Help with carb issues please

[chipthedonkey]

Just had a new thought.  It did start cold realy easy.  And the choke cable never changed the idle.  Even though I know it's a Harley nut and spring and plunger on the end of the cable how would the bike behave if the choke was never getting closed?  Could a choke problem cause it to not idle low enough when backing off the idle screw that some of those hole would stay uncovered by the butterfly?  And would a choke problem affect that mid range spitting and sputtering?

[JW113]

If using the choke cable has no effect, then you have a big clue right there I think. Can you remove the cable and post a picture of it?

What do the plugs look like?

-JW

[chipthedonkey]

Can take the carb back off tomorrow to remove the cable.  It is definitely the Harley nut, spring and plunger.  The Mikuni nut is smaller and the spring and plunger came new with the jets I ordered at the dealership just to make sure they were right.

The elbow was on the cable.  I've got nothing to compare against to know if a Mikuni cable's elbow or the total cable travel is different between a Mikuni cable and a Harley cable though.  I've had Mikuni carbs on other bikes a long time ago so this spare cable in the box could have come from anthing.

If this was a problem the way its behaving it seems like the plunger wouldn't be doing in all the way.  So it'd be like the choke is always on.  I could see how that would keep me from being able to slow down idle speed enough that the butterfly might not ever clear those air holes and that would keep the mixture screw from doing anything.  Would the choke being open cause the mid-range sputtering and spitting though?

[speedzter]

https://www.mikuni.com/fs-choke_cable.html

[chipthedonkey]

That link helps.  I have a harley nut and plunger.  Don't have springs to compare so not sure.  Have a Mikuni cable.  By what is written at tht link this could account for the choke always being open a little.  I understand how that would affect the way the bike is starting.  If that's going on the idle would be higher right?  So maybe that affects the ability to use the mixture screw and get any change?  But would that cause the mid range spitting and sputtering?

I don't want to spend another several dollars for a complete cable kit like the Vtwin kit I found online if not pretty comfortable it'll solve things.  With the money alreayd spent on the old carb if I spend much more will have spent what some of the after market carbs cost.  So rather than buy a cable I could just a carb that includes the cable with it.  Some of them do.

[Hossamania]

I think my new choke cable from Harley was something like $11. Not sure what they are now. That choke cable may or may not be causing your mid-range issues, but either way it probably should be fixed..
Just looked it up in Ronnie's, cable, enrichener, $12.99

[SixShooter14]

https://www.mikuni.com/fs-choke_cable.html

Thanks for that link. My I have the Mik knob and cable. But on mine, the knob is tight in the fully in position, no slack at all. Now I'll go in and adjust that.

for unintentional help

[Hossamania]

https://www.mikuni.com/fs-choke_cable.html

Thanks for that link. My I have the Mik knob and cable. But on mine, the knob is tight in the fully in position, no slack at all. Now I'll go in and adjust that.

for unintentional help

Good idea.
Chip, that may be all you need to do, adjust the cable.

[chipthedonkey]

The cable is just the cable though.  Not the pieces on the business end down inside the carburetor.  Fortunately I know for sure my plunger and nut are Harley.  The spring I can fuss with if I have to since the Harley spring is shorter.  I'll count the rounds on the spring and go from there working from the pictures.

Grabbed a cable at the same indie shop that had the ignition kit.  He also had a good used piece of the seal and elbow at the end just in case mine are different.  Now I know for sure I've got all Harley parts except now knowing for sure on the spring.  Can work with that though.  All the pieces this morning were 20 bucks.  That is cheap by Harley standards so I can live with that!  Have a little bit of real work to do but will try swapping the cable yet this afternoon.  Wish the old bike luck.

[chipthedonkey]

Progress.  It's raining now though so do not know everything.

Swapped the cables and have now have obviously Harley parts end to end on the choke cable.  Now obviously have choke function too.  Works just as you would expect it to. 

At first thought still had no mixture control though.  Maybe it's supposed to be this way but I still don't really like how it works.  It does at least work a little though.  The engine won't die until idle is down just over 550.  Scary slow.  At 800 still no mixture function.  At 700 not either.  At about 650 begin to notice response to the mixture screw.  It's not a huge response but it's definitely reacting.  So adjusted the mixture with the engine idling in the 600-650 range than put the idle speed back up where it belongs.

