First post, I usually never post in forums I just use the search function and can typically find the information I need but I’m getting desperate so here I am. If you don’t care about the story (it's pretty long) feel free to skip to the end, I’ll summarize my problem(s?). I have a 97 sportster 1200 that I purchased at the end of last season, only the second bike I have owned (in addition to an 80 ironhead that I still have). When I purchased the bike it would only run with the enrichener on or if you held the throttle open, it would not even idle. I knew it was sitting for a couple years (previous owner said 2 but who knows) and the battery was weak so a carb clean and new battery were in order.

I get it home and clean out the carb, put in a rebuild kit, replace the accelerator pump diaphragm (it was in pieces), replace the intake seals, throw in a new battery, fresh gas, plugs look brand new so I check the gap and put them back in, try to fire it up annnnnnd nothing good. The bike keeps backfiring through the carb like a shotgun, won’t start at all. I pull the carb about 8 more times, each time thinking maybe I missed something, clean it more, replace jets (I think I replaced both pilot and main jets), blow compressed air through it again, repeat process, same result. I mess with the mixture screw but nothing changes. Finally replace the plugs and it starts and idles! Yes I should have done that in the beginning but they looked so new I was confident they were fine but alas, I was wrong.

At this point it was January or February in Ohio so no riding was going to be taking place so I put it away thinking it would be ready to roll come spring with just some adjusting of the mixture screw. Starts getting warm in March so I go to get out the bike, it fires right up and idles but once warm it runs horrible, barely idles, and eventually doesn’t even idle. When it’s still cold you can give it throttle and it’ll rev right up but once warm giving it throttle usually just kills it. I mess with the mixture screw and nothing changes no matter where I put it. So I figure maybe an ignition problems that starts when it gets hot so I replace the coil and plug wires and nothing changes. Replace ignition with programmable Ultima single fire ignition and coil along with new plug wires, check static timing and nothing changes. Still runs horrible when hot. I mess with the mixture screw some and nothing changes, it idles slower and slower the warmer it gets no matter where the idle screw is set. I remove the idle screw, soak it in carb cleaner, carefully clean it, blow out the passage with compressed air, and put it back in. Put in new plugs again. No change.

My thought now is maybe if I ride it I can clear out some crap in it so I limp it out of the driveway and get out on the road. Whenever I let it coast it almost always dies but when in gear I can give it throttle and it burbles for about 1 second before taking off and it takes off really good. So basically I’m riding and it runs awesome when I’m on the throttle but horrible when off or when first getting on. I ride for about 2 miles and have to slow down, bike dies. Struggle to get it started but I finally do and ride for about 3 more miles. When I turn around to head home it dies and won’t start at all. Finally I get it started with the choke but any throttle and it dies so I limp it home almost entirely using only the choke (yes unfortunately I realize just how horrible that is).

End of story, beginning of summary.

So at this point I’m hopeless, this bike is the first I’ve ever really messed with a carb so I’m trying to learn how to tell rich vs lean and such. As of now the bike has new jets (175 main and 42 pilot), new programmable ignition, new plugs (again), new wires, new coil, new battery, rebuilt carb, cleaned air filter, new intake seals. At this point it just about has to be an air fuel ratio problem right? As of now the bike has screamin eagle pipes and intake (I think the intake is, either way it isn’t stock). Since I’m a carb newb I need help on determining rich or lean so here are the reasons I think it could be either:

Rich:
When cold it smokes if you give it throttle
Runs worse when hot
Idles really low no matter where the idle speed screw is set
Burbles for a second when hot and given throttle

Lean:
Runs with enrichener
175 main and 42 pilot don’t seem very large at all, sounds like many people even use a 45 with not much more than stock setups

Any suggestions? I guess next up I'll either light the bike on fire or pull the carb (probable at least the 15th time) and replace the vacuum diaphragm but it looks perfect and functions like it should from what I can tell. I tested the VOES with a hand vacuum pump and the resistance was good, tested fuel petcock with vacuum and it flowed instantly. If its running lean I can put in bigger jets but I'm not confident that it is running lean. I'm sure I've forgotten some things but any questions, comments, suggestions, or anything is much appreciated!

 

When the bike is warmed up, does it idle/run better or worse if you pull out the enrichner?

Right after you've had it running, pull the vacuum line off the backside of the petcock and check inside the vacuum hose for traces of gas. It should be dry.

 

Did you make sure the mixture screw spring, oring, and washer were still there? Those going missing acts like an intake leak.

 

Thank you both.

When it gets warm the bike will only run with the enrichener pulled out, any throttle at all will kill the bike. I'll start it up and let it get warm and check the vacuum line this afternoon.

The spring, washer and oring were all there. If I remember correctly the washer was on top of the spring? The oring looked fine but I couldn't find a pick to pull it out so I just pushed it back into place and put the mixture assembly back together. I will look into finding a replacement oring just to eliminate that being an issue.

 

Could be a leak in the intake seal thats why when it warms up it runs worse (expansion so the leak gets bigger) but you said you already replaced that right? Its def running lean if you have to keep the choke out. So the carbs not getting enough fuel, or theres an air leak somewhere. Did you say you cant set the air/fuel mix? or no matter how much you turn it, it doesnt matter? That would be my guess is theres too much air not enough fuel. Im guessing since you took the carb off that you cleared out all the old fuel and put in new gas, i know bad gas will make it run like crap. Ive now exhausted all my knowledge.

