Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Good afternoon !

Just joined this forum, because I bought my first hit & miss engine and I'm reading up on them.
I bought an Eachine ETX / M91 vertical hit & miss. A thing of beauty. It arrived damaged (cam follower bearing broken during transport).
They are sending me a new bearing but in the mean time I managed to install a locally acquired bearing.

Now my question. Engine runs great. When it is hot it even hand starts. As I read here I'm experimenting a bit with different springs.
So far so good. But....

What I can't seem to solve is spray coming from the inlet ('carburettor') during the hits. I don't see that happening in any of
the 1000 videos I watched on youtube. And I can't explain how this could happen. Leaking inlet valve ? Valve timing ?

I'm at a loss.

Help.



Greetings from Greece.

Hans

Bonjour Hans,

Among others I have the M91 and also had to solve several issues.

My question is : What do you mean when you write "What I can't seem to solve is spray coming from the inlet ('carburetor') during the hits." ? Sorry, my English is not my native langage   

What could this spray made of because for me a spray is the vaporization of a liquid ? And there is no link between the inlet valve and the carburetor

To my opinion, if you had a leaking outlet valve, your engine would not run and you should feel almost no pressure when you turn it by hand ? => Do you feel a pressure ?

Other test I would kindly suggest you to close the carburetor with your finger and turn the engine in its direction of travel, you should feel a suction => Do you feel it ?

Do you see the spark at top dead center ? This confirms it starts on the correct timing side

And if you could make a little video of your issue, it would greatly help us to analyze it 

Ehr what do you mean "And there is no link between the inlet valve and the carburetor"

Isn't air/fuel from the carburettor sucked in through the inlet valve ?

Bonjour Hans,

Sorry, about the inlet valve, I wished saying that there is no "direct" link between it and the carburetor, the gas does not come from this valve, it just opens while the piston sucks gas so can't push gas through the carburetor.

About the timings, yours seems bizarre for me because mine seems sparkling at top dead center, a bad timing could possibly explain an exhaust valve opened during the compression phase letting a part of the mixture fly through the carburetor.

And about the lever, It was possibly too loose, just after top dead center, mine has a little play of less than 0,5 mm

I also would kindly contact this guy from me, https://www.youtube.com/@ThomasPCGuruENGINES , he is a great mechanic of these engines and likes sharing with us. Bad luck to meet him, he lives in Australia !

It's new. Shouldn't it be lapped and ready to go ?  Anyway I'll try to fix something to put air pressure in the cylinder and see where it leaks. What do you use on these small engines for lapping ?

Before I take the head off I might try adjusting ignition first, that's easier. Right now it sparks a bit before TDC.

But before all that, I have to fix the flywheels. Apparently it moved inward, allowing the lever thingy to hit the cam gear. The flywheel is free and rotating, but doesn't want to come off no matter how I pull it. Both set screws are backed out all the way and the collar on the back is loose. Still it won't budge. 

Also the flywheel on the other side is loose. I tightened that. Raphael in the video you mention you fixed this issue. How did you do it ? I imagine every time the engine hits those poor setscrews get a lot of force to resist...

And what would help me greatly is for someone to measure the flywheel on the cam side, how much is the crankshaft inside the flywheel. It's almost flush now and it sure wasn't like that.

See pic.

Removing the stuck flywheel. I'm now in the "I'm done asking nicely" phase....

Welp. Got it running again. Lots of nervous time getting the flywheel off. But in the end I was victorious. Damage to shaft
and wheel was limited to some burrs. Easily sandpapered away.

Next I drilled the shaft where the setscrews are, so the flywheel will stay in place this time.

I reassembled everything, adjusted spark timing to TDC (it was a little before TDC) and test ran it.

The adjustment of the spark seems to have improved the spray problem. But it's still there. Hope it shows on this video.


Spitting time !!

https://youtube.com/shorts/ixsTS28FPq8

And after a while it just sputters and dies.

Is there an easy way to see if you're running too rich or too lean ? I'm around one quarter turn open, but it has difficulty
staying running for any length of time.

Any tips and tricks highly appreciated. I'm learning. And loving it !!

https://youtube.com/shorts/XvZK0BA0nJY