Author Topic: O.S. Max-s 35 wants to shut off? (Read 2714 times)

Jerry Reider · « **on:** March 18, 2009, 08:16:37 PM »

I have a Brodak 38 Special with an O.S. Max-s 35 on it. The plane flies great and I feel I could do anything with it but....the engine stumbles and misses at 12 o'clock on the 2nd loop of a lazy 8. It has shut off for me one time while doing an outside loop at the top of the loop. It also will stumble coming out of a tight inside loop at the 6 o'clock position. It is fine on large inside loops and if I make the 2nd loop of the 8 large it runs fine with no sign of a miss. It runs the same flying inverted as it does in level flight. It has plenty of power in any manuever, I have a light smoke trail and plenty of castor residue on the plane. I was running 10% nitro 25% oil 50% syn. 50% castor but have recently changed to 5%nitro 28% oil 26% castor 2% syn. It stumbles the same with either fuel. Today I changed from the 11x5 Zinger to a 10x5 to increase the RPM's; no change, still stumbles, same places. I'm using Zingers because they have less pull than my preferred Master Airscrews. The plane is too fast with a Master Airscrew. The O.S. has a .281" dia. venturi and the hole in the spray bar is set to the forward position at 5 o'clock to the vertical center line of the venturi. The C/L of the tank is 1/8" higher than the C/L of the engine. I had the tank mounted lower and raised it by 1/4". The fuel line that goes over top of the fuselage goes to a 90 deg. piece of brass tubing that faces the front of the plane. I only make one change at a time so I'll know what worked. So far nothing has made a difference. This looks like a fuel delivery problem to me but it's got me stumped on how to solve it. I'm considering going to a metal tank. Any ideas?

Dennis Adamisin · « **Reply #1 on:** March 18, 2009, 08:28:47 PM »

K&B Idle Bar Plug, long reach, with two washers.

2nd choice: Fox Idlebar (not the 2V type)

Use the 10% FUEL WITH 50-50 oil, better still try some 10% Omega (less Castor)

Robert Zambelli · « **Reply #2 on:** March 19, 2009, 05:24:41 AM »

What Dennis said should work. Try it first.

I have quite a bit of time on the Max 35, both profile and inverted mounting.

I have NEVER had acceptable results with a clunk tank. The last Max 35 I used was on a Banshee. It ran flawlessly with an old Perfect 4 ounce wedge tank, over/under venting (no uniflow).

Also, your venturi sounds a bit small. The best results I had were with the stock venturi, around .250 as I recall.

Bob Z.

Jerry Reider · « **Reply #3 on:** March 19, 2009, 06:23:12 AM »

Quote from: Dennis Adamisin on March 18, 2009, 08:28:47 PM

K&B Idle Bar Plug, long reach, with two washers.

2nd choice: Fox Idlebar (not the 2V type)

Use the 10% FUEL WITH 50-50 oil, better still try some 10% Omega (less Castor)

Thank you for your reply Dennis. I have a Fox R/C long w/ idle bar glow plug in it. What do you think of trying a Fireball Hot long? But it doesn't have an idle bar. Why 2 washers, to decrease the compression? I changed to the castor after reading Randy Smith's post titled "Fuel , GLO-plug and running tips" that is posted towards the beginning of this section. He stated that the older O.S.'s have smaller bearing surfaces and he felt they needed more castor oil. I had bought some of that because I have a few Fox 35's that I use. I can certainly go back to the 10% nitro 25% fuel if you think that will help solve my problem.

Jerry Reider · « **Reply #4 on:** March 19, 2009, 06:38:47 AM »

Quote from: Robert Zambelli on March 19, 2009, 05:24:41 AM

What Dennis said should work. Try it first.

I have quite a bit of time on the Max 35, both profile and inverted mounting.

I have NEVER had acceptable results with a clunk tank. The last Max 35 I used was on a Banshee. It ran flawlessly with an old Perfect 4 ounce wedge tank, over/under venting (no uniflow).

Also, your venturi sounds a bit small. The best results I had were with the stock venturi, around .250 as I recall.

Bob Z.

The venturi is the one it had on it when I got it. I was wondering if it was the right size. I'll check with my local hobby shop to see what he can get. I know the clunk is not hitting the back of the tank and I believe it's mounted correctly. I was considering going to a Brodak 4oz. wedge because I had some doubts about the clunk tank. As you stated I was looking at trying the tweaks first. Hopefully Dennis' advice will solve it.

