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NGH 38CC 4 stroke

Old 08-09-2016, 10:36 AM
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Well not entirely convinced I have put to bed my kick back issues. Procured a new sensor which I cut away some of the plastic away at the fixings and managed to get the timing back to around 35 deg BTDC. On my initial starts the prop again came lose on at least 3 occasions. So on the third occasion I got a far larger wrench out of the tool box to do both nuts up. Eventually after much finger flicking got the engine to run and found I need to richin considerably the high speed jet by at least 3 or 4 turns to get a clean running engine. Slow running screw needed a tadge of leaning, but at least it ran with smooth acceleration.
Old 08-13-2016, 01:54 PM
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Will this engine fit in a Hangar 9 J3 CUB without having to move the firewall back ? Manual shows 6 inches from firewall to front of prop hub.
Old 08-13-2016, 02:09 PM
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If you use the beam mount 6" is the least you can get but that is not entirely accurate because you still have the carb in the rear so the needle valves will not be accessible. So you will have to modify the installation and trim a little off of the mount to get at 6" so....6" is possible but not practical.
Old 08-14-2016, 12:27 AM
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Using the supplied drilled and tapped alloy mount it comes to around 172mm or 6 3/4" from bulkhead to prop driver, though I guess you could move the engine back on the mount a shade but it would still give around 165 mm, 6 1/2".
http://www.justengines.co.uk/acatalog/GF38.pdf shows the minimum as 162mm


Last edited by robc57; 08-14-2016 at 12:29 AM. Reason: linky
Old 08-14-2016, 12:37 AM
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Originally Posted by discus-fly
Well not entirely convinced I have put to bed my kick back issues. Procured a new sensor which I cut away some of the plastic away at the fixings and managed to get the timing back to around 35 deg BTDC. On my initial starts the prop again came lose on at least 3 occasions. So on the third occasion I got a far larger wrench out of the tool box to do both nuts up. Eventually after much finger flicking got the engine to run and found I need to richin considerably the high speed jet by at least 3 or 4 turns to get a clean running engine. Slow running screw needed a tadge of leaning, but at least it ran with smooth acceleration.
Where did you get the engine from, do you know whether it originated from HK or JE? 3 or 4 turns out on the high speed needle just seems way out to me, I've not got a lot of petrol experience but the 3 engines I have all run around 1 1/2 - 1 3/4 turns out. If your feed is free running and you can't spot any air leaks then I'd flush out the carb filter, if that doesn't help could you borrow another carb to try?
Old 08-14-2016, 06:08 AM
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Like I said 6" is possible with mount... use the first holes on the engine and mount on the last holes nearest the wall mount then drill two new holes. you will have to cut into your firewall a tad and bevel off a wee bit on the corner of the mount but sometimes you do what you got to do so..like I said not practical but dooable



from the angle in the pic its hard to see but I am exactly at 6"
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Last edited by AC2; 08-14-2016 at 06:17 AM.
Old 08-14-2016, 06:16 AM
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I will install two "guide tubes" to reach the needle valves and on lower left fwall mount I will drill another hole up about 1/2-3/4. I have a very tight window to mount my dummy radial so gotta do what u gotta do. I wanted this engine so I had to make it work.
Old 08-14-2016, 03:01 PM
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Originally Posted by AC2
I will install two "guide tubes" to reach the needle valves and on lower left fwall mount I will drill another hole up about 1/2-3/4. I have a very tight window to mount my dummy radial so gotta do what u gotta do. I wanted this engine so I had to make it work.
Lots of work but nice fit. What model plane is that?........I could do the same with the J3 Cub or maybe put in a new fire wall. Would have to cut away most of the original firewall and cut an access in the bottom front of fuselage to do so. Have done others the same way and really lots of work.
Or.....just go with the H9 Super Cub. Manual shows almost 6 and a half inches from firewall to prop hub and cowl can be moved forward a quarter inch if necessary.
Old 08-14-2016, 03:26 PM
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Originally Posted by Boboeing
Lots of work but nice fit. What model plane is that?........I could do the same with the J3 Cub or maybe put in a new fire wall. Would have to cut away most of the original firewall and cut an access in the bottom front of fuselage to do so. Have done others the same way and really lots of work.
Or.....just go with the H9 Super Cub. Manual shows almost 6 and a half inches from firewall to prop hub and cowl can be moved forward a quarter inch if necessary.
Bo,

Its a Kangke Howard DGA-12

http://airshowrc.com/howard_gda-12.html.

