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OS MAX 35 FP Start problems

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Old 03-13-2018, 01:10 PM
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PMracer
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Red face OS MAX 35 FP Start problems

I have a "brand new old" OS Max 35 FP and it is a buster to get running. I don't have the manual so I have been all over the lot with the needle to no avail. There is every indication that it is not drawing fuel even when I cover the carb venturi & turn over by hand, can't see the air bubbles move. During this test I have had the needle anywhere from 1-1/2 to 6 turns out. If I blow in the vent tube on the tank I can fill the venturi with fuel so it appears as though it's open and clear. The best I can get with the Max is with needle out 4/5/6 turns, it will run for a while (drowning in oil) but 4 cycling, can not close needle to get a 2 cycle condition. Additionally it appears as though there is no control with the throttle.
Assumptions:
I have replaced it on the stand with and old faithful McCoy 35 Red Head which runs fine so therefore I am assuming that my tank, lines and fuel are in good order !! Fuel is VP 10% nitro, 18% castor and meth it is old but it is from a new sealed quart and just opened.

Any help appreciated, can't believe a simple little engine like this can be such a B%$#h !!
Thanx,
Bob B.
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Old 03-14-2018, 05:16 AM
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hsukaria
 
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Is the 35FP an airbleed carb? If it is, check that the idle air bypass screw is at least showing halfway into the airbleed hole. I would actually start with it closed all the way to get the best possible fuel draw. Then back it out as needed once the engine starts.
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Old 03-14-2018, 05:40 AM
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Thanx, YES it is. At this point I have tried so many combos that I don't rmember if I closed it off or not, but will try.
Again as I said I can't believe this is such a bugger to start.
Will respond later today.
Bob B.
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Old 03-14-2018, 06:15 AM
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Sounds like you have a couple of contradicting things going on . Not drawing fuel and runing to rich after it starts. It should run find at 1 1/2 turns out on the needle valve and be on the rich side. Here's a couple of things you could try once it is running. Pinch the fuel line off so no fuel is drawn to the engine once it is running. If it speeds up before it stops its probably getting to much fuel . Then i would take a close look at the needle valve. Maybe some crap in it. If it stops abruptly then I would look at the glow plug . Even if it's new could be bad or have some contamination. Good luck .
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Old 03-14-2018, 06:37 AM
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Thanx, I understand how you could draw this conclusion but believe me when I tell you it is so.
At 1-1/2 or 2 turns and covering the venturi there is no movement in the fuel line. Only if I get into the 4, 5, 6 turn range can I get any life out of it and then of course it is toooo fat !!
Needle valve is OK I blow air into it and it shuts down when closed and the starts to pass air again at about 1-1/2 to 2 turns. Will also change plug, just because, but I do remove it and apply power to it and I get a bright filament quickly.
I am aware of the pinch test and if it will run long enough I will try it.
I will post my results later today.
Thanx again,
Bob B.
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Old 03-14-2018, 07:05 AM
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OK. I assume you have run the vent line to the muffler for pressure. Try removing it . See if there is any change . Maybe some problem there.

Last edited by A. J. Clark; 03-14-2018 at 07:09 AM.
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Old 03-14-2018, 09:13 AM
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Originally Posted by A. J. Clark View Post
OK. I assume you have run the vent line to the muffler for pressure. Try removing it . See if there is any change . Maybe some problem there.
Good point!! The muffler pressure nipple could be clogged.
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Old 03-14-2018, 12:48 PM
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Todays SAGA !! UNCLE !!