Thanks,

Alan Hahn · « **Reply #5 on:** March 19, 2009, 03:35:45 PM »

I would check the internal pickup fuel tubing---where it slides over the brass tube. Look to see if there is a slit in the tubing. Possibly it is opening up in the outside part of loop, and then if the fuel level is low enough, pulling in air.

RandySmith · « **Reply #6 on:** March 19, 2009, 05:23:01 PM »

Quote from: Jerry Reider on March 18, 2009, 08:16:37 PM

I have a Brodak 38 Special with an O.S. Max-s 35 on it. The plane flies great and I feel I could do anything with it but....the engine stumbles and misses at 12 o'clock on the 2nd loop of a lazy 8. It has shut off for me one time while doing an outside loop at the top of the loop. It also will stumble coming out of a tight inside loop at the 6 o'clock position. It is fine on large inside loops and if I make the 2nd loop of the 8 large it runs fine with no sign of a miss. It runs the same flying inverted as it does in level flight. It has plenty of power in any manuever, I have a light smoke trail and plenty of castor residue on the plane. I was running 10% nitro 25% oil 50% syn. 50% castor but have recently changed to 5%nitro 28% oil 26% castor 2% syn. It stumbles the same with either fuel. Today I changed from the 11x5 Zinger to a 10x5 to increase the RPM's; no change, still stumbles, same places. I'm using Zingers because they have less pull than my preferred Master Airscrews. The plane is too fast with a Master Airscrew. The O.S. has a .200" dia. venturi and the hole in the spray bar is set to the forward position at 5 o'clock to the vertical center line of the venturi. The C/L of the tank is 1/8" higher than the C/L of the engine. I had the tank mounted lower and raised it by 1/4". The fuel line that goes over top of the fuselage goes to a 90 deg. piece of brass tubing that faces the front of the plane. I only make one change at a time so I'll know what worked. So far nothing has made a difference. This looks like a fuel delivery problem to me but it's got me stumped on how to solve it. I'm considering going to a metal tank. Any ideas?

Hi Jerry

The .200 venturie is Way too small, the engine came stock with a 301 venturie, although most people retro fitted a 280 or so. The very first thing you need do is get a proper sized intake. Then go thru all of the system (tank , filter, etc) and make sure it is all right. Then go from there
let us know how it goes

Rand

Jerry Reider · « **Reply #7 on:** March 19, 2009, 06:27:51 PM »

Oops, I read the calipers wrong. It's a .300 venturi. Sorry about that. I measured that during one of those late night sessions when things are getting blurry. I'll pull the fuel system apart and check for fuel line splits and the like. I didn't mention earlier but the clunk is about 1/4" from the back of the tank,so I'm sure it's not hanging up. Also, it pulls all the fuel out each run. It will be a couple days until I get to it I'm booked full for the next five days or so.

Dennis Adamisin · « **Reply #8 on:** March 19, 2009, 06:34:37 PM »

Quote from: Jerry Reider on March 19, 2009, 06:23:12 AM

Thank you for your reply Dennis. I have a Fox R/C long w/ idle bar glow plug in it. What do you think of trying a Fireball Hot long? But it doesn't have an idle bar. Why 2 washers, to decrease the compression? I changed to the castor after reading Randy Smith's post titled "Fuel , GLO-plug and running tips" that is posted towards the beginning of this section. He stated that the older O.S.'s have smaller bearing surfaces and he felt they needed more castor oil. I had bought some of that because I have a few Fox 35's that I use. I can certainly go back to the 10% nitro 25% fuel if you think that will help solve my problem.

OS's need a "tweener" length plug. The short reach is too short but a long reach is actually a little long. Long reach with two washers is pretty good - that was the combo I always used. Fireball HOT non-idler should work well too. I had some trouble with Fox plugs with consistancy and longevity - after maybe a dozen runs you could tell an RPM drop off when you pull the battery. K&B's seemed more consistant and tougher...

I never ran a OS brand plug in a S35 (!), but those plugs are the right length with a single washer, and they work well in a LA series.

I thought the .200 venturi was a typo, but Randy is RIGHT ON (again!) fix that first before anything else. If you are using the OS needle then go to something around a .260 -.280 throat before you do ANYTHING else!

