First start after VW rebuild (with Leburg)

[TaylorMono]

Hello all,

I wonder if anyone on here can offer some words and advice.

I have a VW 1600 (fitted to a Taylor Mono) that was fully rebuilt over the past 2 years and has been fitted correctly with dual Leburg set-up. The Leburg is all working fine, but I'm having a bit of a struggle to get the engine started and I am slowly and methodically working through the potential diagnoses.

I'm getting to the point where I may need to resort to swearing, general cursing, finger-pointing and stomping - which I understand usually puts pressure on these engines to start first time.

My engine set-up is a little bit antiquated, but to talk you through it:

Fuel is definitely getting from the tank to the fuel pump. All the lines and brand new, no gunked up connections, samples from the gascolator all fine and clean
Brand new fuel pump installed and this is definitely working - lines all primed and fuel is coming out wonderfully
Fuel is definitely reaching the carb bowl which is filling correctly - carb was fully stripped and rebuild, new gaskets, all fine

I've pulled the plugs and there is a definite whiff of fuel, so I'm pretty confident that fuel is getting from the carb into the manifold just fine. Previously, I wasn't so sure - I have quite an old Solex 'HF Assembly 22 carb' which has a slightly dated "bi-starter" unit, but through the magic of AFORS I've tracked down another owner, as well as the original owners manual, and have learnt that there is a knack to starting when cold with these carbs, which involves fulling closing the throttle before drawing fuel into the cylinders.

So, I've got fuel, compression, spark...but then I had a realisation: what about plug gaps?

Having pulled the plugs, I kicked myself a bit as I hadn't adjust them since they were previously fitted when the engine had magnetos. The gaps were set at 0.53mm (but one was flattened and read just 0.18mm) and I've now reset them to 0.88mm, within the 0.8 - 1.0mm Skycraft recommendation.

I haven't yet tried to start the engine with the adjusted gaps yet but will do so this week.

However, I wouldn't have thought that too small a gap would be fatal to the engine starting - I would have expected it to start and run poorly.

Is there anything else I'm missing? I've tried a thimblefull of fuel down the carb throat and I did get a bit of a 'cough' from the engine, suggesting it desperates wants to start, but beyond that not much is going on.

I'm going to try it this week with the spark gaps corrected, but has anyone else got any experiences of the first-start post-rebuild and what you did / do? I don't have a primer and the carb lacks an accelerator pump, so I can't just give the throttle a few squeezes.

Any thoughts / ideas / suggestions very welcome!

[TaylorMono]

Just to follow-on from this, a visit to the airfield this morning failed to yield progress.

With the plug gaps adjusted, the thing still wouldn't start. I checked and am getting nice big sparks on all plugs, so all good there.

So, I tried the nuclear option on the advice of another VW owner - a dribble of fuel direct into each cylinder. Not much - perhaps just 0.25 - 0.5ml squirted into each one.

When I do this, still nothing catching but I do get a sound like a chesty 'whoop' when I swing the prop through the ignition mark; this repeated 2 - 3 times after which point I assume the fuel has dissipated.

It doesn't sound like the fuel igniting - rather, it sounds like exhaust venting.

I'm loathe to put much more into the cylinders directly, but it sounds to me like the fuel just isn't reaching the cylinders. There are pretty much bone dry and no amount of blades will help; certainly no risk of flooding them!

Things I haven't yet checked:

I particially checked the valve clearances - they seem correct (0.006) although one or two are quite tight to get the feeler gauge in there.
I'm considering whether the issue is I need a more 'modern' carb with accelerator pump

The most success I had was when I squirted fuel down the throat of the carb into the intake manifold - one splutter, rather than one whoop.