:wtf:hi guys, I have been handed a 1991 evo monster to sort out ! it has a new s&s super e, checked and set up, and dyna s dual fire ignition, and a very annoying misfire at 3500 revs when under load. I HAVE DOUBLE CHECKED ALL SETTINGS AND CONNECTIONS. the misfire does not appear in first gear, and you can ride through it keeping the power on, any ideas??? thanks
Does your lights "misfire" at the same time?
No other problems, have checked wiring, all electrics,i have even tried disconnecting the rev counter...
Drag pipes?
unfortuantly it has! one is twice as long as the other, too., 2" diameter with no baffles,
I'd wager there's the issue. Bolt in lolly pops and see what happens.
ive been wondering about that, I will give it a try and let you know, cheers
2" drag pipes with no steps are not friendly to stock Evos.
Hell, 2" drag pipes with steps are not friendly to stock Evos.
Is it really possible that 2" drag pipes can cause a misfire at exactly 3500 rpm only, in all gears except 1st?
Wouldn't that indicate a chafed wire short or bad ground at an exact given oscillation?
Well, with certainty, S&S will tell you right up front, their Carburetors are not efficient using Drag Pipes of any type (as most all manufacturers). They will back-fire under load and deceleration.
Is this a "Miss-fire" or a "Back-fire". The ladder is most likely the Drag Pipes. Changing the Jet will just move it to another place in the RPM. So that's one thing you can check.
The Miss-Fire could have any one of a number of culprits. Plugs, Wires, Coil Break-Down, poorly grounded unit, or wire(s) too close to a heat source.
My bet would be Fuel Delivery, affected by the Exhaust, Leaky Intake Seal, or Carb Sealing.
tried bolt in baffles, no change. wired coil straight to battery to eliminate ignition switch, no change !...lifters maybe?
Save yourself the heartache of trying to tune to that exhaust, and get a set of plain old muffled pipes. Or not....
-JW
SORTED....after many hours of testing, riding , changing stuff, turns out to be a bad main jet ! got a new jet, 165, put it in, and BAM!! LOVELY. LOOKS LIKE THE 170 MAIN JET HAD BEEN DRILLED OUT!! every day is a school day. happy trails.
didnt think it was pipes. my shovel runs perfect with baffled drags and s&s b carb
when baffles in the pipes did not make an improvement it was obviously not the exhaust that was the big problem, but it still could be better..
I've seen what fat or short and even regular drag pipes do to the performance of a motor, by direct comparison.
https://www.youtube.com/watch?v=KjKUKhHQLHg
-JW