[]TEX[]

It ran well with the beech prop, but I broke it yesterday due to a stupid mistake. I put the evo prop back on had nothing but trouble the rest of the day. Bought a new beech prop today and will run it some more before I dig into the carb rebuild.

[]TEX[]

Still having problems so I tore apart the carb and cleaned it. Nothing out of the ordinary to be seen and all the parts look brand new, diaphragm was good too. Blew out all the orifices with carb cleaner and re assembled with the cowl off.

I also called HH tech support, they told me to send in the motor.*sigh*

karolh

I'm quite sure they will have your engine humming again in next to no time and remember to keep us updated on how it turns out.

Karol

Lifer

My Feedback: (1)

Tex,

You might just go ahead and send Horizon the motor and let them fix it. Their service is good and they have a fast turn-around. I have been pleased with them in the past.

Lower your stress levels!

arobatx

My money is on the inlet needle. Either there is debris holding it open, the tip is damaged and will not properly seat, the diaphragm is stiff, or the metering lever is out of adjustment. You should have no gas freely dripping from the carb at rest. Pending the prop load and tuning, you could have some 'spit' while running, but that is entirely different from what you explain.

karolh

I think that you are on the right track Chad as my guess is that there is an issue with the inlet needle seating. When I got my G20 the first attempts at starting it met with no success as the carb kept flooding the engine and had fuel dripping all over the place while at rest. Removing the needle and flushing/air blowing the seat area solved the problem.

Karol

[]TEX[]

GOOD NEWS!

Test ran today with flying colors! Ran idle at 2100 for 10 minutes without a burp. Full throttle brings 12k, up from 8k on a 16x6 Zinger on factory settings.

I am a happy camper now![sm=bananahead.gif]

Thank you very much for everyone's help!

AA5BY

Holy Smokes.... 12k on a G-20 sounds under propped unless perhaps your running a tuned pipe. The 16x6 Zinger yielded 12K?

[]TEX[]

As noted in a different forum, it is possible my tach was giving inaccurate readings. I will re tach when I get to the field.

AA5BY

Thanks for the reply

karolh

For a moment there you had me real envious as a 12k reading is unheard of for a G20 spinning any 16x6, as between 8,500-9,000 is more in it's ball park. What did you do to make the engine start singing again.

Karol

willig10

Tex:
Look. Here are some lessons learned in the last 3 weeks with my Zenoah. (i have the G26ei)

1. You need to be running a 17x6 prop. Or a little bigger prop than what you are currently running.

2. Dont fear the needles. Turn them in until they stop (not too tight) and readjust to factory settings then adjust them to what the engine is telling you it needs. This is not rocket science and if you adjust the H needle chances are you will have to adjust the L needle as well. Best is to adjust the top end for best RPM and with an APC 17x6 you should see around 9000 RPM. Then bring the throttle down to say 3/4 throttle and listen. If it bobbles adjust the low end needle until the bobble goes away. Repeat this procedure until the mid range and low end do not have any bobbles. Then go back to top end and adjust the RPM for Best RPM and then back off the High end needle about 200 to 300 RPM. FLy it in this configuration and see how she does in the air. According to temp and humidity once the engine is tuned correctly you should not have to adjust the carb again unless you have changed spark plugs or props. Think about how many times you adjust your needles on your weed eater.

3. Ensure you are running a 4 cell pack (4.8 to no more than 6 volts.) I can tell you right now this is more than likely where your problem is (the ignition box). Mine started to advance uncommanded and I could not get my engine to tune for nothing. I changed to a CH ignition and wahlah the engine runs great. The only way to check this that I know of is to send it to Horizon. The Zenoah ignition is not tolerant of overvoltage and even though it will let the engine run it will cause you fits. The better choice here is either the CH or RCEXL ignition if in doubt.

