Ransomes MG5 Crawler

[The_Yellow_Ardvark]

@Dieselkid 63



Odd question, as I am driven along.
The donky engines at my mates farm used to get air leaks on the inlet manifold, start run and soon cut out.
I guess you checked for that?

 

[Tinbasherdan]

Give it some easy start, if it runs on that it’s not an ignition problem

 

[Dieselman 63]

@Dieselkid 63
View attachment 298409


Odd question, as I am driven along.
The donky engines at my mates farm used to get air leaks on the inlet manifold, start run and soon cut out.
I guess you checked for that?

Yes, all sealed with fresh paper gaskets and hylomar. The exhaust does leak a little, but not enough to inhibit starting… will buy some easy start today

 

[The_Yellow_Ardvark]

Yes, all sealed with fresh paper gaskets and hylomar. The exhaust does leak a little, but not enough to inhibit starting… will buy some easy start today

WD 40 works as well

 

[m_c]

I wouldn't use easy start, as it's far to harsh for something you start by hand.

I personally use a bottle of LPG with a torch, but have in the past used a small gas bottle and plumbing torch.

 

[Tinbasherdan]

I wouldn't use easy start, as it's far to harsh for something you start by hand.

I personally use a bottle of LPG with a torch, but have in the past used a small gas bottle and plumbing torch.

Don’t go daft and it’ll be fine

 

[Brad93]

Remembered a box of fibre washers I got off Facebook Marketplace for $5, and there was one in there that was perfect. Thanks for the tip!

Given the age it would always be a fibre or copper washer. Dowty seals probably not that great with fuel over time unless they're Viton or something

 

[Dieselman 63]

Now it’s firing out of the intake. Shoddy video - holding phone and cranking not easy. It just gave a beautiful flame before, unfortunately the wrong way, I want that power inside the chamber!

MG Problem

youtube.com

 

[Brad93]

Now it’s firing out of the intake. Shoddy video - holding phone and cranking not easy. It just gave a beautiful flame before, unfortunately the wrong way, I want that power inside the chamber!

MG Problem

youtube.com

Timing off?

 

[not done it yet]

Question: Does the magneto have an impulse start ring? If so, and it’s not working, that may mean the timing is set a long way off.

If it does, the timing needs to a smidgen after top dead centre at cranking speeds. I have one engine with each cylinder almost two litres - it has an impulse start on the mag and you don't want to be hand-cranking that if it fires before top dead centre!

 

[Dieselman 63]

Question: Does the magneto have an impulse start ring? If so, and it’s not working, that may mean the timing is set a long way off.

If it does, the timing needs to a smidgen after top dead centre at cranking speeds. I have one engine with each cylinder almost two litres - it has an impulse start on the mag and you don't want to be hand-cranking that if it fires before top dead centre!

I did question that, but it was running only a few months ago and I have never touched the mag (which works, zapped myself with it!). I have taken the carb apart again to test, but it’s too late to fire it now. Maybe tomorrow when I get home…

 

[Ton-up]

Stuck valve or wrongly adjusted tappets, (if applicable!)

 

[Brad93]

You still need to check your timing. The magneto could have slipped on the shaft or something.

 

[Dieselman 63]

You still need to check your timing. The magneto could have slipped on the shaft or something.

Good idea! I like options, gives me more things to try when I’m staring at it in confusion

To demonstrate my technical proficiency I decided to drop a wax crayon and the gasket for the carburettor into the air intake blower. That then had to come off…

Time for bed!

 

[dobbslc]

Have you done a compression test? That would rule out carb or ignition problems if it is low.
I've had spark plugs that worked fine one day then didn't the next! It could be that simple? Sorry if you've already tried this.

 

[Brad93]

Have you done a compression test? That would rule out carb or ignition problems if it is low.
I've had spark plugs that worked fine one day then didn't the next! It could be that simple? Sorry if you've already tried this.

If he is getting a backfire through the inlet I should imagine compression is good, but timing is out. The inlet valve is open at correct ignition time indicating a valve or pushrod issue. I presume this is Push rod not OHC.

Or the spark is too early And is occurring during normal intake cycle, in which case it's the magneto not the valve.

 

[dobbslc]

It does sound like a timing problem but I've had the same popping and farting on a good engine when a plug gets wet.

 

[Dieselman 63]

Stuck valve or wrongly adjusted tappets, (if applicable!)

I took the head (?) off which is just cooking fins and the plug. Valves are in the block, the valves are pushed from within the block, not sure if it’s directly off the cams or if there’s push rods but anyway. They seemed fine, or fine enough for something 70 years old! I applied a thin bead of sealant to the head gasket, a 1mm sheet of copper.

 

[Robotstar5]

I took the head (?) off which is just cooking fins and the plug. Valves are in the block, the valves are pushed from within the block, not sure if it’s directly off the cams or if there’s push rods but anyway. They seemed fine, or fine enough for something 70 years old! I applied a thin bead of sealant to the head gasket, a 1mm sheet of copper.

I wouldn't use a sealant, just anneal the copper gasket

There may be a cover on the side of the block near the valves which should expose something like this on one of my stationary engines

 

[Dieselman 63]

I wouldn't use a sealant, just anneal the copper gasket

There may be a cover on the side of the block near the valves which should expose something like this on one of my stationary engines

View attachment 298924

There is a cover just like that! It was leaking oil badly, so I fitted a cork gasket to it. But one of a raft of problems fixed!