When the rain stops later will do a test ride and see if the mid range is the same or if its better.  Boy I'm hoping for better because I don't know anything else to do.

[capn]

You should adjust that mixture screw at 1000 rpm.

[chipthedonkey]

Yes.  I know this.  But at 1000 the mixture screws has no affect.  At 800 it had no affect.  So I just kept chasing it to see if it ever would.  It finally did so I did what I could than ran the idle back up.  After getting a chance to run it a bit will try it again.  Right now that's what it gave me though.

[chipthedonkey]

Just back from a 30 mile ride.  Going to call it progress but not success.  Don't think I'm going to chase the problems more though.  Think now its time to ride it regularly with some See Foam in the fuel and see what happens.

Getting it up to temp and riding it a bit helped some.  It was idling with a warm engine at 1000 when I left.  When I got back it was at just over 1200.  Readjusted and still didn't get any response from the mixture screw at 1000 but if I turn it down to 700-750 do feel a slight response to mixture adjustment.  That's better than it was and coming my way.  Will ride it a few tanks full and check it after each one.

Choke works fine now.  The bike starts immediately.  I mean like first crank.  That part is really really good.

Slow speed handling is still fine.  Highway riding even better than it was.  Much more responseiveness and snap.  Whether it's carb changes or the new ignition system I don't know but it is a lot more responseive to the throttle.

Mid range is better than it was.  After the first 10 miles or so much better than it was.  Still not nailed down yet.  Coming off throttle it will still occasionally sputter.  It's not a decel pop out the back its a sputter out the carb.  Mid range load got this very light a couple times too.  It's not as harsh as it was and its a way less often but it is still there.  The bike is ride able now without really worrying about it. 

Plan right now unless someone has good ideas that are better is to ride it and see how much that cleans or helps.  A few tanks full before handing it over to the nephew unless the bike gets worse and makes me do something else to it.  Will also check gas mileage to see if that tells me anything too.

[JW113]

Glad the choke is working correctly.

The symptoms now sound like too rich at closed to 1/4 throttle. Have you looked at the plugs? And how did you set the float level? And did you happen to look at what slide needle is being used?

-JW

[chipthedonkey]

Jets are 45 and 170.  Plugs looked good.  Didn't appear real rich at all.  They were replaced in the last couple days though so it's new ones in there now.  The needle that was in to begin with was an aftermarket adjustable needle that had no washers on it and a little bent ring.  I put in a new stock piece.  One that I had in a baggie here was 28025-03.

Float was set putting the carb on a stack of shims to get the angle then looking for .450".  That's how I've always done it.  Have handled the carb and opened it up a couple times since setting it.  So could have bumped something.  Don't think so but definitely could have.

Also, this carb is one with the drain hose in the bottom.  It's never dribbled any fuel.

[Evo160K]

Glad the choke is working correctly.

The symptoms now sound like too rich at closed to 1/4 throttle. Have you looked at the plugs? And how did you set the float level? And did you happen to look at what slide needle is being used?

-JW

I agree. 
If it were my bike, I would now try a 42 low speed jet, then I would add the popular sportster needle.

[chipthedonkey]

I agree. 
If it were my bike, I would now try a 42 low speed jet, then I would add the popular sportster needle.

Have a 42 that was in it previously so can try that.  What is the difference in the Sportster needle?

[JW113]

It sounds like you have the FM, and are adjusting the float to spec. Very good.

The question that I have now, is that if you found one of the aftermarket tuning kit needles in it, what else was done? Lighter spring? Drilled out hole in slide?

The problem seems to be centered on the low speed circuit. The way the CV is suppose to work, is at idle, the throttle plate is mostly closed, all of the fuel is supplied by the idle jet. A/F ratio for idle is via the idle jet screw. That part does not seem to be working correctly. Then, going from idle to just off idle, the transfer jets supply the fuel by way of the low speed jet. That circuit also seems to be not working correctly.

In order for both idle and low speed circuits to work, they need an air supply that's provided from a passage from the front of the carb in the lower air horn area, called the air bleed. If this is plugged or restricted, the idle and low speed circuits won't supply fuel correctly. If you have the FM, it will show pretty clearly the air bleed path through the carb. If you happen to have the carb off again, it might be helpful to eliminate that as a potential cause of this problem.

