EVO Idling problem,please help! : V-Twin Forum: Harley Davidson Forums

faroogoo · 10-11-2009, 03:18 AM

Ok i have an EVO engine fitted with an HSR42 Mikuni which has been running like a dream until today.

Its developed a problem of not wanting to return to normal idle rpm.

It will go back to a normal idle if i wind out the idle adjustment screw but as soon as you give a rev it returns to its fast paced idle.

I pulled a pair of brand new plugs after 4-5 minutes of idling & they
were fouled up pretty bad.

I've removed & checked the needle/float,Cleaned the carb out with carb cleaner.

Checked the choke isnt engaged.

Im since out of ideas,if it was a car with similar problems i'd suspect it was either a fuel or vacuum problem but im unsure if or where there are any vac lines on the evo besides the one that joins up to the hypercharger?

Any help would be greatly appreciated.

blackjackcustms · 10-11-2009, 05:42 PM

my mikuni had an inconsistent idle, and I lubed the slide with Inox, and it stopped. If you have fould plugs , I would look closer at the choke. Might remove it, and clean out the hole real good?

rcsoftail · 10-12-2009, 01:44 PM

Spay some brake cleaner on the intake manifold where it goes into the heads. If the rpm changes, you have a vacum leak there.
Check that the acclerator pump rod is not touching the plastic lever up by the cables. If it is, the engine vibration can cause fuel to come out the accelerator jet while idling. You should have close to a 1/16" gap at idle. Unlikely this is the cause, but you never know.

faroogoo · 10-20-2009, 01:24 AM

Bump still cant find the fault?

Ok so far i've replaced the carb to manifold rubber,replaced the vacuum hoses from the carb,hypercharger etc,removed choke cable/mechanism & cleaned it & the hole out.

Also removed/checked/cleaned the needle & float too.Plus lubed the slide,but its working nicely snapping straight back when the throttle is released.

Also sprayed around the manifold to cylinder join & had no results there.

Must be something im missing though & its probably simple lol.

Locodave · 10-20-2009, 02:20 AM

Hi, Guessing. Take the float out. Fill the sink with some water. See if it has a hole in it or water-logged. ( Drops like a stone. ) Only other thing I could think of.

Take the gas line off the carb, let it drain a bit of gas into a glass jar. See if you got some bad gas with water in it. The water & gas would seperate after a while to see it seperate. Dave

baggersport · 10-20-2009, 04:53 AM

There's a diaphram in the Hypercharger that operates the butterflies. Are they moving when you throttle up? If the diaphram has a tear, it will cause an intake leak.

.

faroogoo · 10-20-2009, 05:27 AM

Quote:

Originally Posted by Locodave

Hi, Guessing. Take the float out. Fill the sink with some water. See if it has a hole in it or water-logged. ( Drops like a stone. ) Only other thing I could think of.

Take the gas line off the carb, let it drain a bit of gas into a glass jar. See if you got some bad gas with water in it. The water & gas would seperate after a while to see it seperate. Dave

Yeah thats a good idea il take it out tomorrow afternoon & test it,hopefully it is just something simple i've taken for granted like the float.

Yeah i forgot to mention in the earlier post that completely drained both tanks & the carb when i thought it might of been bad gas.

Quote:

Originally Posted by baggersport

There's a diaphram in the Hypercharger that operates the butterflies. Are they moving when you throttle up? If the diaphram has a tear, it will cause an intake leak.

.

Yeah i thought the same thing when i was testing the other day so i removed the vac line & plugged it,but yeah didnt work.

I'l report back after i've tested the float with an update.

Thanks for the help so far guys,i appreciate it.

faroogoo · 10-21-2009, 03:38 AM

Update- Tested the float its still good,removed & cleaned out the needle & seat also.

Fired it up & its still idling all over the place,it seems to be returning to normal idle
a little quicker than previously but thats after it idles higher than normal first.

So it seems i've tried pretty much everything that i can think of,might have to make a few calls tomorrow & see what the local indy reckons.

Still keen to hear any other ideas also.

Dan89FLSTC · 10-21-2009, 08:55 AM

Quote:

Originally Posted by faroogoo

Update- Tested the float its still good,removed & cleaned out the needle & seat also.

Fired it up & its still idling all over the place,it seems to be returning to normal idle
a little quicker than previously but thats after it idles higher than normal first.

So it seems i've tried pretty much everything that i can think of,might have to make a few calls tomorrow & see what the local indy reckons.

Still keen to hear any other ideas also.

You might try lubing and adjusting the throttle and idle cables.

blackjackcustms · 10-22-2009, 02:54 PM

If you have an ignition with a mechanical advance, it might be sticking, and that would do it. I've seen it on Dyna "s"s.

baggersport · 10-22-2009, 03:14 PM

Quote:

Originally Posted by blackjackcustms

If you have an ignition with a mechanical advance, it might be sticking, and that would do it. I've seen it on Dyna "s"s.

Oooo...good one!

.

faroogoo · 10-23-2009, 11:54 PM

Ok latest thing i checked this morning was to take the top plate off & check that the whole slide mechanism & everything was workng,its all working nicely.

Quote:

Originally Posted by blackjackcustms

If you have an ignition with a mechanical advance, it might be sticking, and that would do it. I've seen it on Dyna "s"s.

Any advice on where or how i can find & check this???

ironox · 10-24-2009, 07:49 AM

My bud had an 95 with a faulty 02 sensor (I think?) that was bad. It caused a high idle. I don't know, but perhaps you should start looking at the electrical system. It sounds like you covered the carb from top to bottom.

blackjackcustms · 10-24-2009, 02:37 PM

POop off the timing cover, and if there's a movable piece visible, it's got a mechanical advance. Most electronic advance units have no moving pieces outside the ign. plate.

Locodave · 10-25-2009, 12:53 AM

Hi. Guessing as normal. You didn't list the year. I started lookin at my manual for a 99 Fatboy. Ignition system. EVO carb setup. I have a Screamin Eagle ignition box on mine. ( By the by. I wish I could copy-paste a manual here but doing it long hand.) Pertaines to a 99 Evo

The ignition system composes of 2 circuts, primary is battery, ign switch, primary coil, ignition timer & associated wiring.

Secondary circut is the secondary coil, plugs, & wiring.

The computerized ignition system consists of 3 components. Rotor, cam position sensor, and the ignition module, and ( Important. ) the vacume operated electric switch. ( V.O.E.S. )

The rotor & cam position sensor is located in the cam gearcase cover, right side of the motor. Ignition module is located above the oil tank. The ignition module has 2 functions. It computes the the spark advance & opens & closes the circut for the spark. ( Low to hi volts in the coil. )

The vacume operated electronic switch. ( V.O.E.S. ) sences intake manifold vacume thru an opening in the carb body. ( ( I'd hunt for the hose to see if it is cracked & trace it. Back to the switch. Location, didn't list in the book.

Switch open acceleration and hi engine loads. Closed under low engine load conditions. ( Low vacume. )

Hope this helped as a cracked hose would let more air in & increase the idle.

To describe the VOES. Kinda looks like this. Bottom end below the round lip. Rectangle with wires off of it with a 2 wire plug.

Top end above the ring has a vacume line close to the ring just above it with a cyl shaped cone.

It didn't show a vacume advance on the plate. The VOES controls the advance by vacume. Dave