4. With the engine sitting for a little while I dont think the carb is in need of a rebuild. However the kit is very simple to install and takes all of about 10 minutes to do. Make sure the big screen is replaced and if it has the little screen covered with a brass plug leave that one in. Removea needle and blow carb cleaner through the needle port. Watch your eyes and wear safety glasses when doing this. Anyway I believe you will findthe ignition is your problem

Hope this helps.
Glenn

petevans

• Verified Ignition Timing set at 30° BTDC
• Checked carb inlet screen
• Checked carb fuel pump diaphragm and pulse port
• Confirmed clearance on float needle lever
• Set up exponential throttle in Tx to help linearize throttle response and using long throttle arm on carb
• Soldered nipple on Float Diaphragm Cover and ran tubing through firewall to inside of fuselage to ensure constant pressure to atmospheric side of diaphragm[/list]
  I recently found some Internet references hinting the problem might be caused by an air leak downstream of the carb, so I replaced the carb insulator/mount and both gaskets – no help.
  The last time I ran the engine, I noticed that I could actually see the prop and prop hub move a forward when I rev’d the engine.I let it cool down and found that I could move the crankshaft/prop hub several thousands with my hand and noticed some oil deposits on the engine case around the front bearing / seal area.I’d read that front seal leakage can cause my problem, so tore down the engine and found that the crankshaft shim (indicated in the Zenoah Manual Parts Listing) was missing.I measured the end-play with feeler gages and it came in at 0.030”.So, I’ve ordered the shim, crankcase gasket, and cylinder gasket from Horizon and plan to install them and re-test the engine.
  I also did a leak test by pressuring up the crankcase (see photos) and putting a small pool of motor oil on top of the front bearing/seal.There was significant leakage from between the bearing inner race and the crankshaft.Also, noticed that I could easily rotate the inner race around the crankshaft while it was installed in the case – maybe the heat of expansion (while engine is running) helps make the seal?
  So, finally my questions:
  I guess I could just put the whole thing in a box, mail it to Horizon, and get them to fix it, but I’d like to learn how to do these repairs on my own.
  I know this is long, but I’ve been troubleshooting for weeks now and I’m getting desperate for a solution.Any help would be greatly appreciated!
  Thanks,
  Pete

AA5BY

Pete... it seems to me that the fuel ratio has to be changing after the throttle is cut. It might be loading up after it comes back. I'd try leaning up the low end doing so until the idle shows the first hint of stumbling and then back just slightly. If at that point the spool up stumbles, then back out slightly more until the spool up is fine.

petevans

AA5BY,

Thanks for the quick reply. I've done quite a bit of tweeking on the carb screws, both at the field and in my driveway, over the last few weeks and haven't been able to tune out the hanging idle problem. Following Walbro's tuning guide, I can get engine to run very well -including coming down reliably to a very low idle (<2000 RPM);however, when I a make a flight and the plane lands, the engine willsound like it's dying out when I advance the throttle coming back tothe pits - it sounds like it's too lean. So, to cure that, I slightlyrichen the Low needle. I have to repeat this for 2 or 3 flights untilthe engine stops making the stalling sound after landing. Then, itruns well, except at this point the idle starts to "hang" for 30 secondsto2minutes before coming back to <2000 RPM. So far I've been making allmy flights with the cowling off, so I don't think overheating is an issue.

So, that finally led me to think that an air leak at the front bearing/seal was causing the "fast" idle after the engine was warm?

- Pete

w8ye

My Feedback: (16)

Your butterfly may be sticking in the carb

willig10

I think you are on the correct path as to an air leak, however I think it is carb related. Walboro carbs are very durable but the needle valve setting must be exact. Walboro sells a tool to set the needle valve correctly. If you have rekitted the carb with new diaphragms and you did not touch the needle valve it is more than likely ok. However if you replaced the needle valve it might be a tad out of adjustment.

I would check your throws from the servo to the carb and ensure that nothing is hanging up. Sometimes if you are using a golden rod the outer sheath tends to come unglued and move with the inner sheath causing throw problems. I always use golden rod with ball links on the servo and throttle linkage.

If the throttle stop is still attached to the engine remove it and use the radio for your mechanical stops.

Glenn