almost every used saw I've picked up has some damage from loose top cover screws.
Worn trigger parts cause throttle cable length to be too long to reach WOT.
Clutches get excessively tight, don't try to remove them in the field. Use a large impact without any piston stop, just use the compression of the saw.
. Champion plugs for these saws are made in USA still.
