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Old 04-04-2012, 02:51 PM   #1
Victor
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Question OS HZ-R Carb not regulating fuel pressure

Here's an interesting development. ...

For no apparent reason (hundreds of flights on it with no issues) my .91 HZ-R carb seems to have stopped regulating fuel pressure. It gets tooooo much fuel. During flight it will flood out, and as soon as you let off the throttle to land, it shuts off.

It pumps in so much fuel that it runs out of the carbs air intake onto the engine head. If I crank it up and disconnect the engine pressure hose then it will quickly settle out and idle normally. If I reconnect the engine pressure hose and fly it will gradually richer up over the course of a minute or so and run VERY rich and spill fuel out the carb air intake.

I know what your gonna say.... "Tune the engine needles". Well, That was the first thing I tried. Not to mention that no matter how rich you tune it, fuel should never spill out of the carb air intake.

From what I can tell the are only two things that involve engine air pressure, besides the engine itself, there is the check valve (replaced it with no success) and the carb regulator.

Starting to think I need a new carb, but they are expensive, and im trying to be cheap here.

Anyone got any ideas on this?
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Old 04-04-2012, 04:16 PM   #2
LAMAR COOLEY
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Default OS HZ-R Carb not regulating fuel pressure

Victor
" hundreds of flights on it with no issues ". Here's a possibility. The pump needs a rebuild.
It could be that the pump diaphragm is worn: (split or crack/worn out) allowing fuel to syphon into the carb. Since the engine is well below the tank, fuel will gravity feed into the carb. More so with a full tank. Just my two cents. But worth checking the pump.
I hope this is of some small help.
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Old 04-04-2012, 05:34 PM   #3
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I've had this exact issue.

The solution has been to disassemble your regulator, and blow through the inlet nipple. The plunger that restricts flow gets stuck open due to a piece of debris, and just let's fuel flow in.

This voids the warranty, but fixes the issue.
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Old 04-05-2012, 03:53 AM   #4
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It can even be as simple as fuel gunk on the tip of the fuel control needle preventing the needle from being able to shut off fuel flow - cleaning the tip of the fuel control needle inside the regulator will fix this
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Old 04-05-2012, 04:40 AM   #5
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If your diaphragm is okay , then the problem lies between the orifice bringing in the fuel and the poppet valve.
Something is not letting the valve close correctly...debris.
Take out the regulator,open it put a piece of fuel tubing in the inlet nipple and blow..
No air should go through until you press the demand lever with your finger.
When you let go the valve should close .
If the valve does not close...you have some debris jammed in the hole.
Don't forget to use a fuel filter from tank to carb.
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Old 04-05-2012, 04:54 PM   #6
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Thanks for the input and ideas. They sound like good ideas, I'll try that!!

Victor
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Old 04-06-2012, 11:07 PM   #7
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Thumbs up Problem Solved !

Ok, I got it solved! Problem was definitely in the regulator, but wasn't debris in the valve. It was the spring under the lever in the regulator. It was wearing, and not as stiff as it once was.

I figured this out when i blew through a piece of tubing connected to the input nipple (after taking the regulator apart and removing the membrane) and air still leaked through when the valve was supposed to be closed. It wasnt alot of air, but it was some. I dissambeled the valve, rmoved the spring and stretched it out just a little. I then reassembled the regulator, tested it out and Bam! Bobs my uncle!!!

The extra tension added to the valve because of the spring now pressing harder on the lever causes the valve to close more solidly. Problem solved!!!!!!

Thanks for the ideas and input!
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Old 05-17-2012, 07:51 PM   #8
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OK guys I need your help I got a OS.91HZR Speed 3-D motor that is doing the exact same thing as the first post on this thread. I already took the bladder spring and stretched it put it back together and it's still gushing fuel out the carb. I have also set the needles to factory settings some times it will start. But soon as I give it any throttle it wants to die It floods out and then it's vapor locked. I can't even turn it over with a car battery and a high torque starter. I have to remove my fuel line inlet take out the glow plug then turn it over with the starter until it blows all that extra fuel out. Then I put my plug back in and it will fire right up idle is rough run out to set it down try to spool up slowly and blah it floods out and dies. Pick it up tilt it forward gas comes pouring out the carb. Repeated this at least 20 times before the bladder spring stretch and 3 times after. Same result every time? What else can I do? Take the carb off and send it in or buy a new one? Either way guy's I'm stumped BTW I ran two tanks through it day before yesterday and it was a mean SOB today POS I don't get it? Please help me? And this motor has under 2 gallons through it. WTH?
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Old 05-17-2012, 08:23 PM   #9
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Please read my post above before answering this question! My question is I got the motor out the carb off the fan hub off and with the fan hub off I can grab the crankshaft and move it in and out at least a mm or two is this normal for this motor? Edit: OK got the motor apart and the rear bearing is rusted+I found a piece if the bottom right corner of the piston has broken off. Could this be the cause of the fuel gushing out of the carb? I plan on replacing the piston,rear bearing,and possibly con-rod? Any ideas? I know before I got it this motor sat for at least 6 months this sucks man! Edit: Ordered new Piston,Con rod,Front and rear bearing cost $126.00 shipped this better fix this problem or I'm gonna throw this motor threw the window of the OS head quarters and bean some one in the head LMAO! J/K
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Old 05-22-2012, 07:23 PM   #10
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Update: All new front and rear bearing, con rod and piston. Took it out to fire it up it started. (I actually had some hope) As I was heading out to set er down it died. Tried to start it again vapor locked. Tilted it foward and fuel came pouring out of the carb again I'm done with it sending it in to be warrentied by Hobby Co. Waiting to hear from them we will see how it goes?
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Old 05-22-2012, 09:36 PM   #11
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Quote:
Originally Posted by weaselbean View Post
My question is I got the motor out the carb off the fan hub off and with the fan hub off I can grab the crankshaft and move it in and out at least a mm or two is this normal for this motor?
The fan hub and the crank nut locate the crank
Without these there is lateral movement
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Old 05-22-2012, 11:33 PM   #12
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Yes Jafa, the first time I tore it down the nut was loose! After the rebuild I did locktight it and of course used the washer under the fan hub then it was tight and the motor turned over nice and smooth but it still didn't fix the fuel problem with the carb? So it's on it's way to IL Hobbico. Hopefully they can shed some light on the problem.
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Old 06-02-2012, 04:58 PM   #13
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The motor is on it's way back from Hobby Co. I don't know if they are sending me a new one or if they just fixed the old one? All I can tell you for sure is the work order say's that I have to rebreak in the motor. And BTW all the lobor and shipping fee's they said they were gonna charge me were waived! So? I'm wondering...........hummmmm? I will let you guy's know when it get back!
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Old 06-04-2012, 08:11 PM   #14
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News Flash......I got my old motor back today that's right! I said my old motor they replaced the fuel regulator and at no cost to me! GREAT JOB HOBBY CO.!!! Took it out it fired right up and runs like a raped ape!!!! So it's good to have rotor wings back underneath my thumbs So I say to any one having fuel gushing out your carburetor? And you already did the spring stretch in side the regulator! Sorry to say but your fuel regulator is more than likely bad! This is the weasel see you guy's in the air!!
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