Gummed up or seized

[Jon H]

I have a DC Sabre around with a little tank on the back. The AM series of engines sometimes had tanks on them using the same design. 

 

I also see your engines have the man trap fitted Pat. Those recoil starters were an almost guaranteed way to loose a finger! 

[Engine Doctor]

18 hours ago, Rich Griff said:

Think good quality " geometry/engineering drawing set"  and thickish brown envelope for the new gaskets...

 

No real need to remove the prop driver plate ( taper fit ) as no crank case " oil way"......

 

Enjoy this little gem of an engine.

 

Ps is your back plate central spigot hole threaded by chance ?

 

 😀

Your Merlin sure looks in a sorry state ! A prolonged soak in some model diesel fuel followed by a scrub with a old stiff tooth brush will remove most of the castor and dirt coating. Petrol, glow fuel etc wont remove it , even cellulose thinners will tak a while looking at your picks. Also dont be tempted to use any chemical cleaners like oven cleaner as it makes cases look awful. If you really want cases to look good then a thorough clean and a bead blast will bring it up. If you want it bead blasted PM me. 

If you decide to remove the cylinder for a complete strip and clean then make sure that engine turns over freely and piston is not stuck in the bore as the conrod will twist or snap if piston is stuck. Mark the position relative to the crank case before unscrewing the head As piston and liner will be a best fit in that position.

If you can bsg steal or borrow a ultrasonic cleaner  give it a blast in one using model diesel fuel in a closed jam jar in water filled cleaner. You will be amazed at what comes  out of engine. Good luck and enjoy oily hands 😉

[Engine Doctor]

1 hour ago, Jon - Laser Engines said:

I have a DC Sabre around with a little tank on the back. The AM series of engines sometimes had tanks on them using the same design. 

 

I also see your engines have the man trap fitted Pat. Those recoil starters were an almost guaranteed way to loose a finger! 

? Recoil starter springs worked ok Jon and saved slicing your finger along the nylon props of the day sometimes to the bone ! You quickly learnt about flooding and over compressing diesel on a cold day with fresh diesel in a cut finger 😖.   The issue with them was if you over wound them they would bend and when engine was running would vibrate into the spinning prop and cut away the back ; which is why i always removed them. A good flicking technique is an art some never mastered so a spring helped... sometimes . 

[J D 8]

 A clever little spring starter was the one on a Testors 049, A flat coil inside a drum just behind the prop [ bit like a car brake] that engaged itself when prop turned back and let go after turning motor over a few times.

[Rich Griff]

Interestingly, folks on the Cox engine forum have mentioned soaking in warm/hot antifreeze ?

 

Be ware if hot antifreeze fumes.

 

Not sure what type of antifreeze as they are across the pond. Not tried that method myself as petrol ( and some elbow grease ) works for me. I also use warm/hot oil method to good effect on a bad model engine, and other stuck mechanical effect.

 

What ever method you use just be very careful for/of your safety, your property ( shed/workshop ) safety and that of the engine/mechanical stuff.

 

Yes, a good flicking technique essential, flicking via prop blade "flank' rather than sharp trailing edge. Don't overwind spring if it's still fitted.

 

Enjoy.

[Rich Griff]

Yes, mcoy also, until they broke...

 

Moral, don't overwind...

[Engine Doctor]

Ps I forgot to add your Merlin looks like an earlier version noted by thiner cooling fins and a forged con rod. Later engines had far fewer cooling fins probably to cut down on machining times and a turned conrod that was exrtemely soft . The later engine that I have dealt with are generally not worth restoring  and were produced when DC were in decline but the early versions were far better quality materials all round. The Merlin is underated and far superior IMHO to the very popular Mills 75 of the same era.

[Rich Griff]

Hi ed,

 

I don't have an ultrasonic cleaner but your method of d1000 etc. in a jam jar placed in an ultrasonic bath, to reduce the amount of expensive d1000 etc. , do you add say some steel nuts to displace liquid amount needed, and, if so, does that cause a damping effect please ?

 

Just curious if a damping effect happens is all....

 

Thanks...

 

From time to time I need to clean m/cycle carbs etc. and use the petrol and redex ( quite strong solution, taking advantage of bogof offers in Aldi etc. ) fuel system cleaner method in a siutable container.

Goes in like cherryaide, comes out like coke.

 

Never tried that method with a model engine yet, may try in future...

[PatMc]

7 hours ago, Jon - Laser Engines said:

I also see your engines have the man trap fitted Pat. Those recoil starters were an almost guaranteed way to loose a finger! 

Both engines were bought second hand (along with several others) not long before the pics were taken in 2006, I went all electric about a couple of years later. I'm not sure if I got round to removing the "starter" bits from that pair but if I used them I would have done as I found them more hinderance than help.

 

IIRC the tanks fitted to the AM 10s & 15s always leaked, early ones were metal later were plastic. I've got a couple of AM10s & one 15 only ever used them for C/L or RC models but always with separate tanks, in fact I can't remember ever using the supplied tanks on any engines except for Cox & Kiel Kraft 049's.

