Down on power - Retuned carb but correct timing?

[jamesandtheopenroad]

Okay. Engine is a lpg'd 1.9dg with a Solex 34 Pict 4 carb.

Was running lumpy so all new ignition parts, vacuum hoses replaced, brake servo hose replaced and the carb has been off, cleaned up, reinstalled with new gaskets and set up. So it's running a lot smoother, with no - or much reduced - lumpiness through the revs.

However, it's noticeably down on power - on both petrol and lpg - in acceleration, having to go down to 4th on the slightest incline and struggling to get above 50mph.

I'd reset the timing, so currently the V notch is in line with the centre. It was a little off the 5 degrees BTDC mark, (IIRC poss a few degrees advanced) - could this be the problem? Read on the Wiki that with lpg, timing can be advanced another 5 degrees to 10btdc - is that right and would it help?

But as it's a Solex (usually on a DF) on a DG, would the timing need to be retarded? DF timing is 5 degrees ATDC not BTDC? Therefore making the timing just TDC when taking into account the 5 degrees advance because of lpg?

Or is it likely to be something else?

[kevtherev]

I might be wrong here but timing aside, which is OK at 5 deg,
does the vacuum operate the advance mechanism?
But...
Why are you using a solex?

the solex venturi is a smaller diameter, and does it have a 2nd venturi like the pierburg?

[jamesandtheopenroad]

It was the carb that was on it when my younger "green" self bought it. Steve at Gasure did the lpg conversion and said it would be fine.

As for vacuum advance - just wondered exactly the same.

The Haynes manual says that during timing set up, disconnection and reconnection of the vacuum advance pipes should make the timing marks move. Well, it doesn't. And at idle, whilst the mark is pretty much where it needs to be, it does jump a little as does the idle speed - give or take 10-15rpm.

However, I have had the top of the dizzy off and sucked on the vacuum pipe and can see the plate moving, so I dunno.

[jamesandtheopenroad]

Right. Just run back from my folks - 30 miles - a mix of motorway and urban - driving on petrol and lpg.

Here's what it's like.

Idles nicely on petrol and revving when stationary is fine. But under load, especially on an incline, there just isn't any oomph. Occasionally struggles when pulling away from.standstill. At higher speeds I can here it trying but it just doesn't seem to have any beans.

Bit more oomph on lpg but still a little lacking in acceleration. And when it becomes stationary again, the revs drop and it splutters and dies.

Really don't know what's going on. Sort of feels slightly like when you've turned from petrol to lpg too soon.

Anyway, I've ordered a new vacuum advance unit in case it is a leak there but can anyone suggest anything because it's really starting to do my head in.

[itchyfeet]

Did it have plenty of power before this lumpyness started?

if it's running better on LPG i'd say more likely to be ignition but could still be an airleak or a combination of both.

as well as the vac advance/retard there is a mechanical centrifugal advance in the dizzy, I suppose this could have become siezed, try some WD down the dizzy

Have you cleaned up earths also?

[jamesandtheopenroad]

Thanks for the reply.

Well it was never a powerhouse but yes, certainly more so than now.

Ignition stuff has all been renewed - dizzy cap, rotor arm, HT leads, coil - and it starts first time, every time.

As for air leaks, I've tried everywhere I can think/has been suggested, except the vac advance. Will certainly give the inside of the dizzy a clean when I change it for the new one.

As for earth straps, how many are there, where would I find them, and by cleaning them up, I presume you mean the connections at either end?

Thanks again.

[itchyfeet]

earth on the LHS of engine by the dizzy and also the one under the coil, worth a go

try the WD trick, spray it around the carb and manufold a every gasket and pipe and see if the revs change

[jamesandtheopenroad]

Thanks, will clean those up at the same time.

Done the WD40 trick ad infinitum - no change at all. Which is why I think if there is an air leak, must be the vac advance.

[itchyfeet]

I think it's unlikely the dizzy vac unit if you can see the mech moving but as you have already bought one worth a try.

[jamesandtheopenroad]

Well, I'm hoping that, a clean up of the dizzy itself plus the earth straps will sort it. Otherwise I might just set it on fire...

[BOXY]

Have you checked the timing is advancing with a strobe / timing gun? I've had a dizzie with no mechanical advance that I fixed by soaking it with Plusgas. If only the vac advance is working you'd definitely be down on power.