ESC backfire, starting protocol, etc

bruce nickerson · Post by **bruce nickerson** » Sat Apr 19, 2008 6:34 pm

My ESC is back together and I have been getting acquainted with its best starting protocol. It has the the Seagull-AMAL curberetter. When cold, I use full choke, gears in neutral, full throttle. As soon as it starts, I back off throttle to 1/2, open choke, throw it in gear. Goes well with water in trash can just over cavitation plate. As experiment filled trash can more until motor bogged and stopped. Emptied barrel to previous level.

Now had trouble starting when warmed up (but not HOT!) Fiddled, pulled, cussed, groaned. Backfire through carburetter. Repeated the FPCG process and got it started.

Some questions:

Why the backfire?

I saw in a post here that carbs are sensitive to being level, or nearly so. Could this have been the statrting problem? My test stand/transom subsitute is vertical giving a slight forward tilt to the motor.

Second, the air intake choke shutter assembly is made of Godawful black plastic which strikes me as a bit chintzy and fragile. Is there a bettter solution?

Much thanks. I am kicking myself for not preparing eariier, as today is one of those days that makes in worthwhile to live in New England with its too frequent lousy weather and cold sowy climate, and I should be floating rather than fiddling.

redclyffe · Post by **redclyffe** » Sun Apr 20, 2008 1:08 pm

what is your plug gap, contact breaker gap? if either too small it will fire early, on the compression stroke, also any high resistance contact probably around the plug seat could cause problems too. regarding the choke shutter they are brass on earlier motors, but if it 'aint broke.....

Vic · Post by **Vic** » Sun Apr 20, 2008 2:08 pm

Backfire through the carb can be sign that the mixture is weak, which could be due to adjustment or dirt in the jet. (the infamous lean sneeze)

The points gap being too small will delay the spark not make it early, too wide will make it early.

Not had any problems with a vertical mount either on the test stand or the boat transom but i may have set the carb on its fixing so that it is level (Villiers carb)

bruce nickerson · Post by **bruce nickerson** » Sun Apr 20, 2008 6:12 pm

Thx all for comments

Vic: Amal has no mixture adjustment.
Will recheck points and plug gap.

Redycliffe (not HEATHcliffe?): Choke shutter on my Villiers carb is metal also. BUT the AMAL unit is flimsy black plastic. Is there a metal assembly available for the AMAL?

Vic · Post by **Vic** » Sun Apr 20, 2008 7:17 pm

Amal has no mixture adjustment

I was thinking in terms of the Villiers ,sorry. Thank leaves a dirty jet as a posibility then.

bruce nickerson · Post by **bruce nickerson** » Sun Apr 20, 2008 7:57 pm

Vic, et all:

Just checked (not REchecked) points gap. Almost nil. Would motor run at all with points closed, or almost closed?

Took magneto off another motor, in too big a hurry to check point gap! My bad. My VERY bad. Live and learn.

Leaves only plastic choke assembly to deal with!

Again my thx

Rob Ripley · Post by **Rob Ripley** » Thu Apr 24, 2008 12:57 pm

My 102 starts every time (cold or hot) minus the prop. in a tank, and runs smoothly at all speeds.
In the water (I have no clutch) it will start easily on almost full throttle, but runs, misfires, spits out the carby (no choke either) etc, and then after 30 seconds or so settles down to smooth running. It does this hot or cold.

Vic · Post by **Vic** » Thu Apr 24, 2008 11:10 pm

Just checked (not REchecked) points gap. Almost nil. Would motor run at all with points closed, or almost closed

If the points dont open at all it wont run. If the gap is very small it will make the spark very late, but i cant quantify that.

Are you sure you are looking at the points when they are open at their widest?

Post by **John@sos** » Thu Apr 24, 2008 11:53 pm

If a Seagull has the points set up correctly at 0.5mm or 20 thou for points ignitions, and the plug the same, I would suspect the petrol/air mix was weak.

Is it sucking air past the bearings or through the joint in the crankcase? look for bubbles being blown through the same crack.

Try 10:1 mix till you get lots of oil round dry bearings.. just a pint of mix, then go back to 25:1

Watch the depth of the motor too. the straight exhaust tube should have the bottom edge 2 inches under water. Sounds like yours is not deep enough for the pump to be covered... If it is not, it will not pump water... Effects the back pressure in the pipe too....

Regards,
John

bruce nickerson · Post by **bruce nickerson** » Fri Apr 25, 2008 8:44 pm

John: Your comments imply that there may be a maximum and minimum depth under water for the exhaust tube?

Post by **John@sos** » Fri Apr 25, 2008 10:00 pm

Yes Bruce there certainly is.

All seagulls are designed to have the bottom edge of the exhaust tube 1 or 2 inches max immersed. The bottom of the tube, not the outlet ..

Any less and they will not pump, as the pump will suck air and more and there can be starting problems and lower power because of back pressure in the exhaust.

Regards,
John
SOS

Saving Old Seagulls