BillPTC

Trying to setup gasser and a Saito low end using a tach.
Have used three different brand hobby tachs(hobbico, Hanger 9, Globe). Can not get consistent good readings outside in sun light to properly set up my low end needle. Have plane facing sun or direction of sunlight shooting thru prop from back within 4 to 6 inches. Readings are way off or not consistent. Calibrated fine, batteries good. Can not set up my low end with out consistent readings. What am I doing wrong?
HELP

jaka

Hi!
Why for heavens sake use a tach to set idle speed...!

bkdavy

My Feedback: (1)

My guess is that at low speed, the RPMs are wavering high and low (being a fourstroke?) and that's whats confusing your tachometer. I'd just set the low end as low as you can reliably get it, and forget it.

Brad

rcfury

My Feedback: (5)

Agreed, using a tach for setting your hi-end is useful but not your idle. Keep on leaning out low end till your motor wont transition smoothly then richen it up a 1/4 turn. Keep it there. Don't know how experienced you are but bigger props will yield a slower idle due to the flywheel affect.

BillPTC

On my G26 I was going to use RCIGN1 techique but I need to get the tach to work correctly.
"The low is too rich and is affecting the high...Typical low setting is about 1 1/3 to 1 1/2, then with the low leaner you will have to re set the high...
The carb on the G26 is pretty big for the size of the engine and needs to be set a little differently..Open both about 2 turns...Set the idle speed at about 2000 rpm and slowly lean out the needle.(If it won't idle at 2000 it's way rich on the low needle.)..The idle speed will increase..Re set to 2000 and continue leaning..When the speed no longer increase...Go back and try the transition..If not good slowly open the low needle a little at a time until the transition is good, and re set the high...I think you will find both needles open about 1 1/3 to 1 1/2 after adjusting this way...A 16-8 and an 18-6 will both turn about the same, but the 18-6 will pull harder and fly the plane slower..Depends on what you want...A non restrictive noisy exhaust diverter will give you about more rpm..It should idle at 1800 when correctly set.... "
Bill

Villa

When I built by first twin engine plane I just knew I had to have a tach. That is common sense. WRONG!!! First few flights I used it, but it has been gathering dust for years now. There was just too much trouble using it. All that you already mentioned. I tune it by ear. I go for reliability first, last, and always. Slight difference in RPM is not an issue. A reliable idle is better than one set to an RPM.

RICMOD5634

I'm using a Hobbico tach., but it does not want to read from the back and I don't like reaching over the 14" prop to adjust the high end and looking at the tach at the same time. Is there something different about using them from behind, back side of the prop.
Thank You:

BillPTC

Was not using the tach to set ideal but to set the low end needle. Must properly set the low end before the top end, different from glow engine.
Have a great day
Bill PTC