Carb problems?
Thread Starter
|
Advanced
Joined: Jun 2009
Posts: 57
Likes: 2
From: Cincy, OH
I'd forget about it being a rev limiter issue or swapping out ignition modules. The posters above seem to be ignoring the fact that you said the plugs are "chalk white". The bike is (for whatever reason) running lean. IMO, you have either a carb mixture issue or a air leak on the the intake manifold side. Your propane torch test method I assume was done with the bike parked and not at speed where you experience the problem at WOT.
I recently had a similar problem that turned out to be a small tear in the carb-manifold gasket. Bike ran fine until I got on the road and grabbed a handful of throttle.
I recently had a similar problem that turned out to be a small tear in the carb-manifold gasket. Bike ran fine until I got on the road and grabbed a handful of throttle.
Yes, I performed the propane test with the bike parked. I'd imagine doing so otherwise would be mighty difficult!
I would imagine a vacuum leak big enough to cause a problem like this would be very noticeable using propane. I've used it tons of cars before, but never a bike. This is definitely foreign territory to me, so I'm just trying to apply the automotive knowledge I have to my task at hand. I just have no clue as to how finicky these carbs/motors really are. Now, if it was a Holley or a big block chevy, I'd already be out cruising!
When you say the carb to manifold gasket, you do mean the rubber boot deal that the carb slips into, correct? I'll pull the carb tomorrow and look it over real good, and see if I can't find something. This bike did sit for QUITE a while during the build process, and has had this problem since modded, from what the previous owner said.
As for the idle adjustment screw, I baselined everything starting from scratch three times now with very good instructions to no avail. I think it's at about 2 1/2 turns out right now with that big jet in it.
Yes, the bike in the picture is mine. I'll throw a few more pics up here in a bit for your viewing pleasure. Thanks for the compliments!
Thread Starter
|
Advanced
Joined: Jun 2009
Posts: 57
Likes: 2
From: Cincy, OH
Pics as promised!
Just goofing off shots at a friend's shop with "stand up lights".
Mods are:
Bobbed rear fender
Relocated plate bracket
Beehive taillight
Internal throttle cable
Braided lines all over
Old school grips
Relo'd wiring/electronics.
!front fender
!turn signals (using Indy Motor Speedway pennies)
!handlebar controls
Shock Boots
Spoked rear wheel
White walls
'51 Ford Brown, handlaid striping.
Customs trans. plaque
Hand-tooled leather seat
Custom painted rear sprocket
Handmade AC/breather
Handmade 1 7/8"-2" step pipes, wrapped
Sunoco "Blue" sticker on battery cover (not shown!)
Just goofing off shots at a friend's shop with "stand up lights".
Mods are:
Bobbed rear fender
Relocated plate bracket
Beehive taillight
Internal throttle cable
Braided lines all over
Old school grips
Relo'd wiring/electronics.
!front fender
!turn signals (using Indy Motor Speedway pennies)
!handlebar controls
Shock Boots
Spoked rear wheel
White walls
'51 Ford Brown, handlaid striping.
Customs trans. plaque
Hand-tooled leather seat
Custom painted rear sprocket
Handmade AC/breather
Handmade 1 7/8"-2" step pipes, wrapped
Sunoco "Blue" sticker on battery cover (not shown!)
Last edited by Speed Kills; Jul 1, 2009 at 11:07 PM.
Road Master
Joined: Jan 2009
Posts: 1,100
Likes: 0
From: Marietta, Ohio
Just a thought, but check your accelerator pump on the carb. i was putting mine back together and forgot to stick the rod back in it and it was doing about the same thing you're describing. I'd say Charley has about the next best idea.
Thread Starter
|
Advanced
Joined: Jun 2009
Posts: 57
Likes: 2
From: Cincy, OH
Welp, update on my progress.....
I took the carb back off yesterday. Carb to manifold gasket looks brand new. No cracks or anything of the such. Checked my bolts from the mani to the head as well and everything seems to be as it should.
I was looking over my CV carb diagram as well and noticed that I may have a part missing? It shows that under the holder for the main jet there's some kind of collar. If this is supposed to come out when you remove the holder/main jet assembly, it's definitely not in there. If someone could shed some light on that, I'd appreciate it.
Outside of this, I'm ready to tear this whole carb apart so I can ride the damn thing!
I took the carb back off yesterday. Carb to manifold gasket looks brand new. No cracks or anything of the such. Checked my bolts from the mani to the head as well and everything seems to be as it should.
I was looking over my CV carb diagram as well and noticed that I may have a part missing? It shows that under the holder for the main jet there's some kind of collar. If this is supposed to come out when you remove the holder/main jet assembly, it's definitely not in there. If someone could shed some light on that, I'd appreciate it.