It sounds like your main circuit is working well. So regardless of the needle, main jet, diaphragm spring, it is getting the fuel it needs past 1/4 throttle. So I'd be less worried right now about that circuit, and focus on the low speed circuit.

Just to ask the question, the accelerator pump is squirting a nice steam of fuel down the carb throat when you twist the throttle, yes?

-JW

[chipthedonkey]

Yes.  Accelerator pump is obviously working.  And the things you mentioned are what I've come to understand reviewing diagrams of the carb.  Even that drilled out hole thing I've seen referenced.  That maybe something still isn't cleaned out is why I was thinking about just riding it some with See Foam in the fuel.  Hopefully that would help.  As for that drilled out hole sometime in its life I dont' have anything to compare against so just don't know.

[barny7655]

What i do when this happens is get another set of eyes , to look at the carb , its just that some times you over look the problem thats looking at you in the face,under standing how they work will guide you to the problem? a compression test will tell you if there are any valve leaks causing undue vacumme issues,make sure butter fly hasnt been drilled,your vacumme port is capped if it has one , or not leaking at other end ,vos, cheers barny

[Evo160K]

I agree. 
If it were my bike, I would now try a 42 low speed jet, then I would add the popular sportster needle.

Have a 42 that was in it previously so can try that.  What is the difference in the Sportster needle?

The sportster needle is slightly thinner in the straight section, the p/n is 27094-88.  If you want to read an excellent article on CV tuning, try to find the article in American Iron Magazine by Joe Minton (a CV tuning expert and former technical editor/writer? for American Iron)  entitled "By The Numbers."  I trust him completely, he's helped me several times tune my CV's.  Once he had me sand the anodizing off of a portion of a Harley needle.

You'll find some excerpts in this thread:  http://xlforum.net/forums/archive/index.php/t-1091101.html

[lilchief]

The only problem with the Sportster needle is finding one. I remember looking for one about 5-6 years ago and had no luck. I used a CV Performance needle instead, and ultimately I used a small brass washer (#4 I think) under the stock needle, and it worked much better than the CV Performance needle.

Lil Chief

[chipthedonkey]

All good advice and thanks.  Some of the Joe Minton article I'd actually already found while going through all this.  Today the carb was bigger than me though.

Rode the bike about three hours today.  Started same as always.  Ran the same as always.  About an hour in the issues seemed to fade a bit.  Then for about an hour both on the road and going in and out of some small towns it gave no hint of a spit or a sputter.  Had just about convinced myself it was going to iron itself out when it all started acting up again.  I will admit to calling it a few names I wouldn't say in church.

It runs so good on the road and sometimes at other times.  The one tank I filled today got 45 mph.  But this slow and midrange cutting out isn't going to go away.  I've got no other eyes to share it with and why I know I'm no expert the basics I can get apart and back together.  There's just nothing else to do that I know that I know how to do to this carb.  And if I start buying more parts to just eperiment with I'll end up having spent more than I could buy a carburetor for.

So I through up the white flag when I got home awhile ago.  Went to Amazon and bought somehting.  It'll be here Sunday.  Will hope it's not some offshore junk and will open it up before installing.  Just to make sure I'm using jets I want and probably also swap out my known new tube and needle holder and the needle I've got now just because they are known things with a Harley part number.  Basically I'm buying it to get a body that's not years and years old and that set for a long time and had god knows what done to it before I started working with it.

Wish me luck on Sunday!

[barny7655]

make sure your electrics are okay , plugs coil,etc and charging okay , no loose terminals ,check leads , ohm test them ,some times you think its the carb but its else where , keep trying ,

[chipthedonkey]

make sure your electrics are okay , plugs coil,etc and charging okay , no loose terminals ,check leads , ohm test them ,some times you think its the carb but its else where , keep trying ,

Few nights ago did complete ignition system change.  Coil, cam sensor, plugs, wires and the harness between it all.  Took off the stock parts and went to a single fire system.  Had all the connectors and connections in my hand and checked them all.

The bike does start easier with the ignition change.  It's a obvious difference.  I think it's a little more snappy overall too.  But the spitting and sputtering behavior has been exactly the same before and after the ignition parts was changed.