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NGH 38CC 4 stroke

Old 07-27-2016, 10:46 AM
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Thanks Guys got similar advice from here in the UK so will report back after a second set of engine runs.
Old 07-27-2016, 12:58 PM
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Out of the box mine had a vicious kick-back when starting, I had to retard the ignition by about half the available range. Now it's a peach to run and I've just order another from Just Engines, who are supplying them with a nice machined manifold adaptor, 90 degree knuckle and an ASP FS180 silencer. I've ordered the baffled version of the silencer for an extra 10. It will be going in my BlackHorse Macchi 200 to replace the Laser 160 V twin currently powering it.
Old 07-27-2016, 01:00 PM
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Out of the box mine had a vicious kick-back when starting, I had to retard the ignition by about half the available range. Now it's a peach to run and I've just order another from Just Engines, who are supplying them with a nice machined manifold adaptor, 90 degree knuckle and an ASP FS180 silencer. I've ordered the baffled version of the silencer for an extra 10. It will be going in my BlackHorse Macchi 200 to replace the Laser 160 V twin currently powering it.

BTW I found retarding the ignition seemed to reduce the vibration.

Bob
Old 07-29-2016, 07:50 AM
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Well second engine run did not go well.

First the silver solder on the exhaust started to melt at full chat and the down pipe came away so obviously this will now have to be brazed.

Secondly, despite richening both needles and advancing the ignition the engine is still miss firing and loosening the prop. Think I will now have to revert to measuring the timing to see what it is although establishing TDC may be an issue.

Certainly got confused which carb adjustment is the fast and which is the slow jet so with the engine inverted and looking into both screws I assumed the fast is the upper and the slow is the lower. Am I correct?
Old 07-29-2016, 08:38 AM
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Well the engine is out and now have the ability to properly inspect the carb. A lot has been written in the past regarding gaskets leaking. So what do I need to check for air-leaks.
Old 07-29-2016, 01:56 PM
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The easiest way to check for air-leaks is to spray starting gas/engine starter. where you think the leak may be when the engine is running. If the engine change rpm you have a leak.

I 'm not sure the English word for starting gas but it look like this.
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Old 07-30-2016, 07:53 AM
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Checked the timing today and I would say its set at 45deg BTDC. Would 40 deg be a better setting to get rid of the kick backs at starting?
Old 07-30-2016, 09:31 AM
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or try 35deg. The best is if you can adjust it when the engine is running. to get max on top without to much shaking on idle.
Old 07-31-2016, 11:46 AM
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"Certainly got confused which carb adjustment is the fast and which is the slow jet so with the engine inverted and looking into both screws I assumed the fast is the upper and the slow is the lower. Am I correct?"

Yeah, got a little confused myself after I ran the engine upright for a while, then fitted it inverted! Should be a small "H" and a small "L" imprinted on the casting adjacent to each adjustement screw. I would be really surprised if yours doesn't have that!!
Old 07-31-2016, 01:07 PM
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and on a walbro carb. the L-needle always is closest the intake manifold
Old 08-01-2016, 09:46 AM
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Thanks with the engine now out all was obvious regarding the H & L needles.

Note some owners fit gaskets to the teflon carb spacer. Is it possible to buy these, or are they hand cut from suitable paper?
Old 08-01-2016, 12:13 PM
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I couldn't find them to buy, they may exist somewhere but nowhere I looked. I just cut them from thin gasket paper.
Old 08-02-2016, 10:54 AM
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Working on the premise the engine fires on the opening edge of the hall sensor, I have again measured the timing and find it set at 45deg BTDC. This is as far as I can retard the engine. Is there any reason why the timing could be this far out? It would be possible to extend the slots in the hall sensor but this would only gain my a few degrees I suspect and really don’t see why the standard design sets the ignition to such a high value. Desire is to at least get the value down below 40 deg to avoid kick backs at start.
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Old 08-02-2016, 11:29 AM
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How are you determining top dead centre? I've not measured my NGHs but 45 sounds wrong - my first engine starts and runs just fine with the hall sensor at the end of the slot range - that's moving the pickup mount anti-clockwise on the crankcase looking from the front, ie moving it in the same direction the prop turns. Out of the box the mounting screws were in the centre of the slot and it kicked back a little, moved anti-clockwise - no kick back and less vibration. I didn't need to extend the slot.
Old 08-02-2016, 11:35 AM
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I am by no means an expert in timing these or any other engines, all I can do is reflect what I have experienced and what others have posted earlier in this thread.

1. Yes, you may have to file the slots further to get further retardation of the spark. I did, don't ask me what degrees I ended up with but the engine ran smoother albeit I dropped approx. 500 rpm off the top end .

