Feb 25, 2008 Mother necessity comes calling
Changing the Coil
This is, unfortunately, a lot of work. You'll need a drill, 1/8"
drill bit (for the rivets), a rivet gun, rivets, rubber bands (to hold
the starter pawls) and nerves of steal. OK, copper nerves may work but
you'll still need that rivet gun.
Thanks to Robin Rumbolt and Scott Traverse for their willingness to
share the information with us. Scott is, in fact, Mr. Motor and has
contributed other material here.
We must always remember that we are not pilots but rather mechanics
who merely test our handiwork periodically. God I love two-stroke
You guessed it. The coil is out on one of my Top 80's
(Tim's actually, but don't tell him that I use it as a back-up).
The wire came out, more accurately. So I found a
great resource, the Top80 yahoo group. Two pilots who I know and respect
provided the information. I will soon put it to use and will, as always,
Removing the coil
1. Remove engine from frame.
2. Remove the three bolts holding the pull start mechanism to blower
cover & remove the pull starter.
3. Drill out the 16 pop rivets holding on the upper blower cover.
4. Remove the bolts & retainers holding the ratchet pawls and the
5. Remove the bolts holding the lower blower plate to engine. Remove
6. You can now access the bolts holding the pole piece and coil.
Putting it back together is even more fun. You'll need to accurately
guage the distance between the pole piece and flywheel. Robin suggests a
business card and Scott cautions that not all motors can easily have the
space air-adjusted. Hopef your's is easy -- I'm hoping mine is.
Some coils only capture 3/4 of the rotor magnet width, that's OK.
1. Use rubber bands to hold the ratchet pawls out while putting back
the pull start pulley.
2. Be careful not to disturb the position of the flywheel with
reference to the crankshaft or you will have to reset the engine
timing--a black art practiced only by Scott Traverse and Brad Weiss.
3. Don't you wish CTRL-Z worked on maintenance tasks?
4. Some earlier engines have stand-off spacers under the coils with
fiber wahers between the pacers and coil arm. Fiber washers are readily
available from a hardware store (kitchen sink/faucet supplies).
5. When reinstalling the three ratchet pawl/bolts into the rotor,
lube them and put anti-seize on them as well. This is essential for
guys living and flying the sea coast. They should work freely on the
paw bolts. A frozen or binding ratchet paw can break the fan!!!
7. If you have the new aluminum paw stop replace it! They break
easily and can a catastrophic fan failure as some have discovered if
they break. I wish Diego would go back to the steel paw stop.
8. Inspect the fan bolt inserts. They are aluminum and "should not" be
freely rotating in the plastic fan. If they are loose replace the fan.
9. Inspect the rear fan housing for interference contact with the main
plug lead. Take out your handy DREMEL and cut away enough and radius
the edges to ensure there is no contact at this point. Use some clear
fuel line or RTV to insulate this area over the HT plug lead.
10. When installing the pull starter the ratchet paws must be facing
'Left" when installed properly when looking directly at the front of the
11. If you fail to spring load the ratchet paw against the pull starter
ratchet teeth it could destroy your fan and related parts.
12. There are three types of front cover pull starter stand-offs. Some
were easily broken and pulled out of the front housing. You don't want
to use anti-seize on the three pull-start retaining bolts! These 3mm
Allen bolts are sensitive and prone to people over tightening them.