Robert Zambelli · « **Reply #9 on:** March 20, 2009, 06:25:19 AM »

Right on - the venturi on my Max-S 35 is also .300. As an experiment, I tried a .280 and it did not work well.
Stock NVA by the way.
When I was running the engine in the 60s, believe it or not, the best plug was an OK Cub long reach.

Bob Z.

Don Curry AMA 267060 · « **Reply #10 on:** March 20, 2009, 09:31:27 AM »

Look at your tank vent. If you set it up with the vent tube inside the tank poited to the top of the tank like an r/c set up and no muffler pressure the vent will be pluged up while inverted. without muffler pressure you probably need a wedge type tank,

Don

Jerry Reider · « **Reply #11 on:** March 20, 2009, 09:56:42 AM »

Quote from: Don Curry AMA 267060 on March 20, 2009, 09:31:27 AM

Look at your tank vent. If you set it up with the vent tube inside the tank poited to the top of the tank like an r/c set up and no muffler pressure the vent will be pluged up while inverted. without muffler pressure you probably need a wedge type tank,

Don

That is the way I have it set up, with the vent tube bent to the top of the tank.

Jerry Reider · « **Reply #12 on:** March 20, 2009, 09:31:37 PM »

I had some time tonight so I removed the tank and went over the fuel system. I pressure tested all the lines and back flushed the filter. Everything looks good except the stopper was really crushed (see picture). I had bought a bunch of clunk tanks for 2 for a dollar or somethng like that last year at a flea market, this tank is a Sullivan S-4. Fortunately I just bought 3 new stoppers at the Lebanon R/C Flea Market for $1. Although I don't think it was affecting the way it ran I replaced the stopper anyhow. I'll decide from the suggestions you guys gave me which other stuff to try at the field on Sunday. Thanks guys, the replies are really appreciated.

Alan Hahn · « **Reply #13 on:** March 21, 2009, 09:07:39 AM »

Quote from: Jerry Reider on March 20, 2009, 09:56:42 AM

That is the way I have it set up, with the vent tube bent to the top of the tank.

Jerry,
If you position the vent to the outside of the tank rather than the top (referenced to the plane), it becomes a uniflow vent. If you do this, the position of the tip should be nominally a little higher than the center of the venturi to get even runs inverted and upright.

I do this all the time and it works great.

Jerry Reider · « **Reply #14 on:** March 21, 2009, 09:31:33 PM »

Quote from: Alan Hahn on March 21, 2009, 09:07:39 AM

Jerry,
If you position the vent to the outside of the tank rather than the top (referenced to the plane), it becomes a uniflow vent. If you do this, the position of the tip should be nominally a little higher than the center of the venturi to get even runs inverted and upright.

I do this all the time and it works great.

Sounds like a logical thing to do. My tank was vented as you stated, on the top. I changed it to what you said. This engine always ran great, I've never had an issue like this before with this engine, it almost has to be a tank issue. I'll try it out tomorrow. If by chance this didn't solve it I can try some of the other mods the other guys suggested. I can do any of them at the field. If I can't get it solved tomorrow I have a new wedge that's going on it when I get home.
Thanks Alan

Bill Adair · « **Reply #15 on:** March 22, 2009, 05:07:21 PM »

Jerry,

Isn't that black tank stopper made for gas, and diesel fuels?

Glow fuel tank stoppers are typically off white in color.

Those black rubber stoppers can harden, and flake in glow fuel. That may not be your problem, but I'd still replace it with the proper glow fuel stopper.

This is from a Sullivan tech note:

"Designed for High pressure, Racing, or Bladder type tanks.
It includes both Glow (white) and Gas/Diesel (black) stoppers
with 1/8" and 3/16" brass stoppers."

Bill

Balsa Butcher · « **Reply #16 on:** March 24, 2009, 02:26:27 PM »

I run my 35-S' w/ a .285 venturi, ST or Aero Products needle valves, Big Art Mufflers on pressure w/ 15%nitro, 25% castor, 3% synthetic fuel (from Mark Smith/Excaliber fuels), GRW 4 ounce uniflow tanks (from RSM), 10/6 props. Lotsa power, never miss a beat. Just throwing this out for reference as another way to make these engines work.

Jerry Reider · « **Reply #17 on:** March 24, 2009, 08:17:21 PM »

Quote from: Bill Adair on March 22, 2009, 05:07:21 PM

Jerry,

Isn't that black tank stopper made for gas, and diesel fuels?

Glow fuel tank stoppers are typically off white in color.

