Hey everyone! Name is Josh, been a long time reader and joined up the other day to see if someone here could help me with a problem I am having.
All the info I got:

2004 HD Sportster 1200C
16,500 miles
Bought the bike from a local dealer, claimed to have rebuilt the carb and couldn't get it to run right. They could ride it, but once it was idling for a few minutes it would foul the plugs and shut down. Due to this, I got the bike for half the asking price (price based on actually fixing the problem) and in as-is condition.

Once I got her home, I checked everything. Adjusted the carb a bit and took her for a ride. She was burping and sneezing all over the place. I replaced the bad fuel valve on it (gas was back flowing in to the carb due to a bad diaphragm in the valve) and tuned her up. She was stubborn until she was warmed up properly, then she was fine, and all was right with the universe.

Until I took her on the highway. Under normal operating temperatures she ran fine, once I got her up to 65-70 mph and tried to maintain speed, she would start burping again. I ordered a rebuild kit and tuner kit from CVP and went about building the carb. I found all original worn out parts inside the carb, remember the claim from the dealer saying they rebuilt it? Once done, retuned the carb, and she fired right up, had noticeably more power and seemed like a new bike. The burping at 65-70mph still remained.

Back on the forums, did some searching, and came to the conclusion that it had to be an air leak. Took the carb and manifold off to verify that the seals from the carb rebuild kit were still good, they were. Pulled the exhaust and found that the crush sleeve on the front port looked to have a portion of it blown clear out of it. Replaced both seals and the 2 seals on the collector. Readjusted the a/f mixture (adjusting all the way in then all the way out to the point of idle stumble and placing the screw in the middle of the 2 points) and she fired right up, no issues. Revving her up a little sounded good, but every now and then she would sneeze, stumble, then go back to normal idle. Under load she was still burping on me.

Took the carb off, seafoamed it, fogged the motor with said seafoam. After all that, she idles better, revs are a lot smoother, but I still can not adjust the sneezes and burps out of her.

This is were I am at now. The sneezing while revving up from idle and the burping is telling me that I still have an air leak, but have replaced every seal on the outside of the motor that I can. When she does sneeze while revving, it sounds to me like it is coming from around the carb, but that might be a normal sound, just amplified by the air leak. She runs fine but a little sluggish with choke pulled all the way out, still burps and sneezes with it only half way out. No code from the MAP sensor and no check engine light.


List of work done to motor so far:
Rebuilt carb
CVP Tuner Kit
Replaced seals from exhaust to air filter
Fogged the motor
New air filter
New spark plugs (tried SE and stock plugs)
Indexed the plugs

I hope someone here can help, haven't gotten much riding this summer and would like to take the wife bike camping before it's too late.

Thanks, and sorry for the very large first post!

-Tabogon

 

It still sounds like a lean condition to me. I have had it happen from a plugged fuel cap vent in the past.

 

Some additional information would help......

Is the air cleaner stock?

What are the sizes of the carb jets?

Sportys are known for the carb farts, but this sounds outside of the norm for the common carb farts.

 

Sorry I don't have an answer Just wanted to emphasize with your lieing dealer encounter. I took my new 2013 Sportster 72 in for it's 1 k service last month. They claimed they replaced my air filter because it was too dirty. I live in the agricutural area we get lots of dust so I believed them. This weekend I installed a custom air cleaner myself. i discovered not only was the original filter still in place but they'd installed the cover w/o lining up the gasket properly & slit the rubber gasket btn the cover & body Now I wont trust them again

 

Air filters are washable. No reason to replace on a 2013.

 

Excellent Point!

 

The above are excellent questions, and the first ones that came to my mind. Also, what exhaust do you have? Is it stock? My thinking is that possibly the intake was opened but not the exhaust. If so, that is a no-no. You can open the exhaust without changing the intake, but if you open the intake, you MUST open the exhaust. Have you "read" your plugs since changing them? It sounds like an air/fuel ratio that is out of balance to me. Get the maintenance manual for your bike, it will give you all the specs (jet sizes, etc.) and prove itself invaluable over time.

Be sure to let us know how you make out!

 

Check the flux capacitor? It's directly beside the do-hickey that makes the whatchamacallit work!


Just a little humour!

Keep the info flowing and there are tons of guys that can diagnose your issues. Cheers and good luck gettin your scoot healthy!

 

my dad was an aircraft mechanic with delta airlines for 35 years. my dad would say that mechanics is not magic, it's just running your check list! it sounds like the bike has been played with, so i agree you should check the jet sizes in the carb. i had a brand new 1999 and 2001 sportster, and i like the pumper carb, but it is easy to foul the plugs the problem you have could be fouled spark plugs. just a little bit too much choke, and you foul the plugs, i always kept 4 extra plugs around. did you mention how many miles on the bike, you said parts of the carb were worn out. do you have a factory service manual. cheers from montana

 

Air cleaner and exhaust are both stock.

Jet sizes are 45/180, the recommended size from CVP for a stock a/c and exhaust.

Originally, the plugs were reading that the bike was way too rich. A byproduct of the dealer turning out the a/f mixture to try to lean out the stutters.
After I rebuilt the carb, the plugs read what I assumed was detonation. The threads were all black, but the center electrode was white. Figured I had gotten a bad tank of gas. Drained it and filled with new gas, and so far they are reading normal, but I haven't gotten a chance to ride her much. (Plugs were replaced with every repair I have done so far)

Another thought, assuming the previous owner just said screw it and traded it for a new bike instead of trying to figure out what the problem was. And knowing that the dealer continuously ran it too rich. Would a clogged collector cause this? Inside the ends of the pipes are covered in carbon, when I took the exhaust off to replace seals, the collector openings were covered in carbon, and both pipes idle differently. The back port has the normal raspy lope that harleys are known for, the front is a softer really quiet lope that seems more like a car's.

How do I go about checking the cap vent isn't clogged up?

Thanks for the response!

-tabogon