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Fitting Engine

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nigel newby06/12/2018 20:21:42
163 forum posts
40 photos

Hi all, my next great idea. I am about to fit my new ASP 70 four stroke in my Bi-Fly 40. When the engine is sitting in the engine bay I will not be able to get my fingers in to fit nuts to the bolts. So cunning plan. I am going to push each bolt through from the bottom. Then I have some servo rubbers. These are just a single layer of rubber, not the double things that go over the corner. Cut these in half, and put one over each bolt. Then place the engine in the bay and put on my nuts and washers. Now the question is. Can I leave the rubbers where they are. Will they act as shock absorbers, and help quell any vibration. Or will I have to remove them?

I bought the engine on ebay. This engine is brand new never used. The problem is that the exhaust is a little bit too small to screw into the cylinder head. Should there be a small reducing bush with it.?

Cheers Nigel N

Former Member06/12/2018 20:36:55
3577 forum posts

[This posting has been removed]

Denis Watkins06/12/2018 21:02:21
4419 forum posts
111 photos

Tiny rubbers will not cushion vibration at all, and may misalign your motor Nigel

The threads in the silencer, head, and any ancillaries are usually the same, No reducer


The silencer Never goes directly into the head

Always, there is a Header Pipe, all the same thread type and diameter

Put pictures on if you can

Bruce Collinson06/12/2018 21:29:42
529 forum posts

Agree with Denis, post piccies. Can you epoxy nyloc nuts to the underside of the mount using all the usual precautions, fit engine to mount with bolts tightened, Vaseline the threads to guarantee you don’t glue the bolts to the nuts or the mount? Dismantle, fit mount to frame, put engine on mount, carefully introduce bolts then tighten sequentially?

Just an idea.

Having broadly similar issues trying to smuggle a Laser 100 into a Probuild Infinitely-Complex and it’s going onto a plywood crutch with Tnuts epoxied onto the underside, with the crutch bolted down using the soft mount pickup nuts. Have ordered special locking washers from Model Fixings (Nordic?) so they lock down from above, without any access to the underside of the structure.


Geoff S06/12/2018 22:24:04
3659 forum posts
26 photos

In the past, I've soldered nuts onto printed circuit board. To get the nut accurately in place on the board, drill the hole first then bolt the nut in place before soldering. Obviously you can put 2 (or more if necessary) on the same piece of board. Then just epoxy the board in place again by putting bolts through to hold it before access becomes difficult.

It just gives a bigger glueing area. There's also the possible option of using threaded inserts supplied by Modelfixings if that works.


nigel newby07/12/2018 00:42:29
163 forum posts
40 photos

Cheers chaps, You want piccys. I love piccys, every picky is worth a thousand.


This one shows the exhaust system in the cylinder head. As you can see it is nearly the correct size, but not quite. A small reducer would solve the problem, as I don't really want to buy a whole new exhaust system.

Now, Can you tell me why I cannot put the nuts on the engine side and not the fuselage side? I can see and get to the nuts that way, but not when the engine is installed the other way!!


This is the front of the plane where the propeller will be.


This is looking down onto the engine bay.




This is with the engine sitting in the engine bay. Not much room to get my pinkys in there.



And this is the top view of my engine in the engine bay. I had to remove both the needle valve and the whole of the airstop assembly to the carb to get this in. I will most likeky have to take a bit out of the fuselage to get the engine in with the airstop/choke bit for the carb. But only a few thou.

Hope this helps Nigel N



Edited By nigel newby on 07/12/2018 00:44:22

Former Member07/12/2018 01:31:40
3577 forum posts

[This posting has been removed]

Denis Watkins07/12/2018 07:34:48
4419 forum posts
111 photos

Sorry Nigel, that's a 4 stroke silencer, but not the one for your motor

All headers are an exact fit, and need to be, being mounted so high in the vibration cycle.

These heads are relatively soft, so avoid continually trying mounts, and the glow plug as well, avoid continual plug checking, in and out. Just one plug in until it fails.

Engineering wise, a spacer is possible, not off the shelf, has to be made, but it would be so thin that it would be a constant source of trouble, and near useless.

Look at justengines site and get the telephone number, they do engineer some bits

To Add

I would ditch that motor mount, and start again, using it as a pattern, to make a smart new one

To fit that smart new motor

Edited By Denis Watkins on 07/12/2018 07:37:18

Engine Doctor07/12/2018 08:38:18
2506 forum posts
39 photos

Try contacting your ebay seller. They might have included the wrong silencer/header or ask for a correct replacement as they have sold you the wrong/incompatible part . Did you buy from an ebay shop or a private seller? .The silencer you have looks like a 52 size . If opening a case on e-bay fails then just engine will have the parts you need.

Nigel R07/12/2018 09:16:04
3881 forum posts
667 photos

That metal plate isn't tapped for M4 (or similar) is it?

Otherwise, the silencer, I concur it simply looks like the wrong one, a size too small. Time for an ebay exchange I would say.

I would not personally worry about the choke plate too much, if it does not fit, it is not the end of the world. A second or two on the starter and the motor will draw fuel by itself.

