Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
The Regular Stuff: Chat, Buy, Sell, Off Topic, etc. => General Discussion - Scale Model Gas Engines - Hit & Miss - Throttle Governed - Non-Compression – etc => Topic started by: eec1910 on July 23, 2020, 09:59:12 am
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Hello all,
My new M92 engine arrived this morning put batteries and fuel in ,oiled it then in great anticipation
turned the flywheel and nothing.No spark so tried fresh batteries still nothing put voltmeter on and
only 1.4 volts on new batteries can anyone tell me why they are losing strength in 5 minutes ?.
Here's hoping
Trevor.
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Hi Trevor,
I suppose it could be a short somewhere? Did you check each individual battery? I have seen those battery holders make a bad connection sometimes...
Just guessing
Ade
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Hi Ade,
Checked all 3 batteries ,all the same at 1.4 volts after 5 mins
Cheers Trevor
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Hi Trevor,
Nothing worse than getting something new and it is faulty :'(
So the combined voltage at the battery holder plug should be 4.2 volts offload, and when plugged into the ignition and turned on i would guess you would be looking at 3.8 volts? If the voltage is lower check the obvious like reversed connector etc. also check the power on the other side of the switch in case the switch is duff.
Maybe the batteries are not so good, but 1.4 volts is not far off the mark, it is the on load voltage that counts, anything over 3 volts should be fine.
How about the hall effect sensor, no pinched wires? disk on the right way around (air gap not too big).
Banggood sell replacement ignitions for about £35 but i guess if all looks ok it should go back under warrentee.
Ade
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Silly question but... I have read that the on and off switch can be installed in either direction have you checked the switch with a voltmeter? Also have you examined the spark plug lead wire?
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- I would suggest brand new batteries. New AA batteries are not at 1.4v.
- They are typically 1.6v or a hair more.
- Also, check the spark plug lead and make certain it has some wire exposed in the plug boot and that it is pushed in far enough.
- Then take the plug out, put the boot back on and hold it up to a head bolt turn it on and spin it over.
- You should see a nice blue arc from the plug electrode.
- Also use this time to check that it is firing at top dead center on the compression stroke. If it isn't, fix that now.
- There really isn't that much that can go wrong. Of course also make certain the batteries are in the correct position.
- I think you might also unplug the battery holder and test the voltage at the plug. You should be starting there with around 4.8v.
If it remains bad, ask Jin for a refund or replacement. He is good about standing behind his products.
Please let us know.
Gil
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Thanks for the suggestions,i've tried them all but still no spark.
Have pm'd Jin and he's going to send some ignition accessories over so hopefully
that should sort it out, will let you know when i get them.
Thanks again,
Trevor.
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Well the new ignition parts arrived and were fitted ,thanks Jin , the engine ran but very fast, all the timings have been
re-checked and seem ok, came to start the engine a couple of days ago and the compression has gone, taken the
head off to see if valves were sticking but there ok so any ideas as to what my problem is now would be appreciated.
When turning the flywheels i noticed that air is being blown out of the carb does this suggest anything ?.
Thanks Trevor.
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Hi Trevor,
Glad you got the ignition parts.
As it is an atmosperic inlet then it has to be poor seating, probably a speck or swarf or dirt.
You can check the valves with the head off buy pouring some petrol or rubbing alcohol into the port and if it leaks past the valve then it needs attention.
Hope this helps
Ade
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Hi Trevor,
Glad you got the ignition parts.
As it is an atmosperic inlet then it has to be poor seating, probably a speck or swarf or dirt.
You can check the valves with the head off buy pouring some petrol or rubbing alcohol into the port and if it leaks past the valve then it needs attention.
Hope this helps
Ade
Good tip, Ade. Thank you!
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Have tried Ade's idea of pouring down the port no sign of any leakage.
Compression came back and tried to run engine, it ran for about 5 seconds and lost compression again.
Every time the compression comes back it does the same, any ideas folks ?
Have sent an email to Jin but so far no reply.
Here's hoping Trevor.
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I don't have a m92 but I had some eratic compression issues with my m94. After I stained & cleared my box the increased thickness was preventing the mechanism from completely closing the exhaust. Perhaps you can insure the mechanism is allowing exhaust to fully close.
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Hi Trevor,
My M90 would do this regularly, i would hold the exhaust valve open and blow throught the carb with the airline to shift any dirt, or sometimes pushing the valve open and letting it snap shut a couple of times would do the trick. Those valve springs are so soft that any resistance will stop the valve seating.
Make sure the valve stem is lubricated with some thin oil too if you have not already.
In the end i went with a slightly stiffer inlet valve spring, the engine ran so much better but sometimes when starting the exhaust valve would suck open instead of the inlet, stiffer exhaust valve spring fixed that and the engine made so much better power under load and generally ran much more constantly.
Hope this helps
Ade
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Hello to Partcleman, have already altered the exhaust rocker by one turn so it closes just.
Ade will try your suggestion of heavier springs and see what happens.
