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Old Apr 04, 2012, 11:09 AM
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Originally Posted by DoctorX View Post
bizarre... all walbro carbs have a little fuel filtre if I were you I would install one for testing.

tha's not true, you have many supliers around the world even there where you get your engine.
http://www.himodel.com/engines/Rcexl..._90degree.html

The NGH carb is not a Walbro design. Yeah you are correct, I have seen the small filter on the Walbro pumper carbs before.

Interesting I missed that one as the one with the NGH engine parts is on backorder. Thanks for noticing it.
Actually everyone is seemingly out of stock or on backorder on the RCexl 1/4x32 CDI units. That usually means you wait forever if you need one too. The Saito version was the only one in stock at the moment that I saw but they priced it high though. It is good you noticed HiMark had some in a different area. I am sure they'll be out of stock in no time now.
I suppose if you can find the 1/4x32 plug cap assembly you could convert a regular CDI ignition over to the small spark plugs too. But I haven't seen anyone selling them yet. There it is I just saw HiMark sells them too.
Thanks Doctor_X good find.
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Old Apr 04, 2012, 01:10 PM
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The line from the "pump" is not under pressure. It's slightly below atmospheric. That is how the diaphragm regulated pump carb works. Pull the line to the carb and crank the engine over with your starter, no fuel will flow until some suction is present at that line.

There is reason to keep the line as short as possible. There is a pressure drop in that line when fuel is flowing. If this becomes too great you are loosing the regulation function designed into it.

Walbro uses fine taper needles in there rotary valve carbs and they work just like an RC carb, and they work great. It's the pump and regulator system that provides consistent performance.

I run my ignitions on single cell Lithium ion. ~3.7V.

You can buy an RCEXL from countless sources. when did they become scarce? Don't be fooled into thinking this engines needs a special timing curve, it does not.

Greg
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Old Apr 04, 2012, 02:49 PM
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When I was looking for a ignition module with a 1/4x32 spark plug cap, i couldn't find anyone that had one to sell. Everyone was seemingly on backorder or out of stock at the time. Maybe it has changed now. Doctor_X found one where I hadn't looked previously.

The other thought was to use a 1/4x32 plug cap kit and convert some other ignition module over to the small spark plugs. I had trouble finding the kit at the time, but I have one on order now.

Thanks for explaining why there is low pressure in the fuel line between the pump and the carb. Along with the engine heat being absorbed by the fuel pump behind the engine, the lower pressure zone would allow the gasoline to vaporize in the fuel pump and fuel line. Maybe engine vibration has some affect on it, but I don't know yet. I'll try some more test runs this weekend to try some things out on it.

When I let the the two fuel pumps I have hang loose behind and below the engine, the bubbles all go away. When I bolt them up behind the engine I get bubbles. One other thought is the actual fuel pump position and orientation might have a affect on it too. Maybe if the fuel pump is positioned just so, it helps create the gas bubbles. Probably not, but it was a thought.
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Old Apr 04, 2012, 03:28 PM
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Originally Posted by turk1 View Post
Hi guys, I did a quick measurement for ignition advance on my GT9 engine and I found 40+ degree ignition advance.
Can you check yours and any idea, can it be such a degree because engine gets 11000+ RPM s?(RCEXL recommends 28 deg. advance)
I'll have to measure mine and see what I have too. I was thinking about that earlier on whether the drive washer or thrust washer could slip a little when bolting on a propeller or not. I can see that when one determines they have the magnet set just right that they ought to scribe a mark on the thrust washer and crankcase to have a reference point for it in the future.

I am trying to remember what it took for spark advance years ago to go over 10,000 rpms. or even 20,000 rpms. Right now it doesn't seem unreasonable to wind up with a 40 degree spark advance. Way back in the days of the all out motorcycle road racing the Japanese had a number of motorcycles capable of going over 23,000 rpms on the racetrack. Back then even the diminutive 50cc road racing class motorcycles had little single cylinder engines turning eye popping RPMs too.

