Conrod

I have just checked the timing on a RCGF 15 beam mount motor and found it is 40 BTDC, does this sound right seams a little early, as I thought it should have been closer to 28 BTDC.
Anyone help with this?
Geoff

acerc

28-32° is a more appropriate range/setting.

Conrod

OK, with the sensor moved fully to the left turned ccw I can get 35 BTDC.
The motor does have a total of 14deg's of rock at TDC, 7 deg each side of TDC, would this need to be taken into a count when doing the timing?

lean-run

Can't tell you the actual timing, but if I look at my motor from the front (looking at shaft) the sensor is slightly clock-wise from centre.

Conrod

Yes, if I move the sensor to the right of centre (clock-wise) the timing is now triggering at 44 BTDC and with the sensor at the centre line of the crankcase it is 40 BTDC, this is how it was supplied.
Anyone able to measure the timing on their motor?

av8tor1977

My Feedback: (6)

The timing should be set at 28 degrees even if you have to modify the sensor mounting to get there, and yes, you have to allow for the "rock" at top dead center. This problem is somewhat common on Chinese engines.

This video should help: http://www.youtube.com/watch?v=GBXFp...eature=channel[/youtube

AV8TOR

Conrod

Hi AV8TOR
Yes I do the timing as per the video.
If I enlarge the sensor slots to the maximum I think I can get pretty close to 28 degrees BTDC. I have just checked a new in the box 26cc beam mount RCGF and it has a timing of 32 BTDC but think if I move the sensor fully to the left it will give 28 degrees, although 32 is not too bad.
I would be interested in knowing if there are any other 15cc motors with a factory set timing of 40 BTDC, as I believe the early timing may course problems with the rod bearings particularly with the bigger recommended props.
One last thing, I started the 15cc motor ( first start) with timing set at 35 degrees, fully adjusted. 6 - 8 flicks with chock on(pop) 3 flicks with chock off started. Re starts 1-2 flicks and no sign of kick back.
Set needles :- 2000rpm idle, 10300rpm WOT, 14x6 master, 20 - 1, fuel 91 octane.

Conrod

Ok, timing is set at 29 degrees BTDC, by slotting the sensor mount holes to the maximum, motor is running and starting well. Now have 15x6 master prop fitted.
Can not understand how the engine manufacturer got it so wrong.
Still would like to hear from others regarding your engine timing settings.

bcchi

Right in the center of that 14 deg is TDC.Rock the prop back a fourth over TDC make a mark on both sides of the free travel.In the center of the marks is TDC or so darn close it doesn't matter.I have had people check me out on this. Some times I am off one to three .000.
Been there done that.
BCCHI

lean-run

Mine is just set where it came. 95RON fuel 32:1 Cool Power oil. 15x6 MA S2. Starts and runs fine.

Conrod

Yes my engine starts and runs fine also at 40 BTDC ( factory setting ), 35 BTDC and 29 BTDC the motor seems very intolerant to timing.
My main concern is if the norm for small gas engines is in the 28 - 32 degree range why is the motor set at 40 degrees and is this likely to load the rod due to early ignition.

AGNI 5

Mine came set @32 Deg. Changed to 28 * and runs fine Needs a starter to get it to go. 14 x 8 apc prop @8100 rpm on a HK Nemesis 60 size model .Could do with a bit more power.

av8tor1977

My Feedback: (6)

Yeah, I guess you could do with a bit more power. My (BME modified to run on gasoline) Super Tiger .90 (15cc) turns a 13 x 6 prop at 13,600 rpms. That's a good bit more power.

AV8TOR

Conrod

AGNI 5
Have you cleaned up the reed block as this can make starting difficult due to leaking reeds.
My motor is only 3/4 of the way through a 20 oz tank and starts easily by hand hot or cold.
Running 20-1 fuel mix, timing set at 29 BTDC, with a 15x6 master K series prop, idles at 1900-2000 with 9500 at WOT using a TNC tach. At present the motor is only mounted on a stand, but is destined for a GP Piper Cub.