K&B 40 Torpedo RC Rear Rotor Series 71 Formula Won't Sta

Post the general engine topics that here.

Moderators: Frank Klenk, SteveM

K&B 40 Torpedo RC Rear Rotor Series 71 Formula Won't Sta

Postby wjacques » Fri Jun 10, 2011 11:43 pm

I have had this engine for many years sitting around it has flown once in an aircraft that crashed and has never been in the air since. I have been tryin g to start it again but with no luck.

Can anyone help me? Where should I start I am very much a Novice.

Cheers

Warwick Jacques
wjacques
 
Posts: 2
Joined: Fri Jun 10, 2011 11:25 pm
Location: New Zealand

K&B 40 Rear rotor won't start

Postby ffkiwi » Sat Jun 11, 2011 5:41 pm

As with other replies to similar questions ('engine won't start')you need to check a few things-especially as on your own admission the engine had been in a crash previously. I hope it is clean and has no dirt in it-being a rear intake, you shouldn't have got any dirt into it via the intake-however if it was being flown in open exhaust condition it is possible dirt may have entered through the exhaust (if it had a silencer attached you can ignore this concern.
If it has sat for a long time there is a good chance the engine will be gummed up with congealed castor-the cylinder-the ring (this engine uses a Dykes ring)-and the plug. The carb jets may also be blocked. The engine may be stiff to turn over, and/or the crankshaft bearings feel rough or 'lumpy' as the engine is turned over.IF you suspect dirt has got into the engine, DO NOT ATTEMPT to TURN it OVER! I would advise putting it in a domestic oven for about 20 minutes-and on removal, take the head off (the heating will soften any residual castor and make the screws easier to remove) and check the cylinder for dirt once the head is off-if all is OK then a quick wipe of any castor residue with a soft rag and a bit of oil in the bore before you replace the head again. Check the needle jet-making sure you establish the needle setting by screwing it all the way home and counting the turns before removing it to clear any sludge or congealed castor from the jet. When you removed the head, you should also have checked the condition of the glowplug-and seen whether it still works.
These engines had fairly rudimentally throttles-essentially 'full bore' and 'stop'-the pylon rules of the time did not require anything else! They have a fairly large carb bore-so suction is minimal. On the bench you should be able to get the engine to run on suction-but you may well have to play around withe the tank height to help this-but overdoing it will result in gravity feed and easy flooding.
These engines were also designed for high nitro fuels-so use at least 10-15% nitro-and I don't mean the rubbish they sell for model car use-the oil content is far too low! A decent aero fuel with at least 20% lube-your call whether it is castor or synthetic-most commercial fuels are synthetic lube these days. A 10x6 prop (this is not a pylon prop-but is a common size for 'cooking' 40s) but will give you a decent load and a bit of flywheel effect-which is more than the pylon 8 and a bit- inch diameter ones will. And splash out on a new plug if the existing one looks in anyway suspect.

Ensure the engine is solidly mounted, and you have some provision to adjust the tank height, fit the prop (you'll need to ream the centre hole to fit the stepped driver), set up the glowplug for a decent orange glow and try an exhaust prime, and a good solid flick-if it runs on the prime OK you should be in business-try for 3 turns open on the needle to start with-but watch out for flooding. JKeep an eye out for any bubbling around the head or crankcase joints, which would indicate a compression leak-these engines did not use any gaskets, relying on good machining for a metal to metal seal. Be prepared for a racket! It'll be noisy!
These are good honest vice free engines-but totally outclassed for pylon these days. I have 3 of them-I use them in .40 FF Open Power models-but on pressure feed. On a 10x4 or 9.5x4.5 APC they really pull

'ffkiwi'

PS. My reply presumes that you have suitable starting equipment-fuel squeezy bottle, tank, glowplug driver or power panel, glowplug clip etc. Electric starters are optional.

PPS One of the characteristics of Dykes ringed engines is they have very little compression when turned over slowly by hand. The setup of the L-shaped Dykes ring is that it is designed to seal under combustion pressure from above, so turning over 'cold' gives no real indication of the engine's condition
ffkiwi
 
Posts: 91
Joined: Thu Jun 12, 2003 3:59 am
Location: Christchurch, New Zealand

Postby chiefss » Sun Jun 12, 2011 1:34 am

Turn a dykes ringed engine backwards to feel compression
chiefss
 
Posts: 611
Joined: Sun Sep 30, 2007 1:22 pm
Location: Bremerton, WA

Postby wjacques » Sun Jun 12, 2011 1:58 am

Hi ffkiwi,

Thanks for your lengthy reply. I apreciate your comments.

As mentioned the engine did survive a crash, the aircraft it was in at the time it was encosed within the cowel but did not have a silencer on it. The engine was mounted on its side with the exhaust port facining down when the aircraft crashed it was completely wrecked the engine appeared to survive 0k, I don't think any dirt entered the engine. However I recall that I had someone strip the engine and check it so I don't believe that dirt is a problem. The engine seems to be free as I can turn it over without any undue effort so It doesn't appear to be gummed up though come to think of it I did have to free the throttle barrel with CRC which was gummed up however the engine itself seems quite free.

The Engine compression seems to be pretty good and the suction through the carburettor throat also seems to be ok although I don't really know what is adequate.

The fuel I am using I got from the local hobby store here in Auckland and it is 10% nitro with castor & coolpower synthetic oils Brand Name is Nitrowitch.

I have the engine mounted on a test board which is clamped to the work bench. The tank on the test rig (metal tank and has a very small capacity) may need to be altered/changed as the outlet is slightly above the level of the needle valve on the carburettor.The tank is fixed so height can't be adjusted easily at this stage. I might see if I can modify the rig so I can alter the height to see if this makes a difference.

I have also mounted a silencer on the engine that is off an OS engine this was achieved by machining an adaptor to enable it to be clamped on securely. Should I remove this, would this have any adverse effect on it do you think? The silencer has a fitting on the side with a hose connected to it back to the tank breadther tube.

The propellor I have fitted to it is a 10x5 nylon prop.

The glo plug seems to be good I do have a spare and have tried that one as well, made no difference. Both glowed about the same bright orange colour.

I am using a hand held nicad staring booster to power the glo plug for starting.

I don't have an electric starter as yet so have been attempting to start by hand.

I have tried to prime through the glo plug hole then put the plug back in attach the booster and proceed to try and start. Doing this I got very breif pop then nothing. so I am assuming that it could be that the fuel is not getting to the engine adiquately but I am not sure.

I look forward to any further suggestions or comment you may have

Cheers

Warwick Jacques
wjacques
 
Posts: 2
Joined: Fri Jun 10, 2011 11:25 pm
Location: New Zealand

Postby collie » Sun Nov 06, 2011 2:29 am

all of the advice given before is very good advice.only 2 things i like to ad
1 to help starting put silicon tube in intake to reduce size and help suction,make sure it cant get sucked all the way in ,When u prime the enine out finget over hole in intake and make sure it draws fuel to NV,when this done look in exhaust and make sure piston ring above top of exhaust port then squirt a little fuel on the piston through the exhaust .connect glow and flick hard and fast,
2 if this fails to get a pop then find a club in ur area and they have u mobile in no time
enjoy they a nice engine and once set dont alter much
ps a bigger prop also easier to flick start ,say 10*5 or 11*5
collie
 
Posts: 85
Joined: Tue Jun 28, 2005 11:05 pm


Return to General Engine Tech Talk

Who is online

Users browsing this forum: No registered users and 24 guests

cron