MF 35 Petrol/TVO

[DavidP, South Wales]

Hi everyone,
My turn to seek advice! I have a 1960/61 UK-built MF 35 petrol/tvo with a Standard engine.
It has a Zenith 28G carb fitted. I have cleaned the plugs and points and have a good spark at the plugs when the plug bodies are earthed.

I have removed the carb and removed all jets and blown all out with compressed air. Prior to stripping, the adjustment of the jets was noted and all replaced to the same. The float is sound and the float jet appears to be sealing satisfactorily.

The gasket was not replaced but any suspect areas were VERY carefully sealed. The compressions appear to be satisfactory by turning over with the starting handle.The air filter and pipework are clear.

After each attempt to start the engine with different choke and throttle settings (never the two together) there is no hint of the engine firing and the plugs remain dry. After each time, fuel can be seen leaking from the port with the brass mesh on the underside of the carb body. This lasts for 10 to 20 seconds.

I have removed the carb again but not stripped it yet. Any suggestions/pointers/information on what to check/do next would be very much appreciated.

Thanks very much in advance.

DavidP, South Wales

 

[Inno]

When you are cranking it over and put your hand over the mouth of the carb, do you feel suction? If fuel is leaking out I would assume the needle is not seating correctly for some reason.

 

[Tony in Mass.]

And how many cans of ether did you use up so far David? More than 3 or 4 spray cans, and I'd say you have a problem....
I was ridiculed for it...as if I make this $%^& up for entertainment... but my forklift friend, well experienced with the same Continentals as in my very unstartable Cockshutt.... he held a spark plug wire far from the plug as I cranked the starter... he drew the wire closer and closer to the plug... a long blue lightening bolt...the tractor started, he jumped back and fell off the box he was standing to reach over the loader... but it kept running on 3, we shut it off and re-attached the plug wire... that was 18 months ago, never failed to start since. Seems without help, it is so hard for even great compression to draw gas fumes from an updraught (draft) carb. Hench.... constant choking.... and a box of starter fluid is always handy....
I intend to experiment with this.... but it seems on fergies with exactly the same engine...say- Z134's.... a Zenith carb gets far better fuel efficiency... than M-S.... is that why you poms use Zeniths??? Better than TVO by a long shot! Good luck!

 

[Bob N.Y.]

Could the timing be way off?

 

[Masseynut(Australia)]

Hi David,
The fact that the plugs are not wet after cranking using the choke, would seem to rule out a spark problem(at this stage).
First question, did the engine start and run before, or has this problem only occurred after the tune-up?
Was the needle assembly replaced when the carbi was stripped? I have had faulty aftermarket assemblies before.
Have you removed the banjo bolt from the breather pipe on the tappet cover, and checked that the reed is free within the banjo? These can often "stick" and allow extra air into the manifold.
The only other thing that springs to mind is the mounting gasket, between the carbi and manifold. Was it replaced at all?
I have also found that this top face of the carbi that mates with the manifold is more than likely "warped" from years of expansion and contraction due to heat.
You can face it off by gently draw-filing or setting it on a sheet of "wet & dry" till it is flat.
Let us know the outcome,
Evan.

 

[Fergie Bach]

Fire some petrol (a bottle capful?)into the intake and crank it(with ignition on!!) If it fires albeit briefly you will know that it"s not getting fuel somewhere at the carb. Blocked fuelway somewhere?? Good hunting let us know how you get on!?

 

[2tractors]

To me this is like helping "Sir John" with a problem. I've never seen one leak from that little round brass screen so I'd say pull the carb back apart, look for etty bitty washers and the like on the work bench and maybe the one under the needle housing is missing.

 

[DavidP, South Wales]

Hello Evan and everyone. Thanks for your replies. To go through some of the points raised;
No washers etc were left over.
The small amount of fuel in the inlet would probably be the next step only I planned to put a small amount into at least two plug holes.
The engine was on stop prior to the carb removal.
This was done after the points and plugs had been cleaned and gapped.
Evan, I will check the manifold reed that you mention. I made a new gasket from 1.5mm gasket paper. and used silicon sealer at the carb mounting point. It was a place that I thought air might be drawn in through.
Nothing has been changed to upset the timing since it ran last some 3 or 4 months ago.

Laughing gas Tony!!!!!! I would never use that. That's only for certain other makes LOL!!!!!
I will remove the carb lid again but doubt that I will find anything.
Thanks again.
DavidP

 

[Fergie Bach]

Perhaps the dripping fuel is an indicator that the float is sticking a bit and the old girl"s flooded. The Standard engine is usually so forgiving about that sort of thing. Try neat fuel up the intake but with the fuel tap off at the tank and the carb drained out.Once it fires a few times then it will be much easier to make your diagnosis.
Regarding laughing gas I was once working on a T 20 next to a caravan and a butane gas bottle and thought "I wonder"! So poked the dissconnected gas hose up the carb intake turned on the gas and tried it. Off she went!! Just adjusted the revs to get the mixture right and she ran sweet as the veritable nut! Since then I always had a hankering to convert one to LPG. In the war some tractors were converted to run on wood gas. I always thought the Standard engine a brilliant contender for that given it"s long stroke and low compression.I digress!!
Let us know what it was when you find it.