Hi,
1994 fxstc, 32K, crane cam-(unknown type), Cycle shack M series, CV carb has thunder jet and dynajet kits, large aircleaner-rivera/primo.
Here is my issue, the rear cylinder does not fire evenly, especially when cold. At idle it will go “fire,fire,poof/pop”. When held at a constant low throttle setting it breaks up and you can hear it sort of missing when the rear cylinder goes poof. It’s been doing this since 20K when I got it but I thought it was due to the straight drag pipes it had. When you get on it, the thing runs great, plenty of power, no coughing through the carb, 40+mpg, easy starts, no oil consumption, in really good shape and both I and & the PO maintained it well.
What I’ve done and checked to try to fix it:
Autolite coppers look good, rear slightly richer at slower speeds but not much or bad.
Compresion is 149/151, leakdown was <5% rear and about zero front.
VOES tested working, hose good.
Intake gaskets changed, once by me, once by someone else.
New SE coil and wires, switching wires front to back does not change anything.
Tried different jetting and settings, finally got a brand new CV, absolutely no difference.
New b-series lifters and cam bearing @30K, timing good, rockers looked good and readjusted the revteck pushrods.
Two different exhausts and the original drags, new gaskets.
Swapped out the stock ignition for an SE modual.
Correct me if I’m wrong but I think I’m down to either possible trouble in the heads/valves or the cam has too much overlap for a street bike-(this thing really runs strong and has a seemingly endless top end-I never have to go WOT). If it were a head issue I think it would show in the compression, leakdown or make mechanical noises but I’m no engine builder. If I’m right about the cam then maybe getting a single fire ignition where I could adjust the rear cylinder offset would be the way to go.
Your thoughts please?? Anyone deal with this befor?
thanks,
60
1994 fxstc, 32K, crane cam-(unknown type), Cycle shack M series, CV carb has thunder jet and dynajet kits, large aircleaner-rivera/primo.
Here is my issue, the rear cylinder does not fire evenly, especially when cold. At idle it will go “fire,fire,poof/pop”. When held at a constant low throttle setting it breaks up and you can hear it sort of missing when the rear cylinder goes poof. It’s been doing this since 20K when I got it but I thought it was due to the straight drag pipes it had. When you get on it, the thing runs great, plenty of power, no coughing through the carb, 40+mpg, easy starts, no oil consumption, in really good shape and both I and & the PO maintained it well.
What I’ve done and checked to try to fix it:
Autolite coppers look good, rear slightly richer at slower speeds but not much or bad.
Compresion is 149/151, leakdown was <5% rear and about zero front.
VOES tested working, hose good.
Intake gaskets changed, once by me, once by someone else.
New SE coil and wires, switching wires front to back does not change anything.
Tried different jetting and settings, finally got a brand new CV, absolutely no difference.
New b-series lifters and cam bearing @30K, timing good, rockers looked good and readjusted the revteck pushrods.
Two different exhausts and the original drags, new gaskets.
Swapped out the stock ignition for an SE modual.
Correct me if I’m wrong but I think I’m down to either possible trouble in the heads/valves or the cam has too much overlap for a street bike-(this thing really runs strong and has a seemingly endless top end-I never have to go WOT). If it were a head issue I think it would show in the compression, leakdown or make mechanical noises but I’m no engine builder. If I’m right about the cam then maybe getting a single fire ignition where I could adjust the rear cylinder offset would be the way to go.
Your thoughts please?? Anyone deal with this befor?
thanks,
60
