Jerking, sputtering, and dead.
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,077
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From: San Diego, CA
Boy that would suck.....!
I was looking at web sites for Harley repair shops for older engines. There was one shop in Florida somewhere who posted pictures of "mistakes" they fixed. One set of pics was an engine that ate a backing plate screw.... I had never seen or heard of that before those pics... That damage was not pretty...
Last edited by hattitude; Sep 7, 2022 at 12:29 PM.
Stage I
Joined: Aug 2021
Posts: 1
Likes: 0
From: Sacramento
Crank Position Sensor is my guess. I'm no mechanic by any means. On the contrary, I've been wrenching on bikes for less than a year, having just bought my first ride. That being said, shortly after purchase, my bike did the same thing you mentioned. Only difference is mine did the jerk, sputter, cough on a half dozen occasions over the course of a month before it wouldn't start again. But every time it happened, I was twisting the throttle pretty quick trying to get on 'er. Check to see if you're getting spark to the plugs. If not, I'll double my uneducated and inexperienced wager on the crank sensor being the culprit.
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Novice
Joined: Dec 2021
Posts: 24
Likes: 8
From: Vancouver, BC
Thanks for the suggestions.
I confirmed power/connections, clean fuel and delivery, clean air filter, and strong spark. I swapped the plugs (which looked fine), leads, and coil in case they were the issue. Leakdown test confirmed good compression in both cylinders. I even looked for gremlins hiding in the cylinders (LOL). But ultimately it seemed likely to be a faulty crank position sensor so I swapped it out and boom, was back on the road! But other performance problems returned that have me stumped.
It runs pretty smoothly except it chokes and bogs when I give it heavy throttle, kind of like the S&S Super G carb was jetted totally wrong or accelerator pump wasn't working. The carb quite new and has been great all year, but just in case I gave it a good inspection and cleaning, checked for air leaks, even swapped out the jets. But it still runs like crap under heavy throttle, and in fact has occasionally sputtered and misfired again like the timing is wonky.
After consulting with a local Harley mechanic, we're starting to suspect maybe the Dynatek TC88 electronic ignition might be the culprit. Has anyone experienced that sort of thing? Could it be that when the crank sensor was failing it somehow sent whackadoodle signals to the ignition module that damaged its electronics? And if I have to replace it, is there a better option I should consider to pair with this S&S T124 LC crate engine? Or reckon I should just order a replacement TC88 and swap it out?
Thanks in advance for any ideas and guidance!
I confirmed power/connections, clean fuel and delivery, clean air filter, and strong spark. I swapped the plugs (which looked fine), leads, and coil in case they were the issue. Leakdown test confirmed good compression in both cylinders. I even looked for gremlins hiding in the cylinders (LOL). But ultimately it seemed likely to be a faulty crank position sensor so I swapped it out and boom, was back on the road! But other performance problems returned that have me stumped.
It runs pretty smoothly except it chokes and bogs when I give it heavy throttle, kind of like the S&S Super G carb was jetted totally wrong or accelerator pump wasn't working. The carb quite new and has been great all year, but just in case I gave it a good inspection and cleaning, checked for air leaks, even swapped out the jets. But it still runs like crap under heavy throttle, and in fact has occasionally sputtered and misfired again like the timing is wonky.
After consulting with a local Harley mechanic, we're starting to suspect maybe the Dynatek TC88 electronic ignition might be the culprit. Has anyone experienced that sort of thing? Could it be that when the crank sensor was failing it somehow sent whackadoodle signals to the ignition module that damaged its electronics? And if I have to replace it, is there a better option I should consider to pair with this S&S T124 LC crate engine? Or reckon I should just order a replacement TC88 and swap it out?
Thanks in advance for any ideas and guidance!
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Novice
Joined: Dec 2021
Posts: 24
Likes: 8
From: Vancouver, BC
Nope. I'm always careful to Locktite those backing plate screws and none were missing. Even inspected the cylinders and did a leak down test to confirm compression. Seems likely electrical in nature.
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Novice
Joined: Dec 2021
Posts: 24
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From: Vancouver, BC
Bike ran great until a moment in a ride when I gave it some heavy throttle and it started to buck and cough.
Seasoned HDF Member
Joined: Feb 2008
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Coil and cpk too.chrck for spark. If it starts after it coils could coil. I'd check spark,after tightening battery cable.
Little odd to me for carb bike to have fuel problem when running. Change plugs for hell of it.
Do you really need the s&s fuel filter? May need to check jetting if you remove. But I get idea every thing has fuel filters.
I'd check spark first since it turns over
Little odd to me for carb bike to have fuel problem when running. Change plugs for hell of it.
Do you really need the s&s fuel filter? May need to check jetting if you remove. But I get idea every thing has fuel filters.
I'd check spark first since it turns over
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From: poway
I installed a Dynatech and the problems disappeared. For a couple years then it came back but this time a little different.. The lights would dim.. I got to hunting around and found that a wire going to the ignition switch had a crimp lug where the loop was broken from the crimp part. Fixed that and no issues after.
Make sure power to the Dynatech is good.
Another of something like that is simply water in the float bowl..
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