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-   -   Will the YS 60FR bolt in the same as an OS61SF for direct swap? (https://www.rcuniverse.com/forum/classic-rc-pattern-flying-379/11606169-will-ys-60fr-bolt-same-os61sf-direct-swap.html)

SuperViking 11-02-2014 05:07 AM

Will the YS 60FR bolt in the same as an OS61SF for direct swap?
Will they both fit the same mount with out re drilling holes? How about the YS61 Classic?

Jim Johns 11-02-2014 10:29 AM

Nope, not the 60FR - the bolt pattern is different. I don't know about the classic.


doxilia 11-02-2014 11:05 AM

The only classic engines that I believe will bolt on the same mount/spacing are OS and Rossi/NovaRossi. I think the Italians decided that it made sense to compete on this front with the Japanese (or maybe it was the other way 'round) and be able to pull an OS out and drop a Rossi in place if you wanted a "real" pattern engine... ;-)

What I haven't checked is whether OPS/Picco (which is narrower in lug spacing) interchanges with YS.

What I do know is that the spacing of classic YS 60 FR (RE) engines have the same header bolt spacing as OPS and Webra so any RE headers you have for any of these engines will also work on the other two (that you may also have). :-)


doxilia 11-02-2014 11:11 AM

Originally Posted by Jim Johns (Post 11910381)
Nope, not the 60FR - the bolt pattern is different. I don't know about the classic.



we'd have to check but I think YS kept their lug bolt spacing the same between the two types of cases - round and square. The width between lugs might have changed though. Mere speculation on my part though.


SuperViking 11-02-2014 12:38 PM

Thanks, I am looking for a nice machined mount for a YS60 and thought the OS factory mount would work for a tiporare 60 I am getting ready to build from plans.

doxilia 11-02-2014 06:14 PM

Originally Posted by SuperViking (Post 11910434)
Thanks, I am looking for a nice machined mount for a YS60 and thought the OS factory mount would work for a tiporare 60 I am getting ready to build from plans.

Yes, the 905 OS mount for the FSR/SF/FX 61's and 91's won't work with the YS's. It will work with Rossi and NR though as mentioned. You could probably use it by re-drilling and re-tapping though. I think there is enough clearance between the front bolt on the YS (narrower) and the OS. The problem might be the case width which I haven't compared. They should roughly be the same width though. I actually just picked up some OS mounts today so when they arrive I'll be able to compare and check with different engines.

Not many aluminum motor mounts left out there that I'm aware of.


speed-panzer 11-02-2014 11:04 PM

1 Attachment(s)
Some time ago I was wondering the same issue. Would be nice just for comparing different engines if you could swap them right away on the same motor mount...
I created an excel sheet where I put in all available data. Most of those I measured myself, but of course, no guarantee that it is 100% correct!



SuperViking 11-03-2014 12:52 AM

I was just looking through Jett engineering and see he is making some nice mounts. Maybe I can get him to build a few or find one that suits. Thanks for the info with the OS mounts.

KLXMASTER14 11-03-2014 10:59 AM

Originally Posted by doxilia (Post 11910625)
Yes, the 905 OS mount for the FSR/SF/FX 61's and 91's won't work with the YS's. It will work with Rossi and NR though as mentioned. You could probably use it by re-drilling and re-tapping though. I think there is enough clearance between the front bolt on the YS (narrower) and the OS. The problem might be the case width which I haven't compared. They should roughly be the same width though. I actually just picked up some OS mounts today so when they arrive I'll be able to compare and check with different engines.

Not many aluminum motor mounts left out there that I'm aware of.


I believe that you are correct, David. I helped a buddy retrofit a YS into a Tipo that had previously sported a OS. 61 VF. IIRC, we were able to re-use one hole (F or R) and were able to drill a new set withing the OS spacing. The mount was a CB aluminum mount.


doxilia 11-03-2014 01:51 PM


yes, now that I think of it a little better, I recall the exact same scenario on an OS/Rossi pre-tapped aluminum mount receiving a YS AR engine replacement. The rear lug holes were re-used (hence, same width between all three or four brands) while the front holes were drilled anew and tapped leaving about 2 mm clearance between the two engine spacing front holes.

Thanks for confirming that.


there is an auction for a pair (small and large) SIG aluminum motor mounts in progress. Usual site if interested.


SuperViking 11-04-2014 03:29 AM

I found a guy who is going to machine one or two for me. It's basically going to be a machined Dave Brown mount.

doxilia 11-04-2014 06:21 AM


very nice! Will he drill and tap them for the YS and 6-32 bolts as well?

