Sorry about that, sometimes these computers are just too much for the technically challenged user with short stubby fingers.

I understand what you are saying WRT props, mufflers and pressure systems but I do not run muffler pressure, I am using the Cline system.

I am sure that the OEM carby is good, however it may be that my example is one that slipped through quality control. I am not ready to give up just yet, but am reluctant to purchase another muffler fuel pump combination at this stage. BTW I am getting 8900 with the 18X6W APC.

Regards

Peter

There is an option five to consider.

5.) The OS 160 FX comes stock with the main needle valve mounted to the engines backplate, remount the main needle valve to a remote location like the firewall.

Note: Many run the engine in it's stock configuration with good results, however many have complained about tuning problems with their setup, possibly caused by heat and/or vibration of the main needle valve back plate location.
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Schpankme

Just a note of interest. In a normal installation (not a remote needle), the needle valve does not see any of the tank pressure created by the Cline fuel system. It only sees the fuel waiting on the outlet of the Cline waiting to be drawn in by the carb (at zero pressure). Only when the carb draws fuel does the Cline needle move since it senses a drop in inlet pressue. So that tank pressure just makes the fuel enter very quickly to replentish the fuel that the carb is drawing. I always thought that the Cline essentially makes the Carb think that the fuel tank is always 3/4 of an inch away from the needle valve, and always at the same attitude.

When the engine stops and there is pressure in the fuel tank, the Cline needle is fully closed and the carb sees none of that pressure. If it does, and there is fuel leaking out of the carb, the Cline needle is stuck open by dirt or debrees (that happended to me recently).

I too am having a problem with my OS 1.60FX. It has a burble in the midrange that is very annoying. It sounds like it is very rich in one spot in the midrange when flying. I have done everything I can think of to get rid of it. I am looking for a smooth midrange for hovering and flying and this rich condition is right in the sweet spot for hovering and flying making transistion hesitant. I was wondering if installing a 7D carb from the 108FSR would cure this problem even if I lose my remote needle in the process. Here is my setup:

QQ Yak 72"
OS 1.60FX
Bisson Muffler for 1.60FX
Cline PCFS system installed between needle valve and carb
APC 18x6W prop
OS #8,F, and A3 plugs tried

The rpm I acheve with this prop for flight is 9000+ which is more than adaquate for this plane doing 3D just need to get the midrange sorted out. Has been a problem since I owned the engine which also has seen duty in an H9 Edge.

Sport, did you try adusting the low end to tune out your midrange problem? It very well could just need to be re-tuned.

I have tried in the past but cannot seem to get rid of the burble. It will not burble on transition it is when I put the throttle in that particular spot that it eventually starts to burble or sound like it is missing (rich).

What fuel?

I have been running Morgans Omega 10%.

I guess I'd try tuning the low end to get rid of that mid range problem. That's all I can think of. You might want to give Jim Cline a call. He's an engine guru and is very helpful on the phone. His website is below and his phone # is in "Contact us".

http://www.billsroom.com/pcfs/

Isn't an 18x10 2-blade prop slightly too big for this engine? I have not seen any OS 160 that can swing an 18x10 over 8500 rpm on either stock or aftermarket exhaust.

There was another thrend in RCU covering this very topic. I also was having this problem. An easy fix suggested was to increase the fuel flow by using large I.D. fuel tubing for fuel draw to the carburator. This advice was taken and the problem went away. My engine is swinging an 18x8W APC propellor at 8100 rpms'. Fuel is 10% and the glow plug is a #8 O.S..

Was this with or without a pump or regulator setup?

This is without a pump or regulator installed. Read the RCU review on the GP Extra 300S and you will find the information I have related to.

Sport you might want to try a Perry pump, VP-30. It might fatten up your midrange on the OS 1.6FX. The Cline is a demand type, no pressure. The Perry actually pressurizes the carb. That might give you the midrange you need.

Even though there is not pressure on the carb there is high pressure on the regulator. I have my regulator installed between the high speed needle and carb as recommended by Bill Cline. My problem is with having too rich of a midrange which I am going to try to tune in this weekend. If this does not work I wil give the Perry VP-30 a try.

Well, I went ahead and took the advise and replaced the cline with the VP-30 pump that I happened to come by at Hobbytown USA. It also turns out my midrange was infact leaning out and not rich so I richened it up and it runs well now. The perry was a plug and play setup with no adjustment needed to the pump. I believe that people that have problems with this pump on the OS 1.60FX need to make sure that only 3 threads are visable on the pump hex screw. Thanks for the help with this long standing problem!!!

That rocks, glad to hear it.

For you guys using the Cline bear in mind where this gadget was originally used. The Cline is simply a component from a Walbro gasoline carb and as luck would have it is also one of THE most critical adjustments on a gasser. The adjustment is made by bending the lever to reduce or raise it's height, thus changing it's opening and closing characteristics in relation to engine fuel demand.

