Anyone have experience with the OS FL-70 in stunt application? This is the compact, lightweight ringless ABN four stroke that assertedly weighs 20% less than the Surpass 70 (which I have one of). Looks like a great fit with CL use, with a simple carb that should be easy to convert to CL just by securing the carb barrel or some such. Never have seen a reference to this motor in CL, though I learned the Surpass 70 is in common use in Europe. Looks like a good competitor for the Saito 56 and 62.

A few people here in Brazil are using it with the R/C carb. Most of them are not competitive flyers. They use the same prop we use with the Saito 72, TF PowerPoint 14x6,  and as far as I could tell they ran very well.

The reason why not many people use this engine, is because is not easy to adapt a venturi, you need to saw off the manifold to remove the R/C carb.

Good luck,

Martin

Hi Bob:

Thanks for the invite to join your group. I have Surpass 70, 90 and 1.20 in RC use, plus an Enya 46 (a neglected engine with a lot of potential, along with the newer 53) so I guess I qualify as a 4-stroke guy. None in CL yet. Nice to hear from the Boys in Brazil, who seem to know a lot about the big OS strokers. I will send a PM to Bob.

I noted that the FL70 has an integral carb, not a removable one. Might the intake tube for a Surpass fit? Maybe if the rotary barrel is removed a venturi could be adapted.

This may not be of any help but, the FL70 has not received a good rep in the RC circles down here in Socal.  I make it a point to find out what are RC cousins think of their 4 stroke motors. Now, there is no substitute for a large pool of  respondents when making ANY product assessment.  But, I have learned a tremendous amount about 4 stroke motors from talking to my RC buddies on a regular basis down here in Socal.

Radio control 3D flying of any sort is one of the ultimate tests of powerplant setup and reliability.  The hyper violent manuevers and constant close proximity to the ground, demands absolute control over EVERY aspect of the plane.  OS Max's on the 2 strokes, and Saito's on the 4 strokes seem to be about it.

 Alan Hahn,
You have made a good point. Let me put this in the context that it actually is.  In a lot of cases, RC flyers are not always interested in the where and whys of why certain engines don't work. They either do or they die on the vine in that particular region. 

Case in point; today, I was at the NMPRA races here in Socal. I have been watching these races for years.  I have never seen more than 1 Jett motor, (same people who make our Rojetts) at any of these contests. Nelsons, (same people who make our PA's dominate). The reason I have never seen more than 1 Jett is because there is only one guy campaigning it!! It has been the same guy!!! I found out that the Jett is really a regional thing. There is group down in Texas where they are made, that knows how to rock with them.

In addition, you have to understand that I cannot hand out a ten page questionnaire with full likert scales to them when they are kind enough to take time and share there modeling experiences with me. In some cases, they are right in the middle of working on their model or, they could be next up in the flight line.  In a lot of cases, while their responses are extremely helpful to me, they may be in form that may not be useful to you i.e.: "piece of junk", *&^* motor, save your money. I also made it clear in my post, that, there is no substitute for a large sample size in doing any product research.

The FL70 appears to have "top end" problems. The motor is a lower cost, lighter weight, cheaper alternative to OS's premium Surpass line. Apparently the cheaper bushing guides in the FL70 don't seem to standing up to the pounding and abuse that RC sport flyers are subjecting them to. In addition, the carburetors don't seem to be giving them the type of reliable run needed to hover at 2 feet off the ground with absolute confidence.

RC motors have a hard life ahead of them. They have to operate in less than ideal circumstances with less than ideal fuel, under less than ideal setups and perform superbly or else they get the proverbial kiss of death; the dreaded "bad mouth". What is particular interesting is that, engines that may receive wonderful product reviews in the magazines; don’t always pan out over time on the flight line where the rubber meets the road.

I have been doing this for a long time with the RC crowd and, I have found it incredibly helpful and downright fascinating.  RC sport flyers tend to be a great group of people and usually our more than willing to share there experiences with you, if you show common respect and courtesy. It is not my job to interpret their responses for other people. While that is okay for my needs, you may just want to hit the RC flight lines like I do in your region and "get it firsthand" too.

Postscript: If you are really interesting in following model engine usage on a larger scale outside of our own use, I suggest you hook into the controversy between the Saito 91 and the OS Max 91 Surpass usage in the Senior Pattern Association, (their classic group). It is turning out to be fascinating row.

Well, I guess the only way to find out is to get one and modify it for CL! I will volunteer for this dangerous mission...if no go, I will put it in an RC model. My thinking is to put it in my Score as a test bed, a fairly large and heavy airplane. My expectation is that it will perform just fine loafing along at the RPM and loads we put on our bigger CL engines. My experience with OS's superb quality makes me doubt they would leave this on the market (two or three years now) if it had any problems, without fixing them. And, what are "bushing guides?" Does this refer to valve guides? The "problem" with the FL70 could relate to its tapered "pinch top" bore, like the Brodak 40, that requires special care in break-in and starting procedure. We will see!

Well we could also blame that swill the RC'ers use for fuel   , maybe not enough lube getting into the valve area  .

Disclaimer: I also fly RC with 4-strokes!

Mike - you are doing the proper thing regarding the OS .70. Here in R&D, we have a saying: "One test is worth one thousand expert opinions" and it really rings true.

I copied your post and I've added a few suggestions in [----------------]

You stated: "Initial issues will be:"

1. Carb setup. The Boys in Brazil may have useful info here.
[First, try the STOCK CARB, wired wide open. If it works, you're all set. If not, talk to people like Pat Johnson who have lots of experience with venturi setups]

2. Optimal mounting. Sidewinder or inverted or some other orientation (except upright!)
[I have tried all setups and the most reliable (at least on the smaller engines) seems to be sidewinder. Actually, my .56 is side mounted and the run is perfect]

3. Prop type, diameter and pitch. Around a 14-8 or thereabouts for starters, which means longer gear for the Score. If 3-blade could take an inch off diameter if usual rules apply.
[14-8 may be a bit much - buy a few in the 13-6 and 13-7 range for experimenting. Possiblly even a 13-6 three-blade. Take a good look at Master Airscrew - they are making some very fine propellers]

4. Tank size and relation to carb position. Presently has a 6-oz round clunk on ram air uniflow.
[For starters, put the tank on needle valve or intake C/L depending on how the engine is mounted. I HAVE NOT had favorable results with uniflow on 4S engines - others have. Try both. Same for muffler pressure]]

5. Why I got into this and should I have my head examined.
[It's sometimes referred to as a "FINE MADNESS!!!"]

Addendum: FUEL - do yourself a favor - stay with at leat 22% oil. As far as I'm concerned, the Powermaster 10/22 and Brodak 10/23 (both with 50/50 castor/synthetic) are the best for most 4S engines.

You said that you have an ENYA .46 and .53. For their displacement, these are the most powerful engines I've ever tested. We have replaced ST .46s with the same size ENYA 4S and there was no comparison. An ENYA .53 flew the 78 ounce Red Baron better than the  ST .60  that powered it originally.

GO FOR IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
And, by all means, share your results, both here and on my 4S list.


Bob Z.