Backfiring. Is dyno tuning my only option?
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Road Warrior
Joined: Aug 2012
Posts: 1,553
Likes: 36
From: Four Corners
Backfiring. Is dyno tuning my only option?
I have a 2001 SERG with the Moron Mirelli EFI. I took the bike in for a 40k service and had the tech adjust my cold idle as it was running at 650-750 rpms until it got warmed up and I was stalling out at stop lights. Got the bike back and it is running great. Took it for a run over the mountains (durango to silverton & back, the "Million Dollar Highway"!) which had a lot of downhill runs in gear. When the bike hit at about 2200 rpm, it would backfire. Once in town, it backfired at about 2200 rpm while accellerating. Now, it seems to want to backfire at that rpm constantly. It does it in both pipes (true duels).
The dealer said to bring it in this morning so they can throw it on their dyno and "figure it out". I am hesitant to do this because; a) I don't have the $$ to be charged the $80+ an hour dyno rate and, b) I don't want to end up with the snow ball effect on my EFI. I have read that once you start messing with the M/M EFI, you'll always have to mess with it to keep it going. I do not have the $$ to do a carb swap or Zipper's kit either.
I have 3.5" Rhineharts, K&N filter, and the 2001 SE tuner with a tune (done in 2006). So, should I live with the backfiring, mess with the idle speeds to try and eliminate it, or pony up for a stupid tune? All input appreciated!
The dealer said to bring it in this morning so they can throw it on their dyno and "figure it out". I am hesitant to do this because; a) I don't have the $$ to be charged the $80+ an hour dyno rate and, b) I don't want to end up with the snow ball effect on my EFI. I have read that once you start messing with the M/M EFI, you'll always have to mess with it to keep it going. I do not have the $$ to do a carb swap or Zipper's kit either.
I have 3.5" Rhineharts, K&N filter, and the 2001 SE tuner with a tune (done in 2006). So, should I live with the backfiring, mess with the idle speeds to try and eliminate it, or pony up for a stupid tune? All input appreciated!
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
You are paying too much attention to the rumour mill and not enough to the dealer. As with so many aspects of Harley ownership, there is a lot of nonsense out there about MM EFI! If your dealer is confident of working with it, be grateful.
Make it clear to him that you are not offering him an open cheque for the dyno work and make sure you know just what he intends to do, before they start work. Also make it clear they understand your position. They may just be intending to do this at their expense.....
Make it clear to him that you are not offering him an open cheque for the dyno work and make sure you know just what he intends to do, before they start work. Also make it clear they understand your position. They may just be intending to do this at their expense.....
Road Warrior
Joined: May 2006
Posts: 1,479
Likes: 4
From: SoCal
Is there a speed shop in your area as an alternative to this service provider? Our speed shop (Lees Cycle of San Diego) has never been impressed with the SE tuner line for this FLHRI model (HD wanted to buy Dynojet tuners for their accessory line instead of the currnet SE from Day 1 but couldn't agree on the deal). I'm at Stage IV+ with Dynojet tuning, S&S cams, enlarged throttle bodies, 2-into-1 SuperTrapp, etc. and couldn't be more happy with this proven EFI system. My issues with backfiring were related to the SE Stage I EFI flash and are long forgotten. Maybe a different shop can diagnose your issues for a lot less while you consider your options.
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Road Warrior
Joined: Aug 2012
Posts: 1,553
Likes: 36
From: Four Corners
Thank you! I did just that and my tech was able to not only adjust my air/fuel mixture to fix the backfiring, but he "adjusted" the tune on my bike as it was originally tuned for stock pipes and air cleaner. So now, with my true duels & K&N filter accounted for, he got me to 81+ hp and 93+ torque! Not bad for a 95" Screaming Eagle! The best part is that he only billed me for an hours labor! So now, I am going to leave well enough alone and ride the **** out of it! Thanks again!
Last edited by yzergod; May 14, 2013 at 01:45 PM.
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