Those black rubber stoppers can harden, and flake in glow fuel. That may not be your problem, but I'd still replace it with the proper glow fuel stopper.

This is from a Sullivan tech note:

"Designed for High pressure, Racing, or Bladder type tanks.
It includes both Glow (white) and Gas/Diesel (black) stoppers
with 1/8" and 3/16" brass stoppers."

Bill

Thanks for the reply Bill. I double checked the package that the stopper came out of and it is for glow fuel. It's the Dubro brand, that may be the reason for the color difference. One of the three Dubro's that I bought is for gas and diesel and it is brown.

I replaced all the fuel line and bought Sullivan silicon tubing especially made for inside the tank and replaced that and put a new filter on it and a new Fireball Hot glowplug. I had the 38 in the air today and it still does the same thing!!
I have a Shoestring with the same engine, an old OS Max 35 but it has a 4 oz wedge metal fuel tank. Beleive it or not the Shoestring was doing the same thing, stumbling at the top of the 2nd loop of figure eights. The Shoestring has never done that before. This got me thinking dammit, is this contagious or something? Now I'm thinking that the problem may just simply be the cold weather. I'm going to hang the 38 up until I get a warmer day and see what happens then. I'll fly the Shoestring anyhow, it's met the asphalt a few times already and lived to tell about it. I really can't wait to max out this 38 Special though because it really seems like it will do anything. It's easy to fly, it flies smooth and I can do any stunts as well as or better than I can do them with my single wing stunters. It does everything so smoothly but at the same time it is very responsive. Here's a picture of the Shoestring. It's one of my ugliest planes. Seems to me my ugly planes live forever. This is actually a before picture, it's been landed upside down twice now. All it did was make a flat spot on the canopy and rudder and scuffed the Monokote on the one wingtip.

Steve Holt · « **Reply #18 on:** March 26, 2009, 06:45:10 PM »

Jerry,
I have been having a similar problem with one of my Max S 35's. It seems just like a "Fox Burp". I have not worked out a fix for this engine, I just replaced it with another which runs fine. I'm thinking about putting a plug in the bypass similar to the fix for Foxes but there is only so much time. The engine did run well upright, so I may just put it into a Barnstormer I'm building.

It was a really frustrating experience and the first time I have run into it on a Max S.
Steve

Bill Adair · « **Reply #19 on:** March 26, 2009, 07:51:50 PM »

Hi Jerry,

Sorry about the bad information that I gave you.

Didn't realize that Du-Bro used the opposite color scheme to identify their fuel plugs. I'm sure I've used their tanks before, but only remember using light colored stoppers. Learn something new every day on this forum.

Everyone has tried to help with your problem, and this idea seems like as good a guess as any to me.

Perhaps you are running your Max-S too close to peak power, so there is no room for leaner running in that extreme maneuver? You might try launching just a tad richer to see if that helps.

I have an almost new Max-S 35 converted from R/C, but have never run it. The fellow that made the venturi and installed an OS needle valve ran it on the bench when I picked it up, and it had a beautiful 4-2 break by pinching the fuel line. Picked it up cheap at a swap meet, and since I'm just getting back into control line, I haven't had a chance to use it. Perhaps I'll try it on my Skyray 35, if the McCoy Red Head 35 that came on the airplane seems marginal.

Best of luck with your problem solving,

Bill

Jerry Reider · « **Reply #20 on:** March 26, 2009, 08:41:02 PM »

Thanks Steve and Bill, it only took a minute to double check if it was the right plug. Good investment of time considering the elusive solution to this. Funny you should mention the "Fox burp" Bill, another club member brought that up as a possibility just yesterday. Yes I may be running it too close to peak power, I tend to run towards lean because I like them flying fast. A combination of too lean and the colder weather could be the whole problem. I built the 38 mid season last summer and it was fine when I was flying in the warmer weather. We have a mid 60's forcast for tomorrow so I'll try running the Shoestring a bit richer and see if it's better and if that works I'll see if it works on the 38.
Last time I was flying I accidently put a 9x6 on the Shoestring, I meant to put it on a 35 Enya that I'm breaking in on another plane. That Shoestring was so fast, I was having a ball with it. I got so carried away with getting the 2nd loop of the figure 8 close to the ground that I checked the rudder for scuff marks after I landed. I may leave the 9x6 on it. I like to fly faster than most guys in the club and therefore it seems like I crash more often and worse than anyone else. I just glue them back together, no big deal. I used up 2 Flite Streaks last year. I guess that's not too bad 'cause I always flew them on the edge.

