DC Merlin .76 cc

Admin wrote:

qaz049 wrote:

kendias wrote:My DC Merlin refuses to start. It sometimes firs, stutters, then stops. Any suggestions appreciated.

Sounds like it needs a Speech Pathologist.

???

It's a continuation of a circular discussion on the "Everything Diesel" RCUniverse forum Mr Admin.

See: https://www.rcuniverse.com/forum/everything-diesel-87/11601210-need-iformation-old-diesels-10.html

Yes, very very long thread on rcu. He posted a picture of a Cox BB asking what it was.

If it's the same person, he has been on here for some time, mmmmmm

Anyways, he is here now.

Hi ken,
Post a picture of your Merlin as it is now please, and a brief description of its history with you, and things you have done with it to date.

What fuel are you using and where you came by it.

Help us on here to help you.

Coxfledgling wrote:Hi ken,
Post a picture of your Merlin as it is now please, and a brief description of its history with you, and things you have done with it to date.

What fuel are you using and where you came by it.

Help us on here to help you.

Thanks. Any idea where I can get model diesel fuel in Toronto, Canada

Here is a pic of my Merlin which does not run. I mixed my own fuel - 33% ether, 33 castor oil and 33 kerosene. This Merlin did not have a backplate which I managed to get and fitted.

to get and fitted.

Place a starter spring on front.

Not sure if that would help as the engine starts but runs for only a few secs.

Hi ken,

Read all threads on here about dc merlins.

You long thread on rcu is known about.

Read all advice given, inwardly digest and act on it.

Prop still on backwards and looks a bit big. I hope there is a plain washer between nut and prop.

A starter spring and dog plate is a good idea to have but at least the engine is firing.

Not sure about your tank. Is the lid vented to atmosphere, the fuel pick up pipe in the fuel and both ends of yellow fuel pipe a snug fuel tight ( and air tight ) fit on fuel pipe stubs.

No air leaks on back plate.

From memory back plate only goes on one way, ledge upper most.

I notice the compression lever has been backed off.

Screw in gently the spray bar screw until it stops. Be gentle, no force. Unscrew say 3 turns.

With sufficient fuel in the tank, place finger over "carb Venturi" and turn over engine in running direction ( anti clock wise when looking at front of engine rearwards ).

Do you see fuel making its way from the tank to the spray bar ?

Over.......

Read all above back to your last post....

Coxfledgling wrote:I notice the compression lever has been backed off.

Screw in gently the spray bar screw until it stops. Be gentle, no force. Unscrew say 3 turns.

With sufficient fuel in the tank, place finger over "carb Venturi" and turn over engine in running direction ( anti clock wise when looking at front of engine rearwards ).

Do you see fuel making its way from the tank to the spray bar ?

Over.......

Read all above back to your last post....

Yes, I see fuel making its way from the tank to the spray bar.

That is another good sign...

Do you have an aerosol carb cleaner, brake cleaner or penetrant type aerosol, or a bit of clean clean fuel pipe you can blow down.....

Unscrew the needle all the way out and make sure the longitudinal hole from side to side is absolutely clear just to be sure...

Then

Block off one end of the fragile spray bar with your finger and blow down the other hole...

Wear glasses to protect your eyes, and see two jets of penetrant/spray exit the two holes
That you should not see, in the spray bar. These two "jets" facing for and aft inline with the crankshaft and horizontal ( so you cannot see either" ) are the two jets that the fuel is drawn through ( pushed by atmosphere ) as air rushes past on the induction stroke on its way to the crank case.

If those jets are even partially blocked, that can and will cause fueling problems.

The top of your fuel tank should be below the spray bar ( see paw site, engine test run, see Jamjar of fuel well below engine ) say an inch minimum.

The top of the tank must be vented to atmosphere, so the "depression, partial vacuum", created by the Venturi and air induction, will allow atmosphere to push fuel up to the spray bar, through the two jet holes and into the engine.

When that lot is done, attend to prop and washer and fit spray bar needle, home, then say three turns out. Recheck fuel flow up to spray bar using method you used earlier.

When engine not turned over, did fuel flow back to tank ?

When that's done, come back.....

Over....

Wear glasses to protect your eyes, and see two jets of penetrant/spray exit the two holes
That you should not see, in the spray bar. These two "jets" facing for and aft inline with the crankshaft and horizontal ( so you cannot see either" ) are the two jets that the fuel is drawn through ( pushed by atmosphere ) as air rushes past on the induction stroke on its way to the crank case

Not clear on the first sentence about two jets.
Removed the spray bar, there is only one hole at right angles to its length just beyond the threaded portion

Hi ken,

I had a Merlin in the 70's which was quite a while ago now.....

I thought the spray bar had two fuel outlet holes/jets but as said it was a while ago.

Please post a good picture of the spray bar to show fuel pipe stubs, the one hole, and the spray bar rotated 180degrees from the one hole, just to be sure.

A have a sabre, a bantam and some odds and ends for DC's which I will check for you tomorrow.

Back tomorrow......

Post pictures please....

Ps I assume that one hole was completely clear ?

Hi Ken, All I can offer is a photo of mine. It has the OEM starter-spring and hub. There was also a non-specific to Davies Charlton "cold-start" tip in my folder. Maybe you will find it useful.

Nice one Roddie, oe tank, starter spring and ans silencer too !

Mine had a none anodised cylinder back in the day.

Perhaps a "warm air gun" rather than a naked flame pre warmer...less of a fire risk. Sometimes i "held" the cylinder to warm it with body heat for reluctant starters buy from memory had no problems with my DC's.

May I ask, on yours, was the back plate pre drilled and threaded for the centre tank screw ?

Also, the spray bar, two jet holes or just the one ?

If mixture needle unscrewed a bit and an aerosols sprayed into the fuel pipe stubs, the spray will be seen ?

Anyways, waiting for ken's picture of the spray bar.....

Doh !
Forgot to ask, does the tank central screw have a "distance piece, spacer tube" to prevent the tank screw being overtightened and breaking the tank ?

And

A sealing washer to prevent fuel leakage were the tank sits in the reccess in the back plate please ?

Coxfledgling wrote:Nice one Roddie, oe tank, starter spring and ans silencer too !

Mine had a none anodised cylinder back in the day.

Perhaps a "warm air gun" rather than a naked flame pre warmer...less of a fire risk. Sometimes i "held" the cylinder to warm it with body heat for reluctant starters buy from memory had no problems with my DC's.

May I ask, on yours, was the back plate pre drilled and threaded for the centre tank screw ?

Also, the spray bar, two jet holes or just the one ?

If mixture needle unscrewed a bit and an aerosols sprayed into the fuel pipe stubs, the spray will be seen ?

Anyways, waiting for ken's picture  of the spray bar.....

Sent pics.
The starter spring - do you actually use it to start the engine?