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Author Topic: another M91 arrived in the post office today.  (Read 132 times)

crazydoug

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another M91 arrived in the post office today.
« on: March 25, 2020, 11:37:32 am »
jin is back to work and selling and shipping engines, and another M91 arrived today. They usually take a little "fiddling" to get running properly, but hopefully will have it up and running for a video later this evening. It will give me something else to do during this 2 week shut down, so it couldn't have come at a better time.
crazydoug

Stoker

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Re: another M91 arrived in the post office today.
« Reply #1 on: March 25, 2020, 01:11:47 pm »
Hope it's a good one for you Doug!!!
"Information is not knowledge, Knowledge is not wisdom, Wisdom is not truth, Truth is not beauty, Beauty is not love, Love is not music: Music is THE BEST...   
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RedRyder

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Re: another M91 arrived in the post office today.
« Reply #2 on: March 25, 2020, 02:01:29 pm »
Yes... please keep us informed.

crazydoug

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Re: another M91 arrived in the post office today.
« Reply #3 on: March 25, 2020, 08:25:53 pm »
After having several of these already, I have this one up and running properly in about twenty minutes.  There are several things that I have found that need done before even trying to start one of these engines.   

The first is to put batteries in and TAPE them firmly into the holder, as the batteries tend to pop out otherwise.
Secondly, put a meter on the on/off switch and figure out which direction is on.
The next thing I do is to remove and stretch the governor springs slightly to slow the engine down, set the mixer screw at about 5/8 of the turn open.

And last, but most important, every one of these engines I have found to have the same problem.  The main problem that keeps them from running properly is the the push rod for the exhaust valve sticks in the up position, holding the exhaust valve open, leaving the engine with no compression.  Sometimes it sticks every time or immediately on the first try, and sometimes it sticks intermittently, leaving you wondering why the engine runs and quits, runs and quits. 

The first engine I tried lubricating the push rod and even boring the hole in the guide a little larger.  But the easiest solution is to loosen the two screws at the base of the cylinder holding the push rod guide assembly, as well as loosening the two bracket hold down screws that hold the rocker arm that opens and closes the exhaust valve. 
I put a little Loc-tite on the threads to hold the screws in this slightly loosened position, and this has worked perfectly on every M-91 engine I've had since the first one I bought. 

Anyhow, there have been lots of reviews of tweaks to this engine, so this is just my two cents worth.  I hope it helps someone!

https://youtu.be/zkt9RrptthU

Nick

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Re: another M91 arrived in the post office today.
« Reply #4 on: March 25, 2020, 09:10:03 pm »
Very nice Doug and thanks for the tips! By the way, you say you have had several now, have you moved them on or are you collecting them?
Nick

crazydoug

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Re: another M91 arrived in the post office today.
« Reply #5 on: March 26, 2020, 06:53:50 am »
Very nice Doug and thanks for the tips! By the way, you say you have had several now, have you moved them on or are you collecting them?
I found that everytime i take mine to an engine show, someone wants to buy it, so now I try to have a spare on hand. I tell people they can buy them on ebay, but a lot of older guys don't have internet or don't want to buy on ebay. Plus they like the fact that they don't have to fiddle with it or take the chance of damage during shipping, or wait for it. I try to buy them at auction and then be able to sell them for the "buy it now" price so I make a few bucks.
crazydoug

St Paul Steam

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Re: another M91 arrived in the post office today.
« Reply #6 on: March 26, 2020, 07:16:36 am »
thanks for the tips Doug, I've been looking for an air breather for these and haven't found anything suitable yet, I was thinking maybe model airplane engine suppliers  would have something available, but haven't found anything yet .does anyone have any ideas for this fix ?
Bruce
St. Paul Indiana , USA

RedRyder

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Re: another M91 arrived in the post office today.
« Reply #7 on: March 26, 2020, 03:42:01 pm »
Hi Doug, For the sticky push rod, I just loosen the 2 nuts that hold the guide at the base of the cylinder. The holes have some slop. I pull the guide as far as possible away from the cylinder bore and tighten the nuts in that position. This is usually all it needs and everything is tightened as it should be.


Gil

 

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