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Author Topic: M 90 hit/miss misadventure update success  (Read 678 times)

Belugawhaleman

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M 90 hit/miss misadventure update success
« on: January 21, 2020, 07:28:59 pm »
Had a little trouble with my little engine. First; the flywheel on the governor side came loose. The governor
Fly weights and springs need to be removed to reach the set screws to tighten the wheel to crankshaft. During
reassembly, the two tiny clips shot off into space. Luckily, I found one with a magnet in my carpet and the other
one was stuck on the inside rim of the flywheel. I really dodged a bullet there!. Next after reassembly I found
that the engine had no compression. I took the head off the engine and discovered a sooty mess inside. I cleaned
everything up the valve seats were very dirty so I cleaned them. I removed and inspected the o-ring it looked ok
So I cleaned and oiled it an placed it on the lower groove of the piston once assembled the engine ran OK but I noticed
that the compression still seems a little weak and that the engine runs a little warmer than before. I decided to order
New o-rings. Found some on Amazon. I was confused about the size I ordered 20x1mm and 22x1mm sizes. Well the
20mm size was delivered today and I discovered that this size was noticeably smaller than the o-ring that was on the engine. Well, tomorrow the larger rings come. I'll keep you posted. After inspecting the o ring on the engine I noticed
That the outside edge did appear worn.

Paul
PAUL
Civilization is the limitless multiplication of unnecessary necessities.

Belugawhaleman

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Re: M 90 hit/miss misadventure update success
« Reply #1 on: January 22, 2020, 07:52:20 pm »
Well, the correct o-rings came today. These are the 22x1 mm. Fluorine (green) rings I purchased on Amazon. They fit
perfectly and seem to provide a good seal. I turned over the engine at first and discovered the intake valve wasn't seating
properly this was soon remedied. I decided to put the o-ring on the first groove of the piston as it had been originally.
I started the engine and found that it runs well. It now runs cooler and I found I can run it with a slightly leaner setting
on the carb. Well I hope someone may find this useful.

Thanks

Paul
PAUL
Civilization is the limitless multiplication of unnecessary necessities.

Nick

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Re: M 90 hit/miss misadventure update success
« Reply #2 on: January 22, 2020, 07:56:50 pm »
Thank you for the update Paul, I did not have an answer, but glad the right one arrived today. I haven't had to do anything with mine yet... but I will save your post.
Nick

Stilldrillin

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Re: M 90 hit/miss misadventure update success
« Reply #3 on: January 23, 2020, 03:29:37 pm »
Well I hope someone may find this useful.
Paul
Thanks Paul. Sorry for the silence.....

This certainly will be useful.

I have only unpacked and examined my engine, so far. It is up on the shelf, above the computer, as I'm typing.
 There are several other engines needing their wintertime service, before I can turn my attention to my M90.

All useful tips and vids, are being bookmarked, ready for the day.
David....   Still drilling holes. Occasionally, in the right place.
 https://www.youtube.com/channel/UCeKtH_z2OLH8EXDk9ziWl8Q/videos

70Rcode

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Re: M 90 hit/miss misadventure update success
« Reply #4 on: January 24, 2020, 06:14:48 pm »
Hi Paul,...Greetings from a M90
newbie & thanks for posting your M9 misadventure. I also experienced the loose flywheel issue. The speed govenor mechanicals really do complicate the grub screw access. I decided Not to mess with those microscopic sized E-clips (a disaster for sure) & just simply remove the lock-out bar pivot screw to slide the weights floating bushing inward. A lot simpler & no flying "Jesus" clips !!   Have you considered running less of
/ or a different type oil mix to reduce your spark plug & valve sooting issues as the "Instruction Manual" dosen't address any lubrication steps but just "gas it up & go" !  The M90 seems to run a lot  colder than other engines & just never gets hot enough to burn off normal 2 stroke gas mix lubricants. On the o-ring issue, does the cylinder sleeve bore have a starting chamfer at either end to reduce o-ring damage during reassembly as the very thin & fragile looking rubber o-ring looks to be a frequent wear & tear issue even at the heavy oil mix you're using..Thx for any info, tom.

Belugawhaleman

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Re: M 90 hit/miss misadventure update success
« Reply #5 on: January 25, 2020, 09:34:40 am »
I use Coleman fuel and Marvel oil mixture of about 16 to one. I was considering reducing the oil or perhaps
changing to another oil. I had a suggestion that Red line synthetic oil burns cleaner but have yet to give it a try.
I didn't notice any chamfer, but I had no trouble replacing the piston with the new ring. Last night I ran my engine
and I had frequent stalling then I realized it was time for new batteries! Oh well.

Thanks

Paul.
PAUL
Civilization is the limitless multiplication of unnecessary necessities.

70Rcode

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Re: M 90 hit/miss misadventure update success
« Reply #6 on: January 26, 2020, 08:39:36 pm »
The cylinder head "sooty mess"...was that a Dry or Wet nature mess condition that could indicate an over-rich A/F needle valve setting or wet soot usually an excessive oily fuel/lubricant mixture. Thx for any info, tom.


