i had the same issue, would idle fine but on the road no power and very very slow to rev up, I removed the top cover of carb and checked the diapgram and I found a small tear , was hard to see until I stretched it out, replaced it and boom bike was running like a champ again

The other thing that can cause this is the needle jet could be in upside down, this will cause the same thing you describe, remove the main jet and emulsion tube and a silver colored jet will fall out, make sure it is in the correct way, it should prodrude into the mouth of the carb.

 

You may have something there, strange as it may seem, a lot of solutions come to me in my sleep, this morning I woke up at 4:45 thinking about that very piece, whether it goes in with the short or slightly longer side up, in previous jet changes it has never fallen out but did this week. I have been putting the short side up because it did not seem to want to go in any other way and I woke thinking that my emulsion tube was not threading into the body as far as it should, hesitant to force it and risk stripping the threads, I will try to press that up into the body at 8am...( I have no garage, rv park rules, silence between 10pm and 8am) I will let y'all know how that works out

 

Not necessarily, when I visited Florida last year all I could find was that ethanol crap. So before we left Oklahoma I filled up a spare gas can and topped off the bike tank. No problems while there.

 

Robtarra...thanks but that silver jet glide is a 1 way piece, the longer end is .012 wider than the short end...as far as the diaphragm being torn I blew (my breath) into the crescent above the intake which rose the slide so I would have to say the diaphragm in fine and intact...
I, in a desperation move put the original emulsion tube and 170 jet in as it ran great lean but great for a couple of years...same thing, breaks up under throttle...btw the original emulsion tube has a larger id and will not accept the smaller (threaded) 180-190 jets...months ago when I discovered this I spoke to Eddie, the dyno guy at Topeka HD, he said he has never heard of such a thing, I then ordered a 175 and 180 jets and a emulsion tube to fit the jets. I have, up until super bowl sunday (2 years,) ran the 190, that day is when it started breaking up...thru process of elimination and experimentation have come to the conclusion that I wait for the coil at which time new plugs also...tho they look good and a new fuel valve......my finances are a fluster cluck, by then they should be straightened out...

 

TEch slap, just blowing into the vacum port will not tell you if your diaphram is torn you actully have to physically remove the top cap and pull the slide and diaphram unit out of the carb to inspect it. takes all of 10 minutes to do and is quite simple to check, as well if it is torn even just a little bit would cause those symptoms. *also alto cheaper to fix then a new coil pack is*

 

If the emulsion tube won't accept Kehin jets, then someone has changed the emulsion tube...probably a DynoJet kit. Do you have an Adjustable needle? open the top and see. The DJ kit parts would explain why it ran well with the 170 main. DJ numbers do not correspond to OEM (Kehin) cal numbers, and the DJ needle isn't compatible with the Kehin needle jet.

If you're running with mismatched parts, it would explain your issues. Your problem seems to be in the needle/needle jet transition range, and once you get past that point it runs well on the main jet.

Open the carb and replace any mismatched parts with OEM/OEM compatible parts(tuning kit). I think you're having a problem with your needle/needle jet compatability or the needle height.

 

Correct sounds like a Dynojet emulsion tube, that would explain the larger ID jets, as for the diaphragm yes it needs to be removed to check, put it up against a light a slitghly stretch the rubber to check for pin holes or small rip, mine had a small rip in it that could only be seen against a light.

 

Here is a better look at the needle jet, click on the link

http://www.cv-performance.com/harley...tuning-issues/

 

Good link Rob...thanks

 

Problem solved...apparently the silver jet guide is a press fit into the carb body...why it "fell" out remains a mystery...thanks much to RobTarra link to cvp for the solution. Thanks Rob