If he's interested, he might want to machine a few and offer them for sale.

He may also want to consider the BHE design mount - best design for symmetric side/vertical mounting.


SuperViking 11-04-2014 01:55 PM

Yes, I am sending an engine to him this week and it will be pre drilled and tapped. I hope he will consider selling some because I am sure others will want them.

doxilia 11-04-2014 06:45 PM

Absolutely. If the cost is reasonable, I would like to provide him with a BHE 60L mount that would be great machined out of aluminum. It might need some slight alterations to provide rigidity when made of aluminum but otherwise it is a great all around mount for classic pattern 60 size engines - SE and RE without modification.

Also, for what it's worth, I just checked a Picco RE engine (an 80 although the 60 is the same externally) against the YS 60FR and they both share the same mounting pattern, lug length and case width so they are interchangeable without changing the mount. I suspect this will hold true with OPS engines too since Mr. Picco was the designer of OPS engines as well. Although not certain, I suspect the Webra Speed 61 Racing RE will also mount on the same pattern - but to be checked.


doxilia 11-05-2014 03:17 PM

I took the time this PM to pull out some engines and check the measurements to confirm and augment Dominik's great Excel document.

First of all, the interesting fact is that most classic 60 size engines have the same mounting bolt "width" between lugs - 52 mm. This regardless of the case width whcih does vary somewhat between one brand and another. As to the bolt "spacing" on the lugs, as can be seen from Dominik's doc, the spacing is mostly one of two dimensions - either 20 or 25 mm. What this generally means is that any engine which has a 20 mm bolt spacing on the lug can be replaced with any other engine with the same spacing regardless of case width. For example, if we take a YS FR/FS which has a rather narrow case at 40 mm, it can be swapped for an OPS (red and gold heads - same mounting dimensions), a Picco or an Enya. All these brands use 20 mm bolt spacing on the lug. Some of these engines have wider case widths but provided the mount can "stretch" a bit if it sized for YS at 40 mm, the other engines will fit too. All three brands, OPS, Picco and Enya, use 43 mm widths between lugs. Conversely, if the mount is sized at 43 mm for these engines, the YS will drop right in and align with the bolt mounting even though the engine case is narrower than the mount beams.

The other club of bolt spacing is the 25 mm camp. OS (FSR, SF, VF and RF), Rossi, NovaRossi, MVVS and Webra all use the 25 mm bolt spacing and 52 mm bolt width center to center. So all these engines can be swapped out for each other without replacing the mount - they will bolt right in. This means that an aluminum mount such as the OS 905 which is pre-tapped and designed for OS 61 and 91 engines will also work for any of the other engines listed in this paragraph.

Now, for the limiting factor - bolt to thrust washer distance. This is where engines differ a fair bit. I took measurements of several engines I have to see if there was some sort of pattern and by en large, there isn't. The longest engines I have come across are the vintage strong Italian engines - the OPS gold head and the Picco 60/80 RE are at the limit of longest engines and are identical in pattern as one might infer given the same designer - Gualtierangelo Picco. Although these engines are long, they have a nice layout in the sense that there is ample room for between the cylinder and the thrust washer to accomodate the carb. This provides more space in the model for the fingers to adjust the carb without either being hit by the prop or being burned by the running cylinder. That said, both brands came with servo controlled high speed needle valves which avoids one from getting one's hands in there at all - it can all be adjusted from the radio. At the other end of the spectrum, we have the rather short engines - notably the YS which is 78 mm from rear bolt center to thrust washer. Why I'm measuring from the rear bolt center rather than the rear of the case will become clearer shortly. This engine sort of has an integral carb to the case which is practically vertical and by virtue of the metered design of the YS, once the high is adjusted there is very little further need to play with it more. Interestingly, the new NR designs like the Speed/13 share the same short case length so the distance from the center of the rear mounting bolt of both the YS (new Classic included) and the NR is the same - 78 mm. What this means is that if one were to build a model and space the FW and nose ring distance for the YS for example, one could then pull the engine and swap it for a NR, bolt the rear holes of the NR in the same holes as where the YS was mounted and the thrust washer will be exactly where one would want it. The only problem is that the YS has it's front bolts 20 mm further forward from the rear while the NR has them 25 mm further forward. So, barring the drilling and tapping of holes at 25 mm from the rear ones on the same mount, one could just replace an identical mount, drill and tap the rear holes at the same location as the original and then drill the front ones at 25 mm forward.

