OS FS-70 Surpass II RPM changing  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> O.S. Engines Support >> OS FS-70 Surpass II RPM changing
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OS FS-70 Surpass II RPM changing - 4/21/2005 4:43:28 AM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		I’m having a problem with full or near full throttle operation on a new OS FS-70 Surpass II. I have been breaking in the engine as per the manual and it’s coming around nice but I’m having a problem with the rpm’s holding steady when running at full or almost full throttle. I have run seven 8 oz. tanks of 10% nitro with a 20% synthetic / caster blend fuel. The engine starts easy. Its idle is doing good (2700 to 3000 rpm) and the idle to full throttle transition is good. But when running at full or almost full throttle the rpm’s go up and down by maybe a 1000 rpm. I’m using a 12 x 8 propeller. I peek the high-speed needle then back it down a couple of hundred rpm to the point that when you pinch the fuel line the rpm’s go up slightly. Then the rpm’s are around 8000 then jump to about 9000 to 9500 rpm for a second or two then back to 8000 rpm or so for several seconds. It will do this as long as I have it at full or close to full throttle. The engine is mounted in a U Can Do 3D .46 size airplane. I have been running the engine static. The linkage between the servo and carb is solid and not moving around. I checked the valve clearance and it is ok. I would also thing that I would also get more than 8000 rpm at full throttle from this engine turning the 12 x 8 prop. If I lean the high-speed needle for peek rpm it still does the same thing just at a bit higher rpm. Any ideas as to why it would do this.

Thanks
Mike
       Post #: 1

RE: OS FS-70 Surpass II RPM changing - 4/22/2005 7:35:04 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		If the engine won't hold RPM when running at full throttle, then it's not broken-in enough. Initial running should be about 20-30 minutes of running as rich as possible without the engine quitting. Then gradually lean towards peak RPM over the next 30-40 minutes.

You should also check your fuel tank and all fuel lines for blockages. Check the fuel system for crud, lint, dirt, etc. Are you using a fuel filter?

Vibration can also cause air to be agitated into the fuel that's in the tank. This will lean the engine and cause the engine to overheat, it may drop in RPM and then the vibration mode changes. The air goes out of the fuel, and the engine gets more fuel and picks up again.
Vibration can also affect how the fuel flows in the fuel lines. If you have long, floppy loops of fuel tubing, this could contribute.

If all else fails, you need to put the engine on a good, solid test fixture. If the engine runs correctly there, then the airframe is the major contributor to your difficulty. You'll have to see how the tank's padded, how the engine's mounted, etc.

Bill Baxter, Manager
Hobby Services/Futaba Service
3002 N. Apollo Dr. Ste. 1
Champaign, IL 61822
USA
Service Phone: 217 398-0007
Email: hobbyservices (at) hobbico.com


< Message edited by Bax -- 4/22/2005 8:10:05 PM >

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 2

RE: OS FS-70 Surpass II RPM changing - 4/22/2005 8:44:20 PM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill,

I don't have any blockages in the fuel system. The lines are short and not floppy. I don't see any air bubbles in the fuel line. I can put it on a test stand and see if it's a problem caused by vibration. I broke the engine in as per the manual. Running at full throttle with the needle very rich for 10 seconds then turning the needle until the RPM's would come up to near peek for 5 seconds then back to very rich for 10 seconds. I did this for the 1st 4 8oz tanks. Then started letting it run rich for several tanks after that and leaning it out a little with each tank. It may not be broken in yet. I know I need a couple more tanks run through it for the break in. I'll try the test stand this weekend and see how it does. Like I said before it starts easy and idles ok and the idle to full throttle transition is good. I was at full or near full throttle that the RPM's were changing. When running should I run at full throttle now for a few more tanks or vary the throttle during the run time. Some full, some mid throttle and some at idle. The engine does not get hot during the runs so far.

Thanks for your help.
Mike

(in reply to Bax)
       Post #: 3

RE: OS FS-70 Surpass II RPM changing - 4/24/2005 9:18:05 PM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill,

I tried putting the FS-70 Surpass II on a test stand like you recommended. But with the same results. I ran over a gallon of fuel with it on the test stand, and about ¾ gallon before removing the engine from the airplane and putting it on the test stand. I tried changing the glow plug with another OS F plug. It didn’t make any difference. I had one of the local club members who is pretty good with engine problems come by and look at it. He was not sure why it was doing what it was doing ether. There were no air bubbles or foaming of fuel in the fuel lines. Anything else you thing I should do?

Thanks

Mike

(in reply to mlgreene)
       Post #: 4

RE: OS FS-70 Surpass II RPM changing - 4/25/2005 5:43:11 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		it could be your fuel. Try some fresh fuel. 20% oil content is a lot for a 4-stroke. We usually go with 16%-19% synthetic oil content, and 10%-15% nitro.

It may be that the valve lash needs adjusting. It may also be that the engine's just not broken in.

We usually run the first 10-20 minutes of a four-stroke engine's breakin as rich as possible at full throttle without it quitting. We'll then start to lean the engine gradually towards peak RPM using the rich-lean-rich-lean method. After about 40 minutes of running time, we'll have the engine running near peak RPM.