 

[PatMc]

3 hours ago, Engine Doctor said:

Ps I forgot to add your Merlin looks like an earlier version noted by thiner cooling fins and a forged con rod. Later engines had far fewer cooling fins probably to cut down on machining times and a turned conrod that was exrtemely soft . The later engine that I have dealt with are generally not worth restoring  and were produced when DC were in decline but the early versions were far better quality materials all round. The Merlin is underated and far superior IMHO to the very popular Mills 75 of the same era.

I think the non-anodised head means it's an old "standard" version. The Super Merlins' heads were anodised red, supplied with a spinner, tank, tommy bar & propeller also the hint that they were hand picked as having better than the standard power which they weren't & didn't 😉 The standard model was advertised as the budget model with no extras.

I don't think the Merlins were ever under rated. They were very popular as a F/F sports engine, always known to be more powerful & cheaper than the Mills but not as easy to start or tune or as flexible with prop sizes. 

The Mills was the better engine for beginners or anyone who put reliability above a marginal difference in power in the type of model that usually had the engine running deliberately off tune anyway.

[Jon H]

The issue i always had with the man trap spring starters was the fact that you had to deal with a smooth plastic prop while your fingers were covered in diesel meaning it often let go before you were ready for it. I tried the one on my sabre last i ran it using my new and improved fool proof technique and yet it still bit me. A starter stick or rubber finger thingo works best in my experience. 

[John Stainforth]

Jon,

We've had recommended various solvents for cleaning old engines - diesel, petrol, antifreeze, etc. What about WD40, because I imagine that would be pretty effective (but I have not tried it)? I wondered if you had any experience with that.

[Simon Lumsdon 1]

My tip, place in bowl of boiling water for 5 mins, then use prop to gently free it, this usually works 🙂

Edited September 30, 2023 by Simon Lumsdon 1

[Jon H]

9 hours ago, John Stainforth said:

Jon,

We've had recommended various solvents for cleaning old engines - diesel, petrol, antifreeze, etc. What about WD40, because I imagine that would be pretty effective (but I have not tried it)? I wondered if you had any experience with that.

 

I would only ever recommend using the fuel the engine is run on as a solvent to aid cleaning. 

 

9 hours ago, Simon Lumsdon 1 said:

My tip, place in bowl of boiling water for 5 mins, then use prop to gently free it, this usually works 🙂

 

Not recommended. Boiling ferrous components in water causes them to oxidise. The top layer of this oxide is easy to wipe off and in the case of a steel/iron piston and liner combo you can ruin the fit of the parts. 

[Engine Doctor]

21 hours ago, Rich Griff said:

Hi ed,

 

I don't have an ultrasonic cleaner but your method of d1000 etc. in a jam jar placed in an ultrasonic bath, to reduce the amount of expensive d1000 etc. , do you add say some steel nuts to displace liquid amount needed, and, if so, does that cause a damping effect please ?

 

Just curious if a damping effect happens is all....

 

Thanks...

 

From time to time I need to clean m/cycle carbs etc. and use the petrol and redex ( quite strong solution, taking advantage of bogof offers in Aldi etc. ) fuel system cleaner method in a siutable container.

Goes in like cherryaide, comes out like coke.

 

Never tried that method with a model engine yet, may try in future...

Hi Rich . The method of puting the model diesel fuel  (any diesel fuel or appropriate thinners will do)  in a jar or suitable small screw top container is mainly to isolate/ contain any flammable vapour from any source of ignition like static or electrical spark from the cleaner and secondly to reduce ammount used to cover the part . The ultrasonic waves travel well through a glass jar provided its siiting well into the water fill cleaner. If using any flams as cleaner solvent in jar I always do this outside in a safe area just in case.

This method can also be used when using non flammable cleaner / solvent when cleaning small parts to reduce ammount of used. 

I dont use any other pieces in the jar that can cause marks on any parts they rub against . Most parts are not an issue but using something like steel nuts could mark soft alloy parts as they vibrate. 

Using a jar / container doesnt seem to dampen effect of the cleaner. 

Edited October 1, 2023 by Engine Doctor

[Rich Griff]

Cheers, thanks ed.

[PatMc]

23 hours ago, Jon - Laser Engines said:

The issue i always had with the man trap spring starters was the fact that you had to deal with a smooth plastic prop while your fingers were covered in diesel meaning it often let go before you were ready for it. I tried the one on my sabre last i ran it using my new and improved fool proof technique and yet it still bit me. A starter stick or rubber finger thingo works best in my experience. 

I never used a rubber finger stool or glove or a stick with diesels as it's often necessary to quickly adjust the compression screw & they would just get in the way. I always lightly sanded the sharp edges of the prop's TE (& LE as well sometimes) then generally mounted the engine sidewinder or sometimes inverted so that it avoided getting over primed causing over-compression or hydraulic lock problems leading to rapped fingers, bent con-rods & even broken crank pins. 

