Very big tappet clearance

Yes decided to see if the Bleriot was still there. Had been busy getting my Advanced Local pilot license, been on holiday to The Netherlands, then on Xmas holidays tramping in Aspiring National Park….

Its been since July that I last worked on the engine. So I checked the 5 front spark plugs that were still loose and disconnected, cleaned that one black one again, and connected the ignition wires. Next I thought, might as well check the tappet clearance, just in case.
And GUESS WHAT !!!!!! The exhaust clearance of the dirty cylinder wasn’t 15 thou (about 0.4mm) that is should be but 4 – 5mm !!!!!!!!! No wonder that cylinder had problems breathing. That exhaust would have been open for a very short time during the exhaust cycle.

So fixed that clearance setting and tried starting the engine, only to find out that my battery had died, well pretty sure, so will check it out later at home.

That was that session, but quite stoked having found this one issue. Its been there since July. Still think that my old carb is the way to go for now so will stick with that one !

Running again with OLD carb

I connected a new bit of fuel hose again between the carburetor and the fuel pump, and re-connected the throttle cable again. Looks easy, and it was, but took me an hour….. Oh yes also cleaned 4 dirty spark plugs (from last time) in that hour πŸ™‚

So yes ready for starting the engine:

  1. Primer on, throttle closed, mixture rich, ignition off, magneto’s off; Priming the engine by pulling the propeller over a few times. That makes the engine suck the fuel into the carburetor. I noticed that it was dripping a lot of fuel, more then normal, and I wonder if thats because of the higher compression ratio. I think it is, so that’s good.
  2. Primer off, throttle set (10%), mixture rich, ignition on, magneto’s on; Swing the prop, and there it goes !!!

Yes, as usual, no problem starting !!!

These are my findings:

  • The engine runs nicer, no sound of missing cylinders.
  • Not getting above 2000rpm yet, but it will need more running in I would say.
  • After running for 10 minutes or so, it stopped OK, without continuing to run on, as it did previously, because of cylinders that were to hot.
  • 4 Cylinders now have nice clean spark plugs, and only the one that was supper dirty last time, is now a little blacker then it should be. I’am assuming thats because of oil still leaking past the rings, so that should improve.
  • Ran the engine again for 10 minutes or so, and checked that one spark plug. It still looked the same….

Next time I am going to taxi the Bleriot along the taxi way a few times, to get more engine running in time, and at the same time get some real “plane” time πŸ™‚

SU carburetor off, old one back on

With my confusing engine issues, I decided to take the SU carburetor off and start putting the old Stromberg carburetor back on again. Hopefully when I get the engine running again, it will tell me something about what’s happening.

When I picked up the old carb I noticed that I did cut the fuel line, to make it fit for the SU carb, so I knew that I wouldn’t be running the engine with the old carb today. That’s OK. That gives me some time to have another good look at it in the next few days.

To be continued !!! Β πŸ™‚


Today I was going to do more running in of the engine, trying to bed in the new rings a bit more. But I am confused….

Last time I ran the engine I cleaned the spark plugs, as some of them weren’t firing properly. Some were very dirty, and I assumed that that was as because I had oil on top of the pistons in earlier runs.

After cleaning them, the engine ran fine, and the spark plugs stayed nice and clean. A bit to clean, very clean in fact!!!! Also the engine was getting hot and had issues stopping because of it. So yes running to lean πŸ™

So today I dropped the needle in the SU carburetor about 2mm, to get a richer mixture, and yes the engine is running cooler now, but, and here is the confusing bit: Two of the 5 cylinders have very dirty spark plugs, the same ones I cleaned last time (this makes the engine run effectively on 4 or even 3 cylinders).

The spark plugs in the other 3 cylinders are clean, with a bit of a brown “healthy” color. So the mixture they get is right, but its these 2 cylinders that get a richer mixture, or that’s what I think.

I was talking with Nick, who has a plane next to me. and I think he know a lot of engines, think he works a lot with cars.

He was looking at the engine with me for quite a while and there are 3 points he was “worried” about:

  1. The easy one is that the oil I am using in the damper inside the SU piston damper is to thin. This means that the mixture ratio might not be constant because of vibrations of the carburetor while the engine is running. I need to put SAE30 oil in there.
  2. The 2″SU carburetor I am using, if I remember well comes out of a 4L Jaguar engine. So same engine volume, but that engine is running up to 2.5 times faster, so would be drawing over twice as much air (faster air flow). But also there are two carburetors on that engine so the overall mixture speed would be similar, so maybe nothing wrong here…
  3. The pipe in between the SU carburetor and the engine is 2″ as that’s the size of the carburetor. But because the engine is only 1.5″ we had to reduce the pipe size. This is done just underneath the engine. Nick’s concern is that the mixture might be swirling a lot, going through that pipe and through the reduction, and as a result when the mixture enters the engine, more mixture might be getting into one half of the engine and less into the other half. Not due of this is correct, but sounds feasible.

Hope someone has some interesting comments on this !!!

More running in

Today I went back to hopefully get the engine running better. Last time I noticed that with one magneto switched off, it was running on less then 5 cylinders. Also noticed 2 really oily spark plugs.

So today I cleaned all 10 plugs, and ran the engine twice, for about 10 – 15 minutes.

Yes its running nicely now on both magneto’s individually. And checking the spark plugs afterwards, they are all looking good. Some are a bit to clean, indicating a mixture that’s maybe a bit to lean (fuel / air ratio a bit to low, so not enough fuel). This makes it run hotter. And yes that’s what I see. Trying to stop it running, doesn’t work, it keeps on igniting as its to hot inside, so I think I definitely need to change the mixture ratio. Make it richer……. That’s for next time πŸ™‚

Running again

Started the engine again, for the first time after assembling with the new pistons, that now have a new oil collection groove just below the oil ring.

But first I had a good look at the carburetor, decided to take the top cap of my SU carburetor off to put new thin oil in the oil damper for the piston that controls the mixture ratio. I had normal engine oil in there that was to thick at the current low temperatures. So yes did that first before starting it.

After priming the engine, it started first time, as always πŸ™‚

But I noticed that of the two magnetos, the original one isn’t firing all 5 cylinders so that will be my next little side project. Trying to find out why its not 100%……

All cylinders of again

Today I took the 4 remaining cylinders of again, so I can get the piston’s out. I left all pistons inside the cylinder so it’s easier to get them home, but the piston in the top cylinder, #1 piston slipped past the bottom ring. I couldn’t get it back in easily so pulled it out completely.

To my surprise I did find oil on top of piston #1. Wow so hard to believe.

With the new oil grove that Richard is going to add to my pistons, all that oil will be scraped of the cylinder and thrown back into the Β engine.

So even the top cylinder that I thought would be running OK, should run better without that oil in there. CAN ONLY GET BETTER !! Β πŸ™‚