That said, while it sounds like Robert and others have re-drilled and tapped the same mounts to swap 20 mm engines for 25 mm engines, the difference is 5 mm between the front bolts. Given that we usually mount these engines using either 6-32 (3.175 mm OD) or 3.5 mm OD bolts, the material left undrilled on the mounts front holes is at most ~1.8 mm (5 - 3.175 mm) or 1.5 mm if using M3.5 bolts. I find this a little too "thin" for my sense of security in engine mounting so I would personally want to swap the engine mount and drill properly for the new 25 mm bolt spaced engine. My feeling is that Cesare Rossi and NR didn't casually re-dimension their latest pattern engines to be "interchangable" with YS engines (and vice versa) but rather, this was done intentionally. It also made sense from a power standpoint to have a short and massive crankshaft. So the only "planform" differences between these two engines when it comes to a mount is the 20 vs 25 mm bolt spacing between the two. Otherwise, when rear mounted at the same distance, they both present the same dimensions in the model.

I have yet to measure the rear mounting hole to thrust washer distance of the various engines (although Dominik provides several "M" measurements at between 55 and 57 mm) but there is likely to be a fair bit of intersection between brands. The minor difference of 1 mm between OS and Rossi (55 and 56 mm respectively from the front mount hole) is again immaterial and just offsets the spinner an additional mm if swapping from an OS to a Rossi as an example.

While this may be of little interest to anyone but me, It's down here for posterity and hopefully it will be of some use to others when considering power plants for classics.


SuperViking 11-07-2014 02:57 AM

I will give an update on the engine mounts this weekend. My contact seems receptive to making them available once we try a few out. Sicilian you have done your homework for sure. Can you tell me about the other engine mount? BHE? I am not remembering it for some reason.

computermonkey 11-07-2014 12:19 PM

speed-panzer, thank you for the spread sheet. I have several of those engine and have been trying to narrow down what to put on a Curare ARF. I"m leaning towards the Moki 61 LS rear exhaust or the Webra 61 black head short stroke or ?

SuperViking 11-08-2014 02:42 AM

Have no idea why my typing said Sicilian, I meant Doxilia.

speed-panzer 11-08-2014 03:02 PM

Computermonkey, I didn't run the Moki LS RE yet, but It looks to be a good engine.
I do like all the Webras, and the short strokes like to rev. The 61 Speed is the engine the original Curare was designed around, so I would go for this one. Take the Dynamix carb, and your throttle response is like that of a Kawasaki...
Interestingly I read somewhere to program some 0,5-1sec delay to throttle servo, maybe that was in Hanno's tips for the Curare.

Thanks David. Usually I would bolt all 61 engines by M4 screws to the mounts. But most often I prefer to omit a conventional motor mount, and rather utilize a 3mm Al plate screwed to the engine's backplate. This plate is drilled to accept 4 M4 bolts which attach to the firewall. Advantage is that you can decide yourself where to place those firewall bolts, e.g. to create space for a retractable nose landing gear.


doxilia 11-08-2014 06:58 PM

Originally Posted by SuperViking (Post 11913864)
Have no idea why my typing said Sicilian, I meant Doxilia.

Hey SV, Sicilian here...:D

I'll get back to you tomorrow with some info on mounts that would be cool to machine. The BHE mounts were the symmetric ones made by Bridi's company subsequently bought and branded by Great Planes. I'll get some more details in the AM.


Huang 11-08-2014 10:28 PM

I'm not next to my engines/planes right now but I've done a lot of toying around and mock mounting between the OS 61RF-P and YS-60/61 as well. Mainly I wanted to replace the OS on two of my classics with the YS, but it wasn't that easy to do so. The planes are the MK Aurora and Arrow, which both came setup with the OS mounted on the MK wood beams.

The problem is the YS uses shorter bolt spacing, and if you reuse the forward bolts, the spinner gap becomes too large. Also, you would have to re-drill for the rear bolts, but it is too close to the original holes. For the MK kits I have to somehow fill the original holes in the wood rails, and it'll be hard to drill straight as the drill will tend to slide.

BTW anyone know what material to use to fill the original holes on the wood mount? I've heard baking soda? I'll probably swap the whole setup with a MK soft mount, but curious how others solved this.