With this type of plane I had to go 4 stroke so its worth the extra effort but not really too much considering its an ARF in the first place. Most of the work is already done. Of course if it were built from a kit the engine would be easier by moving the firewall back

Last edited by AC2; 08-14-2016 at 08:11 PM.
Old 08-17-2016, 01:29 PM
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AC2

Nice project..... My NGH 38 cc is a recent purchase and has about a half hour of break in running time on it. With a Zoar 18-8 prop and the recommended 20:1 synthetic oil ratio for break in I'm getting 7300 max RPM , good transition and a reasonable idle at 2000 RPM. Starts by hand best when throttle is at high idle setting after it pops while being choked. Only 24 oz. of fuel through it so far and all should improve with more time on the engine. So far I have no complaints.
Old 08-18-2016, 10:35 AM
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Would anyone know the thread size of the crankshaft. Damaged the prop nut thread so need to run a die over it.
Old 08-18-2016, 01:19 PM
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Originally Posted by discus-fly
Would anyone know the thread size of the crankshaft. Damaged the prop nut thread so need to run a die over it.
3/8-24 thread
Old 08-19-2016, 05:52 AM
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Thanks, 3/8 UNF die now on order so I hope it solves the problem.
Old 08-20-2016, 02:43 AM
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Had very quick delivery in ~18hrs of a 3/8 24t UNF die which quickly resolved my sticking prop nut issue.
Old 09-18-2016, 07:42 AM
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Hello,

I have problem with my engine. It was running fine for about 5 liters of gas. But few days ago I went to airfield and started egine. It was running for about a minute and then stoped. I noticed there is no compression. After inspecting the engine at home I noticed broken intake manifold.
Exactly the same as another guy from Italy reported here http://www.flyinggiants.com/forums/s...d.php?t=186673. After further inspection of the engine I also noticed damage in the camshaft (again the same as it happened to that guy from Italy).

I replaced intake manifold, checked cam shaft setting, valve clearance, ignition, but just can`t start the engine. I never used electric started before and never had problems with starting the engine.

Compression is really low, maybe I should buy new cylinder and piston rings.
I`m out of ideas...

I used 3% Stihl HP ultra oil.
Old 09-20-2016, 07:11 AM
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ernestino......looks like mark in cam lobe was caused by a valve pushrod. If you had pre ignition while running or starting , prop back lash and exhaust thru carburator, then mark may have been caused by intake valve being held open when engine fired, causing push rod to slam against cam lobe. This pre ignition may be caused by timing too advanced.
You may be able to correct this by retarding timing, using higher octane gasoline, and making sure you have adequate valve clearance.
The lack of compression may be caused by valves not closing or seating. Check for weak or broken lifter springs or damaged valves before replacing piston or rings.
Old 09-20-2016, 07:52 AM
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Originally Posted by ernestino
Hello,

I have problem with my engine. It was running fine for about 5 liters of gas. But few days ago I went to airfield and started egine. It was running for about a minute and then stoped. I noticed there is no compression. After inspecting the engine at home I noticed broken intake manifold.
Exactly the same as another guy from Italy reported here http://www.flyinggiants.com/forums/s...d.php?t=186673. After further inspection of the engine I also noticed damage in the camshaft (again the same as it happened to that guy from Italy).

I replaced intake manifold, checked cam shaft setting, valve clearance, ignition, but just can`t start the engine. I never used electric started before and never had problems with starting the engine.

Compression is really low, maybe I should buy new cylinder and piston rings.
I`m out of ideas...

