Bruce Macbeth Engine, European Version

[Kim]

Could you angle the upper ones outward?  Away from the others?  That would give you a little more clearance, but you still have the center one snaking between two other posts...

Kim

[fumopuc]

Hi Roger, Kim thanks for watching and and your comments.
I am afraid also that all is to close at these distributor cap there in my way to do the wiring,
But step by step.
Here are first some pictures of the final wiring.
And how the main HV cable find its way from the base to the distributor.

[fumopuc]

Hi everybody,
some progress here.
Before Christmas I have been able to get the first pops, when suddenly the CDI stopped working totally.
Roy from S/S was very helpful at the diagnostic support.

At the end I have a new CDI system here now, it is assembled and is working quite well.
The engine does fire and does burn fuel also, but currently it will not really run on its own.
[youtube1]https://youtu.be/PcMTY4QMZIo[/youtube1]
I can feel that it starts to get power and sometimes it is turning faster than the cordless screwdriver, but if I take it off is does not go ahead alone.
Any ideas are very much appreciated.
Compression test was done again already before Christmas and was fine.
   

[RReid]

Well, it's certainly close and it sounds great while it is running. I have no doubt you will soon get it sorted. You've done a wonderful job on that engine, with very nice detailing. Congratulations! 

[Kim]

Yes, you're certainly close!  I don't have IC experience so can't give you any input there, but it looks great and sounds really good while it's going.  I know you'll get there!

Kim

[fumopuc]

Hi Ron, thanks.
I have an enemy to attack already.
I have the feeling the carb is with the 3 mm Venturi a bit to small.
Just checked the recommendation of Doug Kelley again and he has written 0,17" (4,318 mm) Venturi should be fine.
A 4,5 mm venture carb is available, so next to do is making an adapter.

[fumopuc]

Yes, you're certainly close!  I don't have IC experience so can't give you any input there, but it looks great and sounds really good while it's going.  I know you'll get there!

Kim

Hi Kim, thanks.

[Admiral_dk]

Sounds very promising - so you can't be far of a sustained run

I can't make out if you are trying to open the Throttle fully with your finger in the video and if that is where you are closest to it running by itself ....

Next thought : if you require an adapter to fit the bigger Carburetor - will you get a bigger area in the smallest diameter all the way to either where the Manifold divides or will it not be the Venturi that is the smallest ?
It should make a difference, if it's still the Venturi with the bigger Carburetor.

The model looks great 

[fumopuc]

Sounds very promising - so you can't be far of a sustained run

I can't make out if you are trying to open the Throttle fully with your finger in the video and if that is where you are closest to it running by itself ....

Next thought : if you require an adapter to fit the bigger Carburetor - will you get a bigger area in the smallest diameter all the way to either where the Manifold divides or will it not be the Venturi that is the smallest ?
It should make a difference, if it's still the Venturi with the bigger Carburetor.

The model looks great 

Hi Per, thanks.


The throttle in the video must kept totally open, otherwise the engine will stop any firing.
I have had this never before with my engines builds so far.


The other questions I will try to answer with some pictures.
They are showing the overall situation at the engine with small and bigger carb.
The bigger carb with 4,5 mm bore in the throttle barrel will be installed as a experiment.
Here I will have the chance to reduce the air flow easily by decreasing the hole in the adapter, may be to 4 mm.
If it will be the right way than I will try to overcome my awe and build a suitable carb with right dimension by my own.
Some planes, which can be suitable adapted are available.
So let´s start the experiments.
I am curious what will happen.

[Admiral_dk]

That should help, as far as I can tell from your fine documentation.

I would consider having the same inside diameter in the adaptor as the output diameter of the Carburator - in order to have as few changes in the flow as possible - but this is just a detail.
Sorry I just looked again and see that this isn't possible - so just camfer the edges of the adaptor.

Per

[Roger B]

Almost there       

Have you rechecked the valve and ignition timing in case something has moved/slipped?

[fumopuc]

Almost there 

Have you rechecked the valve and ignition timing in case something has moved/slipped?

Hi Roger, thanks.


Just in with my head, in the middle of the cam gears.
Last night at the end of my experiments I have played around with the ignition timing also.
One time I have been to early I assume.
One lobe of cylinder one came loose and one roller and pin falls off. I have been really early 
But this morning with old and new carb no firing anymore.
The engine is pumping pressure into the inlet manifold, so now there is definitive something slipped.

[gbritnell]

Hi Achim,
The very first thing to check when an engine has trouble starting is the cylinder sealing, rings and valves. Most times with small engines it's the valve sealing. Once you have proven that the sealing is good and therefore the compression is good it's time to go to the ignition timing. Usually I start at 15 degrees BTDC. This should always get you close. I left the carburetion for last for good reason, it's generally the least important of the 3 elements. Without a specific size you are always better to start small. An engine will run with a small carb easier than it will with a large carb. Start with the throttle about 1/4 open and the needle valve about 1/2 turn. While turning the engine over put your finger over the carb inlet for just a second to choke the engine. It should fire and try to run. If does run but stalls right away then open the needle another quarter of a turn. (3/4 open). Now do the same thing. Crank the engine and choke it just for an instant. Keep repeating this process until the engine continues to run. Now you can adjust the carb for the best running.
I would advise against trying to start the engine with the carb wide open. At slow starting speeds there isn't a good vacuum signal with the carb wide open. If you are using an air bleed type carb once you get the engine running try to throttle it. If it stalls then the needle valve needs to be opened a little more. The needle valve is only for high speed running and the air bleed screw is to adjust the mixture at idle or slow speeds.
gbritnell

[fumopuc]

Hi George, thanks for poping in and the, as always, very good and useful comments and advises.
The way you have recommended here to start an engine is nearly 100% the way I go too.


In this case here the throttle in the carb is always fully open, otherwise there will be no firing
Closing it a bit only and no firing anymore.
That is the reason why I will try a bigger carb, as mentioned before, my here used carb is by the surface, d=3 mm/ A=7,069 mm².
Doug has recommended a carb with d=0.17"/ 4,318 mm / A=14,644 mm²
That means I am trying it with half of the recommended surface here, that is the reason for me to change this.


My try and error with the advanced ignition, without any proper figures and measuring two days ago has cause a movement of the crown wheel at the camshaft.
After taking the distributor cap off I could see the mess.
Crankshaft at cylinder #1 at TDC, the hole gear train is in the right position, including the crown wheel at the camshaft.
I have marked the top position for better orientation. That was a good idea.
In this position the distributor finger should point exactly to cylinder #1, that was the basic adjustment.
Now its position is nearly half between two ignition cable points at the cap, ca. 45° before cylinder #1.
That would explain why I have measured all cam timing (all lobes) nearly 90° after/later the originally adjusted positions.
The hole camshaft is now nearly 45° behind the crankshaft.
My conclusion, during the experiments with the advanced ignition the mass of the crank train has been one time a bit to big for the connection of the crown wheel to the cam shaft. There are 2 grab screws at two spots at the shaft.
How it can slip I have not understand so far, I try to find out.

[Roger B]

The shock loadings from the camshaft can be quite large. Is there a possibility that the crownwheel and pinion driving the camshaft could be jumping teeth?