Author Topic: misfire aaarrrggh  (Read 609 times)

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Offline barhopper72

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misfire aaarrrggh
« on: July 26, 2019, 08:44:28 AM »
 :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

Offline xlfan

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Re: misfire aaarrrggh
« Reply #1 on: July 26, 2019, 11:05:44 AM »
Does your lights "misfire" at the same time?

Offline barhopper72

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Re: misfire aaarrrggh
« Reply #2 on: July 27, 2019, 01:12:01 AM »
No other problems, have checked wiring, all electrics,i have even tried disconnecting the rev counter...

Offline rigidthumper

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Re: misfire aaarrrggh
« Reply #3 on: July 27, 2019, 05:22:49 AM »
Drag pipes?

Offline barhopper72

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Re: misfire aaarrrggh
« Reply #4 on: July 27, 2019, 05:53:50 AM »
unfortuantly it has! one is twice as long as the other, too., 2" diameter with no baffles,

Offline rigidthumper

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Re: misfire aaarrrggh
« Reply #5 on: July 27, 2019, 06:04:26 AM »
I'd wager there's the issue. Bolt in lolly pops and see what happens.

Offline barhopper72

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Re: misfire aaarrrggh
« Reply #6 on: July 27, 2019, 06:06:36 AM »
ive been wondering about that, I will give it a try and let you know, cheers

Offline Hossamania

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Re: misfire aaarrrggh
« Reply #7 on: July 28, 2019, 12:07:13 PM »
2" drag pipes with no steps are not friendly to stock Evos.
Hell, 2" drag pipes with steps are not friendly to stock Evos.
« Last Edit: July 28, 2019, 01:59:55 PM by Hossamania »
No shirt, no shoes, and I still get service. Why?
Girl, look at this body!

Offline xlfan

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Re: misfire aaarrrggh
« Reply #8 on: July 28, 2019, 02:29:11 PM »
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?

Offline PIRSCH FIRE WAGON

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Re: misfire aaarrrggh
« Reply #9 on: July 28, 2019, 07:47:26 PM »
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.
Tom

Offline barhopper72

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Re: misfire aaarrrggh
« Reply #10 on: August 09, 2019, 08:12:04 AM »
tried bolt in baffles, no change. wired coil straight to battery to eliminate ignition switch, no change !...lifters maybe?

Offline JW113

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Re: misfire aaarrrggh
« Reply #11 on: August 10, 2019, 08:25:41 AM »
Save yourself the heartache of trying to tune to that exhaust, and get a set of plain old muffled pipes. Or not....

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber