1965 misfire under load

[cajun1957a]

This just started a week ago.  Under Load the bike misfires and pops.  It idles great, revs in neutral real good but when i crack it open it bucks as the revs come up.  I have set the timeing, changed the plugs and wires, and reset the s&s E back to baseline then adjusted accordingly.  Still bucks and missess.  Any ideas?

randy

[Lew]

Intake leak?  Low coil voltage? Worn advance unit?  I got water with my fill up awhile back that caused me fits.  Would run fine but would break up under a load.  Recently had a condenser go out too.  It didn't go out all at once, instead was intermittent until finely leaving me parked on the side of the road.  That one was a head scratcher while it was in the process of going out.  Good luck!

Lew

[Pynzo]

Try installing a Yost Powertube or a DaVinci Venturi kit to get rid of the Intermediate to Main Jet transition stumble common to S&S carbs.

[cajun1957a]

Initially I thought it could be the carb and or a leak but I have rulled that out.  The bucking and jumping under load is definately a miss fire.  I am trying a new set of wires and a coil.  Im using a 3ohm coil and solid core wires.  The ignition is Mallory Electronic and they suggest 2-4 ohm in the coil.  Im thinking a while back when the bike was first on the road, i got approximately 50 miles on it and it did the same thing.  I had an old coil off of a 75 xlch lying in a basket and tried that.  It has worked since now.  I suppose its possible that the electronic ignition/distributor is frying the coil or at least not married up with it proper.  I dont know the ohms on the 75 one though.  Will let you guys know how i make out tomorrow. 

On another  note, I sent my fishtails off for replating.  They were scratched badly when my kicker came loose.  I put on a set of straight drags with no baffles.  My gosh the world shook when i cracked it open, even with it missing it sounds tough.  I might try knocking out the baffs in the fish tails. 

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[cajun1957a]

Well still no luck with this thing.  It starts right up....idles sweet yet when the revs begin to build on the road it will missfire.  No backfireing either.....just starts jumping and cutting out.   Let off the throttle and its fine.   Im going to try setting the rods again this weekend, but i really dont think that is it.

randy

[irnhdmike]

Water??

[Lew]

Huh....wonder if the coil is receiving full voltage.  Sounds like a weak spark blowing out under a load.  Might hook up a volt meter to the coil primary feed and going for a ride.  I've heard of some Mallory units going tu and they exhibit this symptom.

Lew

[nibroc]

worn dist shaft or bearing?

[wreck74]

ya might try a couple of mufflers. no back pressure = ?

[Maddog]

have you replaced the condenser??   found that on my ironhead when it did pretty close to what yours is doing??