Engine Doctor

Hello Gonzo. Some excellent pics of conversions of supertiger's especially the needle roller big end. The carb adaptors at £20 arent bad value : add  the cost of the con rod conversion ,an  ignition module and a suitable walbro carb and the cost soars .   I doubt though that these parts  would fit a os 70 cz which started this thread but nice conversion for big two strokes.   E.D

Hello stephen . Try checking the valve timing . Its a simple job . remove the rocker covers and the glow plug . Now turn engine to TDC(top dead center) with the valves on the rock. (one valve closing while the other is just starting to open . This should occur just on TDC and both valves should be open the same ammount at TDC. Ifits either side then the valve timing is out. It only has tob e one tooth out and the engine will not runn properly. Symptoms are ability to tick over very slowly and no top end or good top end and no tick over . On later engines with high lift cams it causes bent valves as they can be hit by  the piston . Hope it helps E.D  

Hello David . I forgot to mention the carbs on conversions . As you point out any successful conversion need the proper carb to get the metering right , and as you cannot use ex haust pressure for petrol ,it has to be a pumped walbo type carb. A few years back a lot of large Supertiger conversions were about . An aftermarket needle roller con rod was available but no adapter for a proper carb  so they disappeared from the market. The reason I believe was that they were notoriously unreliable (deadsticks) even as a glow engine so converting to petrol just made matters worse. I know someone will say "they have  an XYZ engine they converted to petrol X years ago and it hasn't missd a beat but they are the lucky ones. To sum up if its designed for methanol then thats what it will run best on and vice versa for petrol.  

Used My CRRC 26 again yesterday and it popped ! Started well and all seemed ok then lost lots of power .The compression was almost non existent. I decided to end the session and went home to strip the engine down . Inside was a big dissapointment . Metal swarf that had been gouged from the backplate by a badly finished con rod had got the cylinder and removed a groove of chrome from the cyl .I had checked in the c/case for any swarf but didnt notice the badly/ unfinished job on the con rod. This is the second CRRC engine that I own that has done this .  I have smoothed and polished the  the gind marks and sharp edges from the big end . Hope fully the new cylinder will stand a chance . It will cost about £50 to rebuild . Has anyone else had any similar problems ?

As said in earlier post petrol will not give same power etc as methanol and as the application was for a high reving engine in heli he would be wasting his time .Petrol engines are designed with needle roller bearings in both big and little end bearings and ballbearing mounted crank. They also have ringed piston to reduce friction ,all this designed to use tiny amounts of oil . Petrol conversion in a fourstroke for use in a plane is a diferent matter and should give  give bags of torque and as fourstrokes dont rev  like the two strokes the lube requirements  will prob be ok but should still be higher than the 30 to 40:1 that petrol engines are designed for .Dont confuse the ratio with a percentage as 40:1 is only 2.5% oil and glows run on 20% oil ,a big difference  ; most f/s engines are ringed and crank and most cams are ballraced . the only plain bearing on most is the con rod so for safe running you would probably need 10 to 15 % oil (approx 10 to 6.5 :1 ratio ) . Even the Saito  petrol F/s use a higher  oil content. Has anyone had a bad experience from a petrol conversion ? Lets hear from you . Regards. E.D

My CRRC 26 has been fitted in a seagull Ultimate Bipe . Running a tank 30 :1 through on the ground I tried the next tank in the air . 18 X 6 prop was obviously too low pitched as plane limped around . Engine is getting better though . I am fitting a 17 x 10 prop for extra thrust . will see what its like as soon as I can getit to the field.   Mal . I reckon you need to open the HIGH end needle a half turn or so as it sounds weak to me , then retune as required once its running. 5.3  volt for a 4 cell pack seems ok and it should run on that . Have you checked the voltage on load ?

Hi Carl , Brian is right the conrod should slide back when the piston is at TDC . Sometimes  if the little end bush is a sticky fit on the gudgeon pin it will be difficult to slide back and clear the crank pin. A little warmth can help from a hot air gun or similar .

H Stephen . i believe giant cod has some  glass fibre wheel spats on his website at reasonable price . Not sure wether they still on there or price  but worth a look.   E.D.

