OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk SB Model 45 - Cutter Clutch Balance Device

We need to find out more about the whole clutch bore and captive cotter saga.

We know that quite a lot of SB45s with twin-rail decks, have cracked either the front or both rails, at the inboard engine mounting points. We know that a fair number of SB45s with captive cotter engine-side clutch halves, have had the bore of the engine-side clutch half wear and come loose, after long service. We now know that Rover's service people believed that if you used a set-screw engine side clutch half (the type that replaced the captive cotter type after the Rover take-over of SB) together with a fairly tired 8 cubic inch Briggs engine, there was excessive engine vibration.

There are more than enough SB45s owned by Outdoorking members to solve this issue properly, if we collectively want to do it. There are some basic questions that members will already have information on - we just need them to post it, preferably in this thread.

Question 1: Do all of the SB45s that have cracked their frame rails, have 8 cubic inch Briggs engines (mostly 80202, but perhaps 80102 and 81202 models as well)? Does anyone have a Kirby Lauson SB45 with a cracked frame rail?

Question 2: Do all of the SB45s that have cracked their frame rails have captive cotter engine-side clutch halves?

Question 3: Do people with SB45s with 8 cubic inch Briggs engines, find that the engine vibration gets worse when they replace the captive cotter engine-side clutch half with a set-screw clutch half?

If we can get answers to those questions, and they point to the 8 cubic inch Briggs engine being a common factor in pretty much all of the cracked frame rails, we could confirm the diagnosis with a fairly simple test. Someone could just get a Briggs 80202, sit it on a concrete floor, and fire it up. If it pogoed around the floor like some of the old British engines did, that would tell us something. If he or she then repeated the test with another engine (say a Honda GX120 or a 6 cubic inch Briggs) and found the other engine didn't pogo, we would be close to being able to say the 8 cubic inch Briggs looks like a strong suspect for the underlying cause of all of the SB45 vibration, frame rail failure, and clutch bore failure problems.