Bill Baxter, Manager
Hobby Services/Futaba Service
3002 N. Apollo Dr. Ste. 1
Champaign, IL 61822
USA
Service Phone: 217 398-0007
Email: hobbyservices (at) hobbico.com


< Message edited by Bax -- 4/25/2005 5:50:06 PM >

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 5

RE: OS FS-70 Surpass II RPM changing - 4/25/2005 9:16:05 PM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill,

I’ll get some synthetic fuel and try it. I guess total synthetic oil fuel will be ok? I think the hobby shop had some but not sure of the synthetic oil content. Maybe 16 or 18% total synthetic at 10% nitro. I guess I was under the impression from reading other threads and talking to others that 4 cycle engines needed more oil content than a 2-cycle engine. I thought the engine manual said to use at least 18% oil content. But if you say 16% is ok I’ll see what the local shop has in stock.

I have run almost 2 gallons of a 20% synthetic / castor blend fuel at 10% and 15% nitro through the thing as of this past weekend. I would think it would be close to being broken in by now.
I did check the valve lash and the .04mm gauge was a very tight fit on both valves but would fit. According to the manual that should be ok, unless you can tell me different I’ll leave it at that.

Once again thanks for the help,

Mike

(in reply to Bax)
       Post #: 6

RE: OS FS-70 Surpass II RPM changing - 4/26/2005 4:39:53 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		Total synthetic is just fine for 4-stroke engines.

As long as the engine's not run too lean, a 4-stroke can accept a bit less oil than a two-stroke. O.S. likes 18% oil, but slight variances won't hurt.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 7

RE: OS FS-70 Surpass II RPM changing - 4/28/2005 1:45:59 AM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill,

Ok, I picked up a gallon of 18% synthetic oil at 10% nitro and a gallon of 18% synthetic oil at 15% nitro. I have run about ½ gallon of the new fuel with both the 10 and 15% nitro at 18% oil and it’s still runs the same, rpm’s up and down, up and down. That’s about 2 and ½ gallons or more of fuel run through this engine since I started. I have about 2 hours of run time on it just today. I also noticed that there is fuel coming from around the front bearing when the engine is running. Is this normal for fuel to come from around the front bearing? I checked and reset the valve clearance and it made no change in running at all. I don’t think it’s a fuel problem and I don’t think it will make any difference how much break-in time this engine has is going to make any difference. I’m pretty much done with this engine unless you have any ideas as to what to do next.

Thanks for you help,

Mike

(in reply to Bax)
       Post #: 8

RE: OS FS-70 Surpass II RPM changing - 4/29/2005 7:58:12 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		Some fuel coming out of the front bearing is normal. That's how it's lubricated.

If your engine is still within the warranty period, then send it into the shop per the thread at the top of the O.S. forum. Maybe out guys can find something.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 9

RE: OS FS-70 Surpass II RPM changing - 4/29/2005 9:10:49 PM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline

Bill,

Ok on the fuel from the bearing no problem.

Yes it is under the warranty period. Purchased 12/19/04.
I'll get it boxed up and sent off next week.
I'm sure this varies but how long is the normal turn around time?

Again thanks for the help.

Mike

(in reply to Bax)
       Post #: 10

RE: OS FS-70 Surpass II RPM changing - 5/2/2005 7:35:42 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		Normal turnaround is 3-4 business days from arrival here.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 11

RE: OS FS-70 Surpass II RPM changing - 5/11/2005 2:59:11 AM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill

I just received my OS 70 Surpass II from UPS today. Let me say…WOW that was fast. I shipped it on 5/5/05 and it came back on 5/10/05. That was quick.

Anyway they made repairs, replaced the cylinder liner and piston ring. Right away I have noticed much more compression. My question is with a new cylinder liner and ring will it need to go through the break in procedure again? I wanted to find out before I get it running on the engine stand.

Thanks

Mike

(in reply to Bax)
       Post #: 12

RE: OS FS-70 Surpass II RPM changing - 5/11/2005 4:09:13 PM   
Bax


 

Posts: 12677
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		With a new ring and liner, treat the engine as if it's never, ever been run before. Do a full breakin...run the engine super rich for about the first 20 minutes or so before you start to lean it. Gradually work the needle towards peak RPM. It should be ready to fly after about an hour's running. Please note that this is very conservative, but will give you a better breakin.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to mlgreene)
       Post #: 13

RE: OS FS-70 Surpass II RPM changing - 5/12/2005 4:05:46 AM   
mlgreene


 

Posts: 77
Joined: 11/7/2003
From: Seymour, IN, USA
Status: offline 		Bill,

I started the break in of the FS70 tonight. I ran it for about 20 min with the high sped needle set open to about 6 turns. Then after that I started doing the rich-lean-rich-lean tuning. Probably have 40 min on it so far. It seems to be working just fine. None of that rpm speed up slow down thing that it was doing before so far. The only problem is I found was one of the screws that hold the back cover in place fell on the ground during the break in run. Minor problem. I checked the other screws and another was backing out. I tightened them up. But so far it’s looking good. If the weather holds out I hope to test run it back on the U Can Do 3D 46 in a day or two to finish the break in.

Thanks

Mike

(in reply to Bax)
       Post #: 14

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