I have 2 1.60's and both have Clines, one ran great right off the bat and the other had the annoying richness in the midrange. Dissasembly of both Clines revealed that the lever on the rough running engine was set way too high and was allowing the Cline to open early and open much further which was slamming the engine with too much fuel in the midrange. This makes sense when you think about it because the low end is set by the low speed needle and the high end is set by the high end needle. The midrange has a point in the transition where the carb stops being metered by the low needle and the spray bar is in effect at wide open. If the Cline is flowing too much fuel at this point the engine goes rich and we get that annoying gurgle. You really don't notice it on the ground when slamming the carb from idle to full open because you transition through the range so fast the engine doesn't have the time to load up. The problem is that once you take off you don't throttle the engine that fast and we do most of our flying at around half throttle, right where the over rich condition occurs.

The solution I found was to try bending the lever down, slightly below the level of the plastic housing side of the Cline. Cline's instructions state that the lever should be level with the flat part of the housing it sits in but I found that it needs to be a bit lower. If you get it too low the regulator will not open at all so test it by scucking air through the regulator to be sure it's working before you put it back on the plane.

I was amazed at the difference in performance that just a snall bend in the lever would provide. Bending it down leans the total fuel flow and up richens it.

Oh and before anyone asks...

I run Morgan 5% fule, OS 8 plugs, Bisson BGX mufler and a MenzS 18 x 6 prop. My Cline is installed between the HS Needle and the carb, medium tubing and the Cline check valve.

i have had one since new. as far as the richness. get used to it. its the only way this engine runs . it runs best wide open. soon as you start backing off it will burble but wont quit. if you guys got this engine for 3d forget it. its more for pattern. i love the engine. i had one on a 160 greatplanes extra and it was very fast but not areobatic. it wont hover well with this engine. also you can not lean this engine to much. it will bite you on the ass quick. DEAD STICKS WILL ACCUR IF THIS ENGINE IS IS A NOTCH ON THE LEAN SIDE SO BE CAREFULL!!!!!! the best recomended set up for this engine is a 18/6 apc propeller.. os no.8 plug slimline pitts style muffler. is a little more expensive but worth it. and lastly 10% to 5% nitro. do not use 15%... and another thing dont crimp your exhoust stack on this muffler. thats ridiculous and does absulutly nothing. there are about 5 people in my club with this set up and no problem ever. remember keep it basic and simple and once you get it tuned leave it alone.... i hope this helps...... just my experience ...

I have never had a problem with either of my 160's. The biggest problem is people leaning the low end too much which leans the midrange. A clubmember had his on a 3d plane without a pump or regulator and no problems but replaced it with a four stroke for more low end grunt.

I was having a lot of dead sticks with the OS160 but have sincw solved most of the problem using only 5% nitro fuel with castor oil and keeping the engine to the rich side all in an effort to keep it runnig cooler. It still sounds gurgly in the midrange but does not quit.

I have a 1.60, with the stock muffler and upright installation in a 4*120 it ran perfect ( unbelievably perfect ). When installed on its side with a pitts style muffler it was rich in the mid range. I ended up using a remote servo controlled needle valve ( used a throttle curve function on my radio) and onboard glow to tame the problem ( but never made it perfect ). Eventually plugging one of the exhaust stacks to get it correct, but it hurt performance.

But as I understand, a sliding barrel carb is designed for a specific fuel pressure. If you change the muffler or any thing else the fuel pressure is no longer optimal. Hence requiring a pump and regulator set to the proper pressure to perform properly.

This is a common problem on Super Tigre engines, especially the big ones.

If this problem occurs, the idle needle valve can typically adjusted to get good mid range and throttle response from mid range to WOT. But, the idle will most likly be far to lean.

I have machine the slot in the barrel to change the low end mixture rich while keeping the mid range just right. Effectively I changed the carb to perform optimally with a different fuel pressure.

Search the ST threads for more info. Also search for "pe reivers" ( he is a 2-stroke expert ), he has documented modification I described ( it wasn't my idea ). check out his site: www.mvvs.nl

The carb modification will make the engine run well, but you need to have the resource to modify the slot. Some have done it with a dremel tool, I am a perfectionist so I set it up in the mill and machined it that way.

interesting reading...i think the most common diagnosis is 'rich in the midrange'...i agree...my 1.60fx used to load up and quit when i reduced throttle...by carefully adjusting the needles, 1/8 turn at a time, the problem disappeared...imho, the first thing is to realize that the poor midrange and throttle response from midrange is a rich condition...my gp ss starts on the first backflip, pulls like a horse, and taxi's back to the flight line every time...no pump, stock muffler, 17x10 apc, wildcat 15%nitro/18%syn...however, if you don't fly where i fly (sunny hawaii at sea level) your 1.60fx might not be as happy as mine...lol...ken