The XLS .25 Combat Engine

Tell us what you do to get the best performance from your engines.

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lightning
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Re: The XLS .25 Combat Engine

Post by lightning »

Cemented the carb in place, fuel tubing on the needle and this thing still will not quit running!
Next to try is the remote needle so I can see if there is an air leak at the NV or not.
Otherwise, air has to be getting in around the barrel, and I have no cure for that!
It runs slow enough that the prop stops (without breaking) as it hits the ground but that's not what I'm used to!
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Re: The XLS .25 Combat Engine

Post by Blue Note »

Keep us posted. On some of my XLS15s, I can completely close off the carb barrel with my finger and the motor will still idle all day long. Hopefully, the remote needle conversion may help the issue...unless the problem is just relocated. Hopefully, it will be the solution, especially since most will run with the remote before competing.
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lightning
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Re: The XLS .25 Combat Engine

Post by lightning »

Blue Note wrote:Keep us posted. On some of my XLS15s, I can completely close off the carb barrel with my finger and the motor will still idle all day long. Hopefully, the remote needle conversion may help the issue...unless the problem is just relocated. Hopefully, it will be the solution, especially since most will run with the remote before competing.
Yes Chris, my 15s are the same way and I have tried the same remedies, including a remote conversion. They all do it, but some are worse than others. Some will eventually quit if I kill the engine about 30 seconds before I plan to land, others, as you say, will idle all day long!
It's not a huge problem and is more than offset by the benefits of the Magnums over LA15s, but I would like to figure out what causes it.
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Re: The XLS .25 Combat Engine

Post by Blue Note »

Might be worth letting Global know about the problem and see if Mike can have his crew identify the problem and a suitable solution. These issues should be known to the manufacture so they can be handled by them, where they should ultimately be addressed. I have found that often times they just don't really know about these things, such as the need for the 25 in combat and the RPM restrictions for the SSCs. In the future, I wonder if they will need to help us address RPM on the 25 XLS so we can be legal for Limited B and 2948. i guess time will tell. Thanks for the testing updates.
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Re: The XLS .25 Combat Engine

Post by Yankee Samurai »

Has anyone tried adjusting the low speed needle. Try adjusting it by turning it clockwise 1/4 turn at a time.
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Re: The XLS .25 Combat Engine

Post by lightning »

Yankee Samurai wrote:Has anyone tried adjusting the low speed needle. Try adjusting it by turning it clockwise 1/4 turn at a time.
Yes, have done that. It certainly makes sure then engine will not idle, so yes, it quits when shut down but this is not a satisfactory solution as it dies as soon as I pull the throttle back. ANY position of the idle screw that allows the engine to idle will also ensure that it will not stop either!
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Re: The XLS .25 Combat Engine

Post by gsjames »

Here is an "off the wall" possibility as to why it doesn't quit correctly. Does this engine have any "sub-piston induction"? If there is any space under the piston skirt when at TDC then there is the possibility that air is getting into the crankcase that way. We used to modify our CL combat engines to achieve sub-piston induction to increase the max power by getting more air into the case than was possible through the venturi. I rather doubt that this is the problem, but it's worth taking a look at.
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Don Holmes
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Re: The XLS .25 Combat Engine

Post by Don Holmes »

A new set of sealed front bearings could be a fix.. As some of magnums bearings bleed or leak air...
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Re: The XLS .25 Combat Engine

Post by lightning »

Don Holmes wrote:A new set of sealed front bearings could be a fix.. As some of magnums bearings bleed or leak air...
OK, that would allow air to bleed in, but where would the fuel come from if the air is not being drawn thru the carb somehow?
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Re: The XLS .25 Combat Engine

Post by lightning »

gsjames wrote:Here is an "off the wall" possibility as to why it doesn't quit correctly. Does this engine have any "sub-piston induction"? If there is any space under the piston skirt when at TDC then there is the possibility that air is getting into the crankcase that way. We used to modify our CL combat engines to achieve sub-piston induction to increase the max power by getting more air into the case than was possible through the venturi. I rather doubt that this is the problem, but it's worth taking a look at.
Hi Gary, if that was the problem, wouldn't ALL engines exhibit this issue? At the moment it seems to be hit and miss - some shut down just fine and others (like mine) don't.
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Re: The XLS .25 Combat Engine

Post by David Drowns »

Kieth, My thoughts were that it may be through the front bearing. Not likley but possable.

Meanwhile here is my new test bed I'm finishing up for my new engine.

Image

One of these days I need to keep one of these as strictly a sport plane.
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Don Holmes
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Re: The XLS .25 Combat Engine

Post by Don Holmes »

David Drowns wrote:Kieth, My thoughts were that it may be through the front bearing. Not likley but possable.

Meanwhile here is my new test bed I'm finishing up for my new engine.

Image

One of these days I need to keep one of these as strictly a sport plane.
Is that all Coroplast ? Sure looks GOOD!
Don Holmes RCCA #957
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David Drowns
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Re: The XLS .25 Combat Engine

Post by David Drowns »

Don Holmes wrote:
Is that all Coroplast ? Sure looks GOOD!
Sure is.
Image

We've uploaded free plans.

http://members.cox.net/pfcombat/index_files/Page548.htm

If you're so inclined. I can help if there's any problems. (eg. the 25 size difference being only the firewall placement. not uploaded yet.)
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Re: The XLS .25 Combat Engine

Post by gsjames »

lightning wrote:Hi Gary, if that was the problem, wouldn't ALL engines exhibit this issue? At the moment it seems to be hit and miss - some shut down just fine and others (like mine) don't.
Yeah, you're right. I'm just grasping at straws here.
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Re: The XLS .25 Combat Engine

Post by Don Holmes »

Alright, Someone write Global and get the answer.
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