How much choke to start a Jab

[garfield]

Hello all my first post ,

 

Have a new Jabiru 170C 20 hours ,it needs full choke closed throttle to start cold is this normal ? if one closes choke after motor first starts it will stop give it a few seconds then close choke open throttle and all is OK is this what other Jabs do ?Thanks Rod

 

 

[Tomo]

Each Jab seems to be slightly different, but the general consensus is too -

 

# Throttle closed fully (it won't start 'without' closed throttle when cold)

 

# Choke on fully, doesn't hurt to hold it out rather than letting the friction try and hold it.

 

# Keep choke on until you notice an increase in RPM (about 8-10 seconds depending on the day.)

 

# Tickle on a little throttle, then close choke quickly.

 

I've been doing that on the 2200's I fly and have never had an issue - and yes it is normal as far as I know.

 

As for closed throttle, the reason is the choke will not work without a fully closed throttle.

 

Have fun! Are you coming from a GA background? I can kinda sense it :big_grin:

 

 

[garfield]

Hi Tomo,

 

Thanks you that ,we have been told that the reason for closed throttle is to make it suck the from choke jet not sure if that the correct expo.

 

I have been reading your posts for a while ,must get in touch with you as we are local Taroom any way , not GA we come via Gliders moved to light power ,over the moon with the 170 .

 

talk to you later Rod

 

 

[Tomo]

No worries at all mate, yes that's pretty much the reason for the closed throttle.

 

The reason I asked about being GA as a lot of them try to start it with a bit of throttle on - and think it strange not too!

 

Gliders are good fun, I do a bit in them from time to time.

 

Will have to catch up one day indeed!

 

Take care

 

 

[bushpilot]

We do same as Tomo suggests - but in our cold clime we leave choke out for couple of minutes on the 2200 engines. The 3300s only need choke for few seconds.

 

Also, if you every experience difficulty with Winter starts, try gapping the plugs down to 20thou.

 

 

[Relfy]

When i picked up my Jab, Neil at Jabiru told me to do exactly as Tomo suggested. A bit of throttle on turning the choke off helps it come off the choke jet.

 

Works every time! :thumb_up:

 

 

[Guest check-in]

This may not work on a freezing day, but has worked for me in temperatures down to about 5 deg C. Ignition OFF, pull prop thru 8 to 12 revolutions by hand (the colder the ambient the more I pull it through). Electric fuel pump ON for about 5 seconds then OFF. With throttle just cracked (to give about 1000 rpm) crank about 4 to 5 revolutions on starter with ignition still OFF - then while continuing to crank- ignition ON.

 

Have never needed choke (in fact wouldn't even know if it works!). This technique ensures oil pressure is already on the way up before the engine fires and also gives some indication that the engine-driven fuel pump is OK. Engine is a Jab 2200-J, which as far as I can tell is absolutely the way it left the factory as regards carby etc - but is not fitted to a Jabiru aircraft. Maybe it won't work if you have a lean-burn carby set-up and maybe in a Jabiru airframe the fuel doesn't get to the engine as readily without some initial help from the choke. But no harm in trying it once anyway.