[TR] fast idle problem

[Cliff Hansen]

Bob,

Are you sure the linkage is allowing the butterflies to close completely?  That was the problem I had when I first put the rebuilt carbs back on my car.

Cliff


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From: Michael Marr<mailto:mmarr at albiontechnical.com>
Sent: Tuesday, May 12, 2020 9:03 PM
To: Bob Leaver<mailto:boleaver at gmail.com>; Triumphs at autox.team.net<mailto:Triumphs at autox.team.net>
Subject: Re: [TR] fast idle problem

The Moss reamer cuts a hole that is 10 thousands (nominal) oversize, and requires you to use ten thousandths oversize throttle shafts.  The reamer has an extended pilot, so that, even when reaming by hand, the alignment between the holes on each side of the throttle body is maintained.  To that extent, it is a special reamer, which accounts for its price.  I found other piloted reamers, but they are chucking reamers and the pilot is quite short, so you would have to set the carb body up on a good drill press (or vertical mill, preferably) with the axis of the throttle bushing holes perfectly vertical.  The body would have to be clamped to an angle plate in some manner.  Such a reamer, of the right size, can be found here...

https://www.panamericantool.com/high-speed-steel-reamers/high-speed-steel-piloted-chucking-reamers.html

Part number 99-703 is what you would want.  But, unless you've done this kind of set-up before, I wouldn't recommend doing this.  I think sending the bodies out to have new oversized shafts fitted might be the most expedient thing.

Mike


Michael J Marr, P.E., CEng.
Albion Technical Services
W5918 Hackbarth Rd
Fort Atkinson, WI 53538

Cell:  630-202-0065
Email:  mmarr at albiontechnical.com

-----Original Message-----
From: Triumphs <triumphs-bounces at autox.team.net> On Behalf Of Bob Leaver
Sent: Tuesday, May 12, 2020 4:58 PM
To: Triumphs at autox.team.net
Subject: [TR] fast idle problem

I have a 1965 Triumph TR4a that I rebuilt the SU carbs and now I can't get the idle below about 1500. I've tried all the screws and checked all gaskets and nothing. The only possibility I can come up with is air getting around the shafts. When rebuilding the cars I didn't replace the shafts because I didn't have a reamer. Moss has a reamer for $290.00. I looked on line and can't find a less expensive replacement. The book states the size of the reamer is 5/16" + 0.0105". What kind of measurement is this? Can you use a 5/16" reamer?
Does anyone have ideas how I can get the idle down? Does anyone know of a cheaper reamer to use? Thanks, Bob
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