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Member postings for Engine Doctor

Here is a list of all the postings Engine Doctor has made in our forums. Click on a thread name to jump to the thread.

Thread: Exhaust thread worn out
20/06/2018 12:41:19
Posted by Biggles' Elder Brother - Moderator on 20/06/2018 09:46:59:

"Exhaust thread worn out", I wish the Electric Car thread was,.....sad


yes and the football and tennis were finished !

Thread: Zdz 40re engine
20/06/2018 12:36:54

Yes ,check little end roller hasn't siezed , if ok check that piston hasn't picked up (siezed slightly when running in).

Edited By Engine Doctor on 20/06/2018 12:37:41

Edited By Engine Doctor on 20/06/2018 12:38:27

20/06/2018 09:42:58

It sounds a bit obvious but have you checked the prop bolts? Does engine make noise when turned over with backplate and rotary valve removed?

Edited By Engine Doctor on 20/06/2018 09:43:28

Thread: Exhaust thread worn out
20/06/2018 08:43:32

If the head thread is worn ,usually due to exhaust loosening , then you will have to buy a new head I may be wrong but I don't think anyone repairs them as there isn't enough metal to tap into to insert a heli-coil or similar.

You may find an model engineer who can cut a new stub thread a bit oversize that will screw into the existing thread or whats left of it .

Best bet is to try and source a good secondhand cyl head but may be difficult. There must be thousands lying around in workshops but modelers seem reluctant to break or sell old four-strokes ?.

When you get it sorted the best way I have found to tighten the exhaust into the head is as follows .

First and very important is balance the prop . Its the vibes that shake the unsupported exhaust loose..If engine still vibrates badly then sort the problem as exhaust will keep loosening on a badly vibrating engine .

Screw the exhaust into the head until it wont go any further then back of to adjust angle and tighten lock-nut using a good fitting spanner. Run engine up to temp and stop it ,then quickly re tighten the lock nut firmly while engine is still hot.

Hope you manage to source a new head .

Thread: LIFE receiver pack not fully charging
19/06/2018 09:30:00

Might be worth investing in a Fusion Smart Guard.Not expensive , you simply plug in your battery via the balance lead and it reads the total voltage and/or individual cell voltage . Unbalanced cells can be instantly be seen and a balance charge given to rectify the problem . Hobbyking do a similar version that has a servo centering device built in.

18/06/2018 15:42:05

LiFe batteries only go to 3.3 volts per cell so 6.6 volt  is expected and your 6.5 volt should be fine. Lipos charge to 4.2 volts per cell as different chemistry .


Edited By Engine Doctor on 18/06/2018 15:43:35

Thread: Unexplained crash
18/06/2018 15:39:44

A club member had a similar scenario recently . Plane took off rolled without any input and went in . Three crashes and repairs later he spotted the culprit was a broken servo lead causing servo to go full over to the stop . Once the plane crashed and installation was shook up it all worked perfectly . Worth checking servos individually for faults .

Hope you find the culprit as its very frustrating

PS Did you range check with engine running at full power as vibrations can shake any bad connections and show up problems .

Thread: Bent snakes!
16/06/2018 09:30:55

Providing they run freely , are fixed securely at both ends and supported along their length if long runs then they will be fine and slight/curves bends ignored .

Edited By Engine Doctor on 16/06/2018 09:31:24

Thread: Hi Nitro Glow Fuel
14/06/2018 10:51:06
Posted by David Davis on 12/06/2018 11:34:15:

Thanks for the advice ED. I am a long way from the nearest Westons Pro-Synth supplier but I have some Southern Model Craft 85/15 straight. Guess I could add some nitro to that!

Hi Worth trying SMC fuel first I reckon ,it might be fine on it.

Weston do post fuel via courier . Might be worth a call for cost ?

Southern model craft is a good fuel . I use that with reduced oil 17% synthetic and 10 or 20% nitro depending which engine/ model I'm using . I wont use any fuel with castor oil in it unless its a diesel or vintage engine with iron piston/cylinder.

12/06/2018 11:23:44
Posted by David Davis on 11/06/2018 17:17:28

As for me, I was always brought up to be careful, some would say tight, with money and the thought of spending 154€ (about £136,) on an OS 35AX and plus the cost of some fancy pipe to use it in a light-hearted competition for three channel trainers, goes against the grain! I will be campaigning an SC32 which I picked up for peanuts on eBay. I've bought a Weston pipe for it and that's extravagant for me!

Hi David . The SC 32 with a Weston pipe is a really good combination and the 36 is even better.. SC 32 is virtually identical inside and out to the OS 32 at a fraction of the cost and you don't have the problem of the chrome plating shedding from the cylinder liner , a known issue with OS engines inc the AX range ! I ran my OS 32 SX set up for years and they really went well. They went even better if oil content in fuel is reduced . I had my fuel mixed to 17% synthetic oil and 20% nitro. If you use Westons Pro-Synth 2000 fuel it will really howl and will run a lot cleaner.

