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YS 63S Surges Above Half Throttle

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Old 03-22-2018, 05:13 AM
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ben beyer
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Default YS 63S Surges Above Half Throttle

I have a YS 63S that I bought used a while back and it was running fine. Recently it only runs fine below half throttle. Once I get to half throttle the engine starts slowing down like it is running out of fuel and then speeds back up when I get to half throttle.

Any ideas of what could be wrong?

I thought maybe it was the fuel tank so I hooked it up to a Tettra and it's still doing it. There is pressure in the tank after running.

Fuel is Ritch's Brew 20/20.
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Old 03-22-2018, 06:15 AM
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Surging is normally associated with a lean condition. Are you running a fuel filter on the engine? If not you should be. Clean fuel is a necessity with YS's. Does the pressure in the tank hold for a good amount of time or does it go away in just a few minutes. Check the regulator diaphragm. If it is distorted, you might consider replacing it. Also check the plunger. In my experience a good cleaning usually fixes that problem. I have had to clean the regulator two or three times to have a satisfactory result. Flush the needle valve and fuel lines. While you are working on the engine it might be worthwhile to check the valve clearance for kicks and giggles. I like to use brake parts cleaner. It is convenient in the aerosol can and it evaporates fast so seems to be safe ,at least in my experience, on silicone parts. Some of the less expensive cleaners have a good portion of methanol in them. Just take a gander at the label.

Ken
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Old 03-22-2018, 10:25 AM
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Originally Posted by kenh3497 View Post
Surging is normally associated with a lean condition. Are you running a fuel filter on the engine? If not you should be. Clean fuel is a necessity with YS's. Does the pressure in the tank hold for a good amount of time or does it go away in just a few minutes. Check the regulator diaphragm. If it is distorted, you might consider replacing it. Also check the plunger. In my experience a good cleaning usually fixes that problem. I have had to clean the regulator two or three times to have a satisfactory result. Flush the needle valve and fuel lines. While you are working on the engine it might be worthwhile to check the valve clearance for kicks and giggles. I like to use brake parts cleaner. It is convenient in the aerosol can and it evaporates fast so seems to be safe ,at least in my experience, on silicone parts. Some of the less expensive cleaners have a good portion of methanol in them. Just take a gander at the label.

Ken
Thanks Ken. Any tips for cleaning the cleaning the regulator and needle valve?

I.E. put on a new piece of fuel tubing and put that on the end of the straw for the break cleaner or anything like that?

I have never had to do that so I'm just trying to make sure I do it correctly. I am comfortable disassembling and reassembling if need be though. Just want to make sure I disassemble properly though.
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Old 03-22-2018, 07:35 PM
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Originally Posted by ben beyer View Post
Thanks Ken. Any tips for cleaning the cleaning the regulator and needle valve?

I.E. put on a new piece of fuel tubing and put that on the end of the straw for the break cleaner or anything like that?

I have never had to do that so I'm just trying to make sure I do it correctly. I am comfortable disassembling and reassembling if need be though. Just want to make sure I disassemble properly though.
Fuel tubing will work or just spray the parts directly. I have direct experience with new fuel tubing having "chunks" of silicone inside it. Flush any tubing you are going to use for cleaning and also the tubing on the model. The break cleaner is ideal for this as it give a really good spray.

First have a very clean work area. I like to lay my parts on a clean lint free cloth. It keeps them from rolling around so much . The Micro Fiber cloths from Harbor Freight work good for me. Clean all your parts (regulator) and lay them out. Then when I am ready, I give plunger and stopper one last spray to make sure there is nothing on then and reassemble the regulator without laying down the plunger and stopper. The spring is next recleanded and then the adjuster screw. It's kind of tricky getting the stopper back on the plunger. Just take your time. There is not a good way to hold it as it is small and an awkward shape.

It is not a hard job to clean the regulator. Just a bit fussy as the parts are small and cleanliness is next to godliness. lol I hope this helps a bit. Post again if you need some more tips.

Ken
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Old 03-23-2018, 05:37 PM
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Ken, my apologies but I have a FZ63 and not a 63S.

I'm guessing the steps to try and fix are about the same though.
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Old 03-24-2018, 07:36 AM
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Originally Posted by ben beyer View Post
Ken, my apologies but I have a FZ63 and not a 63S.

I'm guessing the steps to try and fix are about the same though.
Yes. I "assumed" you had the FZ63. I also own the FZ63 so was speaking from that perspective so you should be good to go. I also have had to clean a regulator a couple, three times to get a satisfactory result. It doesn't take much to foul the works. I've also had a regulator fix itself but that is a rare occasion. lol

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Old 03-24-2018, 04:47 PM
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Ken is right about fuel filters. After I found a cat hair inside the spray bar on an engine that had been running for years I put fuel filters on all my planes. Yes my cat is a shop cat and wanders all over the shop when I am in it. Reclines on top of the tool box in the path of the overhead heater. I even use a fuel filter in on my fill line on the fuel bottle. When defuelling I have a short piece of tubing and another filter that filters from the tank to bottle then it comes off when I fuel the next time. This stops any contaminates getting from the tank to the front end of the bottle fill filter which would end up putting it right back inside the next tank. Clean fuel is a must for those small openings in the spray bars and such.

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Old 03-30-2018, 03:45 PM
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Would this be a suitable cleaner?
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Old 04-03-2018, 05:18 PM
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Yes that will just fine. The only silicone part will be the little stopper in the regulator. Shouldn't be an issue so spray away, let air dry and assemble. Sorry for not checking back quicker.


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Old 04-04-2018, 03:38 AM
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No worries!

Thanks for your help.

It might be a few weeks before I get around to working on this as I have a trip for work coming up but it I run in to problems, I'll post them here.
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Old 06-04-2018, 07:37 AM
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Still working on this issue. I cleaned the regulator with the Brake Cleaner and put in a new diaphragm. It is running a little bit better but still having the same issue. It looks like it is getting flooded now and the high speed needle doesn't seem to do anything. I disassembled the carb and couldn't find anything.

I checked all the fuel lines and no holes. I tried a different and new tank and I'm still having the same problem.

I asked about this on the D6 Pattern group too (lot of YS fans there too) and someone suggested the regulator plunger spring could be bad. Does this sound like a possibility?
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Old 06-06-2018, 05:51 PM
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Now I'm wondering if you may have an air leak. I always take the valve cover off and sand the sealing surface on a flat place and seal it on the head with a little RTV silicone gasket maker. I do the same for all the gasket surfaces EXCEPT the back plate as that gasket provides clearance for the crankshaft to rotary valve clearance. The backplate gasket is usually not problematic anyway. Also check all the O-rings for hardness, splits and tears. Especially so with the intake pipe rings.

I had a 53 that had a hole in the carb causing some issues. Post 26 &27. https://www.rcgroups.com/forums/show...g-issues/page2 Here is how i repaired that hole. Post # 70 https://www.rcgroups.com/forums/show...s-Thread/page5

Ken
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