Bill Adair · « **Reply #21 on:** March 26, 2009, 09:55:35 PM »

Jerry,

Pushing the envelope by flying as fast as you can, may be a good thing for sharpening your skills.

What counts is having fun, and it's all fun as far as I'm concerned. I'm content that I can fly at all, even if I do fall on my behind at the end of most of the half A flights I've made. The great guys that I fly with get a big kick out of my post flight antics, particularly the falling down part.

Can't hurt to richen up the mixture a click or two on your Max-S, and that will eliminate yet another idea, even if it doesn't help. Next you might try a different fuel, but only if you have been using the same fuel in both engines that are showing the problem. Cooler weather is supposed to require less nitro, so you might check that out.

Bill

Jerry Reider · « **Reply #22 on:** March 28, 2009, 09:55:18 PM »

We had warmer weather the last two days and the Shoestring is over it's "Fox burp". Must have been the cold weather. I have to swap the tank out though because I have a repaired tank on it and it starves on outside loops after about 2/3's of the fuel is run out. I pushed it through tight eights and high and low outside and inside loops and couldn't make it miss a beat on a full tank. I'll take the 38 up on the next warmer day and I'm thinking that will be fine too since they both have the OS Max-s 35's on them. Also, the Shoestring runs better on the 10% nitro 22% 50/50 castor/syn. than it does on the 5% nitro 28% 26/2 castor/syn.

Jerry Reider · « **Reply #23 on:** April 28, 2009, 07:40:20 PM »

Yep, that was it, the 35 O.S. Max-s's didn't like the cold weather. The 38 runs great in 70deg.+ weather too. Having a ball with it. Now I can see what I can wring out of this thing. I was afraid to push it because of the potential shut off situation. I wouldn't write off the changes I made from the advice you guys gave on this thread. I made some of the changes and I'd say it was all for the better. I also learned a bunch of possible cures for in the future. Thanks guys.

James C. Johnson · « **Reply #24 on:** April 29, 2009, 01:16:55 PM »

Quote

Also, the Shoestring runs better on the 10% nitro 22% 50/50 castor/syn. than it does on the 5% nitro 28% 26/2 castor/syn.

This engine likes 22-25% if you don't run it too lean.. The engine that likes 5/28 is the Enya... that is one engine that will run on anything.. no nitro to 20 % nitro.. Dukes Fuel and Super Fuel.. it ran great.. I have one Enya 35 that I flew in 1970-73 ..gallons through it.. I even ran it with a broken front intake lug.. fuel spilled every where but it ran great.. I didn't know better and didn't have any money ..

I remember flying RC in the winter and found that switching to more nitro really helped.. 15% and a little less oil. I was running the old OS 25s from the 1980s. Some of my small engines wouldn't even start by hand, I suspect the Castor was the problem , you can also make a cover that retards cooling out of a tin can, drill some 1/8th" holes in it so not to completely block all cooling, attach with a spring. This is a kin to covering the radiator with cardboard in sever winter conditions. .. when I was a kid, we would pour fuel on engine and light it on fire to warm them up.. I never owned a starter until about 2001.

The Max S 35 is one of my all time favorite engines.. I also switch to a thinner prop.. I use the Master Airscrew wood 10x6 and the TF 10x6 or 10x5 but another good prop is the Black plastic Master Airscrew 10x6 worked real well.. I sure wish I could switch props on the LA 46 the same way.. I love how the APCs run but I hate the look and they are a real bear to fit on a spinner..

The other issue I have had with this engine is burnt castor oil on the Head fins and cylinder.. running a new engine on half synthetic/half castor helps .. I stick with all castor on engines that have been run that way.. used ones from ebay can be a gamble... because of RC fuel..

Also if you have an early one (shiny case) with the black rubber exhaust plug don't leave it in the engine.. they get hard and deteriorate.. they are a mess to clean up once they do this..

I use a tongue muffler on one but am using the original Slipstream Muffler on my Dolphin .. a great little muffler but a bear take off and on in a hurry.. I also use a Dremel and "gut" the inside for less back pressure..I believe this engine runs better on a tube muffler than a tongue muffler. currently studying connecting rods .. a guy could sell 'em if they were made.. other than that, drilling the bottom crank bushing so more oil gets to the bushing it a good thing.. I only do it on new motors.. I am glad these engine are still plentiful ..

