Good Morning Fellow Scions of Stanpart,
(or Good Afternoon, Evening, or Night, to be PC)
I received many helpful replies to my question about the best way to
repair my leaking throttle shafts. For those of you just tuning in, this
is for my TR3B, with stock SU carbs.
Several listers suggested sending the carbs to TRF for their rebushing
service, I think Greg Petrolati had TRF do his carbs and was happy with
the results. Another lister had Apple Hydraulics rebush his carbs with
good results. I would have been tempted to go this route, but it's
driving season!
John Lye had an excellent point about using oversized throttle shafts.
We really have no way of knowing if the oversized shafts will be
available in the future. Reaming out the carb bodies for the oversized
throttle shafts today might be a wasted effort if you can't get new
oversized shafts in the future.
Stu Bollen gets the award for most inventive fix. He went the oversize
shaft route. He drilled out the carb body to accept the oversized
shafts, but decided to forego the p-reamer as he could press fit the
shafts without the reamer. He chucked the end of the shaft in a drill,
and lapped them in with grinding compound. Good going Stu!
Bob Wanta replied the oversized shafts affect perfomance. OK, I thought,
I want to hear about this. I called Bob and we chatted about rebushing.
Bob told me 90% of the wear on a leaking throttle shaft is the shaft
itself is worn, not the carb body. Since I am pressed for time, he
suggested I fit new standard shafts to get my idling problem under
control and worry about installing the bushes later. (Also got lots of
other great advice...)
So, my new standard sized throttle shafts came yesterday. Sure enough,
the old shafts were worn heavily where they ride in the carb body. A
test fit of the new shaft showed a very good fit. Not perfect, but a
huge improvement. Rebushing will be necessary, but the air seal is
pretty good as is. As added insurance, I installed some little o-rings
(hint from Ted Schumacher) where each end of the shaft enters the carb
body.
The installation was pretty straightforward, with one tricky part. The
throttle stop lever is pinned to the shaft, so you need to drill a hole
in the shaft. My shafts came with a pin that required an 1/8th inch
hole, but the pin the old shafts was a bit smaller. Make sure you are
using the correct sized drill! Not having access to a drill press, I
carefully lined everything up by eye and used my hand drill. Both came
out perfect.
After final assembly of the throttle shaft, I determined the throttle
shaft did not snap closed. From full open, the throttle would snap shut,
but when open a little, the throttle did not have a positive snap
closed. I figured out the o-rings put side pressure on the shaft,
binding the disk to the wall of the carb throat. I loosened the two
screws securing the disk to the throttle shaft and the disk centered
itself. I retorqued the screws and got perfect throttle action.
Before replacing the worn shafts, the air leak was so severe the engine
would run at 2000 rpm's (hot) with the throttle stop screws backed off
to where they did not touch the stop. Now, the engine will not idle
unless the throttle stop screws are at least 1 1/2 turns in. I did not
have a chance to tune the carbs yet, but it is obvious I am much better
off then before. I am hoping I might run a tad cooler, as I was running
pretty lean with all that air leaking.
Thanks again to all who gave me input, especially Bob Wanta. His help
guided me to a very workable solution.
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Henry Frye E-mail - thefryes@iconn.net
TR3B TCF1927 L http://www.iconn.net/thefryes/
TR250 CD8096 L A Little Town In
TR250 CD1074 L Connecticut, USA
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