 

Alright so I went and let it idle for a few minutes to let it get warm, had to leave the enrichener out but there was no fuel in the vacuum line going to the fuel petcock. I did notice however that the front cylinder was getting hot while the rear cylinder was still pretty cool, slightly warm but still cool. So I did a compression test and the front cylinder was ~120 psi whether the throttle was open or not, and whether the vacuum slide was held up or not. Now the rear was ~120 psi as well when the throttle was open but would sometimes show ~120 psi and sometimes only show ~95 psi if the throttle was closed. Since both cylinders showed ~120 psi with the throttle open I imagine they're both okay? Is it possible there is something like a rats nest in the rear exhaust that could be restricting flow sometimes showing lower compression if the throttle is closed since the engine has to work harder to pump air or am I grasping at straws with that? On second thought even with an extreme amount of extra back pressure that shouldn't change the compression reading... So any suggestions on why the rear cylinder could be firing when cold but misfiring when hot? The front plug was black and dry while the rear plug was black and wet but that could just be because I had it idling with the enrichener on. Also on another note I tried removing the vacuum line while the engine was running and the idle went up (yes I know, air leak=high idle) but whenever I try to set the idle speed using the idle speed screw I can never get the idle above 1000 rpm, only around 600 rpm once the engine is warm. So to me introducing an air leak made the bike run "better", pointing to the bike running rich???

In response to saltlick, yes the intake seals are new but at this point I'm almost to the point of replacing them again just to be sure. Whenever I try to mess with the mixture screw it doesn't seem to make a difference whether I make it richer (screw out right?) or leaner (screw in right?). It has new gas but when I get a chance I'm going to drain it all again and check the petcock screen to make sure it isn't clogged, the previous owner said he replaced the petcock so I'm wondering if whatever the issue ends up being is the reason why the bike stopped being ridden. I would like to put on a non-vacuum petcock to eliminate that as a potential issue?

Keep the suggestions coming the weather is too good to not be able to ride.

 

Here's a link to a site that's worth a read.

https://cv-performance.com/harley-cv...-tuning-issues

Some good stuff there that may help you with a methodical approach.

It might be possible you have more than one problem but confirming the carb is 100% isn't a bad thing to do if it was all grungy.



Although you've replaced the intake seals, have you confirmed they're not leaking by spraying around them?
In the link you'll see a mention about the jet needle, if that's in wrong it causes lots of strange running issues.
Your idle mixture screw should be assembled with the spring, then the washer, then the o ring. The washer is to prevent the o ring being damaged by the end of the spring.
A reasonable starting point for the idle mixture would be around 2 & 1/2 to 2 & 3/4 turns out from lightly bottomed.

Do you see the accelerator pump nozzle actually squirting fuel? Unlikely to cause idling issues I know but, might cause blipping the throttle and acceleration issues.

Have you checked the float height? If you have a float bowl drain screw you can use a clear hose the same diameter as the standard black rubber hose as an initial rough guide by lifting it up by the side of the carb and the fuel level will equalize in the drain hose to give you an idea of the level in the bowl.

Make sure the diaphragm in the top of the carb is not pinched or has a pin hole in it.

You might think about getting one of those ultra sonic bath machines. They're fairly cheap, and can be put to lots of good uses other than carb cleaning. They really clean out all the hard to reach places.

cHarley's suggestion about the vacuum hose check for fuel in it is certainly worth looking at. I've not seen that problem too often, but it can be an issue.

from an ignition point of view, have you checked the spark when the motor has warmed up?

Edit........
Just saw your new post and you've checked some of the things I mentioned.

There shouldn't be a need to replace the new intake seals unless they're torn.

120 psi is pretty much spot on for a stock Sportster.

 

I removed the fuel petcock and the screen looked clean, a few little things but not clogged unfortunately. I put it back together and was going to start it and let it warm up to check for intake leaks and check for spark when warm but when I checked the oil it was all the way to the top of the reservoir, as in almost overflowing. I tried to see if it smelled like fuel but since I was just messing with the fuel petcock everything smelled like fuel. Drained it and it all looked like oil but still I'm not sure how in the world it could have gotten so full, maybe riding the bike home yesterday with the enrichener on soaked the piston enough to allow fuel into the oil? It has never seemed like it flooded but I have never experienced a flooded vehicle so I wouldn't really know. Maybe I'm just being paranoid about every little thing now.

j_bee
I have tried setting the mixture screw out to 2.5 turns out with no luck. I also replaced the fuel float valve and set it to spec with the carb tilted at whatever angle the service manual called for but not luck, first time digging into a carb but I'm fairly sure I got it right. I don't exactly follow how to use the clear hose to check the fuel level, I understand the concept of checking the level just not how to actually get the carb to drain into the hose. If I loosen the flathead screw by the drain will it make the carb drain and allow me to check the level in the hose? The accelerator pump squirts with the throttle, I replaced the nozzle with one from J&P because I lost the little check valve weight under it when cleaning out the original one. The diaphragm in the carb looks good but I have a replacement so I'm going to put that in next time I pull the carb anyways.
I removed the bowl and soaked it in carb cleaner but I don't think I soaked the main body of the carb. In order to soak the main part of the carb is there anything not obvious I should remove, obvious items being the mixture screw(and oring), main and pilot jets, the plastic cap along with the diaphragm, the float and its valve... That's all I can think of.

Next up I'm going to put in new oil and plugs, check for intake leaks and spark in both cylinders when warm. If everything seems fine there I'll pull the carb and start soaking.

 

jesus youve done alot of stuff. Cant believe its still giving you hastles.

 

Dang sounds like a mean gypsy put a hex on your bike. Keep after it and good luck. Its probably something simple.