...........................I have a Top Flite Tutor(C/L)airplane,with an almost new O.S. .35 FP C/L engine,propeller APC 10.5" X 4.5" and 5% (nitro)fuel,and I have a problem with this motor,it always runs steady,two strokes and never 4strokes like old Fox.I wonder how can I do,in order my O.S. runs 4 strokes flying horizontal,and 2 strokes flying vertical.
Thank you for your help.


Carlos

Only the old cross-flow, loop-scavenged engines can automatically shift into a classic 4-2-4 breaking stunt run. There is no good reason to screw up a perfectly good OS Max FP (which is Schneurle Ported) by cutting, grinding, and trying to turn it into something it is not.

Use either a 10-4, or an 11-4, depending on how heavy the plane is, and set for a "rich" two-stroke run. Be VERY sure to use a fuel with LOTS of oil, at least half of which is Castor. I use 25%, half and half Castor and Synthetic oils, with 10% Nitro in my FPs, and they run like a high quality brand of sewing machines, smooth and steady.

On a largish profile stunter, my 40 performed very well with an APC 11-4 prop. One of my 35s, while attached to a terribly overweight foam-wing "Slow Combat" model didn't like that brand 11-4, but was very happy running with a Taipan 10-4.

I have 15s, 20s, 25s, 35s and 40s from the OS Max FP line. I may have a 10 as well, which would be at least one of every size that they made, other than the 60.

Kiwi

.....................I really appreciate all your help.I´ll try to do your good advice.Right now I´m using some APC 10.5" X 4.5" propeller,I wonder if there is other better propeller I can use,for example some wood propeller or other nylon lighter propeller.


Thanks

Carlos

There is a 20 or 25% difference in pitch (depending which direction is the desired direction) between the 11-4 I have used and found worked well, versus the failed choice you have made.

K.

Once again, than you for your help.
I´ll change the APC propeller,and I´ll put 11" X 4".But there is another problem with the accurracy in setting the needdle valve,it´s very sensitive,and it´s quite difficult to set the engine running steady.I wonder if spray bar is installed in my engine in a proper way.I´d like to know if spray bar has to be installed with hole facing to specific side.


Thanks


Carlos

This is how you normally position the hole in the spraybar, twin + single hole types.....

I tend to agree with Kiwi. I know those engines like plenty of oil and more than anything I'd make sure I have good fuel with that 25% lube in it. I always set my needle valves with the hole staight down but i doubt that is your problem. You other option would be to do like I did and convert all your controline planes over to electric. That will end the bad engine runs permanantly.

Hi Carlos,

If you're really after a nice 4/2 run, have you considered replacing the FP with a Max-S 35? They're not hard to get hold of, and will reliably produce the sort of run you want. The mount pattern is slightly narrower, but this wouldn't be much of a problem.

Steve

Gluehand is correct as to how to set the hole in the spraybar. But, in fact, if you can't see it, it will be fine. The prop you are using should be OK. Castor oil in the fuel is necessary; 20- 25% total oil should be fine. I prefer a steady 2 cycle run to a 4-2-4.

Carlos,
If you are not getting the engine run with a 4-2-4 break that you are looking for, you need to call Tom Dixon. He reworks engines to give you the 4-2-4 break. His website is Tom Dixon model airplanes His phone is 770-592-3279, he will answer your questions about plug,fuel and props
Happy flying
LeRoy Polk

Several engine tuners have been known to put their talents to use making over these fine engines into something that they were never meant to be. Not saying Mr. Dixon's modifications are either bad or good, just totally unnecessary. There were several east European producers of engines that offered a natural classic 4-2-4 run, and I think that Tom used to import at least one of those to sell.

I've not heard much about those since the CL people interested in stunt competition mostly abandoned classic power systems.


Kiwi

That engine isn't going to give you a 4-2 break, as others have pointed out.
I run a 40 0n that prop and I'm thinking you might like a 10-5 or 4 for it.

Inconsistent engine runs are almost always one of 3 things.

First...is the tank in a good location with no leaks and is it tight?

Second....change glow plugs. When it won't stay the same...it's the plug.

Third.....Tom Dixon throws the OS needle assembly in the trash. The braze that holds the needle into it's body fails and you have a needle floatind around giving you contsant changes.

Could also be the venturi is too large. A quick fix/check is to block one side of the needle body with a piece of wood, or less restrictive, a piece of panty hose over the venturi opening. Secure with a rubber band or small tiewrap. If this works, either get a smaller venturi or make a restrictor out of aluminum tubing.

Norm

I always used a Fox 35 , OS Max 30 and 35 . I used the OS Max , Fox and Enya spray bars and needles and never had any issues . They all ran really great with the 4-2-4 stroke using 5-10% nitro and 25% castor .
The newer engines run totally different with less oil and using synthetic oil . Maybe I was lucky but I never had a problems and all my planes flew great ! I used a 10x6 on my 35's and a 9x6 on my 30 . I did build a twin engine profile using 2 Enya 19's with 9x6 props . Flew great too . Now back then I used SIG fuel for control line engines and just ran great ! Was 5% or 7% nitro with 25% caster oil . Wish they still made that fuel !!!!!

As the old country song says,"Just give it away!"