Thread: ASP 61 fs Timing
12/06/2018 11:03:42

Glad to hear you have sorted it .

09/06/2018 13:04:40

My tablet spell checker thinks timing gear teeth are brothers ? smileyOnly just noticed it , should bee tooth obviously.

09/06/2018 11:32:11
Posted by Pete Willbourn on 06/06/2018 21:17:38:

Thanks chaps ,

and Jon the lazer man , this is what I suspected and thats why I asked if anyone actually had the timing diagram .

We have two identical air craft , Magnatillas , one has an ASP52 and the other an ASP 61 , both newish engines , but the 61 has the power of a 40 , no where near that of its little sister , hence my question on timing ,

I shall play about with a tooth plus and minus and see what happens.


Pete W

Does the 61 have an excellent idle ? If it does that will be the giveaway that the timing is retarded by a tooth. I had this on a Magnum 120 fs . Fantastic slow idle and threw prop when opened up putting a good dent in my caravan 20 feet away ! Always stand behind engine after starting.

If timing is advanced b one tooth engine will have poor idle/ low speed and excellent mid to top end but still very likely to throw prop. Any more than one brother out runs the risk of bent valves.

Thread: Charging Lipo
09/06/2018 11:22:10

I find I only have to balance batteries that have been discharged at high rate as in EDF models every couple of flights. All other I check for cell discrepancies after flight or before charging and balance if needed. I used an old 4s battery in a FM's zero last week as it's a comparatively low power installation . Battery was useless for EDF but fly's the zero a treat. I checked the label I stick on for first use/charge and date was May 2004! How time fly's ?

Thread: Old fuel / nitro
07/06/2018 11:26:40

It depends largely on how and where its been stored . If un-opened and kept in a cool dark place then it will keep for a few years no problem . If kept in warm a or in sunlight it will deteriorate quickly . If its a part used container then moisture will have got in in the air so may be ruined . Try it and see . Erratic running, difficult starting and a poor idle are signs of water absorption.

I know diesel fuel is different as its not hygroscopic ,a mate was given a bottle ED diesel fuel . A dark brown glass bottle approx half a pint that was found in a cellar. It was till in perfect condition and ran an engine starting very easily even the label was good . Bottle must have been from about 1947 !

Thread: 2 Stroke deadstick issues
07/06/2018 10:48:09
Posted by Tim Cheal on 06/06/2018 21:33:20:

Here is the corned/crankcase I described above:

os 55 crank.jpg

Check plating at top of cylinder for flaking by quickly removing Cyl Head. If thats ok then it must be a fuel issue ie air leak or bit of debris in the jet. Try setting carb a little richer to see if it improves . then let us know your findings

Thread: Servo extension leads
04/06/2018 09:02:16

As Per BEB used this method many times for custom leads and works well I have also used a Lipo balance lead and make up a loom so that one plug connects all servos? Saves messing with multiple plugs every time you take the wing off. .I have used it on a Zero with wing lights , retracts and flaps in the wings . For the Zero I used a 6 S balance lead . These can be bought in different lengths on e-bay. Do a bit of research and check for quality as wire quality can differ considerably I looked for leads with silicone covered wire and these are very flexible with good quality copper wire similar to quality servo leads Use common earth and positive leads and separate signal leads . It tidies things up and cuts down on the wire jungle and the possibility of plugging in to the wrong socket

Thread: Engine cuts at full throttle.
30/05/2018 10:11:10

Brian is correct in his assesment of MDS engines as many will agree ,while others ,not many to be honest found them ok. Some larger dealers had stalls at many shows that sold either complete returned engines for peanuts or boxes of bits that you could build a engine from for around a fiver. They even changed the appearance and the name to RMX engines ,that were just as unreliable. I have come across a few that run really well over the years . They still turn up now and again and people buy them to remind themselves just how good other makes were/are.smiley

The thing is that Roberts engine ran perfectly when put away a few years ago. It must have been a decent one so should run ok now provided it's not corroded inside by methanol like so many engines I deal with.

Edited By Engine Doctor on 30/05/2018 10:14:49

30/05/2018 08:53:44

The MDS range were known for having poor carb quality at the time and many chose to fit carbs fromOS or Sc engines with varying result. As you say it ran perfectly before being stored six years ago the carb must have been fine so whats changed , is anything different ? Is the fuel the same mix ? Did you check engine for internal corrosion,ie rusting bearings ? Debris being thrown into cylinder can affect the ignition process. Have you checked any "o" rings for cracks or brittleness ?as this can affect the seal.all points worth checking .

29/05/2018 22:08:38

Cutting out instantly can be due to the fuel mixture being too rich as well as too weak . If it hunts and sucks air before cutting then its too weak . If it cuts instantly then try closing the needle completely and re-setting mixture . I recently had this with a West engine .It ran perfectly at anything up to half throttle. Anything more and it cut instantly. Closing the main needle one full turn sorted it . If all this fails then make sure no fuel has set in the jets .


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