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Author Topic: miniature opposed twin R90S boxer engine review  (Read 544 times)

Adirondack Jack

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miniature opposed twin R90S boxer engine review
« on: September 28, 2021, 04:57:45 pm »
The latest offering from Microcosm and others, the R90S opposed twin engine has arrived.

Overall I’m really impressed with the engineering, and only have a quibble or two with execution.
The rope starter is essentially useless. The starter pulley is simply too small for the provided rope. A smaller gauge rope works better.  The adapter to start the engine with a drill motor works fine, and once tweaked for easy starting, the smaller gauge rope works well also.

As shown in the video, the engine initially started and ran on one cylinder, flooding the other side until warmed and tweaked enough to clear itself. Further adjustment when cold will get it sorted.

One non-critical but irritating issue is a poorly aligned and sloppily soldered right side muffler.  Not a huge deal, but not great. Otherwise it’s a cutie. 






Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #1 on: September 28, 2021, 05:10:22 pm »
More thoughts on the review.

JinMachine

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Re: miniature opposed twin R90S boxer engine review
« Reply #2 on: September 29, 2021, 08:27:14 pm »
GOOD,Thanks Jin

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #3 on: October 01, 2021, 08:02:00 am »
Unfortunately the good news turned sour.
First I noticed a poorly soldered connection and crooked exhaust. Easy enough to fix, simply replace the right side exhaust assembly.

Then I noticed the LEFT side intake manifold is incorrectly formed, so the intake blocks the oil filler plug from removal from the crankcase. That obviously is unacceptable, as there is no access to the crankcase.

All that would not have dampened my enthusiasm. I emailed the service person at enginediy.com, as directed on the invoice should one have problems. I even told them I was waiting on a response before posting my review.
I got no response in two full HK work days, headed into the weekend now. So I’ll go ahead and report.

I could not in good conscience recommend this series of engines.  Poor quality control and no reply from service has me feeling suckered. I’m done donating to them.  Anybody wanna buy an inline four?  They were less than helpful there also.

MadeForThat

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Re: miniature opposed twin R90S boxer engine review
« Reply #4 on: December 15, 2021, 09:23:57 pm »
Hi Jack, the very man who commented "GOOD" is the very driven man behind many of these designs. (microcosm) I would be willing to buy the inline 4 from you Jack, shoot me a message

St Paul Steam

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Re: miniature opposed twin R90S boxer engine review
« Reply #5 on: December 16, 2021, 05:51:28 am »
I would like to hear more about the inline 4 cyl & why you are unhappy with it.
Bruce, St. Paul Indiana, USA
"Originality thrives in seclusion free of outside influences beating upon us to cripple the creative mind."
  Nikola Tesla

txlabman

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Re: miniature opposed twin R90S boxer engine review
« Reply #6 on: December 16, 2021, 09:42:05 am »
So sorry to hear Jack.

It sounded so good in your first video.

I believe/hope that Jin will make it right.

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #7 on: January 24, 2022, 01:33:17 pm »
I got zero help. I’ve had some health issues of late, but opened the boxer and found a couple of damaged pushrods, and a scored piston. I cleaned up the piston, replaced the o ring, and cleaned up the wonky pushrods. I’m gonna try reassembling the last bits today, see if I can make it go.
I get no help from these guys. If they were more responsive, I’d continue my off grid workshop village. I’ve got half a sawmill built. Maybe try powering it with a flathead whippet.

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #8 on: January 24, 2022, 01:35:21 pm »
I meant to say damaged lifters.

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #9 on: January 24, 2022, 01:49:38 pm »
The inline four in question, also purchased as a first issue, is the yellow or gold color 32cc oh inline four.

I bought from the early issue, and before it even arrived, early videos showed horrid oil blow by with the rubber rings.  So when they came out with hard ring piston and sleeve sets, I bought them for over a hundred bucks, before I even got the engine. At some point Lucas, who now is now culprit on the boxer oil snafu, told me I didn’t need the upgrades because my engine already has them. I don’t know because I never got it running enough to find out.

Following common nonsense, I tried to start it with zippo, the first night, once I had the optional 109 Buck starter installed. Ut ran five second or less then quit. Two problems. It wouldn’t even fire on zippo, which of course I tried until I had the carb out of whack and a dead battery. Next day couldn’t even make it pop. Discovered online info that the seventy cc oil was too much. Drained and refilled with about forty cc
At some point I heard zippo doesn’t play well in Walbro clone carbs, so I replaced that also. I have been there and back, can’t get it sorted and my vision becomes a problem working alone. I’m just tired of the poor responses.

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #10 on: January 24, 2022, 01:51:56 pm »
Should say it won’t even pop on tru fuel now.

St Paul Steam

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Re: miniature opposed twin R90S boxer engine review
« Reply #11 on: January 24, 2022, 01:56:02 pm »
It's a shame , I seem to see this same response over & over again , maybe runs good at 1st ,then problems (sometimes Major) and 0 help after the purchase.
Bruce, St. Paul Indiana, USA
"Originality thrives in seclusion free of outside influences beating upon us to cripple the creative mind."
  Nikola Tesla

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #12 on: January 24, 2022, 02:26:36 pm »
That’s the problem as I see it.  As you say, it’s too bad. I admire Jin and his CAD happy friends. His prototype work and the CNC engines are awesome. The trouble is, they’re kids in Hong Kong who might have seen the inside of a Honda scooter engine once, but otherwise it’s like us playing with da Vinci designs, building stuff we have only seen in books. That craziness building the oil filler into a trap under the intake is a cad issue. Nobody fully prototyped it, or they let dimensions on the intake creep. But they didn’t understand the problem, misled me into using a two stroke mix, and galled two lifter faces. Wether I’ve sorted it is unknown. I get pissed thinking about it. The parts are zip locked and stowed right now.

St Paul Steam

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Re: miniature opposed twin R90S boxer engine review
« Reply #13 on: January 24, 2022, 02:56:41 pm »
Well said , pretty much summed it up.
Bruce, St. Paul Indiana, USA
"Originality thrives in seclusion free of outside influences beating upon us to cripple the creative mind."
  Nikola Tesla

Adirondack Jack

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Re: miniature opposed twin R90S boxer engine review
« Reply #14 on: January 24, 2022, 04:57:04 pm »
What’s killing me right now, a year ago, when Jin was playing with the Holt engine, I quipped it’d be awesome if they came out with a flathead four like a model A engine. Now they have, and I’m afraid to pull the trigger.