2. If its that far out have you checked the valve drive cam? There have been posts on that, search the thread, but basically at TDC the dot on the cam drive should align with the web in the crankcase.

3. CH ignitions supplies a ignition unit for this engine which has been programmed to give more appropriate spark timing at different rpms. It appears the stock unit is not programmed/programmable and may be pre-set at a very advanced spark. Just search the thread.

Might be of some assistance, might not. Good luck!!
Old 08-02-2016, 03:23 PM
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Originally Posted by discus-fly
Working on the premise the engine fires on the opening edge of the hall sensor, I have again measured the timing and find it set at 45deg BTDC. This is as far as I can retard the engine. Is there any reason why the timing could be this far out? It would be possible to extend the slots in the hall sensor but this would only gain my a few degrees I suspect and really don’t see why the standard design sets the ignition to such a high value. Desire is to at least get the value down below 40 deg to avoid kick backs at start.
C&H Ignitions makes a module for this engine with 45* of retard built in. You can then set full advance @ 45* BTDC and have 0* for easier starts & better idle characteristics..
Old 08-02-2016, 03:48 PM
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Hi Discus-fly, i think you will find the ignition fires when the magnet leaves the senser, not when it comes up to it.
Check some of CH Ignition videos for more information.
Old 08-03-2016, 09:56 AM
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Thanks all for the advice. Timing was determined by position the prop vertical at TDC by looking at the cylinder head and then monitoring the output of the sensor using a detector. Angle between both being the angle in question as pictured in my post above. Going on the opening edge of the detector tone the timining was 45 deg. On the closing edge of the sensor this would be something in the region of 50deg BTDC.

Have ordered another sensor and now plan to butcher that one rather than the original to try and further retard the engine. Certainly will be cheaper than buying another ignition system.
Old 08-04-2016, 09:05 AM
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Wondering if an auto retard CDI would solve my problems. Has anyone tried these http://uk.agmhobby.com/list/gas-engi...m-c-16_44.html
Old 08-04-2016, 09:07 AM
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Wondering if an auto retard CDI would solve my problems. Has anyone tried these http://uk.agmhobby.com/item/rcexl-automatic-angle-cdi-ignition-for-dle55-gas-engine-p-236.html

Afraid cant get the link to work "
http://uk.agmhobby.com/item/rcexl-automatic-angle-cdi-ignition-for-dle55-gas-engine-p-236.html"

Last edited by discus-fly; 08-04-2016 at 09:12 AM.
Old 08-04-2016, 11:22 AM
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the ignition is an auto retard ignition. I think they use the same ignition on the ngh38cc as they use on 2-stroke engines. But a 4-stroke need a higer timing om higg rpm than a 2 stroke so thats why they set it to 45degrees and not 28degrees that are normal on 2 stroke. and the timing wil be to high on low rpm. if I shoud try another ignition i would try the ignition for os or saito 4-stroke engines.
Old 08-05-2016, 07:14 AM
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I favor a mechanical advance using linkage to couple the throttle to a advance on the prop hub. Set the timing at idle for smoothest running then set the total advance at top RPM for best Hi speed running. Ralph (Antique) had such a system. It worked great. The engine then has the right advance from low to hi RPM. I will post a photo of it when I get a chance. Best Regardrs, John
Old 08-05-2016, 02:29 PM
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Originally Posted by tyor
the ignition is an auto retard ignition. I think they use the same ignition on the ngh38cc as they use on 2-stroke engines. But a 4-stroke need a higer timing om higg rpm than a 2 stroke so thats why they set it to 45degrees and not 28degrees that are normal on 2 stroke. and the timing wil be to high on low rpm. if I shoud try another ignition i would try the ignition for os or saito 4-stroke engines.
Most 4-strokes do just fine with 28* of advance. For some reason, this engine wants 45* which is an outrageous amount of timing advance. Usually about 36* is all that a water cooled 4-stroke will tolerate W/O detonation on gasoline.. Air cooled even less.
Old 08-06-2016, 05:31 AM
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I checked the timing on a Saito fg14 engine today . and it is set to 40 degrees from the factory
Old 08-07-2016, 01:58 PM
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Well, whatever the factory timing is yesterday my second engine started first spin of the starter and ran it's first half tank on 20:1 with a Master Classic 18*6, no kick back on starting or audible knocking. Restarts were instant, again no kick-back. Second runs today were with 35:1 mix and a 20*8 HK wood prop, again good manners and easy starting. I had to richen the high speed needle about 1/4 turn and lean out the low speed a touch, it's still a bit lumpy at 1/4 throttle but spins up quickly and is happy holding full throttle. The only fly in the ointment is that the exhaust bolts have come loose twice despite being tightened both cold and hot, so I've reseated the manifold with engine grade silicon. I can't remember what I used on the first engine so I hope this fix works.

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