I used 3% Stihl HP ultra oil.
Originally Posted by Boboeing
ernestino......looks like mark in cam lobe was caused by a valve pushrod. If you had pre ignition while running or starting , prop back lash and exhaust thru carburator, then mark may have been caused by intake valve being held open when engine fired, causing push rod to slam against cam lobe. This pre ignition may be caused by timing too advanced.
You may be able to correct this by retarding timing, using higher octane gasoline, and making sure you have adequate valve clearance.
The lack of compression may be caused by valves not closing or seating. Check for weak or broken lifter springs or damaged valves before replacing piston or rings.
Looks like severely excessive valve lash to me. Possibly caused bu a stuck valve or broken valve spring.
Old 09-20-2016, 10:01 AM
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Boboeing,

What is the right direction of camshat marking when motor is at TDC - 6/12 o'clock?

Last edited by ernestino; 09-21-2016 at 12:45 PM.
Old 09-21-2016, 05:17 PM
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Originally Posted by ernestino
Boboeing,

What is the right direction of camshat marking when motor is at TDC - 6/12 o'clock?
Not sure...look for both valves to be closed at TDC on compression stroke. Turn crankshaft by hand and observe valves. If both not closed at TDC... reverse direction of the camshaft mark.
Old 09-22-2016, 12:19 AM
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She ain't exactly pretty
Ain't exactly small

Just thought I'd post a picture of my exhaust mod. A quick test with a cheap meter showed around 80dBa at 7M running a Fiala 19*8 at 7150rpm, and in the past that meter has shown 1-2dBa high compared to a calibrated unit. It's a JMB A30 can grafted on in place of the ASP FS180 unit I started with, the ASP was clocked at 83dBa and the same rpm.
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Old 09-25-2016, 12:23 PM
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Is it just me but are these things doggedly resistant to hand starting? I have almost a gallon of fuel through mine (20:1 Klotz gas burner synthetic oil) and it is starting to run pretty well and evenly on a Master Airscrew 18X8 but it refuses to hand start. No starter, no run.

D.H.
Old 09-25-2016, 04:09 PM
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Originally Posted by DaveHickey
Is it just me but are these things doggedly resistant to hand starting? I have almost a gallon of fuel through mine (20:1 Klotz gas burner synthetic oil) and it is starting to run pretty well and evenly on a Master Airscrew 18X8 but it refuses to hand start. No starter, no run.

D.H.
Try hand start as follows for cold start.....Ignition off... open throttle all the way and close choke. Flip until you see fuel in line just entering carburetor. Ignition on....flip until it pops. Reduce throttle to just slightly open ..(what would be about 3000 RPM if it were running) ...open choke and flip briskly.
If it starts and dies...just repeat as above except draw more fuel by giving it an extra flip or two after it pops with choke still closed.
Old 09-26-2016, 12:00 AM
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Mine has started as per BoBoeing's routine but it's just easier and safer with a starter. Once it flooded but then started first spin with the throttle wide open.
Old 09-26-2016, 10:13 AM
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It is a nice looking engine, but you see it here with a lot of replies. Too bad because most the data shows its not a real good engine to buy...maybe if one was too wait until all the bugs was worked out. That may be a heck of a long time. Its best to buy real proven engines. A lot less stress.........
Old 09-26-2016, 03:56 PM
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Originally Posted by captinjohn
It is a nice looking engine, but you see it here with a lot of replies. Too bad because most the data shows its not a real good engine to buy...maybe if one was too wait until all the bugs was worked out. That may be a heck of a long time. Its best to buy real proven engines. A lot less stress.........
Mine runs quite well out of the box with 25:1 Rd Line oil. Very little exhaust residue with the needles set just a tad on the rich side. Power output somewhere between a 30 and 35 cc two stroker. Hand starts easily. 7500 RPM with a Zoar 18-8 and smooth instantaneous transition. I ordered the engine July 2016. Seems as though earlier bugs have been addressed.

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