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Old 06-28-2019, 05:43 AM   #21
hk4fvj
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Re: Best Glow Plug OS AX 75: 7, 8, 10?


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Quote:
Originally Posted by David Ford View Post
HK4FVJ,
Did you solve your issue? Reading your comments it seems to me you may have other issues and not just the plug. I too live in your area and can run a medium or medium hot plug in any 2 stroke glow engine that size with your fuel without much or any change in the engine response.
Do you have some pictures of the installation? Is the engine cowled in? Are you running the mfg. recommended prop? Stock muffler?
What about the fuel lines and the tank are they in good shape and installed correctly.
You might consider getting the engine out of the plane and on to a test stand where you have a known tank/lines/prop etc and see how it performs.
I run engines in a test stand based on the recommendations of Dub Jett who makes engines, he is a wise man.

I hope it turns out ok
Hi David
Thank you for asking those questions. I have attached pictures that may answer most of them. In terms of the prop, I am using 14x7 which is in range. I have not added any gasket between muffler/ engine and I have been told that is not needed as this engine is very well built.
One thing that I noticed is that the tank cannot be placed as suggested by the OS AX 75 manual as per Escapade structural design. I have added a screenshot of the manual picture. (If this screenshot infringes any copyright or forum rule, feel free to remove it or ask me to do it)
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Old 06-29-2019, 06:55 AM   #22
David Ford
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Hi Al,
The pictures are a help to eliminate some running issues.
Clearly the engine is getting plenty of cooling.
The tank is low and I can see why based on the airframe but it should not cause issues if everything else is ok.
It appears you use a simple fuel line setup, fuel line direct to the carb, filling from line to the carb, I am a big fan of that. (KISS principle).
I see an exhaust extender on the muffler, they can cause issues, but not always.

If the plane was mine, I would do a few things to make sure everything was ok. Just the basics, but a good place to start.
Remove the cowl so you can see the fuel and pressure lines, check them for kinks and splits, especially where they go through the firewall,
Remove the exhaust extender, you can put it back on later.
Pressure test the tank
Set main needle rich per the manual.
Try running the engine in the airframe with all stuff removed. Please tether the plane.
When its running look for bubbles in the fuel line, foaming in the tank and fix anything you find. That type of tank can damage the fuel line in the tank,when putting in the stopper, it pressure tests fine but leaks air into the fuel when the fuel in the tank is lower.

I hope that helps, you may have done all these things, but maybe not.

Dave
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Old 06-30-2019, 10:05 AM   #23
hk4fvj
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Quote:
Originally Posted by David Ford View Post
Hi Al,
The pictures are a help to eliminate some running issues.
Clearly the engine is getting plenty of cooling.
The tank is low and I can see why based on the airframe but it should not cause issues if everything else is ok.
It appears you use a simple fuel line setup, fuel line direct to the carb, filling from line to the carb, I am a big fan of that. (KISS principle).
I see an exhaust extender on the muffler, they can cause issues, but not always.

If the plane was mine, I would do a few things to make sure everything was ok. Just the basics, but a good place to start.
Remove the cowl so you can see the fuel and pressure lines, check them for kinks and splits, especially where they go through the firewall,
Remove the exhaust extender, you can put it back on later.
Pressure test the tank
Set main needle rich per the manual.
Try running the engine in the airframe with all stuff removed. Please tether the plane.
When its running look for bubbles in the fuel line, foaming in the tank and fix anything you find. That type of tank can damage the fuel line in the tank,when putting in the stopper, it pressure tests fine but leaks air into the fuel when the fuel in the tank is lower.

I hope that helps, you may have done all these things, but maybe not.

Dave
Grat Note, Dave, thanks. I forgot to mention, the fuel tank is brand new as well as fuel lines. A couple of guys told me to replace it even though this plane/engine set is only three years old. I have not tested it yet, it has been too windy yesterday and today. I may go in the evening and will try all your tips. I will let you know how it goes.

BTW, someone else told me to remove the carburator and give it a good wash with alcohol. i will probably try it first.
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Old 06-30-2019, 11:06 AM   #24
David Ford
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Best of luck Al,
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Old 07-01-2019, 08:14 PM   #25
hk4fvj
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Quote:
Originally Posted by David Ford View Post
Best of luck Al,
Hi David
I did not fly it but played with everything. I was able to make it run from 2500 to 9000 RPM. It seems to be responding well if I push the throttle fast from 0 to max. I also left it idle for more than ten seconds then push it fast again and still is responding. It will though, cough and die if I leave it idle for a while (30 secs or more).

The engine is almost new. It has three years but does not have more than probably 15 flights including breaking-in. What I noticed is that it is producing a dark residue. I bought a new 15% fuel jar and this new one has both synthetic and castor oil. Is that an issue? I heard that castor oil produce a darker residue than synthetic. I was also told that new engines tend to produce darker residue until is fully broken in. This is second time I start the engine this year.