Dont waste your time and money as you wont get the same sort of power from the engine with petrol . You will also have to keep a high oil ratio as the engine will have plain bronze big and little end bearings that will sieze if you cut down to normal petroil mixes . Try some of Southern modelcraft fuel . Fully synthetic 20% nitro costs about £15 a gallon and unlike the stuff with fancy coloured oil etc . Good luck E.D

Hello Herri I run my petrol engines on 4 cell Nimh packs at 2000 mah capacity . They will work all day without recharging . I have'nt checked the current draw on the ignition unit but it cant be very high  as recharge only takes about 7 or 800 mah. Beware of any high voltage back surge from the ignition unit doesent damage your regulator as it did when I I tried to incorperate an LED into the ignition circuit to indicate power on . As soon as the motor started it blew the LED . Its worth checking out before committing to the air and possible engine failure.   E.D

It sounds  a bit like the saga with OS 32sx engines and the chrome/nickel plating peeling off the cylinder . At the time ( about 6or seven years ago) Ripmax eventually rebuilt the engines without charge . I have just used one that was rebuilt and unused in my cougar and its blown after a couple of hours use !  Engine is  not worth repairing now but a 200 fs is  a seriuos bit of money . Hope you get one that lasts OK .   E.D 

Hello Alan . Yes it was tempting but have quite a few bits already so thought I should use them . EDF is not my main interest but is addictive so I have to make sure I dont get pulled in too far.   Phil 

Just a warning re the Pond shop epoxy . It great if you want "the never setting variety" This gives you ages to position  the job . Geuss howI know . I have bought some in the past and its been excellent for keeping in the flight box but latest lot is rubbish . Beware ! E.D. Phil

After reading your posting Alan I had a look at the Overlander Website and placed an order and have just received my F 16  . Excellent bit of kit with retracts etc  delivered for £52 !   I was amazed at the speed of delivery as I ordered in the afternoon and it was delivered early the next morning and only £3-00 postage . I dont know how the retracts will stand up to the grass strip but the kit is cheap enough to play with . I have just upgraded a Kyosho T-33 kit I found at a bring and buy with a D/F bought from Hong Kong with a 4s lipo .It has really brought it to life  with proper jet like vertical performance . Very unlike the original back in the 90's gasping for air .  I plan to fit a similar D/F in the F16 or possibly go to a 5s set up as the motor is supposedly capable  . No rush still enjoying the T33 . Thanks for the Bargain Tip.   E.D Phil

We all hear of the bad experiences but just had a good one with Overlander. I ordered a model that was being sold at half price rrp,thats  good. Then the postage was really cheap  £3-00 for a large model box , thats really good . Then it was delivered at 9-30 the next morning ! Thats excellent .

Hello Eric .I havent noticed it on e-bay but Pica kits IMO build into good looking models that fly well  but are heavy by modern standars.The materials supplied are also poor with rubbish grade Ply and furniture grade balsa .If your not careful then the back end becomes very heavy.The hardware supplied is also below par . If youre willing to replace said items then a reasonable model can be built . I have built the Pica  P40 War-Hawk for a club mate and am currently sorting a Pica 1/5 Mustang that I bought part built. I now wish I had started from scratch with another kit/ plan . I have just finished a DB hurricane for a mate and would recomend that route . The DB kits have been re-designed with bult up wings instead of heavy foam . Had they had a Mustang in the range I would have tried it .As always with E-bay or any auction "Buyer Beware" 

Hello Ed . Do you know any one with a lathe  ? If so get them to tun the end of the spinner nut (engine end) to a taper ,similar toto the lock nut  . Then pue a split in it with a hack saw agin copying the original lock nut . Use this and put original  lock nut away for future use  . Simples  PS dont be tempted to use a plastic spinner on a four stroke .. Sooner or later it wil compress and let the prop slip or worse fly off , Ouch . Hope it helps E.D.

