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Old Apr 21, 2012, 07:49 PM
Augernaut
Wookster's Avatar
United States, KS, Overland Park
Joined Jan 2010
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Here's a new one, need help getting an EVO to STOP running.

This is getting rediculous. Watched a guy at the flying field just about lose a finger to this stuff. Seems like all of us with Evo engines have the same problem. We can't get the motors to shut off. i've tried liquid gasket on the carb, but it seems its the carb barrel iself that is letting air past. is there anything I can do to get these little monsters to turn off? is there anyone out there who makes a quality carb to replace the OEM carb?
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Old Apr 21, 2012, 09:20 PM
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USA So. Cal.
Joined Sep 2010
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Strange. I have had 3 EVO's, 2 .46 and 1 .61 and never had a problem with the cuttoff on my DX7 stopping the engine. If the barrel is bypassing enough air to keep it running I guess a different carb is the only answer
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Old Apr 21, 2012, 10:08 PM
Augernaut
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United States, KS, Overland Park
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Originally Posted by Fokker DII View Post
Strange. I have had 3 EVO's, 2 .46 and 1 .61 and never had a problem with the cuttoff on my DX7 stopping the engine. If the barrel is bypassing enough air to keep it running I guess a different carb is the only answer
Thankfully its not every engine. my .52 has been a dream. the .60 needed some work to get right, but it is reluctant to stop. the .45 is super reliable and a fuel sipper. For me it's the big problem, when you hit the throttle kill it doesn't even slow down now.
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Old Apr 21, 2012, 10:40 PM
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Danville, GA
Joined Aug 2010
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Try putting your finger over the carb air inlet and see if that kills it. If not then obviously air is leaking most likely in the rubber "O" ring. If you put your finger over the carb and it stops, then servo and linkage might not be setup correctly. If servo and linkage is truly setup correct (so kill switch gets carb totally closed) and it's not the "O" ring then the barrel might be letting air pass.

Is your throttle servo travel adjusted correctly in the Tx ?? Most servos tend to travel more then the throttle arm can move.

OK so this post might have been stating the obvious.
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Old Apr 22, 2012, 01:28 AM
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United States, LA, New Orleans
Joined Sep 2011
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Some common locations to check when an air leak is suspected are the carb o-ring, idle stop screw, carb seat, front bearing, back plate, main needle seat, and the throttle barrel itself. As far as carbs go though, just measure the diameter of the venturi and the carb throat and find another that matches.
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Old Apr 22, 2012, 09:03 AM
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USA, TX, Grapevine
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Since they already mentioned the likely reasons why. Anyway, you can always toss a small towel the prop while the engine is idling to kill it. Many years ago, before we had computer radios, if a engine's carb didn't allow for you to use the TX throttle trim to kill the engine, people would drop a towel into the prop to kill the engine while it was idling.
But if it is the carb letting it suck air and you have checked the other air leak sources then maybe trying a different carb would work. Perry Carbs are easy to obtain and they make them in just about any size needed.
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Old Apr 22, 2012, 11:24 AM
Augernaut
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United States, KS, Overland Park
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started her up and put my finger over the carb. sure enough she died right away. looks like new carb it is.
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Old Apr 22, 2012, 07:54 PM
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Danville, GA
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Originally Posted by Wookster View Post
started her up and put my finger over the carb. sure enough she died right away. looks like new carb it is.
If you put your finger over the carb and she dies then there is nothing wrong with the carb (unless the barrel is just plain not right for the carb.)

Most likely the problem is in your linkage and the amount of servo travel on the throttle. Most servos over-travel the throttle so you need to hook your linkage one or two holes in on the servo and one hole in on carb.

When you press the kill button/switch the throttle barrel should close completely.

With the throttle in the down position and throttle trim 1/2 way your throttle should be open just a smidgen to allow idle. When you go to full throttle on the Tx the barrel should open all the way but no more. Check this very carefully I think you'll find the problem is in the linkage and a new carb won't solve that issue.
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Old Apr 22, 2012, 08:31 PM
Augernaut
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United States, KS, Overland Park
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Quote:
Originally Posted by ckreef View Post
If you put your finger over the carb and she dies then there is nothing wrong with the carb (unless the barrel is just plain not right for the carb.)

Most likely the problem is in your linkage and the amount of servo travel on the throttle. Most servos over-travel the throttle so you need to hook your linkage one or two holes in on the servo and one hole in on carb.

When you press the kill button/switch the throttle barrel should close completely.

