Fuel spitting carbs

[Jambo]

To all the carburettor gurus.

On my motor I have 2 Bing 54 carbs with the following jetting:
Idle 40
Main 180
The needle is a 11H2 and is connected on the second groove from the top.
I am based in Jhb area so 5400ft ASL.
During flight my EGT's are also low indicating overfuelling which is probably bad for the motor as well.

I have noticed that my firewall is always messy and after recently cleaning and redoing the fuel lines I have run up the motor and again found a fresh mess all over. I have then noticed the aircleaners are wet with fuel and even dripping.
I removed the aircleaners and ran the motor up again (on paving during rain drizzle, so no dust)
I saw the fuel actually spraying out of the carbs.

My question is am I using the correct jets or should I start by dropping the needle first.

Any suggestions and solutions welcome.

ZU-BRV
102HP Bushbaby

[The Agent]

What engine bru?

[Jambo]

Does it matter?
I left it out to get info irrespective of engine make.
But if it is required it's a Simonini V2P. :D

[IFLYHI]

Does it matter?
I left it out to get info irrespective of engine make.
But if it is required it's a Simonini V2P. :D

This happened to me, the solution was a dirty filter/ or filter that had been washed in fuel (not by me) previously. This collapses the fibre of the K&N filter

[Jambo]

But it does the same even without the filters.

I have washed the filters with dishwashing liquid and rinsed them thoroughly. They are busy drying and the I will spray them with K&N filter oil. BUt I don't want them to get washed with fuel again, hence I need to get to the bottom of this.

[flykr]

I had the same problem on my 503. Changed the needle & seat's and problem was sorted (these need to be replaced every 150 hours). Also make sure the breathers are not blocked.
Happy hunting

[Duck Rogers]

What engine bru?

Very valid question

Does it matter?

Yes, it does.

The Simonini is not as popular as the Rotax and therefore not as much technical info available.
In my opinion, the jetting does seem to be a little odd. The idler jet may be a little lean at 40 but it will help smooth out the idling though. The main jet should probably be in the region of 160 - 165. The jet needle size that you quoted is also richer than the standard Bing issue. The "11" indicates a richer mixture over halway throttle and the "H" indicates a richer mixture below the halway throttle position. So, in all respects, it's jetted quite rich with the exception of the idler jet which is on the lean side.

I wouldn't bother too much with the groove of the needle jet for now. Get the jetting right first. Dropping the needle down (top groove) will make it a bit (not much though) leaner.

Both the posts by IFLYHI and flykr are valid for the symptoms described.

You should have enough info now to go hunting :D

[Jambo]

Thanks for the info Duck Rogers. flykr and IFLYHI

I also remember reading something like that in a copy of the Microflight magazine somewhere in 2003. Unfortunately I cannot find my copy anymore. That exact one is missing.

I will get myself some new jets and try them out.
I makes sense since the motor is factory tested and run at just about sea level.

Regarding motor make: I would assume all two stroke engines could have the same symptoms and technical info would be valid for all.?

Regarding needle and seat: probably very valid but the motor has only run less that 50 hours so I hope this shouldn't be a problem.

Regarding dirty filters: absolutely but I had the same symptoms even when filters were removed.

[Jambo]

OK after doing some reading see Sticky "usefull technical documents"
I have come to the following conclusions which will be tried this weekend.

My prop was not ideal and my jetting is too rich.
I have bought a new ground adjustable prop but I am looking for some 170 Main jets. Anybody know where I can get them? Aviation Engines don't have and don't bring them in.

Thanks.

[Smiley]

OK after doing some reading see Sticky "usefull technical documents"
I have come to the following conclusions which will be tried this weekend.

My prop was not ideal and my jetting is too rich.
I have bought a new ground adjustable prop but I am looking for some 170 Main jets. Anybody know where I can get them? Aviation Engines don't have and don't bring them in.

Thanks.

Howzit Jumbo

Please just make sure from Aviation Engines that those are the right size jets for your specific motor at Petit altitude!!!! Otherwise you are going to burn "the hole in the piston"..

My pilot friends carb was spitting out petrol. You could see this when the filter was off. Spoke to the Aviation engine guys and got the right settings for that motor and now she's perfect.

Jet sizing was right, the needle was one groove to low...

[Jambo]

Thanks for that positive reply Smiley,

I was at Aviation engines but they could not recommend anything. I finaly got an answer from Simonini themselves telling me I need a 170 main jet and 45 Idle jet. This is what I managed to work out aswell from the tech. docs.
But AE does not sell that size jet.
I have also replied the Simonini mail to find out about the needle and its setting.

The spitting is so bad a Pax once asked me to land as he was getting nauseous. Who knows what could happen to the pilot suddenly if this is not rectified.

Thanks again to all that replied. Now I just need new jets and I can report back.

[Jambo]

Firsltly I must commend Simonini in Italy.
They sent me new jets and float needles free of charge to try and help me sort out the problem.

Although I only fitted the float needle as a last resort it was the actual problem of why the carbs were spitting fuel.

Now I should be able to get better range as I don't waste half the fuel.

Thanks again for the replies.