Tach adapter or interface

[Dan_]

I see a phone call to Scott Cassler in your near future.  Ask about his mass balance service and running a tiny tack on that mag.

Carb heat ain't the end of the world...

The mass balance puts most of the shake at 2 nodes.  One below idle speed and the other about 1500.  There will still be a "rocking couple" due to the offset of the cylinders.

May as well see what the damage on his aluminum cylinders is.

Builders have discovered the engine will not take full throttle well with the larger throat carbs.  I think most run 26 MM.  The smaller venturi keeps the velocity up and allows better atomization...

[Mark Kramer]

Carbs are vm26s. I had read about too much air thru the larger carbs. Bought the 606s as they are for 4 stroke engines. Aluminum cylinders are on my Christmas list for sure. For the moment I am gonna keep trying with Dennys phone app method to try and smooth things out. Not sure how much I can re set the float levels.

[Dan_]

Sounds like a plan, keep us posted on the saga.  You will be rewarded with a good engine in the end well worth whatever the trouble.

[Mark Kramer]

Thanks, I so appreciate guys who take the time to help a fellow Eagler. I’ve learned a ton on this forum

[Mark Kramer]

I’m back. So I removed my brand new vm 26’s, and installed the single Zenith with the drop down manifold. Runs great and no spitting gas. Starts first hot flip every time. Took a while, but I also built a carb heat box and control. At this point my problem still remains that I cannot get one of those little tacos to work. I hooked up a tiny tach and a cheap amazon one. The results are very similar in that they agree til about 2000 rpms, then go nuts. Would very much like to know what the wot number is. Also need to borrow somewhere a scale to measure thrust. Not sure what a decent thrust number is, but if I get one, I’m gonna fly it.

[Mark Kramer]

Ok, so I hit the post button instead of the preview button. Also wanted to talk about carb setting and spark plug color, 1 white ish and the other yellow ish. Maybe I should find another topic for those kind of questions?  Also have a few pics. Any help with a few little bugs would be awesome.

[Mark Kramer]

Oh, I know what I wanted to ask... the tiny tach and the 25 dollar amazon tach both have to be told about sparks per revolution. A one cyl 4 stroke engine would have 1 spark per 2 revs, right? So how about a 2 cyl 4 stroke with a lost spark system? 1 spark per rev? Does it know that it has a spark every rev because of the lost spark thing? What would a normal idle rpm be for one of these little motors?

[Dan_]

Tiny Tach instructions attached...

[Dan_]

This is another route you can go: https://www.kitplanes.com/build-your-own-optical-tach/?fbclid=IwAR2cAyxiYe0lrWmImXnGodZ6MQxsne_m2CDw1iApkzGhSYl5jEXZxQv3qAE

[Mark Kramer]

I have the instructions for both tachs. Just wasn’t sure about the initial set up. 1 spark per rev gave me a 1200 to 1400 rpm idle. 2 sparks per rev gave me a 600 to 700 rpm idle. Both tacos do this same thing, just not sure which idle rpm is correct. Now since both tachs seem to go nuts above maybe 1800-2000 rpm, the problem maybe is how they are attached to the plug wire. Maybe they just don’t like the Fairbanks Morse mag.
This optical tach could be the answer. Wonder if it would need some reflective tape on the back side of the prop?
I think I will spend a bit more time playing with how the sensor wire connects to the plug wire before I give up.

[Dan_]

Try this before walking away... https://play.google.com/store/search?q=acoustic%20tachometer&c=apps&hl=en_US

I think you're right about fooling with the sensor.  Number of turns, leaving the spark plug wire at 90 degrees, not running along parallel to any wires and not letting any reflected interference (firewall?) be picked up.

Sounds like when that mag gets to honking you possibly start getting something you don't need picked up by the sensor wire.

[Dan_]

This one worked... https://play.google.com/store/apps/details?id=com.francesco.carmeter&hl=en_US

I tried it and one other on my 4 cylinder car.  Standing beside the car holding the phone in front of the steering wheel up to the gauge cluster, the above app had to be set to 8 cylinder, then it was dead on rock solid with the dash tach.  950 rpm.  The one thing I did not do was rev the cold engine.

You can use the app to pick which mode to set your tiny tach.

The first app I tried was called "Acoustic Tachometer (RPM)" a POS...  It was all over the place no matter what settings you used.

[Dan_]

update:
I drove it today... Had to put it back to 4 cylinder, but it should still help you set up the TT...

[Mark Kramer]

Cool! The stuff you can do with these phones. I have one of those inexpensive optical tachs coming. Would try the phone thing in the meantime, but I had to pull the carb back off. Plugs were bright white, so I kept richening the high speed adjustment looking for a little color on the plugs. Only got some on one side, in fact the other plug was almost a funny yellow color. If you remember I’m now running the single Zenith carb. I found that the throttle shaft bushing on the yellow plug side of the carb is quite loose, and with the manifold vee junction right on top of the carb, I think a stream of plain air is going up that side. Also on the same side I found a tiny pin hole in one of the factory welds on the intake manifold. Gonna fix these issues before the next run. I think I’m on to something here. Now if I could just find a carb kit and bushings. Oh, and an airport with some available hanger space. Doesn’t seem to any within a reasonable distance, and being in Maine, well winter is coming soon.

[Dan_]

Progress good... Pinhole bad.

A little blue Loctite on the throttle plate screws will go a long way in the peace of mind dept.