The CDI unit, retards or delays the spark advance at low RPMs and as the engine speed increases it the lets the spark timing advance along a preset curve programmed into it up until it reaches what the sensor is set for. So it may never get to 40 degrees as set. But my memory has failed me at the moment.

I am also curious if the RPM sensor connector would do anything useful if one hooked up a RPM sensor to the RCexl CDI unit or not. Plus what kind of a sensor setup would it use too?
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Old Apr 04, 2012, 04:31 PM
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Quote:
Originally Posted by earlwb View Post

I am also curious if the RPM sensor connector would do anything useful if one hooked up a RPM sensor to the RCexl CDI unit or not. Plus what kind of a sensor setup would it use too?
I think this one for direct use.
http://www3.towerhobbies.com/cgi-bin...?&I=LXZRM8&P=0
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Old Apr 04, 2012, 05:23 PM
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Respectfully noted ;)

Quote:
Originally Posted by earlwb View Post
I saw that, but I haven't tried it yet. I was mainly concerned with folks trying to plug things in directly and then killing their ignition module and discovering much to their dismay, that they couldn't buy another module to replace it.
Fully understand and I just hope people are a little more cautious. Not to mention read the instructions and if not understood ask here on the forums or at the field.
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Old Apr 04, 2012, 05:29 PM
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Thanks Turk1, I don't know why I thought it was a input instead of a output. My mistake in logic. My RCexl instructions are for older versions that don't have the extra RPM connector on them. Thanks.

Brace, I hope people do peruse this thread as my NGH engine did not come with instructions about the RCexl ignition module in it. The only instructions were about the engine itself.
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Old Apr 04, 2012, 05:31 PM
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Tachometer

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Originally Posted by turk1 View Post
Ordered one a couple of days ago, should arrive next week so will post.
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Old Apr 04, 2012, 06:39 PM
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Still small bubbles coming out when rev's increased, no problems when on idle or low constant. Just on the increasing rev's ?
Looks like I am going to have to visit the pump again.
Wonder if there is an exploded diagram of the pump available?
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Old Apr 04, 2012, 06:52 PM
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this is the genuine tachometer from RCEXL.

http://www.sdshobby.net/ignition-use...f19043bea6c1e8
http://www.redwingrc.com/accessories/minitach.htm
http://www.valleyviewrc.com/estore/r...chometer.html#
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Old Apr 04, 2012, 07:09 PM
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Looks to be the same as Towerhobbies?
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Old Apr 04, 2012, 08:46 PM
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Agape has generic Rcxel ignitions and plugs of all sizes. Check them out. They ship fast and the shipping costs are low. A. Culei has taken over the CH line and also can supply ignitions for any voltage. The TechAero IBEC works great and has opto-isolation. I run my ignition fron the gear channel on my Futaba and it is a nice "kill" switch/adjustment safety. Bob
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Old Apr 05, 2012, 12:49 AM
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Quote:
Originally Posted by brace View Post
Still small bubbles coming out when rev's increased, no problems when on idle or low constant. Just on the increasing rev's ?
Looks like I am going to have to visit the pump again.
Wonder if there is an exploded diagram of the pump available?
http://www.rcgroups.com/forums/showp...&postcount=121
Hope helps.
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Old Apr 05, 2012, 01:08 AM
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Originally Posted by earlwb View Post
I didn't see a fuel pump filter when I had taken apart one of the fuel pumps I have.
I wasn't using one in my engine bench tests.
if I remember right one of my 50cc engines has a little screen filter built into the pumper carb on it.
According to engine s manual,Maintenance of the engine:......
-There should be a- fuel screen in the pump and should be carefully cleaned.(Under the pump membrane).
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Old Apr 05, 2012, 02:49 AM
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Ran the motor for 15 minutes, up and down through the rev's, No bubbles! Did nothing to the pump since last time.
Motor is running smoother and now that I have almost a litre of fuel through it is a lot easier to start. Still using a starter motor and probably will until I am at a stage where I can lean it out a bit and the compression improves. Great how little fuel this motor uses, good reason for going with gas.
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