Evo Dyna bogging down in midrange.. possible causes?

[TeeJayE]

I just picked up a 95 FXDL and I think it might be running a bit rough. It's pretty much stock with Screamin Eagle mufflers.

Seems pretty responsive from standing, but then quickly bogs down pretty bad, especially if I accelerate hard. It Idles fine.

I checked the carb (CV) and it's clean, jets aren't clogged, plug gap is ok but they look a touch pale. There's also no vacuum leak/intake leak.

Any ideas?

Thanks

[Hoghead]

Is the diaphragm OK in the carb? Is the screen atop the fuel tap clean?Check the accelerator pump is working too. If it's not fuel, it could be the VOES switch

[TeeJayE]

Diaphragm seems fine, I haven’t checked the screen yet but the accelerator pump is good.

How do I test the VOES switch?

[farmall]

Ditto everything Hoghead said.

Test VOES by connecting an ohm meter and sucking the hose. It's a simple diaphragm switch.

What are the cold compression test numbers? We test every bike that comes in the shop on a "need it or not" basis and it pays off because what's not measured is not known.

Any new-to-me HD gets a complete carb dip/strip/reseal and Evos get new intake seals since the carb is off anyway and they're old, even if I believe they ain't leaking.

Find out what number size jets are installed because owners often fuck that up. It's also common NOT to rejet when un-strangling the exhaust so your bike may never have been tuned for slip-ons. The stock crossover pipes breathe very well (fuck drag pipes, they kill midrange) so slip-ons are fine but the stock factory jetting was lean even with stock silencers.

I replace plugs (and wires) since they can look good and still malfunction under load. I do a charging system test, "need it or not" so I know that status too since it takes longer to get the meter off the shelf than do the check. Cycle Electric's website has a page on that.

I inspect the alternator/regulator connector for burning and damage, then add a blob of dielectric grease and reconnect. That won't be your problem but doing it as part of your "receiving inspection" can save ya pain.

1995 was an incredibly long time ago (I could still see my toes) and your ignition module or pickup may be dying of old age. The potting on pickups can revert and melt but that doesn't make them good or bad, though I replace the pickup if it's melted.

After verifying everything else is correct I'd swap ignitions.

[TeeJayE]

Thanks a lot, I’ll run through those things.

Should the petcock have a vacuum barb? I just found a vacuum hose with a screw bunged in the end. The petcock doesn’t have a spot for another hose so I’m guessing it’s a non-standard tap hence the bung in the hose.

Could that be causing issues?

[Hoghead]

Where does the other end of the vacuum hose connect? The inlet manifold , or maybe the carb? If so, I suspect that it was originally connected to the VOES.

[farmall]

Where does the other end of the vacuum hose connect? The inlet manifold , or maybe the carb? If so, I suspect that it was originally connected to the VOES.

A vacuum leak would certainly make it run poorly.

[JBinNC]

The vacuum line on that bike went from the back of the carb to a tee, and one leg connects to the VOES and the other to the stock vacuum petcock. If the petcock has been replaced (and the stock ones are prone to vacuum leaks), the end of that hose should be plugged. You need to check the VOES to be sure it functions AND that it does not have a vacuum leak itself. And while you are there, use a new piece of vacuum hose to connect the carb to the VOES, eliminating the tee.

Jim

[TeeJayE]

Thanks guys.

VOES is fine. Soaked the carb overnight and it’s running waaaaay better. Like night and day.

Still sputtering a bit under load but I also didn’t run it for more than 15 mins so probably still cold. It also sat for 2 years so I’m hoping with a few more blasts it’ll open up.

[farmall]

It also sat for 2 years so I’m hoping with a few more blasts it’ll open up.

I hope ya drained the fuel tank by removing the tank, removing the fuel valve and pouring it out completely since it sat for two years.

If not, do that and slosh around whatever fuel you put in it first to flush out the crud. That will keep it from re-clogging the carb.

[TeeJayE]

Ok I take it back. Just been out for a proper ride for a couple hours and it’s running like garbage. It pulls smooth and really well up to about 2K revs and then literally zero power from there upwards in any gear. Hard to describe but regardless of how quick I open the throttle, it just loses all power over 2000-2200 rpm.

Maybe I didn’t check the VOES properly.

[TriNortchopz]

sitting for two years and carb soaked overnight...did you actually take it apart to ensure all passages and jets are clear?
What size jets in there? Is the float set right?

Harley CV Carburetor Tuning Issues & Troubleshooting

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

[TeeJayE]

I took it apart. Jets are 45/180 and they got a soak too. They’re clear as daylight now. I didn’t adjust the float but thanks for the CV link I’ll go and do it now.

I need to drain the tank and check the screen so there’s still that but other than the float (and assuming the jetting is correct) I think the carb is good.

[Guest]

Maybe reaching a bit here but are you 100% sure its bone stock? A lot of Evo owners put EV27 cams in these things. I know when I tried to run a 180 main jet in mine it didn't like it as it was too lean. Wouldn't pull in the midrange until i had at least a 185 in there.

Also, might be worth looking at the needle. Is it a stock factory item or does it have notches and an adjustment clip?

[Tattooo]

Post a pic of your plugs once it's running right before you start moving needles or changing the jets.........................