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Stumped, Need Help...Sportster Running Rough!

V

vcataldo

Member
I've got a 2004 1200 Custom with low miles and stock engine. It is running rough and excessively rich. Checked the jets, changed the carb to one I know works well and the bike still ran rough and very rich. I then changed the crank and map sensor...still doing the same thing. Then put a new ecm -same problem. There are no vacuum leaks and compression is 120 on each cylinder. There are no trouble codes - I don't know what to do next and am just stumped. Would appreciate anyone's assistance or pointing me to next steps to look for. Thanks!
 
Welcome to THE forum. Lots of smart folks here and they'll be along soon. I'm not a sporty expert but am wondering if maybe you checked the fuel tank venting system? If the vent is not open and free, the gas will warm and expand. If the vent doesn't work it will pressure the tank and force it through the carb.

Bodeen
 
I don't know the exact spec for the compression on a 2004 1200, but wouldn't 120 PSI be considered pretty low. I know on just about any other motor it would be.

Have you changed the plugs/and or wires?
 
Hoople said:
I don't know the exact spec for the compression on a 2004 1200, but wouldn't 120 PSI be considered pretty low. I know on just about any other motor it would be.
Click to expand...

Agreed.

Bodeen
 
Throttle plate wide open and Carb piston lifted up. 5-7 Full compression strokes a 1200 Should have 200-225psi ... this is for a 2007 didnt have a older manual .. if compression below 150 psi inject 1/2 oz 30 weight oil and retry if reading is way higher then rings shot if not go for a leakdown test


Also what spot is the needle at ?
 
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Told you the smart guy's would be along quick!

Bodeen
 
Thanks for the responses so far...120 psi is a little low but still shouldn't make it run rich - never has done that to any bike I've had, be it sporty or big twin.

I changed spark plugs, checked the venting system and put 2 different carbs on the bike that work well. This is driving me nuts...
 
It's not the carb, I took one off another Sporty that is running perfect and put it on mine and it's still running rough and rich.
 
How many miles on that sporty has it been sitting , fresh fuel in tank , also any backfiring issue, or just runs rough thru the rpm range, battery condition did you check the all mechanical grounds.
 
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