Suddenly my 2000 Fatboy started sputtering at take off from stop. Let it idle up some to get to 5th gear. Then ran fine. Every time I stopped at an intersection, I had to feather to get it up to speed and at times, it just kicked in and road fine. Only thing I found of the carb was the vacuum slider had a pin hole in it. Slapped a tiny piece of first aid tape on it and got half way 15 miles home and it got to the point where I pulled carb apart the first time to see what the hell was going on. Idles, just won’t take off without sputtering. At times it would just light up and go. Trying to think about physics as im trying to pull away from stopping. What is the common? Id say throttling up is consistent. Sputters until I get it up to the speed limit, which was 50 in the county.

 

A sudden carb issue could be dirt in the carb... This is an OEM CV40 carb, right?

Since you found a hole in the slider diaphragm, it would seem it's time for an overhaul.

CVPerformance sells kits with all the wear parts that can/should be replaced during an overhaul.

https://cv-performance.com/harley-cv-carburetor-parts

Do a complete disassembly, serious inspection & cleaning, then reassembly with the new parts, and retune with mixture screw. Don't forget to set the float..

The jets, if you get them clean and haven't made engine mods since last disassembly, should be fine...

Also pay special attention to the manifold seals.... I usually replace them too when I do a complete carb overhaul...

Good luck with your overhaul...

 

In addition to dirt in the carb, old fuel or any fuel that has water/moisture in can cause intermittent problems like you’re experiencing. A tank drain and some fresh fuel could help here too.

 

I Replaced the slide. Still did it after a few minutes of running. Removed fuel filter looks, brand new. Petcock is flowing well so gas is flowing well on RES and in ON position going to carb. I only have 23k miles on this fatty. I just ran it into the dealership few weeks ago for a multipoint check. Only thing they suggested was choke lever replacement. I use a clothes pin in between bracket and back of **** for years. It stays open all the time without it. Front shock seals are worn and a front tire showing signs of dry rotting. Only about 4k miles on that tire! Funny thing is, when I left the dealership, it died a few blocks away. I believe it’s the same gas. They shut the fuel off when they were done. But I rode it home 27 miles without an issue. I hope no one there is looking for business!! That would be very shameful. Not to mention very unsafe! That said, I drained the tank tonight. Was about a gallon and a half left. I will replace the fuel from a station other than the last one I went too. Carb is now apart. Very clean still. Removed jets and those are clear. The front left Venturi looks dark. Can’t see the brass color anymore. Probably the grime that the engine blows back into the carb has discolored it. But I’ll look under the scope to be sure. Can’t feel where the air i blew into this hole escapes. But I will take it to work to clean and inspect it. Right side is clear and shiny again. I am a supplier quality professional, so I have a bit of engineering background and some tools at work that may help me make sure the carb passages are clear. I also checked the accelerator pump. That’s shooting very well in two directions. I replaced that 7 years ago cause it tore open and squirted gas out the pump arm hole. Now I’m hoping it was bad gas, and not a crank position sensor, cause it’s never acted like this. Just with this tank of gas so far
Thank You , will let ya know tomorrow how it goes!

 

Sadly, that does happen, and they are out there... luckily they are in the minority...

As far as the carb goes, sounds like you are on top of it.....!

Report back how this plays out...

 

And wouldn’t ya know, it has to happen when one of the biggest rides in five years comes back to Milwaukee, my fat bottom girl decides she wants to stay home. I’m one county south, hearing all the bikes run by my work on way to celebrate the 120th! Broken hearted, here I sit… thought she farted. No, she ****!

 

So, long story short as possible. Wednesday I flew to House of Harley to pick up a new vacuum slider. Current one had a pinhole. Got home pulled carb completely apart. Soaked it in solvent at work. Drained gas, fuel filter clean as a whistle. Petcock disassembled. Flowing well! Replaced fuel line. Vacuum on petcock, no leaks. Removed choke cable, cleaned and working. Still using a close pin still pinched in between bracket and ****. Thing never stayed shut anyway. Assembled carb and back together. Plugs changed. Started and accelerator diaphragm pump rod hole had gas blowing like a whale at throttle up. Good grief! Took that off a second time. It was ripped like a mouse ate through it. Back to the shop for a new one. Tore off carb and went through it again with carb cleaner. Reassembled and put back on bike added new fuel from another station. Fired right up and drive to the Harley museum last night. 48 mikes round trip. Ran like a top! My suspicions are, bad fuel as suggested, or that small pinhole in the diaphragm on the vacuum slider. Because when I left the accelerator pump diaphragm in the carb when I soaked it in solvent, I used a little bit of penetrating oil to free up some of the gunk in the throat of the carb hoping anything else that may have been stuck in a passage would free itself. That was the first thing I looked at when the sputtering started! It was just like new when i replaced it five years ago. When I pulled it out after seeing a whale sighting, it was almost ripped right through and looked like a mouse was gnawing on it. Small shards of rubber in the cap.
Nothing electrical, just a mechanical fuel issue. Or, the gas was that bad. And I filled it less than a month ago, had half a tank left and had just washed it last Monday preparing for the Rally. Going to look into the seals on the fuel cap and fuel gage next to make sure there are no seals leaking. Bout all I have left to look at.

Thank you guys for the advice. When I was at the House of Harley, the poor guy helping me had just got off the phone with a screamer. I heard the conversation for the most part, and he kept his cool pretty well. I get it, you gave thousands of people to serve and one guy is yelling for his bike, yet it took a few days for him to reach a decision to let them repair his bike. If you know a big rally is upon you and your bike is in the shop, you’d better giddy up!! Shop mechanics need to keep things going. They don’t go home and sit on their *** waiting for a decision. Your bike gets pulled and sits in staging while they get someone else’s repaired. He was lucky they put it back on to begin repairs.
One more thing. I also need to look at that solvent and the penetrating oil. Something attacked the accelerator diaphragm. And I did catch the CV website. First one that popped up on my web search. Interesting, we saw the same page!


Again, thanks for the support guys, it helps us mechanically inclined people continue the learning process and keep our costs down so we can have fun in the sun!!
Peace and Ride on!
DougO from Racine, Wi

 

Glad you got it figured out. Good job.

 

Dude, I’m glad I stuck with it. I was able to go up to the rally Friday Saturday and Sunday!! My wife bought FooFighter tickets and I am not really a fan. I think I am now! What a show. The On Milwaukee review the next morning was spot on!! I rode up with my brother in law Saturday with not one issue! Hung out with him and his buddy and wife on Brady St before Joan Jett came on. When the headliner started, they gave it 100 and 10 percent!! My wife even made eye contact with David Grohl as his bus passed my fatty within a foot!! What a spectacular band to close officially, the 120th! You few guys that chimed in, I took in all your advice. If I could, I’d buy you all a round of shots and a chaser! You were part of my experience and I had to break down and tell my wife I got advice from a bunch of cool dudes I didn’t even know that walked me through things I take for granted sometimes. Fundamentals! I did what they said and I got to go to the rally! God Bless you brothers!

We were close

46 plus thousand people!