Zenoah 38 carb oreintation

[RichardVaughanDavies]

Part way through building the SIG Spacewalker kit (1/3) and will be fitting a Zenoah 38 with a 90 deg bend on the carb inlet.
My question is:- Does it matter if the carb is upside down?

Normal fit, needles uppermost. Fuel entry at the bottom.

carb normal.jpg (144.88 KiB) Viewed 12137 times

carb inverted fuel entry now at the top

carb inverted.jpg (142.35 KiB) Viewed 12137 times

Having it inverted would keep the fuel pipe further away from the silencer box. My preferred option.

Your thoughts would be appreciated.

While I'm here , do the inlet trumpets only come in one length?

Thanks
Richard

[John Greenfield]

Richard

What is important in the carb orientation is that the pump hole in the engine side face of the carb lines up with the hole in the carb bend and insulator plate. As long as these align the carb will be fine but if they do not the carb will not work at at all.
Practical Scale make a 2 part trumpet consisting of a base flange and separate trumpet that you can cut to the length you want and then join the 2 parts.

Hope that helps.

John

[RichardVaughanDavies]

Yes it does John, thanks for your reply. An order to Toni is on it"s way.

Richard

[Phil Clark]

The carb must be orientated as per photo #1......rotating it through 180 degrees as per photo #2 means the pump holes in the cylinder, bend, gaskets, insulator & carb will not line up and the pump won't work.

Trumpets in stock here - http://www.fighteraces.co.uk/product/zg38-sc/

.......will save you some postage from Germany!!

Phil (Fighteraces)

[RichardVaughanDavies]

Hi Phil

Too late , I've already ordered with Toni. Thanks anyway.

I'll just have to find some way of routing the fuel line a reasonable distance away from the silencer box. Don't know how hot it will get, but I'd still feel more comfortable with a space between them.

Richard

[Steve Mansell]

Richard,
I have used woven heatproof sleeving on one of my fuel lines. I bought 2 different diameters, so one slid over the other for a double layer. Can't remember where I got it from now, but it might have been Mick Reeves.
Cheers
Steve

[John Greenfield]

Sorry Phil, I did not realise you stock Practical Scale bits. I will remember for next time.

John

[Bob Thompson1894]

Evolution do black petrol tube which they claim is heatproof. A lot of model shops stock it, its good stuff.

[Tony Collins 1073]

Hi Richard. I needed to invert the carb on my Zenoah 62 and made my own carb bend but still
had to line up the pressure holes. I simply drilled the bends two flanges to line up with carb and engine and joined them with copper tubing.
I know you are thinking that's no good for me cos my bend is aluminium. Well If you are able to use aluminium technoweld it can be done. It is possible to tin the copper with technoweld first and then weld it to aluminium. I've done it very successfully a few times. of course you
could use ali tubing but that is less durable.
Hope this helps.

Tony Collins.

[RichardVaughanDavies]

Hi Tony.
Your skills are way above mine, I'll be going with the carb as in photo #1 and a different route for the fuel pipe. When I get the inlet trumpet (posted on the 4th) I'll have a better idea of the engine fitment.
Thanks for all the help.

Richard

[Peter Smedley]

Just been reading this thread with some interest. I have just run up my Zenoah 38 with the carb bend, though I have the engine upright. The tank is a couple of inches below the carb. The walbro has no difficulty drawing up the fuel.
How about a sleeve heat proof material over the fuel pipe? Just a thought?
The bend and gaskets came from Toni Clark. Great service. Yes, the pulse ports must always line up or be connected in some way- this is what drives the pump valves.

[RichardVaughanDavies]

All the bits have arrived and engine (temporarily) fitted.

IMG_3059.jpg (145.39 KiB) Viewed 11812 times

From the photo above, I feel the fuel line is sufficiently away from the silencer box. Please say if you think different. :-)

More pics for your interest.

IMG_3058.jpg (155.87 KiB) Viewed 11812 times

IMG_3062.jpg (192.68 KiB) Viewed 11812 times

IMG_3063.jpg (173.69 KiB) Viewed 11812 times

IMG_3065.jpg (165.59 KiB) Viewed 11812 times

[Steve Mansell]

Richard,
How did you turn the fuel inlet round on the carb? I need to turn mine around about 45 degrees, after fitting a bend on mine. I don't want to break it as it's a new carb.
Cheers
Steve

[Peter Smedley]

I put my carb in a vice protected by a bit of cloth.
I got a set of long nose pliers. Put them around the body and neck of the fuel inlet. You want to move the body and barbed neck together. If you just move the short tube it will snap off. It will take a bit of muscle....then crack it moves around.
Make doubly sure you move it the correct way you want. It will be tempting fate to move it, get away with no damage, only to find its facing the wrong way.
I will try and find the thread somewhere that has an explanation of replacing the nipple.

Here it is
http://www.modelflying.co.uk/forums/pos ... ?th=104433

[Steve Mansell]

Many thanks
Steve

[RichardVaughanDavies]

I didn't Steve, it came like that. I did try and move it but chickened out after I put a lot (I thought) of effort into it and getting nowhere. :-)
The carb has now got an extension for the pressure equalising hole to the trumpet side of the firewall/engine mount. Throttle cable is sorted. Just the choke to sort out and then the engine will be completed.