Bob Cotsford07/12/2018 09:49:08
8566 forum posts
477 photos
Posted by Geoff Sleath on 06/12/2018 22:24:04:

In the past, I've soldered nuts onto printed circuit board. To get the nut accurately in place on the board, drill the hole first then bolt the nut in place before soldering. Obviously you can put 2 (or more if necessary) on the same piece of board. Then just epoxy the board in place again by putting bolts through to hold it before access becomes difficult.

It just gives a bigger glueing area. There's also the possible option of using threaded inserts supplied by Modelfixings if that works.


I've done this in the past, soldering nuts to a (in my case) tin plate, though I attached it to the engine bearer with a small self tapper. I've also used the threaded inserts from Modelfixings, that was in a Marabu and a Mustfire both of which featured wooden bearers with plenty of meat to accept the insert. I used the screw-in inserts with a good smear of epoxy.

Bob Cotsford07/12/2018 09:49:41
8566 forum posts
477 photos

Double post!

ps - forget the choke, I've never found a use for them and always binned them.

Edited By Bob Cotsford on 07/12/2018 09:50:59

Martin Harris07/12/2018 10:25:41
9330 forum posts
249 photos

I would remove the plate, fix the engine to it and then replace the assembly using the 6 screws.

I'd certainly agree that you have the wrong pipe (and silencer if it fits that header).

Like others, I don't fit the choke. Assuming you use the pressure tapping from the silencer, you can prime the engine by turning the prop (glow OFF) a few times with a finger over the exhaust outlet, throttle wide open, until fuel is drawn into the engine. Do this until you detect a squishy wetness and the engine should fire up immediately - 4 strokes generally like to be quite wet and a reverse flick or twisting action on the spinner will usually suffice to start them.

Just don't forget to close the throttle again after priming and before connecting the glow - and keep your body parts out of the prop arc as you connect it as it isn't unknown for an engine to fire if there's compression in the cylinder!

Edited By Martin Harris on 07/12/2018 10:26:40

nigel newby07/12/2018 18:30:14
163 forum posts
40 photos

Well chaps good news. And well done to those who got the correct answer. There are thread things in the engine beams. Most likely M4 (I Hope). So I will get some bolts for it. Do I put a washer underneath the bolt. Should I try for hex bolts or allan bolts?

AS to the exhaust I have had a word with the seller, and he is giving me a partial refund.

Just engines have no exhausts in at the moment, but should be coming in next week.

Now I have an extension exhaust pipe. See Photo


Now the question is. Can I use it. This one is about 12" long I also have another one about 8" long. Could they be used to save the cost of the header pipe. Also when fitting the exhaust, do you have to put anything on the threads , or is it just tighten the thread and nut. That's all for now I think.


cymaz07/12/2018 18:33:44
9246 forum posts
1194 photos

JB weld some nylon nuts onto a bar of aluminium.

Martin Harris07/12/2018 18:39:21
9330 forum posts
249 photos

You could use either of the pipes without any significant losses - just depends if you like it aesthetically. Oil the threads before inserting them - get as much of the thread as possible into the head and tighten the locknut well to avoid any fretting.

Don Fry07/12/2018 18:50:07
4557 forum posts
54 photos

I have to offer a slight reality check.

Now I don't know the model, but a Bi Fly 40 (Flair, President?)) suggests a 2 stroke 40. And it's an old airframe, and an old 40.

Is a modern 70 just a little hot for this airframe. With a beginner moving the sticks.

My thoughts, happy to be contradicted.

nigel newby07/12/2018 19:44:48
163 forum posts
40 photos

Hi Don, and thanks for your wise and cautious words. I am not a complete beginner, although I have not flown for several years. When I last flew 2.4 ghz was just emerging from the shadows. Since then I have not really flown. So will start out with my old glider with an electric fan up front. Then move on to the Hepcat and the Carnival. Both 3 channel planes. Then onto the Arising star, and Precident Hi Boy. By then I hopefully will not be such a learner. That of course is if we ever get a break in the weather.

The thing is, since I last flew things have moved on at a cracking pace. One of the beauty's of coming on here, is that there is a wealth of knowledge from folks who know the new ways. So I ask questions sometimes just to make sure I have it correct.

The reason a 70 fourstroke is going in there, is because the guy who built it, built it with that in mind. So the engine mount bay is already for the engine. Even the holes for the needle valve are drilled and fit perfectly. Also I will have my chief test pilot there to start the flights if required.

As the weather is so bad, and this plane has been in the loft for a few years then I thought It was about time I finished it off. After this one I have a D.H.71, which is a single wing Tiger Moth, followed by my old STOL, which crashed when the wings folded. So a bit to keep me going through the winter.

Thanks again Don All the best Nigel N

Caveman07/12/2018 20:45:53
292 forum posts
241 photos

Nigel, that looks like the exhaust for a 52/61 size engine.

If you want the standard exhaust manifold & silencer then you can get them from Just Engines, £14.86 for the FS manifold 65-91, and £17.15 for the 65FSSIL silencer, total £32.01

But Weston UK list the manifold/silencer for their RCV58CD engine, item no. R120601, is listed at £18.95 complete.

See here **LINK**

I have both the SC(ASP)70FS and the RCV58CD and can confirm that the manifolds/silencers are interchangable. The only difference is that the RCV manifold is about 10mm shorter than the SC/ASP one.

Worth a call to Weston UK?


Nigel R07/12/2018 21:53:27
3881 forum posts
667 photos


I'd put a 90 in it.


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