  

[Jon H]

My technique is to flick with one hand with the other on the comp screw. This doubles as a safety measure as i am already holding the comp screw and do not have to reach around/through the prop arc to grab it in the heat of the moment. 

[leccyflyer]

I'm not having much success starting a couple of diesels at the moment using a chicken stick, but then I'm only really trying to get them to start on the prime at first and do not have the tank set up properly in the test stand. I'll do that this week and make a concerted effort to get the PAW 1.49 up and running, because the duplicate fuselage for my diesel powered Outlaw is now complete.  

[Jon H]

There is a bit of a knack to diesel flicking and it takes a little practice. I often see people flicking engines from the shoulder like swinging a very small rounders bat at their engine. In reality a little flick with the wrist is all you need and it helps to get it right near the hub. Its also important you make sure the prop is in the right position and i favour about 20 minutes to 2 position for the start of the compression stroke. 

 

After that it is a matter of getting to fuel and compression right, and that too takes practice. Once it fires up i normally need to crank a good bit of extra compression in the first few seconds to keep it running. My PAW149 is also really pants at shooting the prime up from the crankcase to the cylinder. This could be due to the fact that i rarely run it so its all gummy. In any event, a port prime with fuel usually gets it fired up in short order. 

[Christopher Wolfe]

It can be quite educational (and fascinating) to watch an experienced Control Line team race mechanic in action.

 

Catch (a moving model), refuel, one flick start and away in less than 5 seconds.

 

As the great Arnold Palmer once said "the more I practice, the luckier I get"

 

* Chris *

[Engine Doctor]

My tip for difficult diesels is not to overprime the carb just a few turns with a finger  over the carb/ venturi once the fuel has reached the inlet then a light prime in the exhaust port .  Too much fuel in the crankcase is often the cause of difficult starting as the puddle in the bottom will be shot into the cylinder as soon as the engine fires instantly flooding it .

Obviously some engines are more difficult than others due to  design,wear or just poor mechanical fits especially in the bottom end. Crankcase compression is more important than cylinder compression in any two stroke as without it the fuel transfer cannot happen . 

Old diesels rarely corrode internally and a good soaking and clean usually gets them up and running in no time but occasionally if left in a damp, loft shed or garrage etc  corrosion can set in via open ports . If the crank shaft of a plain bearing engine wont turn even after a good soak in some fuel and some heat then it could be rust locking shaft to case. More soaking an heat should eventuaĺly loosen it .

I was once given a large quality street tin full of old and some rare engines . All had been gummed baddly and nearly all of them had snapped conrods where the previous owner had tried to unscrew the cylinders witout freeing them off first !

Another thing to consider with a gummed ballraced diesel is that if you successfully free it the ball races could still be gummed and will feel free yo turn. If run like that the ball bearing can dkid causing a lot of damage . Beware and if in doubt fit new beatings.

Edited October 2, 2023 by Engine Doctor

[extra slim]

I do EXACTLY as Jon describes, prop position, wrist, other hand on comp. And my PAW 1.49 is exactly the same in that the prime to cylinder takes about 10 flicks +, so a port prime, shortens the time. Just need some 'feel' as the port prime might mean you back off the comp a little.. I have found each diesel I own has its little nuances when starting, just keep practicing and develop a 'feel'.  I'm actually pretty decent at it, after learning from the older members in my club, about 4 years ago..

[GaryW]

39 minutes ago, Jon - Laser Engines said:

There is a bit of a knack to diesel flicking and it takes a little practice. I often see people flicking engines from the shoulder like swinging a very small rounders bat at their engine. In reality a little flick with the wrist is all you need and it helps to get it right near the hub. Its also important you make sure the prop is in the right position and i favour about 20 minutes to 2 position for the start of the compression stroke. 

 

After that it is a matter of getting to fuel and compression right, and that too takes practice. Once it fires up i normally need to crank a good bit of extra compression in the first few seconds to keep it running. My PAW149 is also really pants at shooting the prime up from the crankcase to the cylinder. This could be due to the fact that i rarely run it so its all gummy. In any event, a port prime with fuel usually gets it fired up in short order. 

 

I've recently come back in to diesel flying with @Engine Doctor's help and my PAW 19 RC on my Ben Buckle Scorpion  is a doddle to start,, A tiny squirt of diesel down the carb,,,,, Throttle set to full,, a few flicks and away she goes, Till now Ive not flown diesel for over 20 years and I'm enjoying it that much Ive now got 2 PAW 1.5cc powered 7.5pg gliders coming on thursday and looking forward to flying them

 

[Martin Harris - Moderator]

I suspect that the key is to get some heat into the cylinder so the technique I adopt is rapid repeat flicks - usually after 4 or 5 flicks you start to hear the odd “barp” and a start will follow soon after.