New carb socket fits loose

Kelsie, what advise or instruction did Dean at Lockwood provide? Had they heard of this before?

Jim Isaacs wrote:

Kelsie, what advise or instruction did Dean at Lockwood provide? Had they heard of this before?

Dean was very interested in the issue. He stated that this is a possible explanation for an issue he's been seeing where it really seems like air is leaking past carburetors into the sockets, but he hasn't nailed down yet what the cause is. He requested that I do a report to Rotax, take a video showing the looseness with the clamp tight down to the spacer. I have made that video, and I'm compiling pictures to catch him up on the current state of this.

There is an interesting new development in this. I was re-reading the Vans RV-12 engine installation manual for other reasons, and I noticed a sentence that says:

"Tighten the band clamp against the spacer provided by Rotax which automatically sets the proper gap (.276 in. or 7mm) between the clamp lugs to prevent over tightening."

This is significant, because as I shared in a previous reply to this thread, the spacers I have are 8mm, and the amount of "wedging" in that is happening on the old clamps is... you guessed it... roughly 1mm. I had not previously noted the significance of the 7mm being documented last time I read through the engine installation manual because it was before I measured the new spacers and noted them to be 8mm.

Does anyone following this thread know if Rotax has made adjustments to the size of the spacer after it was introduced? I'll obviously be following up on this with Dean at Lockwood, but just curious if anyone has first-hand knowledge of this.

I realize I'm re-opening a can of worms by bringing this up, considering half the people following this thread have been telling me to just shorten the spacer all along. I would appreciate if you would recognize the significance to me of finding official documentation of this discrepancy rather than just doing it because it seems good.

hi Kelsie

The 7mm spacer was for the old part number 267787.  With the change in 2004 (from 267787 to 267788) they used a 8mm spacer as the material of the socket is thicker and new compound.  The replacement for the 788 was a 267789 and it also uses the 8mm spacer.  It appears to me that the clamp is badly formed and perhaps that is the issue.  The RV12 information was most likely generated a long time ago and appears to be out of date.  I would ask Vans to clear this up as that information was not based on the newer part.  

I believe you are correct, the change has to be given by Vans if they wish to allow a 7mm gap as it is not wise to overclamp the socket.  This may create splitting inside if the clamp is overly tight.  

Cheers

To all

There is an old bulletin that covers when the change from 7mm to 8mm spacer was introduced back in 2004.  In the event anyone wishes to see when that happened.

Also I checked, the change actually happened in 2001 and the SB had a revision in 2004.

Cheers