First up, I initially stated that this is a BRAND NEW OLD engine and that is exactly what I mean, has not seen fuel prior to 3 days ago !!
I guess what I am saying is nothing is clogged up, just out of box.
Today I disassembled the needle valve from the engine and spray cleaned and blew out with air, nothing in there.
Changed the plug to a new one, nuttin.
Changed both the position as well as the tank, moved closer to engine and raised it so that now I have siphon feed, no help.
Three different types of plug igniters, nothing.
Air bleed from 1/2 turn up to and including 4 turns, nothing.
Needle valve from 1/2 to 4 turns nothing.
What it is doing: I blow air into the tank through the vent line to fill venturi and try to start, it fires and evidently it is only burning off what is in the crankcase. Plus the throttle up or down has no effect on it during this short run time and incidentally it does not rev up to actual operating speed either. I am familiar with the pinch test, but I don't think this is too effective unless you can get a decent RPM out of it.
Lastly, I have run both with and without muffler without any change.
Hard to believe that a simple engine like this can be such trouble. I must just be missing something but just don't know what it is. I'll try anything else anyone has to offer
Thanx to all and for everything,
Bob B.
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Old 03-14-2018, 04:07 PM
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Originally Posted by PMracer View Post
Todays SAGA !! UNCLE !!
Air bleed from 1/2 turn up to and including 4 turns, nothing.
.
I am assuming that you screwed the idle screw IN to increase fuel draw? Remember air bleed idle setting is backwards. I would try screwing the idle screw all the way in to see if fuel draw improves. That might help isolate the source of the problem better.
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Old 03-14-2018, 06:34 PM
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What i do when that occurs, is set the needle to about 3 turns, crank the starter with the igniter on, and put my finger over the back of the muffler for a second or so. This primes it, and fills the line until the backpressure in the muffler is enough to pressurise the tank like normal. The airbleed I normally leave in the middle of the hole. You can check with a pin in the hole and make it snug. This is normally about right, and only a turn one way or the other is correct. Airbleed carbs are kind of fickle anyway. Things will improve after a minute of running. Oh, and give it some throttle. The airbleed carbs don't normally start at idle.
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Old 03-15-2018, 05:10 AM
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Default MAX 35 start !!

Originally Posted by aspeed View Post
What i do when that occurs, is set the needle to about 3 turns, crank the starter with the igniter on, and put my finger over the back of the muffler for a second or so. This primes it, and fills the line until the backpressure in the muffler is enough to pressurise the tank like normal. The airbleed I normally leave in the middle of the hole. You can check with a pin in the hole and make it snug. This is normally about right, and only a turn one way or the other is correct. Airbleed carbs are kind of fickle anyway. Things will improve after a minute of running. Oh, and give it some throttle. The airbleed carbs don't normally start at idle.
Will try as written to a word and get back to you, Thanx !!

From HSUKARIA, Thanx I should have been a little more detailed on my part. I am aware of how bleed works and only mentioned 1/2 to 4 turn setting as a general statement of conditions during times I tried to start.

Once again, THANX to all.
If you don't hear from me again it just means I jumped off a bridge somewhere (sic).
Bob B.
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Old 03-15-2018, 09:09 AM
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Ok, going to desperation mode: I would check all the cylinder head and crankcase backplate bolts at this point. Also, the carb o-rings at the carb base and needle valve if it has one. Heck, you've checked everything else...
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Old 03-15-2018, 05:21 PM
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Originally Posted by hsukaria View Post
Ok, going to desperation mode: I would check all the cylinder head and crankcase backplate bolts at this point. Also, the carb o-rings at the carb base and needle valve if it has one. Heck, you've checked everything else...
BEYOND DESPERATION MODE !!
YES previously I did that too !! Had the back plate off to check condition of gasket and it was fine, had head off just to look around and reset it, then I removed carb to check "O-ring" and it to was good. I figured since it was an older piece that was some of the first things I did.

aspeed,
I did as promised and tried word for word your directions and I got it to run for at least an extended period. The thing I had not been doing was running it with the muffler. Now for the "BUT" I still can't get any RPM out of it. With everything as you stated it would start and even when I advanced the throttle there was only a very slight increase in RPM i'm guessing no more than 3 to 4000 (prop is a 10-6 should't be over propped for a 35) and when I tried to close the needle by reducing it 1/2 to 1 turn it would die. Also this is with out the igniter disconnected & the engine on its own.

