Engine problems, please help... getting desperate
Thread Starter
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Cruiser
Joined: Feb 2012
Posts: 160
Likes: 2
From: North Florida
Engine problems, please help... getting desperate
So I recently performed an MM-EFI to carb conversion, I'm not an HD mechanic, but not an amateur either. Swapped the ignition for points, the EFI for a CV off a 95 Roadking.
Bike fired the first try, but was rough as hell. The advance cam was off center, narrow lobe .018, wide lobe +.006-.009 wider. I couldn't get it smoothed out, so I replaced the points with a Daytona TwinTec VT-i.
The carb was bone stock, so during the rebuild, I swapped out a #45 slow and #185 main jet. Stock needle. New coil, new wires (and old, same symptoms) new plugs.
Here I am, a couple weeks later, bike runs, but idles rough. I can close the mix screw all the way, and after a few seconds it will die, but throughout the range, no change in smoothness from almost in to all the way out and about to fall out.
The front cylinder is firing crisp, steady and clean. Rear cylinder feels like it's either missing a bunch, or firing a little. Took a test ride, and while it accelerates like a bat out of hell, like holy crap great, it stutters and stammers and misfires at idle or at steady throttle.
This morning I found and fixed an intake leak on the rear head, didn't fix the problem. Talked to my mechanic friend, he said the idle air circuit is f***ed (carb came without the lead plug, someone jacked with it perhaps).
Could a screwed up idle circuit cause the rear cylinder to misfire but not the front?
Anything else to check for, look at? I'll order a carb this week, but I don't want to drop a few hundred bucks if it isn't going to fix it. I may have missed something trying to keep it brief, let me know if there's something else to consider or more info needed.
Bike fired the first try, but was rough as hell. The advance cam was off center, narrow lobe .018, wide lobe +.006-.009 wider. I couldn't get it smoothed out, so I replaced the points with a Daytona TwinTec VT-i.
The carb was bone stock, so during the rebuild, I swapped out a #45 slow and #185 main jet. Stock needle. New coil, new wires (and old, same symptoms) new plugs.
Here I am, a couple weeks later, bike runs, but idles rough. I can close the mix screw all the way, and after a few seconds it will die, but throughout the range, no change in smoothness from almost in to all the way out and about to fall out.
The front cylinder is firing crisp, steady and clean. Rear cylinder feels like it's either missing a bunch, or firing a little. Took a test ride, and while it accelerates like a bat out of hell, like holy crap great, it stutters and stammers and misfires at idle or at steady throttle.
This morning I found and fixed an intake leak on the rear head, didn't fix the problem. Talked to my mechanic friend, he said the idle air circuit is f***ed (carb came without the lead plug, someone jacked with it perhaps).
Could a screwed up idle circuit cause the rear cylinder to misfire but not the front?
Anything else to check for, look at? I'll order a carb this week, but I don't want to drop a few hundred bucks if it isn't going to fix it. I may have missed something trying to keep it brief, let me know if there's something else to consider or more info needed.
Thread Starter
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Cruiser
Joined: Feb 2012
Posts: 160
Likes: 2
From: North Florida
I was thinking of putting the #42 back in, but the later carbs came with a #45, no? I figured with straight pipes and open air cleaner plus an EV27 I'd need more than the older stock slow jet.
I don't have a known good carb available. checked with everyone I know, couldn't come up with one. I was thinking about a new carb this summer, I'll do it now, but I'm a bit concerned it's not the fix I need, that it's really something else.
I don't have a known good carb available. checked with everyone I know, couldn't come up with one. I was thinking about a new carb this summer, I'll do it now, but I'm a bit concerned it's not the fix I need, that it's really something else.
Outstanding HDF Member
Joined: Jul 2011
Posts: 2,052
Likes: 6
From: North London, UK
I'm no expert, but an exhaust leak is the first thing that springs to mind.
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Thread Starter
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Cruiser
Joined: Feb 2012
Posts: 160
Likes: 2
From: North Florida
Used carb cleaner, didn't have any WD40 in a spray can handy. That's how I found the initial leak, didn't make any change I could tell. Hit around the o-rings and the carb to manifold seal, as well as around the carb itself.
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Thread Starter
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Cruiser
Joined: Feb 2012
Posts: 160
Likes: 2
From: North Florida
Cruiser
Joined: Sep 2011
Posts: 122
Likes: 5
From: western PA
Is the choke shutting off 100%? Should have good adjustment using mixture screw. Sounds as though pilot/slow jet is too big. Is the carb super clean inside? I know, dumb questions but a small piece of dirt restricting air flow in an idle circuit can cause havoc.