Outside of this, I'm ready to tear this whole carb apart so I can ride the damn thing!
Club Member
Joined: Feb 2007
Posts: 16,320
Likes: 306
From: Boynton Beach, FloriDuh
Yep, the part you are describing is the Main (high speed) needle jet. It's held in place by the needle jet holder, which is what the main jet screws into.
With the A/C removed, if you look into the throat of the carb you should see the needle jet protruding up from the bottom of the throat about ~1/8 of an inch. The needle, which is attached to the slide passes through the needle jet and on down into the needle jet holder. The needle jet will often stay stuck in the carb throat when you remove the jet and jet holder.
Have you by chance replaced the main needle jet holder? If so, how many tiny holes does the holder have in the side of the tube?
With the A/C removed, if you look into the throat of the carb you should see the needle jet protruding up from the bottom of the throat about ~1/8 of an inch. The needle, which is attached to the slide passes through the needle jet and on down into the needle jet holder. The needle jet will often stay stuck in the carb throat when you remove the jet and jet holder.
Have you by chance replaced the main needle jet holder? If so, how many tiny holes does the holder have in the side of the tube?
Grand HDF Member
Joined: Sep 2007
Posts: 4,112
Likes: 40
From: Boise Idaho
You know drag pipes especially ones that are too large can cause all kinds of weird side effects, and drilling a jet pretty much destroys it, there is more to a jet than a chunk of brass with a hole in it, jets have a bevel like a small velocity stack leading into them when you drill it you are removing that bevel and can completely screw up the fuel flow throw the jet.
I also hope your home made aircleaner has some sort of bevel/stack leading into it as that can cause more wierd side effects.
I also hope your home made aircleaner has some sort of bevel/stack leading into it as that can cause more wierd side effects.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Thread Starter
|
Advanced
Joined: Jun 2009
Posts: 57
Likes: 2
From: Cincy, OH
1 7/8" pipe seems pretty common in the exhaust world to me? And you can see in my pictures, the section of 2" step is the last 10" or so of the pipe. I don't see how this is considered "too big" or how this could cause all these mystery juju problems that everyone seems to hear about, but never have an answer for.....
As for drilling a jet, A jet is a jet. Simple as, it doesn't matter how the fuel gets into the metering block/emulsion tube/whatever, as long as it gets there. Drilling a jet has ZERO to do with my problem at hand, as I've already exhibited. Not to mention this was done with machinists bits measuring down to thousandths of an inch, that in no way, shape, or form disturb the bevel you're talking about. I've done this more than once with Holley's on jets and air bleeds, in a pinch or for test purposes, with good results.
And yes, my custom fabbed (not some cobbled together "home made" junk, thank you) air cleaner has a beveled air horn leading into the carb.
cHarley, just so we're on the same page, here's the diagram I was talking about. I shoulda done this the first time, but i was just posting in passing:
As for holes in the main needle jet holder, I ave not a clue. I haven't personally replaced it, simply checked that it was free and clear of any dirt particles and reinstalled.
As for drilling a jet, A jet is a jet. Simple as, it doesn't matter how the fuel gets into the metering block/emulsion tube/whatever, as long as it gets there. Drilling a jet has ZERO to do with my problem at hand, as I've already exhibited. Not to mention this was done with machinists bits measuring down to thousandths of an inch, that in no way, shape, or form disturb the bevel you're talking about. I've done this more than once with Holley's on jets and air bleeds, in a pinch or for test purposes, with good results.
And yes, my custom fabbed (not some cobbled together "home made" junk, thank you) air cleaner has a beveled air horn leading into the carb.
cHarley, just so we're on the same page, here's the diagram I was talking about. I shoulda done this the first time, but i was just posting in passing:
As for holes in the main needle jet holder, I ave not a clue. I haven't personally replaced it, simply checked that it was free and clear of any dirt particles and reinstalled.
Last edited by Speed Kills; Jul 5, 2009 at 03:29 PM.
Ultimate HDF Member
Joined: Mar 2008
Posts: 7,604
Likes: 38
From: Landrum, SC , elevation 986'
If I may? Just for the hell of it, take off the intake and replace or grease the rubber gaskets between the intake and the heads and put it back on. their cheap and its better to replace them. You seem confident of your Carb to intake gasket. But put a little petroleum jelly on the 3 of them when you put them back on. I had the same problem years ago. At least then you can rule out a phantom air intake leak. Seems like your going to have the carb off anyways. 
Beautiful bike man, focking beautiful.
Beautiful bike man, focking beautiful.