I have an additional question on the fuel: the fuel is 3 years old but it has been stored in original sealed container 10% nitro 18% castor and balance meth. Although I ask about this I must state that 2 or 3 days ago I switched out the engine on the stand with an old 35 McCoy Red Head and it ran up just fine, so I have been assuming the fuel is good, what think you ???
Made some headway, but not enough to keep me from bugging you guys, but enough to keep me on the roof for now !! (HUMOR)
Thanx,
Bob B.

Last edited by PMracer; 03-15-2018 at 05:24 PM.
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Old 03-15-2018, 07:35 PM
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Originally Posted by PMracer View Post
BEYOND DESPERATION MODE !!
YES previously I did that too !! Had the back plate off to check condition of gasket and it was fine, had head off just to look around and reset it, then I removed carb to check "O-ring" and it to was good. I figured since it was an older piece that was some of the first things I did.

aspeed,
I did as promised and tried word for word your directions and I got it to run for at least an extended period. The thing I had not been doing was running it with the muffler. Now for the "BUT" I still can't get any RPM out of it. With everything as you stated it would start and even when I advanced the throttle there was only a very slight increase in RPM i'm guessing no more than 3 to 4000 (prop is a 10-6 should't be over propped for a 35) and when I tried to close the needle by reducing it 1/2 to 1 turn it would die. Also this is with out the igniter disconnected & the engine on its own.

I have an additional question on the fuel: the fuel is 3 years old but it has been stored in original sealed container 10% nitro 18% castor and balance meth. Although I ask about this I must state that 2 or 3 days ago I switched out the engine on the stand with an old 35 McCoy Red Head and it ran up just fine, so I have been assuming the fuel is good, what think you ???
Made some headway, but not enough to keep me from bugging you guys, but enough to keep me on the roof for now !! (HUMOR)
Thanx,
Bob B.
I had a fuel jug that sat in my basement for 11 years (and an engine). I was able to start the engine right away. As long as it was in a cool and relatively dry place with the red cap, it should be fine.
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Old 03-16-2018, 05:49 AM
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I have had fuel go bad in three years. The LA .25 would not even start. Other motors did. It may pick up after a while. I would only run it at full throttle with new fuel for a while till it is broken in, OS stuff is not usually really tight. Maybe get some new fuel and use that for the McCoy. A 10-6 is about right, maybe a little smaller for break in. Mine is set at 2 1/2 turns, I did not seem to have written any notes on it, but assume I have ran it.
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Old 03-19-2018, 12:48 PM
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The great mystery is over !!
This little OS 35 I have and as I have said is brand new old, I honestly don't remember where or how I got it but I did. That was a preface to my tale: 4 or 5 days back when I finally started to fool with it during one of it's slight runs I noticed fuel at the head case seam so I tightened it up and yes the bolts were loose. This was my bad because I know better having spent many years with automotive situations. I should have dis-assembled it right then and there for inspection but I didn't. Any rate long and short of it is I started having thoughts that this is too simple a device to have all the problems I went through and in particular with not drawing fuel and there were no other openings in the engine to loose vacuum. I then took the head off and discovered that this engine had been gremlinized, some idiot took it apart and did not put the liner back in in proper registration with the crank case ports. The net result was that I had both intake and exhaust ports open at the same time, consequently the engine could not develop a vacuum, this is much in the same as installing the cam in a 4 cycle engine a couple teeth off which screws up the valve timing.

Bottom line: it runs like a bear and is smooth as glass and will probably run for a long time.
Thanx again to all that offered up help and put this little tid bit away for future reference,
Bob B..
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Old 03-22-2018, 11:25 AM
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Good to know you found the problem and have it running . It's nice when a person comes back and tells what the solution was. Happy flying.
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