Self tappers are fine as said previously ,in Glass reinforced mounts . Make sure to use the correct size screws as some of the horrors Ive seen have bee caused by using too big a  screw. Drill a  pilot hole, making sure its big enough  and pre thread them before fitting engine by screwing the screw in and out . Do this to be sure that the screw will tighten ok without getting so tight that its head shears off ; this will also enable the screw to go in straight. I have been asked many time to repair engine mounting lugsthat have been broken by using too big screw or screws going in at funny angle . Tip to mark the mount accurately for drilling. Hold engine in the mount making sure its in the correct poition. Next get a piece of  piano wire that is an easy fit through the engine mounting lug and grind to a point . Hold in some pliers and heat pointed end with gas lamp to red hot. Now slide through engine lug and int the glass/nylon mount this leaves a marker  hole ready to drill out to the correct size pilot for the screws. Simples   E.D

hello Rob . You could also try Southern Model Craft . They are based at Tonbridge which is a fair bit nearer and will save a couple of hours travelling .They make all types of glow fuel from cheap castor based straight to fully synthetic high nitro . Google for the contact details and give them a ring . Suggest 10% Hi-lube for your fourstroke . It contains 20% synthetic oil , ideal for running in.

Medway MFC invite you to a            Swapmeet/Bootsale       followed by a fly-in At their Stickfast Lane site Near Iwade Sittingbourne   kent Sunday 8th August  starts at 10 am £5-00 a boot  £1 entry Modelling related items only Anyone wishing to fly must have proof of insurance Will be sign posted from McDonalds at Bobbing And from Iwade Village center Just off A249  For further details contact Phil on 01795-476535 or Colin on 01634-317187 Edited By Engine Doctor on 19/07/2010 22:10:28

Just a small problem that occured with one of my petrol engines and gave all the indication that the CDI unit was faulty . The engine had been removed for some work and then started to play up . The fault was eventually traced to some metal filings/dust that had been atracted to the sensor magnet . Quickly removed with some masking tape and problem sorted. worth a check and it wont cost . As said in previous post , check the plug . The cheap chinese plus provided can be very poor . replace with an NGK equivalent .As said they appear to spark in open air but uder compression the spark will take the shortests route and that can be straight to earth . Main thing is to try just one thing at a time starting with the cheapest first. My Crrc 45cc had a duff cdi when new wich when replaced run the motor very well until it gave up mechanically. The 50cc seems a much better produced unit than the early models . I would have thought that the electrics should have been  improved as well  . Good luck E.D

Helo Bob. I must agree with A.A.Barry . Check the baerings before you attempt to start up. If the bearings in your engine are corroded then they could (and probably will) start to break up when started . Even if the actual bearing doesn't break up the bits of rust and debris will act like a grinding paste and damage the cylider etc wrecking the rest of the engine . Four stroke ,while not as bad as two strokes do suffer from bearing corrosion while stored. Its far cheaper to fit new bearings(typically £15-£20) than to shell out for a new engine. Tell tale signs are a notchy feel as you turn the engine over and/or up and down play at the crank web .you feel if there is any wear in the bearings by fitting the engine in a stand or model then fit a prop. Now turn the prop to vertical and hold at the tips now try to rock the tips back and forwards (to and from the engine) any play in the bearings will be felt at a click. in extreme cases you can see the movement where the prop drive meets the crankcase  .Dont forget the camshaft bearings as well . These dont get much lubrication on the older fourstokes . The play in all the bearings adds up affects the timing and the performance of the engine . Good luck , hope you get in the air soon.   E.D Edited By Engine Doctor on 29/06/2010 10:01:52

If snake are tight then there must be a cause and lubrication wont cure it . It may ease it for a whil but it will tighten up again. Make sure the iner snake is made for the outer. Different makes will not fit one another  Try replacing the inner snake or if the outer is damaged replace the whole thing. Too tight a bend will cause sticking and sticking will cause the servo to stall ,greatly increasing the consumption from and duration of the battery. Better safe than sorry  Fix fault or replace  then try the lube and it will be even better. E.D.

Hello twilightflyer . I think you'll find most Saito engines oose quality . The older engines are very economical to run ,very torquey and are reasonably quiet .The later high lift cam series are much more powerful and as expected use more fuel .They are also fitted with a muffler that really muffles !. The 82 being a real powerhouse (superb in a wot four) .If looked after they will give years of reliable service .IMO they are well worth the little extra cost .

Hello Clive .Try to find out from Just engines the "NGK" equivalent  plug number . The cheap and cheerful chinese plugs supplied with most engines are prone to breaking down , causing eratic running and difficult starting. Once you know the NGK number ,most car spares factors will be able to order you one at a sensible price,usually a lot less than model suppliers .