Belugawhaleman

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Re: M 90 hit/miss misadventure update success
« Reply #7 on: January 27, 2020, 02:34:49 pm »
At first dry. I had been running my engine excessively, sometimes 30-40 minutes at a time before I first removed my
Cylinder head. Now the engine runs a little cleaner. I think I'll run the engine at 20 to one or try the synthetic oil. I  now put a little Marvel oil at the bottom of the cylinder before each run.
PAUL
Civilization is the limitless multiplication of unnecessary necessities.

70Rcode

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Re: M 90 hit/miss misadventure update success
« Reply #8 on: January 28, 2020, 02:10:48 am »
As no mention to running or maintenance lubrication per instruction manual, it would seem, as marketed, this rubber O-ringed engine series is really intended for short run, novelty duty cycles. I'm not aware of any serious working engine design, 2 or 4 stroke, that attempts to adequately
 lubricate the piston skirts, rings or cylinder wall via fuel mix thru the intake port on the Combustion Side of the piston/rings assembly as it would have to be so oil ratio rich as  to have serious sooting issues. With open crankcase, No lubricant splash features, direct pre-run oiling of cylinder wall, piston skirt & pin for short demo runs is about it unless you accept early parts replacement & frequent head off soot clean-outs of fuel mix only lubrication, imho.....My M90 runs so cold, that straight, non-lubed Coleman fueling is probably going to cause plenty of incomplete combustion soot generation alone without trying to add more partial combustibles in a "Top Down"  fuel lube attempt..just my newbie, re-evaluating this cool but very unique, out of the box, probably needs a few lube tweeks, well done execution...tom.

rodnoc

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Re: M 90 hit/miss misadventure update success
« Reply #9 on: January 28, 2020, 03:10:37 am »
..... this rubber O-ringed engine series is really intended for short run, novelty duty cycles.....

Yes, in my opinion, and enjoy it for the very affordable little gem that it is.  Machine an IC engine from scratch sometime for maximum appreciation of what JIN provides us.

Belugawhaleman

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Re: M 90 hit/miss misadventure update success
« Reply #10 on: January 28, 2020, 05:05:08 am »
I've enjoyed running this engine as I have been doing and so far so good. The engine shows no signs of wear and removing the cylinder head and the ring really was no problem really. The new ring I added was of better quality than
the original one. Lately I have been running this engine for shorter periods with lubrication at the piston skirt. And everything's been fine.
PAUL
Civilization is the limitless multiplication of unnecessary necessities.

RedRyder

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Re: M 90 hit/miss misadventure update success
« Reply #11 on: January 28, 2020, 06:34:35 am »
..... this rubber O-ringed engine series is really intended for short run, novelty duty cycles.....

Yes, in my opinion, and enjoy it for the very affordable little gem that it is.  Machine an IC engine from scratch sometime for maximum appreciation of what JIN provides us.


I submit to you that if set up right, these engines work fine for long runs.


I set one up for the slowest possible run. I had retarded the spark to top dead center, I put much softer springs on the governor weights or stretch the original springs and remove one of them. Removed the lower O-ring (this was well before Jin started shipping them with 1 O-ring). Massaged the piston and bore with Simichrome polish before re-assembly. about once an hour, I put a drop or two of high grade synthetic clock oil at the piston skirt end of the bore. When completely full of the fuel/oil mix (about 16 cc), I got a run nearly 5 hours long with no load. It was 4:56 to be precise. Even toward the end of the run the head temperature read out on a laser thermometer was never over 98 degrees and was 95-96 most of the time.


For details on the run see reply #9 on this page:
https://www.officeofsteamforum.com/general-discussion-scale-model-gas-engines-hit-miss-throttle-governed-non-compression-etc/2-hours-17-minutes-running-time-with-full-tank-(10-cc)-with-a-jin-m90/ 


Gil

rodnoc

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Re: M 90 hit/miss misadventure update success
« Reply #12 on: January 28, 2020, 10:00:24 pm »
> I submit to you that if set up right, these engines work fine for long runs.

Agreed.  Outdoors, I've run mine (a silver ET1) over 4 hours at a time--continuously except when I didn't refuel it soon enough and it required a restart.

Belugawhaleman

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Re: M 90 hit/miss misadventure update success
« Reply #13 on: January 28, 2020, 11:47:35 pm »
I agree. I when I first got this engine, I ran it for a long times at a stretch , stopping only for tank refills.
Until now I thought that I was probably abusing this little engine. After hearing that a five hour run is possible I've changed
My mind. While I haven't been able so far to reduce the firing intervals as others have despite changing the springs for some purchased from McMaster-Carr I've become satisfied with the rate at which my engine fires and will leave it
alone for now. My engine starts out fast at first and soon settles down to about ( I think) firing 40-60 times a minute. I think this rate will be useful for running a PM Research generator.
Thanks all for your advice and opinions. This forum has for me, and I hope others, been a wonderful learning resource.
Once again, thanks all.

Paul
PAUL
Civilization is the limitless multiplication of unnecessary necessities.