SuperViking, I'd love to buy one of the aluminum mounts for the YS-60/61. I'm completing an Atlanta with a YS-61 classic that could use it. How can I get one? :D

In general, what's the best rigid mount people have used for the big block .60s? Richard Verano said when he first mounted a YS on a cheap Hangar 9 nylon mount for the P7, it vibrated so much it took a lot of power away. He had to change to a better a mount to get the power back. What about the Dave Brown glass filled nylon mounts? What engine mounts do you guys use?

flywilly 11-09-2014 09:19 AM

Hi Huang,
First the hard mounted engine issue. IM used to make steel plates with drilled/tapped holes which fit both OS and YS and located the drive washer in the same place. The entire plate was screwed to the wood mounts. You can make your own with a little effort. You can get steel plate at Lowes, Home Depot, etc. It available in 1/8" thick by 1" by 36" lengths (maybe shorter lengths). You will need to drill and tap the mounting holes for the engine or engines (I prefer 6/32 stainless cap head bolts) and drill the mounting holes to attach the plates to the airplane. A little oil (like 3 in 1) helps when drilling and tapping.
I rarely hard mount engines any more. I prefer the Hyde mount when possible (the 91-115 predrilled mount fits OS 61s perfectly), but have used the MK mount with great success. Too bad they aren't made anymore. Dave Von Linsowe produced a beam type soft mount. Dave Brown bought the rights to manufacture and may still make them. They also work well and there are replacement parts available (especially the rubber vibration dampers).
If you choose to hard mount an aluminum mount is preferable. If you can get one from Dub Jett it will be well worth the price, his stuff (engines and accessories) is all first class.
Good Luck,

Huang 11-09-2014 09:55 AM

Hi Will,

Thanks for the info. I didn't mention that I actually have a set of the original IM steel plates with tapped 4mm holes for both the YS and the OS. They are wonderful quality and that is what is on the Aurora right now - Aurora plans showed these steel plates as well.

The problem is if you swap out the OS for the YS using the IM plates, the spinner gap is too large. The IM plate is drilled with 6 holes, two of which is shared between the OS and the YS. If you already have the plate mounted and only swapping the OS/YS engine, you cannot adjust the spinner gap, only one way which is too long and the other way which is too short. To get it right you would still have to move the plates, which goes back to the same problem of filling the original holes for not the engine but the plates.

I actually like the MK wood mounts. As you know they are a very strong hardwood and spread the vibration and load over the entire front of the plane. Anyone have recommendations on what to fill the holes with?

For the Atlanta, I've inquired Central Hobbies on the Hyde mount last week, but they replied that the only one that would fit the YS-61R Classic is one of the adjustable mounts, which looks basically like a cheap Great Planes adjustable nylon mount in front of the Hyde damper. I've used the predrilled Hyde which is awesome but I'm not sure how solid that adjustable nylon mount is.

I looked at the gator soft mount still available at Central, which has aluminum beams, but I've not had experience with them. Any suggestions? Thanks and I hope this isn't too off topic!

doxilia 11-09-2014 10:25 AM

It sounds like even the Japanese had some dimensional issues with their products. I intend to solve this problem and figure out the dimensional requirements "spinner back" for the more popular classic 60 size engines. In the case of beam hardwood mounts like were used in many of the MK designs, this should be very straight forward. The metal plates are drilled at a standard width on the beam and the location of the mount bolts are placed according to where the nose ring is located. A dual purpose plate like the IM you're describing Matt, seems unnecessary given the cost of sheet steel and even if they were properly drilled we've already established that a combined 20 and 25 mm spacing leaves too little clearance for comfort between different brand engines (e.g., YS & NR).

The dimensional stuff will work equally well for beam aluminum hard mounts as for hardwood/metal plate systems. The vertical "backplate" mount systems are easier to deal with since putting the thrust washer where it needs to go is a matter of spacing the fixed FW with some ply spacers. Using 1/8", 1/16" and 1/32" ply spacers one can fine tune the spinner position. The main problem arises when one swaps out a modern short engine such as a NR or YS for a vintage engine such as a Rossi, OPS or Picco. On slide mounts this can usually be addressed but on typical FW mounts (Al or FRP) or backplate mount this is not quite straight forward as the space in the engine bay is often not sufficient unless planned for a priori.


doxilia 11-09-2014 10:40 AM


if you need to fill the MK hardwood beams, boring the holes out to a standard hole size like 1/4" and filling with a similar HW dowel, epoxy and MB is usually doable. You can then redrill and tap as needed even if you go partially into the dowel/seam area. If there is any concern, go bigger on the dowel if you can (like 3/8").


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