question Strange Features

[skippydiesel]

Hi All: There is a Rotax 912 ULS for sale in the Classifieds it has (to my eye/experience) two unusual features that some of you may be able to explain;

• Cooling, oil & fuel hoses that look like flexible metal ??
  
• Muffler that looks to be about 1/4 the size of a standard Rotax and flat on the bottom??
  

[facthunter]

Rolled stainless flexible like my shower has. Plenty of corrosion. Is there a nut missing from the LH carby rubber mount? Nev

[FlyBoy1960]

The nut is not missing because there is not one there

 

This hosing normally has a rubber core

 

Muffler is VERY small compared to normal

[IBob]

I'd say that's the front end of a Savannah. The muffler comes with the kit. As does the air box.

 

And so does the flexible stainless hose, and the beaut thing about that in the engine compartment is that it can be bent into very precise profiles, and it just stays that shape, rather than springing back. Furthermore, you can put a tight bend in it without it collapsing, which is what happens if you try to tight bend regular hose. The end result is that it is easy to make a very compact installation. The downside is that the ends are fitted using a short piece of regular hose and 2 hose clips, as you see there. Which is a lot of hose clips, but it certainly works!

[Blueadventures]

Hi All: There is a Rotax 912 ULS for sale in the Classifieds it has (to my eye/experience) two unusual features that some of you may be able to explain;

• Cooling, oil & fuel hoses that look like flexible metal ??
  
• Muffler that looks to be about 1/4 the size of a standard Rotax and flat on the bottom??
  

[ATTACH type=full" alt="1590195355351.png]53434[/ATTACH][ATTACH alt=1590195355351.png]53434[/ATTACH]

That’s the fuel line ipc use at times. I personally don’t like the look of it as I hear sometimes they get leak. Looks like a sav.

[IBob]

The muffler works fine and isn't noisy.

The metal hosing does not have a rubber core or any other lining.

[IBob]

That’s the fuel line ipc use at times. I personally don’t like the look of it as I hear sometimes they get leak. Looks like a sav.

 

Yep, Blueadventures, we circled that hose like dogs that have found a new lamp-post.

But they've been using it for a while now, and there has been no news of leaks in the Savannah world, that I know of. So I went ahead and fitted it, and am very happy with how it went together.

Where have you heard of leaks?

[IBob]

BTW, Skippydiesel, that minimal 'muffler' also contains a heat exchange for cabin heating.........

[Blueadventures]

Yep, Blueadventures, we circled that hose like dogs that have found a new lamp-post.

But they've been using it for a while now, and there has been no news of leaks in the Savannah world, that I know of. So I went ahead and fitted it, and am very happy with how it went together.

Where have you heard of leaks?

Sav owner heard form an owner north of us so he fitted normal hose. I gave him a help. We used like for like. Cheers I expected they must work good. The guy that had them just wrapped them up and put in normal hose again. Cheers

[IBob]

Sav owner heard form an owner north of us so he fitted normal hose. I gave him a help. We used like for like. Cheers I expected they must work good. The guy that had them just wrapped them up and put in normal hose again. Cheers

Thanks for that Blueadventures. It would be interesting to know just what sort of leak he had, whether it was the pipe itself or the system of terminating it.

The smaller diameter stuff is about 9.5mm OD from memory, and I do know of one builder who had trouble tightening hose ends down onto that, though I suspect he may have been using a larger hose clip: I know that if you go up a clip size, it almost fully tightens, then you run out of adjustment. I had no problems after carefully sorting my clips into sizes.

I also went to some trouble securing the various lines to avoid any gross vibration.

I guess time will tell!

[Blueadventures]

Thanks for that Blueadventures. It would be interesting to know just what sort of leak he had, whether it was the pipe itself or the system of terminating it.

The smaller diameter stuff is about 9.5mm OD from memory, and I do know of one builder who had trouble tightening hose ends down onto that, though I suspect he may have been using a larger hose clip: I know that if you go up a clip size, it almost fully tightens, then you run out of adjustment. I had no problems after carefully sorting my clips into sizes.

I also went to some trouble securing the various lines to avoid any gross vibration.

I guess time will tell!

I'll chase up detailed info when I next see them.

[facthunter]

Then the bolt is too long. It's only supposed to protrude about one thread. Got called to the phone .See if it will send..??Nev

[Head in the clouds]

Then the bolt is too long. It's only supposed to protrude about one thread. Got called to the phone .See if it will send..??Nev

Not meaning to be pedantic but it's supposed to protrude at least 1.5-2 threads. There is no limit on how much more it may protrude. On my 912 it is the same ... just inconvenient to wind the bolt in that far.

[facthunter]

It's extra weight for no purpose and the thread could be damaged and ruin the thread in the manifold flange when extracted.. It's $#1t workmanship to have extra length. It would look pretty silly on a castellated nut.. Nev

[Head in the clouds]

It's extra weight for no purpose and the thread could be damaged and ruin the thread in the manifold flange when extracted.. It's $#1t workmanship to have extra length. It would look pretty silly on a castellated nut.. Nev

 

I couldn't agree more Nev. However, it's how the factory supplies it. Personally, by preference, I would cut the excess thread length off. But then it wouldn't be compliant on a cert engine would it? So what would be your personal advice to Rotax engine owners whose engines have carby bolts like these?

[onetrack]

The problem with bolts that are too long and have quite a number of exposed threads, is that the exposed threads corrode, and then it becomes difficult to unscrew the nut.

If the exposed threads are projecting excessively from a housing, the housing threads will become damaged when the bolt is unscrewed.

[M61A1]

The problem with bolts that are too long and have quite a number of exposed threads, is that the exposed threads corrode, and then it becomes difficult to unscrew the nut.

If the exposed threads are projecting excessively from a housing, the housing threads will become damaged when the bolt is unscrewed.

Given that they are factory Rotax bolts that appear to be standard automotive types, and are plated, I doubt there will be much of an issue. I have not noticed it be be a problem on any Rotax engine I have seen.

[facthunter]

I've never seen things like that on a" production" engine. You might say it's nothing but it could easily injure someone working under a cowl, catch a wire or rag when wiping the motor over. Studs and bolts just don't protrude like those do on anything I've seen or worked on. A part that has to be removed like those carb rubber mounts could do with more length of thread in the flange, to allow for loosening of the fit over time. Bex as to a fix, I'd probably just put a nut on it or purchase a shorter bolt. Shortening bolts and cleaning up the thread is often done badly making them hard to start or likely to damage the thread of the flange. Nev

[IBob]

You certainly raise valid points, Nev. But as far as I know, they're all like that. Presumably there is or was some good reason: maybe the application is between standard sizes, in that the shorter standard is too short, and this one too long?

[facthunter]

Are the inner bolts the same? Nev

[IBob]

I believe they are, Nev

[skippydiesel]

Hi IBOB - very nice clean/neat installation pity about the throttle & choke cables ( )