Last edited by hk4fvj; 07-01-2019 at 08:39 PM.
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Old 07-01-2019, 09:10 PM   #26
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Just curious, which plug did you go with?
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Old 07-01-2019, 10:49 PM   #27
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Unless yours are extremely short, black coming out the exhaust should be gone after 15 flights and is most likely metal wearing from inside the engine. It should not be present after the length of time it has on it unless something is unusual.

Might be worth it to pull the head and check the piston for erosion or signs of metal burning away. I had that on a Fox Eagle IV 60 until the new design head buttons were installed that tolerated higher nitro, (was running a pair to test on one of my planes).

Pitting on the piston top or combustion dome may be a sign of the following: Black exhaust can also come from bearings so may be a good idea to open the rear cover to have a boo. Once they start to go the degradation will be exponential, with microscopic bits growing larger as the wear accelerates and doing damage to other internals.

Castor has reportedly a higher flash point than synths, (making it a better, if messier lube component) and will produce a black hard residue when burnt, usually a sign of lean runs or inadequate cooling. Mixing castor and synth is fine and I buy my fuel that way.

From my own experience a small amount of burnt castor on the piston top or dome are fine. Externally it is just visually a bit annoying but should not affect performance. Cleaning is more difficult and I often find need to soak in hot glycol to remove.

If it dies on throttle up after 30 seconds you are likely also still a bit rich on the LS setting.

Having said all that, mixture can be more finicky and usually tend to require richer settings until break in is complete.
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Old 07-02-2019, 07:36 AM   #28
David Ford
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Hi Al,

It looks like you are getting ahead some, I agree with the comments about the new fuel, it should not be an issue.

The black residue in the exhaust needs some attention. It does suggest issues with the engine. The rpm range you are getting suggests the prop is a big load for the engine, OS suggests the practical rpm range is 2000 to 15000 so 9000 at full throttle seems low.
If you smear some of the black residue on your finger, are there any metal bits? If you remove the glow plug is it black too? Looking down the plug hole, is the piston top black?
These things being really dark brown or black suggest a hot engine, usually by being lean (Cougar noted this) too much load ( big prop) or a plugged exhaust.

Before you take the engine apart or have someone else do that, consider doing 2 more things, take the exhaust extender off the muffler and check to see that fuel flows freely through the carb. You can do the last one by taking a short piece of fuel tube, attach it to the carb and blow into it. At full throttle and an open needle valve ( say 5 turns open) it should feel like lots of air is getting through.
If the carb blows freely, reset the main needle to OS specs and open it 1 more turn. Start the engine like this and run it at full throttle. it should run really rich with a tell tail smoky exhaust, perhaps it will sound rough so lean it in slowly until it just smooths out but still has a smoky exhaust.
If there is still black exhaust residue, it's time to open the engine and look inside like Cougar says. If you don't feel comfortable doing that perhaps some one on the forum can suggest a good engine guy, or ask the retailer where you bought it to send it out for service.

Good luck.
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Old 07-03-2019, 06:24 AM   #29
hk4fvj
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

Quote:
Originally Posted by David Ford View Post
Hi Al,

It looks like you are getting ahead some, I agree with the comments about the new fuel, it should not be an issue.

The black residue in the exhaust needs some attention. It does suggest issues with the engine. The rpm range you are getting suggests the prop is a big load for the engine, OS suggests the practical rpm range is 2000 to 15000 so 9000 at full throttle seems low.
If you smear some of the black residue on your finger, are there any metal bits? If you remove the glow plug is it black too? Looking down the plug hole, is the piston top black?
These things being really dark brown or black suggest a hot engine, usually by being lean (Cougar noted this) too much load ( big prop) or a plugged exhaust.

Before you take the engine apart or have someone else do that, consider doing 2 more things, take the exhaust extender off the muffler and check to see that fuel flows freely through the carb. You can do the last one by taking a short piece of fuel tube, attach it to the carb and blow into it. At full throttle and an open needle valve ( say 5 turns open) it should feel like lots of air is getting through.
If the carb blows freely, reset the main needle to OS specs and open it 1 more turn. Start the engine like this and run it at full throttle. it should run really rich with a tell tail smoky exhaust, perhaps it will sound rough so lean it in slowly until it just smooths out but still has a smoky exhaust.
If there is still black exhaust residue, it's time to open the engine and look inside like Cougar says. If you don't feel comfortable doing that perhaps some one on the forum can suggest a good engine guy, or ask the retailer where you bought it to send it out for service.

Good luck.
Thanks Cougar, David for your reply. I forgot to mention, I used glow plug #8 and no muffler deflector. I have attached some pictures showing the residual oil on the plane body and the exhasut pipe.. Again, this was the second time that I started the engine this year.
I have attached also a couple of video clips
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Old 07-03-2019, 06:27 AM   #30
hk4fvj
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Re: Best Glow Plug OS AX 75: 7, 8, 10?

I tried to upload the video clips but was not allowed.
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