engine makes poping sound when first started on choke

[ANVIL99]

hello guys.my 1992 fj that I just purchased makes a popping sound out of the exuast when I start it cold with the choke on,not a lot and the problem quickly goes away as
heat builds in.I believe the motor is running rich as when I changed the plugs they were carboned up pretty good also seems to use alot of fuel.I would like to start by turning
my air/fuel screws in 1/4 turn to see if this helps but want to avoid a lean burn situation.bike has 75,000 k on it and runs well except for this problem.

[Dan Filetti]

Make certain you do not have a mouse nest or some such in the air box, or perhaps more commonly, a badly clogged air filter,  -I have seen the mouse thing be a cause of a rich condition before.  Then I'd mess with the mixture screws. 

Make sure you're reading the plugs correctly, search for the plug-chop method elsewhere on this list...

Dan

[andyb]

The engine is running rich while on the choke?

Uh, you grasp what the choke is supposed to do, right?

[movenon]

New to you FJ, congratulation ! As Dan said check the filter / intake area. When you say it's new to you, has it been sitting for some time with old fuel in it ? If so I would run it for a while. Then I would balance the carbs and set the fuel /air screws out at 2 - 3 turns. To a "blip" test.

Also I find it easier to adjust the fuel /air screws if I crank the idle down to around 500 RPM (she will rattle and make some noise at the low setting, don't be alarmed) after adjusting set her back up to 1150 RPM. If she till pop's a bit then your next step would be to probably be to clean out /rebuild the carbs.

Or you could just leave her alone. If it's only while the choke is on for the first few minutes and it's not to noticeable then enjoy the day

George

[ANVIL99]

thanks George I was thinking the same thing it runs well and a few pops here and there under choke does not bother me. Just going to ride it and enjoy the day.ordered a new emgo
air filter of ebay today $18.00 (yamaha dealer wanted $52.00).Just to add to the running rich problem when I run the bike in my garage with the door full open the exhaust fumes are
eye watering bad in 1/2 a minute, going to pull the new plugs I put in and see if they are carboning up.Question any advantage to running the higher octane pump fuels in an fj.

[ANVIL99]

Im not an idiot andy.bike runs rich with choke off. thanks for nothing......

[ANVIL99]

Hello Dan . Removed 4 very old looking champion plugs and all were equally black from carbon build up,replaced with ngk plugs.Could my choke not closing completely perhaps be
the problem here?

[fj11.5]

Could be that the choke isn't closing,you might have it pin pointed mate 

[Dan Filetti]

Could my choke not closing completely perhaps be the problem here?

It is possible.  It would not be all that hard to check.  Pull the (right?) side cover and engage/ disengage the choke.   Ensure the choke rail moves through it's full range.  I have read where the rail-keepers oval-out after too many engagements, which *could* cause choke hanging issues. 

I rather suspect your mixture screws are improperly adjusted.

Dan

[andyb]

Why tune the carbs based on a short-lived problem of how the engine sounds when cold rather than how it runs when you're using it?

Pulling very old plugs to read?  Do a proper plug chop at the rpm/load that you want to test, and get a good clean reading.

If you haven't personally been through the carbs within the last few years, a bike with that many miles probably has the fuel heights well out of spec, and likely ovaled the emulsion tubes.  Lord knows what shape the needles are in.  Pull things apart and have a look, doesn't take much time and gives you a more accurate way to assess things.

[ribbert]

Mine pops back out the carby cold on light throttle.
It's done this for years. It pulls like a train at all speeds and runs like a Swiss watch and the economy is good.
What have I done about it? Nothing. Am I worried about it? No!
Noel

[ANVIL99]

thanks Andy , now thats advice I can use.