Good morning every one,

 

I have bought recently a Favorit 135LS Sport Line, 53 700km.

For last years the car was used only for short trips, and was given basic maintenance.

I drove back the car home (240km), it ran OK, normal fuel consumption, but slightly unstable idle and above 1000rpm (at running temperature), and jerks at very light throttle, especially when decelerating.

I have started to maintain the car; the spark plugs where black (but dry) showing a too rich fuel mixture. A plug was even cracked.

Fuel filter, air filter are now new.

Starting at cold condition: the engine doesn't crank immediately and the idle is low (800rpm) and slightly unstable.

Using the nice resources from this forum and other places, I have started to look for vacuum leaks on the carburetor.

The pull-down unit was leaky, I have replaced it with an OK one dismantled from a salvage LEKR 28-30 carb.

 

Now the idle at hot condition is still slightly unstable but closer to 900rpm, cold condition, still too low and slightly unstable

Cranking is not easy when engine is hot; needs full throttle to start.

 

What would be the next step to verify? Enrichment valve? Then?

Could the automatic starter or the thermal valve be faulty, or is it more likely a remaining vacuum leak?

 

Thank you in advance for your help!

I will post pics of the car when it is polished.

 

 

 

 

 

47 minutes ago, Degriottier said:

What would be the next step to verify? Enrichment valve? Then?

Could the automatic starter or the thermal valve be faulty, or is it more likely a remaining vacuum leak?

Replace the enrichment valve. Replace the acceleration pump diaphragm.

Completely dismantle the carburetor, clean all inner channels.

Vacuum tightness is paramount.

15 minutes ago, RicardoM said:

Replace the enrichment valve. Replace the acceleration pump diaphragm.

Completely dismantle the carburetor, clean all inner channels.

Vacuum tightness is paramount.

Thanks for the swift answer! I will do so, in this order.

It is a pity that in France we cannot find the carburetor paper sealing easily.

I have trained by dismantling the salvage carb, but not surprisingly, this paper sealing is getting damaged.

Will have to ask my contact in Czech Republic... or go for DIY from a sheet.

The enrichment valve sealing doesn't look fresh indeed, but not cracked.

I guess its ok-ish

2 hours ago, Degriottier said:

DIY from a sheet

Use gasket paper 1mm thick

How do you setup the perfect air/fuel mixture?

14 hours ago, RicardoM said:

How do you setup the perfect air/fuel mixture?

So far I haven't touched the air/fuel mixture, trying to find leaks first, following the French Technical Manual carburetor verification list.

As the 1st verification suggested was the pull-down unit and it was already NOK (unit and hoses), I though, better not to touch the settings before making sure there was no faulty or leaky component.

Would it be worth to try to play already with the fuel mixture to see how it reacts?

 

3 hours ago, Degriottier said:

Would it be worth to try to play already with the fuel mixture to see how it reacts?

If a vacuum leak, when you screw all the way in the mixture screw, the engine doesn't stall.

Also if a vacuum leak the noise the air makes in the carburetor venturi area sounds like a gargling, coughing. If perfect vacuum, there is a constant hiss.

The mixture setup is an art but you can go for maximum vacuum at idle.

Few pics prior to dismantling.

The base gasket looks in pretty good condition, probably replaced (I saw in previous posts that the quality is questionable, so I will plan liquid gasket.

The paper seal looks weird, maybe reused + silicon?

I have noticed a very corroded grounding connector at the base or the carb.

 

On 13/06/2021 at 02:49, RicardoM said:

How do you setup the perfect air/fuel mixture?

Plug test

On 14/06/2021 at 00:28, Degriottier said:

The base gasket looks in pretty good condition, probably replaced (I saw in previous posts that the quality is questionable, so I will plan liquid gasket.

Let's see how it looks after removing it. Agree with the liquid gasket from Victor Reinz.

On 14/06/2021 at 00:28, Degriottier said:

The paper seal looks weird, maybe reused + silicon?

Easy to make another one from cardboard for gaskets. Avoid silicon as 1) it might seal inner passages and 2) it doesn't hold on fuel. Mount it only dry.