With the throttle in the down position and throttle trim 1/2 way your throttle should be open just a smidgen to allow idle. When you go to full throttle on the Tx the barrel should open all the way but no more. Check this very carefully I think you'll find the problem is in the linkage and a new carb won't solve that issue.
i have played with that quite a bit. the servo on the throttle is pulling as hard as it can. at this point the thing is fast idling with the barrel closed, and hitting the kill moves the barrel, but does not change the rpm. something aint right.
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Old Apr 23, 2012, 06:41 PM
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United States, OR, Portland
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Try rotating the throttle stop screw on the top of the carb out 1/4 of a turn. I have had to do this on all my Evolution engines after they are broken in. I believe Evolution sets the throttle stop high so new owners can get their linkages setup right and not have an impossible to start engine. If that doesn't do it then loosen the carb retainer bolts - press down on the carb as hard as you can and re-tighten them. I have three Evolution engines and all of them run great.
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Old Apr 23, 2012, 09:03 PM
Augernaut
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United States, KS, Overland Park
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Originally Posted by SEMiller View Post
Try rotating the throttle stop screw on the top of the carb out 1/4 of a turn. I have had to do this on all my Evolution engines after they are broken in. I believe Evolution sets the throttle stop high so new owners can get their linkages setup right and not have an impossible to start engine. If that doesn't do it then loosen the carb retainer bolts - press down on the carb as hard as you can and re-tighten them. I have three Evolution engines and all of them run great.
had to do that at first too. I should probably add, this is not a new engine. it probably has 12 gallons of fuel through it. What im finding is that after it sits few a coupe days it stops fine, then after running a bit it won't stop. I think the castor oil is thick enough it stops the air leakage, but when you run it and it starts getting mixed with fuel it thins out and leaks air. I have a new carb on order. Hate spending $35 on a $90 engine.
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Old Apr 23, 2012, 09:39 PM
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United States, LA, New Orleans
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Originally Posted by Wookster View Post
had to do that at first too. I should probably add, this is not a new engine. it probably has 12 gallons of fuel through it. What im finding is that after it sits few a coupe days it stops fine, then after running a bit it won't stop. I think the castor oil is thick enough it stops the air leakage, but when you run it and it starts getting mixed with fuel it thins out and leaks air. I have a new carb on order. Hate spending $35 on a $90 engine.
this sounds to me like it is definitely an air leak as described previously. good bit of info here.
my next guess may be a far fetched one, but I did have ONE engine that did this. if you put your finger on the carb and the engine stops fine, it could be that the seal between the carb throat and the engine is faulty but just barely.. and barely to the point where the simple pressure of your finger pushing the carb down seals the leak. have you tried some rtv around the carb throat and or a new o ring? i'll be a monkeys uncle if thats not where your leak is.
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Old Apr 23, 2012, 11:55 PM
Augernaut
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United States, KS, Overland Park
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Originally Posted by GeetarJoe View Post
this sounds to me like it is definitely an air leak as described previously. good bit of info here.
my next guess may be a far fetched one, but I did have ONE engine that did this. if you put your finger on the carb and the engine stops fine, it could be that the seal between the carb throat and the engine is faulty but just barely.. and barely to the point where the simple pressure of your finger pushing the carb down seals the leak. have you tried some rtv around the carb throat and or a new o ring? i'll be a monkeys uncle if thats not where your leak is.
heh, carb is coated in RTV at this point. im not sure if this is a good indicator or not, but i can take the carb off, full close it, blow on the intake and air will pass through. I think the ol carb is just wore out. we will see. makes me wonder about my other engines. if over time the barrel wears and lets air pass then hopefully buying a barrel will fix the problem, but i beleive the barrel is steel, the housing is aluminum. so itmay be that i have to replace the housing itself. either way, kinda frustrating part to wear out.
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Old Apr 24, 2012, 07:06 AM
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United States, MD, Elkton
Joined Oct 2011
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I have a spray can of carb cleaner in my small engine repair shop .If I suspect an air leak I start the engine and,carefully avoiding the carb air intake,apply little 'puffs' of cleaner to various parts that might leak...(shaft seals,gaskets,intake adapters) and see if the rpms change...That pinpoints the leak every time..Give it a shot. pun intended.
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Old Apr 24, 2012, 05:40 PM
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Neenah, Wisconsin, United States
Joined Jun 2004
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I believe a OS 4B or 4BK carb will work. These carbs came off of the FSR series of engines and were very good carbs.

I have a EVO 52 in the junk box so I will check.
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