Glow Engines Discuss RC glow engines

OS Max 25 sf engine wont run

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Old 09-17-2017, 09:37 PM
  #1
mkjohnston
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Default OS Max 25 sf engine wont run

Hi I have an OS Max 25 sf rc engine that will not run. I purchased this engine in the mid 90's and broke it in. It ran well for the longest time and then about 10 years ago I crashed the airplane it was in at the time. I took the engine out and and took the carb off and cleaned it up and lubed it up with Marvel Mystery air tool oil and put it away. I recently got back into RC airplanes and put this engine back in an airplane. I had a problem with a pinched fuel line and I fixed it but the engine was hard to get running. I broke 4 spinners trying to start this engine to start with my electric starter and now I can not get it run at all. it pops like its going to run and yes i did change out the glow plug. I was thinking that the front bearing was bad as I found fuel all over the bottom of the crank case. Any suggestions would be helpful Thank You Michael
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Old 09-18-2017, 07:39 AM
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hsukaria
 
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You will very likely need to replace the bearings due to rust. However, that may not be the only reason it is not starting. Also, I would soak the engine with WD40 to free it up if you haven't done it yet. Check the o-ring at the base of the carb, it might have dried up and not sealing well. That would cause an airleak around the carb that would cause starting and running problems.
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Old 09-18-2017, 08:19 AM
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mkjohnston
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Hi husjarua, I am going to replace the O ring at the base and the needlevale gasket and go from there! Thank You Michael
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Old 09-18-2017, 12:58 PM
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GREG DOE
 
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Here's something worth trying. Sounds like it might still be loaded with Marvel oil. Pull the plug out, and spin the engine over with the starter. Hold a rag over the head to keep from blasting oil, and fuel everywhere. good luck.
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Old 09-20-2017, 10:20 AM
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mkjohnston
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Quote:
Originally Posted by GREG DOE View Post
Here's something worth trying. Sounds like it might still be loaded with Marvel oil. Pull the plug out, and spin the engine over with the starter. Hold a rag over the head to keep from blasting oil, and fuel everywhere. good luck.
Hi Greg the weird thing about this was that I broke 5 spinners trying to start it the other day and it was flooding real bad. I guess i need to play with the mixture screw which I have never really messed with that much. I think you turn it in until it stops then turn it out 2 turns is what some one told me the other day. I will give that a try and see what happens
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Old 09-25-2017, 06:07 PM
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mkjohnston
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Hi Ya all I think maybe I found the answer to my problem. It seems that I did have an issue with this engine not wanting to run about three weeks in my trainaire 20. well I had a pinch fuel line and i took care of that problem but in doing so I took the 25 out of the airplane and took of the back cover to see I could see the rear bearing and in low light I thought the bearing was rusty. well I put the cover back on and didn't tighten the 4 cap screw all the way as I found all 4 loose today and it makes sense why I had fuel all over the engine. I am going to put it back in the test and run it again and see what happens. BTW does anyone know which prop to run on these engines. I have ran 9x4's on it for years but I seem to have problems getting it to run right. The other day I had my brand new 25 AX in the stand and put a 9x5 on it and it ran so well and had such great power.Thanks to all that gave me suggestions out there. Long Live Nitro Powered Airplanes and cars! Michael Johnston
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Old 09-26-2017, 08:10 AM
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i use an 8-6 on a .25 so you are not far off with the 9-4 or 9-5. It depends what you fly with it.
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Old 10-03-2017, 08:53 AM
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mkjohnston
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Yesterday I put the 25 back in the stand and filled up my test tank. It took a while but I finally got it running right and it ran pretty good. I had to readjust the mixture screw and once I did that and it fired up and ran! I have an issue with my airplane that I had in and it seems that the fuel tank is too high and it drawls way too much fuel into the engine so I have to solve that issue today and see if I can get this running right!
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