Running Rich? Where's the "Extra" Fuel Go? - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
 
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post #1 of 7 (permalink) Old 11-20-2016, 09:24 AM Thread Starter
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Running Rich? Where's the "Extra" Fuel Go?

Where does the "extra" fuel go when running rich? I had ridden about 4 miles yesterday with the bike on about 1/3 choke (forgot to move the choke lever), and noticed some smoke coming from the rear cylinder exhaust manifold on the exterior of the manifold as some fuel was coming from the the area of the top of the head and dripping down. For all I know, it could have been coming out the breather and made it's way to the top of the rear cylinder. If I was running rich (from running with partial choke or from not having the PMS screws correctly adjusted), where would the un-burnt fuel end up, and would it be the same for choke/PMS? I would've thought out the tailpipe.

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post #2 of 7 (permalink) Old 11-20-2016, 09:45 AM
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I have left my choke on before with no ill efects that I noticed, the only thing that would happen is early fouling of the spark plug. Any unburnt fuel should go through the exhaust, I think you may have a leak somewhere.

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post #3 of 7 (permalink) Old 11-20-2016, 10:01 AM
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If your engine is running rich for any reason, I dont think there is any un-burnt fuel (as a liquid or a vapor).

I think the fuel would not burn correctly, in that instead of making carbon dioxide and monoxide, you would have free carbon (soot) in your exhaust. This is what fouls up your plugs and catalytic converter after time.

I guess in a sense carbon is 'fuel' but its not gasoline, and the hydrogen in the gas is consumed.

If you got something dripping its a leak. If I remember correctly running an engine choked/rich makes it run very hot. This will rainbow chrome exhaust and make your heads hotter than normal - not a good thing to do repeatedly.
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post #4 of 7 (permalink) Old 11-20-2016, 03:04 PM
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Actually, running richer normally causes the engine to run cooler. It's running lean that will cause heat issues. It's having the unburned fuel ignite and finish burning inside the pipes that can cause yellowing. The engine is usually fine, just some carbon build up that will hopefully get cleaned out with your motor oil.

As far as where the fuel goes, anything unburnt will end up in your pipes. When it ignites, it causes a backfire, which can cause serious damage depending on how severe it is.

I've always set up my carbed air cooled bikes just slightly on the rich side, it is not quite as efficient but it keeps things slightly cooler.

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post #5 of 7 (permalink) Old 11-20-2016, 07:40 PM
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Mick is right, running lean makes your engine run hot, and it will discolor a chrome exhaust, at least right at the cylinder head.

Everyone leaves a manual choke on too long from time to time, you dont have to worry about that. Any carbon produced will be gone the next few times you get on it at high rpms for a bit.

One thing that is helpful on a motorcycle is to make some things a ritual, like getting on the bike, getting off, starting and checking your lights and brakes.... Do it the same way every time you ride and the chances of doing something stupid, like jumping off the bike with the kickstand up, are greatly diminished.

For example, for me starting the bike cold:

Turn gas on
pull choke out
turn key on
check neutral light
turn kill switch on
hit the starter
engine starts
push choke in partway...

you have to do all those things, if you do them in a random order you are more likely to forget something.
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post #6 of 7 (permalink) Old 11-20-2016, 08:00 PM Thread Starter
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"like jumping off the bike with the kickstand up" - Did that once.

Thanks for replies.

2002 V-Star 1100 Classic
Memphis Shades Batwing Fairing
Dragbar Handlebars
National Cycle Cruiseliner Saddlebags
7" LED Headlight with 4.5" LED Driving Lights
Corbin Seat
Engine Guard with Kuryakyn Pegs
Chubby Intake with TimB's PMS Thumbscrews
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post #7 of 7 (permalink) Old 11-20-2016, 08:07 PM
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I know someone that did it with a brand new Harley 1200 sportster

rode the bike 100 miles home from the dealer (in the next city over)

pulled in the driveway, turned the engine off

jumped off and went to put the kickstand down like a bicycle...

104 miles on the odo..... ouch!
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