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Evolution 45GX will not draw fuel ???

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Old 08-10-2012, 05:26 PM
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Default Evolution 45GX will not draw fuel ???

I have an Evolution 45GX ( MVVS 45 IRS) that doesn't draw fuel. The original problem was that the engine would start up, rev up and then die. I sent the engine to Horizon to be diagnosed and they told me the problem was the ignition because I was using a C&H ignition at the time. The original ignition broke during a crash and I replaced it with the C&H unit. The engine worked fine with the C&H ignition for quite some time.

Under Horizon's service department advice I purchased a Vlach to ICU conversion Electronic ignition (for 2S LiPo) from Mr. Reivers. The ignition has proven not to be the problem since then I found out the engine is not drawing fuel. I replaced the carburetor diaphragm and the mesh filter, and that didn't fix the problem. I noticed that the there is hardly any pulse pressure coming from the crankcase and when I blew air into the pulse line air came out of the crankcase thru the carburetor. I removed the reed valve assembly and found out the reeds don't seat fully in contact with the reed housing so I suspect this may be the lack of pulse pressure.

I am ordering a new reed valve assembly from Horizon but I will like some feedback in regards this problem to make sure I am on the right track. Have anyone out there experience a similar problem? I don't want to keep throwing money at this engine in order to troubleshoot the problem. Any assistance will be greatly appreciated.
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Old 08-11-2012, 02:25 AM
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Default RE: Evolution 45GX will not draw fuel ???

Not fully seating is not a big deal as long as the reeds are not warped or damaged.
The seating can be restored though.
1) de-burr the screw holes
2) dress the reed cage on a flat 200 grit sandpaper board
3) assemble using very little torque to avoid warping the reeds. (tighten about 1/16th turn after touching)

If there is no crankcase compression, check the front seal for leaks. Also check cylinder foot gasket for leaks.
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Old 12-04-2012, 12:11 AM
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Default RE: Evolution 45GX will not draw fuel ???

what should fully seated reeds look like? I have exactly the same issue.
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Old 12-04-2012, 02:57 AM
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Default RE: Evolution 45GX will not draw fuel ???

They are flat against the cage seats. Just, or just barely touching. If proper cage dressing is done they should close well. (even without the dressing). Just fasten the reed screws lightly so the reeds do not warp.

@ airtech:
Does the engine have good compression? It's an old lady I suppose.

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Old 12-04-2012, 05:16 PM
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Default RE: Evolution 45GX will not draw fuel ???

Pe, you are a treasure. Mine are not seated, one is way off. I didnt know what I was looking for when I saw the reeds...... Back out to the shop to pull the engine off the plane....again.

Thank you again!

Donn
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Old 12-05-2012, 10:36 PM
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Default RE: Evolution 45GX will not draw fuel ???

Alright, now the frustration. Fixed the reeds, they are very nearly touching, like half a reed thickness or less. I then did a carb rebuild with new metering diaphragm and pump diaphragm as well, installed new pulse line and I am now drawing fuel. Choke on, flip, starts and goes 1/2 a second. Choke off, just above idle on throttle flip, run for 1/2, die flip, cough flip run for 1/2 a second die. over and over..... for 5 minutes. Tried re choking got 3/4 of a second run once then repeat of above. I am loving this[:'(]. New Ch ignition timed to 28 BTDC, strong spark on a new cm6. Good fuel with Stihl Ultra @ 40/1. Any advice would be appreciated.
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Old 12-06-2012, 08:58 AM
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Default RE: Evolution 45GX will not draw fuel ???

If after a choke start-choke-off-start the engine dies, then the idle needle is too lean. Also indicated by a long choke on run. A few pops is normal, any extended running beyond that raises questions about the low needle setting OR air hole dimension (in choke butterfly)
Be very sure there are no crankcase leaks, like reed housing gaskets, and cylinder base gaskets. The front crankshaft seal may be damaged.
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Old 01-29-2013, 09:11 PM
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Default RE: Evolution 45GX will not draw fuel ???

So just before I round file the engine I try another ignition and wham! I have a runner. Several great flights and now I have an another issue, I can turn the H needle out 4 or 5 turns and no change, from 1.5 turns out nothing occurs. I am spinning a 22x8 JXF at 6900 to 7000 But after 10 seconds or so I loose 200 rpm. The exhaust is a Proflow can and I get good transition but the idle is weird, after a run it will drop to 1700 then climb to 2200. My engine has a Walbro 613 on it, is that the correct carb for a first generation 45gx? My reed block is good, and fuel delivery is perfect. Any advice? Crank case leaks?
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Old 01-30-2013, 04:26 AM
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Default RE: Evolution 45GX will not draw fuel ???

Walbro 613 is not standard on the 45 engine. Open the idle needle more. The carb depends on sufficient fuel flow from the idle needle to get the WOT mixture right. Climbing to 2200 rpm after throttle down also points towards too lean idle settings.
Power loss is quite normal in a two stroke as it heats up, especially with restrained engine operation on a test stand, when the engine can get VERY hot quickly!

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Old 02-10-2013, 09:11 AM
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Default RE: Evolution 45GX will not draw fuel ???

Thank you Pe, I bought a WT76 and will report back.
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Old 02-10-2013, 02:13 PM
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Default RE: Evolution 45GX will not draw fuel ???

Since Walbro WT201 is the standard carb for the 45, I am very interested in your results. WT76 has a very good reputation in general. WT201 tends to have a lean top end too.
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