OS Max40 H questions

Hello I am in need of some info on my OS Max 40H engines.I have a .275 venturi with a .155" needle assembly, which shows to be on the lower side of the optimum range with the .155 needle assembly.It shows .275 to .291" roughly for venturis.I am running a tounge muffler and this is going in my brodak full fuse Oriental.My question is prop and fuel tank size.Is a 4oz tank enough for this motor?And I understand this motor is a torque motor not a rev motor?I hope to run it on a test stand on the weekend.I am thinking 11x5?This well be on Sig champion 10% with a extra 4oz of castor.Thanks For any Help.
Dennis

Dennis,

An 11-5 sounds pretty good. That's what Mike ran on his. His was on a large Silhavy Gypsy so I think it should yank an Oriental around fine. You probably should have a 4.5 ounce tank though!

LAST EDITED ON Jan-06-04 AT 09:36 PM (CDT)
 
>
>my brodak full fuse Oriental.My question is prop and fuel
>tank size.Is a 4oz tank enough for this motor?And I
>understand this motor is a torque motor not a rev motor?I
>hope to run it on a test stand on the weekend.I am thinking
>11x5?This well be on Sig champion 10% with a extra 4oz of

Based on my experience, Jim Pollock is right on the mark. I use 10% nitro fuel in my Max-H 40s. I have gone with both 22% 50-50 blend, and 25% all castor. Both seem to work fine. Best props seem to be the BY&O 11-5 and the Taipan 11-5. My engines like to run a steady, slow 2 cycle.

I would look at possibly shortening the nose 1/4" or so if you go with this setup. The Oriental has a relatively long nose, and was designed to balance out an unmuffled Fox 35. Dee Rice himself has mentioned that he shortened the noses of Orientals he built if a heavier engine warranted it. The stock Oriental can handle between a 5.5 and 6 oz tank, so shortening it a little will neither make it inelligable for classic competition nor will it leave you short on tank space.

My Max-H 40 engines run between 4.25 and 4.5 ounces for the pattern. Your mileage may vary, but a 5 oz tank would be prudent.

I hate to be bearer of possible bad tidings but I have a OS Max H40S ringed motor and was told by both Leonard and Tom Dixon that this motor was sold in two different types unfortunately I had the ring changed by Bowman rings and he told me I had a pylon liner and piston, this news also arrived the same time as Tom Dixon wrote a reply to me that this motor may not be suitable for stunt apparently the way to check externally is if the cylinder head is squared and not slightly domed at the fins then it would be a stunt motor but if it was as I just said slightly domed or convex then it would not make a good stunt motor, I am talking about the motor with round cylinder, if in doubt you could try e-mailing Leonard and checking with him, Tom Dixon doesn't use e-mail to reply but he was able to describe with a small drawing what he was talking about.
I do hope what you have is a stunt motor as I was given mine by the wife of a dear friend that drowned that I know bought it as a stunt motor.
Now I am talking about a 1970's OS MAX H40S not one of the new motors.

OK so you are saying the head should be flat at the bottom of the fins?The fins at there tips have a slight curve but the heads are flat under the fins.These are both new in box Max-H 40 R/C motors.I had heard that the ones with a circle around the 40 on the side of the case where good for stunt?I just sold a piston to Frank Bowman I guess I should have asked him about my motors?I also have a new piston liner assembly for them.I wonder which one it is.If I had it to do over I would just buy some new Stalkers or RO Jetts ect.Some times trying to do things to save a few dollars just costs more in the end.Well I hope I have the right ones.If not I can say I have one hot Oriental maybe!
Dennis

do a search for "os40h" in here and you will come up with a lot more information about these engines.

LAST EDITED ON Jan-07-04 AT 03:15 PM (CDT)
 
>OK so you are saying the head should be flat at the bottom
>of the fins?The fins at there tips have a slight curve but
>the heads are flat under the fins.These are both new in box
>Max-H 40 R/C motors.I had heard that the ones with a circle
>around the 40 on the side of the case where good for stunt?I
>just sold a piston to Frank Bowman I guess I should have

Dennis;

If the engine is a box stock Max-H 40 prior to any mods, then you should be all right. OS did make the Max-H 40P, which had the piston/sleeve/crank timed for pylon racing. There was also a Max-H 40RC, and a Max-H 40S for CL Stunt. The latter are fairly uncommon but are reported to be good stunt engines. I have never had the opportunity to run one, so I can't verify that with personal experience. I don't know if the Max-H 40RC is timed differently than the Max-H 40, either.

Bottom line is that based on my experience, you should be fine with the Max-H 40. For peace of mind, you might want to sent one to Frank Bowman to check the timing.

The only problem I have ever had with these engines is that OE ring life can really vary. Frank Bowman's rings fix that pretty well.

best thing I can suggest is e-mail Tom Dixon and see if he can put you right maybe ask if U can send one to him to check it out mine has "40S" stamped on the side but as I said Frank said it had the slightly smaller pylon pisto/liner in it. I was talking about the top of the fins being slightly domed, but dont take my word for it I was just passing on information I received from Tom Dixon and Leonard plus what Frank Bowman told me about the size of the piston liner being the size fitted in the pylon motor and I had sent the complete motor to him because I couldnt get the wrist pin out of the piston.

I did the search and from what I have read it appears I should have 2 good motors.Both my motors are the dual ball bearing models.I also got a new ring from Frank Bowman.Now all I have to do is fly enough to some day need it.O well maybe in april all the snow while be melted and I can get back at it with some new ships,motors and handles to learn!!
Thanks guys.Looks like I need to get a new tank on order!
Dennis