Thanks for your help,
Trevor.
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There is 6 to 8/1000ths exhaust valve lash clearance. This is not much but is clearly there and I would say necessary.
Gil
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Finally got the engine to run by using a stiffer spring on the exhaust valve, thanks for the
Suggestion Ade. The engine moves about a lot due to the sloppy fit of the wood the engine sits on
Will have to make a new box. It still runs a bit fast but can,t slow it down anymore as the governor spring
Has been trimmed, still spits out a lot of fuel and runs for about 5 minutes could do with a tank much bigger,
Has anyone else noticed the short running time ?.
Thanks Trevor.
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Hi Trevor,
Good news you got it running :D
I have a M90 box that is unused if you want it, i found running a bead of epoxy around on the inside to fix the top sheet to the sides really firmed it up and stopped the oil etc. from getting inside. Mind you, to stop them hopping around takes a ton of weight, that M90 with the PM research dynamo i posted the video of ages back has two 15mm thick brass plates, one on top and the other underneath with lead filling all the free space inside and that just about held it still...
Best regards
Ade
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Hi Trevor, Watch this and try similar with yours.
Gil
https://youtu.be/mY-rgVnZiKU
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Thanks for the ideas Gil ,had already trimmed the governor spring and the linkages on my engine
don't move as much as yours but it still runs a bit quick compared to your engine .Just one question,
how far retarded have you made the timing on your engine ?.
Ade the suggestion of running some epoxy round the inside of the box has cured the movement
problem thanks for that.
Cheers Trevor.
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My M92 is set to fire just a hair after top dead center.
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Here's a video of my M92 engine running finally, the exhaust has been extended and the sensor wiring
hidden, i've also retarded the timing and cut 1 1/2 turns off the governor spring.
Thanks for all the help in getting it to run.
Trevor.
https://youtu.be/DLQFoW83Cps
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That sounds good Trevor, i like the idea of the wood around the box to stop it wandering off.
Best wishes
Ade
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Hi Trevor, Good to see you have it running. Now you need to make the governor allow it to hit and miss.
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Is it running comtinois rather than hitting and missing?
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Yes, that is what is happening
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Trevor, by the looks of things you can straighten it out by stretching the tiny spring in the governor fineal.
(a little at a time until you have the desired result)
Gil
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Now that's unique you don't see every day..... Consistent Hits (no percectable misses) at such a strangely pleasantly low rpm speed !! Please revealed the secret ....I've got the "hit, miss miss miss miss" down good but still a bit overall, too fast rpm....I could deff use some of that action to make my M90 run very realistically scale slow speed......tom.
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I know it's been a while but i have noticed when running my M92 that the
flyball governor isn't rising and falling to create the hit and miss.
Can anyone tell me what is causing this to happen and what do i need to
do to fix it ?.
Thanks Trevor.
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Hi Trevor,
I suppose it could be a short somewhere? Did you check each individual battery? I have seen those battery holders make a bad connection sometimes...
Just guessing
Ade
Hi Trevor, watch my videos on you tube under Desert Goldfever I think you could pick up some tips on these engines later Ike
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Hi Trevor,
I suppose it could be a short somewhere? Did you check each individual battery? I have seen those battery holders make a bad connection sometimes...
Just guessing
Ade
Hi Trevor, watch my videos on you tube under Desert Goldfever I think you could pick up some tips on these engines later Ike
Just had a quick look Ike at one of your vids and subscribed and I will look at them all later.....wow....that's one very bice hobby shop you have!
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Just had a good look.
Trevor, In your last video, your latch out lever is constantly latched out and the push rod and/or push rod collar is badly adjusted.
In other words, your governor won't move because it has no where to go.
I believe it only runs because the pushrod set-up is out of sorts.
Gil
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Thanks for the replies everyone.
Well it looks like the problem was the bolt on the lever that you take off
to remove the cylinder head, for some reason it was tight, once slackened
off the govenor works fine.
Think we'll put that one down to operator error, me !!!.
Trevor.
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Thanks for the replies everyone.
Well it looks like the problem was the bolt on the lever that you take off
to remove the cylinder head, for some reason it was tight, once slackened
off the govenor works fine.
Think we'll put that one down to operator error, me !!!.
Trevor.
Hi Trevor, my best advice of the cam follower lever is to tighten it to where it won't move, then back off just a half a smidge like a couple degrees... just enough to let it move freely but not enough to flop around. Then put a drop of synthetic oil on it's pivot point if you haven't already.
Gil
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Sometimes it’s the simple things. If the valves aren’t happy, a dribble of marvel mystery oil or automatic transmission fluid straight onto the valve stem (needle spout bottle works nice), and leave it overnight. It should soften any carbon on the valve and seat, slick up the stem, and leave the valve guides slippery and happy happy. It might blow a bit smoky for a minute, but you should have compression enough to rope start it. I’m mindful of a photo of an early Indianapolis racer with exposed valve train, and the driver is half out of the car oiling a sticky valve on the fly.