I just finished my first conversion and got it up and running this week end. It's a Homelite style engine from a Craftsman weedeater.
I also bought a tach from the LHS since I lost or broke my old one a few years ago. Can't remember what happend to it.

Anyway, photos of both the engine and tach below.

The tach just gives random readings all the time regardless if I'm inside or outside. The guy at the LHS said it was what most
are buying. Yeah, right. My old tach was just a small black box with readout and on/off switch but rarley gave false readings.
When it did it was because I was real close to a floresent light. I used to build my own brushless motors.

I'm also wondering if the ignition of the motor is causing so much static that it's interfering with the tach. I'm running a Champion
DJ7Y plug in it now and I don't think it's a resistor plug. I do have a Bosch RO 285 plug, is that a resistor plug? I've read that the
plug # is supposed to have an R in the # if it's a resistor plug.

I'm leaning more twords the tach as being the problem but I don't want to rule out the ignition tho.

If you guys have any ideas on this I'd like to hear them.

John

Many time the suns position throws my tach screwy. Try turning your engine so you can try it from different angles. I can never tach inside either.

I've had the same problem with the GloBee tach. To test it, point it at any household light and it should read 3600 rpms. If it does, then the tach is ok, and the irratic readings are just the "nature of the beast". You can usually move the tach around behind the prop until you get a believeable reading. A stock Homelite 25cc should turn a 16 x 8 prop at around 7000 to 8000 rpms, depending on lots of variables. If your tach reads 10,000, or perhaps 4800; those aren't reliable readings. When you get a reading that is in the range you expect, that's the one to "trust".

You might have a little more luck if you can get the sun in front of the engine while you take tach readings from behind. Another (semi-desperate) way is to do it at night with a light shining through the prop arc. (Note that it has to be a battery powered light to work right.)

If you want a really good tach, spend the bucks and get a "TNC" tach. They cost around 80 bucks or so, but really work great. They are not sensitive to position, lighting conditions, etc., and I have verified their accuracy as being excellent.

Let me know if you find any way to make the Glo Bee function better. I even put a tube shield around the photo sensor on mine but it didn't seem to help much.... It is too bad, because except for the erratic performance, I like the tach. []

AV8TOR

I used to have a Glow Bee. It's up under the back of the work bench on the floor some where?

Anyway, If the ignition is messing with it you should be getting all kinds of funny numbers

I had to have good clean sunlight for my glow bee. There couldn't be any tree leaves flipping around in the breeze with diverse shadows

I tried this but still random readings.

I done everything but use a flashlight to get it to read right. Indoors I get nothing but random readings if pointed at a light or whatever, it never reads a steady 3600 RPM. My old tach worked fine inside as long as the light was incandecent and not pointed at it. The little homebrew brushless motors turned some pretty high RPMs and I verified my tach in the sun and the reading were usually steady inside or out. The Glow Bee never locks on any RPM, it's constantly changing from a few hundred to tens of thousands.

I still have the receipt so plan to take it back tonight after work.

Oh, I might try another battery. The one supplied is pretty cheap.

That sounds like the thing to do because with a fluorescent light that thing should be rock steady at 3600

Yeah, mine is not that bad. Sounds like yours might be bad. Like you said, try a new battery and if that doesn't fix it then take it back and exchange it or get another brand.

AV8TOR

New battery didn't help, constant random readings regardless if it was outside or in.

I took it back and they checked it against another one. It wouldn't hold steady while the one in the store was rock solid 3600. So we traded. Got home as it was getting dark so I started up my Homelite in the shop with the door closed. I got some readings but they were jumping a bit so I set a flash light up in front of the engine and stood behind with the tach. At full throttle I got a constant 6840 RPM. Not bad considering it's a stock 7.9mm venturi carb with no velocity stack. The muffler is gutted, tho I did not remove the small pipe. Havent drilled any larger holes yet so this is a restriction.

So all in all, I'm pretty happy with the conversion!

John

If you are with in 50 feet of a florescent light it will not work. The R/F off a florescent like does all kinds of funny thing with the Glowbee tack.

Paul

GET A TACH THAT READS OFF HIGH TENSION WIRE AND THROW THE OPTICAL TACHS IN THE GARBAGE!

you could blink your eyes and count the revs and get a better idea of the rpm you were turning than using an optical tach.