Engine Adjustments #4

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Setting ignition timing

In the days before the Omaka air show, we had problems starting the engine, with kick-backs. We decided that the timing was slowly moving. So the levers on the two magneto’s are now locked into place, and I did set the timing to the required 30 deg before dead centre.
Starting became easier now.

Dripping carburetor

We saw fuel dripping from the carburetor, and suspected that the float valve could be stuck. So there the carburetor came of the engine, all stainless steel locking wire cut and opened the two halves. The valve wasn’t stuck, but noticed that it was worn. By the way, I did see this in the early stages, but thought it would be OK.

I decided to have it machined. I went to Tony from CAMS here at Omaka. This was during the show, but Tony didn’t have any problems helping me, so 10 minutes later it was done.

I mounted the valve again, but because it was now a little shorter, I thought I should adjust the float a bit to compensate for the shorter valve. That evening we started the engine again, and nothing had changed, it was still running very rich and rough. BUT the fuel that was dripping from the carburetor now seem to come from the prime valve:

Closing priming valve

So this morning, the last morning of the show, I was going to try one last thing. Lap and permanently close the priming valve, or at least for now. The engine ran very nice, but was very hard to start as the priming valve was not usable now, and also the engine slowly ran out of fuel.

So two conclusions:

  1. The float level is probably to low as a result of yesterdays float valve work.
  2. The priming valve seems to be sealing so after it was lapped. So needs to be made operational again.

Measure carburetor fuel level

Now the Bleriot is back home, I started working on the float level.
I took out the drain bung at the bottom, and replaced it with a fitting to connect a bit of clear tubing to measure the fuel level inside the carburetor. A friend from a previous work place Brett Sewell gave me the idea, and it worked perfectly !!
The manual indicates that the level should be 9/16″ below the split level (where the carburetor splits in half).
What I measured was 15/16″ below that split level, so very low indeed, as what we expected!


After adjusting the float and the hinge a few times, I got it perfectly at 9/16″ below the split level 🙂

Oh yes this was with 30″ of fuel head, in stead of the 39″ the manual says. But as the minimum height for flying is shown in the manual as 24″, I think setting up the level with a fuel head of 30″ is probably OK.

Tomorrow I will assemble the carburetor again and also fit the purge valve lever 🙂

Below a closeup, where you see the clear tube with the fuel in it at 9/16″ below the split level.


Running pretty good I think

Had the engine running again today after I fixed the float level in the carburetor, and re installed the priming valve.
I assumed that after the lapping I did on this priming valve while still in Omaka, and the good run there, proving that it didn’t leak anymore, that I could try the valve without modifying it.

And yes:

  • Starting is not to hard really right now.
  • Running at idle speed sound nice.
  • And running at sort of max speed sounds very powerful, and I think it’s running good.

Have a look here:


Mockup ring exhaust

Made the “ring” of the mockup ring exhaust of flexible drainage pipe, and as expected, it looks good.

Next step will be ordering the 1.5″ bits of mild steel to form the stubs that go into the exhaust outlet of the cylinders. They will need some rings welded on and machined to the right shape to suit the exhaust nuts. And when that’s done and mounted into the cylinder exhaust outlets, I am going to do the final measurement of the ring diameter 🙂




Mild steel exhaust stubs

Started cutting the mild steel exhaust stubs for the ring exhaust. This one going into the exhaust outlet, is 1.5″.

Before it is going be used, a ring needs to be welded onto it and machined to the right dimension and shape. More on that later !


5 exhaust outlets stubs

Finished cutting the 5 stubs to go into the exhaust outlets. Taking them into the car exhaust company where I got the tube from, so they can cut one end that will butt onto the 2″ ring “collector”.

Also had to clean the exhaust outlet as there was a lot of carbon build-up. I noticed that the old bits of stub that came with the engine had been “crimped” a bit to make them fit. All they would have had to do was clean the bloody thing. Oh well, fits nicely now 🙂

Collector ring

During the week I also made some rings (will show you later) that Warren is going to weld onto the stubs shown above and machine to the right size and shape, so they fit inside the exhaust nut.

Also this week I had the “collector” made from a 2″ tube.


Cutting it into segments, also made short bits of sleeve, of a tube one size down so that fits inside the 2″ tube. These sleeves going to be welded on one side and on the other I will use rivets to attach them again.
The main reason for doing this, is so the ring can move a bit when the engine and exhaust gets hot. Other reason is that the whole ring can’t be installed as a whole ring as the engine is installed on the engine frame….



More cutting

Right: finished cutting the 2″ OD ring. The “top” 3 segments are the correct size. The bottom 2 are still un-cut and will be cut when top 3 are mounted on the engine.



Left: found a “free” piece of stainless steel flexible exhaust tube with internal diameter of 1″. Exactly what I needed for the heat exchanger on the carburetor. Some of the exhaust gasses will be diverted through this heat exchanger to heat up the carburetor to stop it from icing up where the fuel evaporates inside the carburetor.

Oh yes also bought a bit of 2″ bend tube (with a small radius) that will be welded to the bottom, so the exhaust gasses will exit downwards.

Welding exhaust


Today Warren came in to start welding up my exhaust. It all went so well, couldn’t be better.

Super happy.

Have a look yourself. Photo’s are a bit hazy, not sure why, maybe the light conditions, might make more when its all welded up permanently.

So a very very big thank you to Warren !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!





Fuel pump

Installed a little fuel pump today. Reading the carburetor specs on my engine, I found that I needed at least 24″ of fuel pressure, and with my tank position I didn’t have that. This little electronic pump creates a pressure of about 3 PSI, not a lot but that’s what the specs required. After I installed it I had it running for a few minutes without running engine and no flooding of the carb, so the fuel control needle valve inside the carb must be working nicely. As soon as the ring exhaust is back, I can try it out.

Oh yes, when pump is not running, the fuel still flows, so that’s good.

In the past when the engine was running, it looked OK with the fuel pressure, but once or twice in the early stages, the engine stopped on us with not a lot of fuel left in the tank, so maybe that’s what it was.


Nicely going down, all the way from the tank to the carburetor.



Exhaust back

Got my exhaust back today from Warren (colleague at work). After last weekend, tagging it all together, he finished welding it this weekend. One basket full of “ring exhaust” 🙂

Just weighed it, 6kg more in front !


Next job will be spray painting it with high temperature black exhaust paint, but a high heat primer first…..




Painting the exhaust

Yesterday I started cleaning and priming the exhaust to prepare it for the final black mat colour. Went really well. I used primer (white) and final coat (black mat) Flame Proof from VHT. I think it worked well, all that needs to happen now is cure the paint by heating up the exhaust. can’t wait !!!!!

Looking good anyway 🙂

Oh yes and I need to secure the sleeved sections of the ring by drilling little holes through the sleeves, inserting a little steel pin and a clamp over it.