Sorry if this is a re-post. I sent this from home address (which is not on
the list) on Saturday, and it still hasn't shown up on the digest version.
Many thanks to all who contributed suggestions:
Sid, Paul Bauman, Lee Ehinger, Adam Bradley, Gordon, and Victor. (hope I
didn't leave anyone out)
Tried everyone's suggestions without resolve, finally decided 3-5 minutes
running on the ramps was a good enough safety check and climbed underneath
while it was running. Started feeling the frame until I seemed to find the
epicenter of the rumbling, and sure enough when I got a retired oven mitt
and shoved up on the exhaust between the frame X's, the rumble immediately
went away.
Background: had the exhaust redone long ago, and had the muffler mounted too
close to the floorboard, (aka: carpet-b-q). But, they had mounted a bracket
with 3 vertical holes right before the axle loop, so when the bolt dropped
out, I pulled the pipe down to the bottom hole, away from the floorboard.
3-5 months go by. Then, one fine day, when everything HEATED UP (including
the downpipe getting longer, right?) it started to clash with the frame
pass-thru's. The reason it rumbled on compression slowing was the engine
torquing on the loosey-goosey mounts. And the rumble while idling, once
warmed, is due to a stumbling idle, caused by my nearly non-existent carb
tuning skills.
Thanks to all. I really like the inexpensive solutions. Visiting Mario the
Muffler Man this week. Fergus O, 69 2000, HB, CA
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