Jim

dennis lipsett · « **Reply #25 on:** April 29, 2009, 02:08:22 PM »

Quote from: James C. Johnson on April 29, 2009, 01:16:55 PM

This engine likes 22-25% if you don't run it too lean.. The engine that likes 5/28 is the Enya... that is one engine that will run on anything.. no nitro to 20 % nitro.. Dukes Fuel and Super Fuel.. it ran great.. I have one Enya 35 that I flew in 1970-73 ..gallons through it.. I even ran it with a broken front intake lug.. fuel spilled every where but it ran great.. I didn't know better and didn't have any money ..

I remember flying RC in the winter and found that switching to more nitro really helped.. 15% and a little less oil. I was running the old OS 25s from the 1980s. Some of my small engines wouldn't even start by hand, I suspect the Castor was the problem , you can also make a cover that retards cooling out of a tin can, drill some 1/8th" holes in it so not to completely block all cooling, attach with a spring. This is a kin to covering the radiator with cardboard in sever winter conditions. .. when I was a kid, we would pour fuel on engine and light it on fire to warm them up.. I never owned a starter until about 2001.

The Max S 35 is one of my all time favorite engines.. I also switch to a thinner prop.. I use the Master Airscrew wood 10x6 and the TF 10x6 or 10x5 but another good prop is the Black plastic Master Airscrew 10x6 worked real well.. I sure wish I could switch props on the LA 46 the same way.. I love how the APCs run but I hate the look and they are a real bear to fit on a spinner..

The other issue I have had with this engine is burnt castor oil on the Head fins and cylinder.. running a new engine on half synthetic/half castor helps .. I stick with all castor on engines that have been run that way.. used ones from ebay can be a gamble... because of RC fuel..

Also if you have an early one (shiny case) with the black rubber exhaust plug don't leave it in the engine.. they get hard and deteriorate.. they are a mess to clean up once they do this..

I use a tongue muffler on one but am using the original Slipstream Muffler on my Dolphin .. a great little muffler but a bear take off and on in a hurry.. I also use a Dremel and "gut" the inside for less back pressure..I believe this engine runs better on a tube muffler than a tongue muffler. currently studying connecting rods .. a guy could sell 'em if they were made.. other than that, drilling the bottom crank bushing so more oil gets to the bushing it a good thing.. I only do it on new motors.. I am glad these engine are still plentiful ..

Jim

Leonard Neumann had rods made fopr the OS max 35. They are bushed at both ends and cost $15.00 apiece. A worthwhile piece for your engine.
Dennis

Jim Pollock · « **Reply #26 on:** April 29, 2009, 09:27:56 PM »

Not much help now, but, back in the late 60's and early 70's I ran my OS .35S with a Champion Plug
it never missed a single beat until a plugged up fuel filter caused it to quit just before the top of the reverse wing over!

Jim Pollock

Jerry Reider · « **Reply #27 on:** November 20, 2009, 03:06:11 AM »

Problem solved. I switched to 10% nito 22% oil 50/50 mix and my Max-s's run great now. They don't miss a beat no matter what I do with them. In fact I just bought another one off Ebay. This is an R/C version. Looks like it has very little time on it and is well taken care of. Couldn't go wrong for $20.

Colin McRae · « **Reply #28 on:** **Yesterday** at 11:45:32 AM »

I'm glad I found this (very-very) old post concerning in-flight issues with an OS Max-s 35. I have my first one, a Max-s 30, (totally stock CL engine) on a SIG Banshee and am experiencing the same type of issues. Fox 35 burp type of issue when going inverted, and engine wants to quit on the second loop of an outside.

The original author said he went down to 22% oil on his engine and the in-flight problems went away. So, it sure does sound like the high oil content was the root cause.

I have been running 10% nitro and 28% total oil (50/50) on my Max-s 30 engine. The OS owner's manual for the Max-s 30 I found actually recommends 25% oil. I'll try the lower 25% oil and see how the engine does in the air.

Motorman · « **Reply #29 on:** **Yesterday** at 04:57:20 PM »

Oil content over 20-22% is just a tool you can use for more cooling. If your engine is flaming out I would not hesitate to go down to 20% oil and let some heat stay in. That being said, have you tried rasing your tank 1/8" above the center line of the engine?

MM