so tell me about the MM FI
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Cruiser
Joined: Feb 2006
Posts: 204
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From: USA
so tell me about the MM FI
I'm a carb man so don't know much about this Italian sounding MM FI system I've read about on the EVO's. Seems to be more bad than good input on this system. What year and models came with this system? Was it until the twinkies? 99? I been kickin tires on some 96-98 Ultras and Road Kings and really prefer a carb but the majority I see are all FI. Is this damn thing a death sentence or what. I know personally a feller with 117K on a 97 RK with FI so they must have built one that held up.
Stellar HDF Member
Joined: Feb 2007
Posts: 2,558
Likes: 280
From: Russellville, Arkansas
I've had my '98 Ultra for several years now.....of course the old style MM EFI system. At first, it was nearly impossible to start as the idle was way too low. I actually had to twist the throttle a little just to get it started. I first had a Harley dealer adjust the system....they didn't make it any better or worse. It was basically the same.
After that I picked up a factory shop manual and quickly discovered several things were wrong with it. Finally got everything in right order or at least close to it. I still had cold/hot idle issues from time to time.
I recently came across the Harley Scanalyzer.....I then discovered things were still out of adjustment including the TPS which was set from the factory. Got everything adjusted to factory spec. and it ran pretty well. Everything in the MM system must be adjusted deadon or you'll have problems. Close enough or good enough.....really doesn't work very well here.
The ISC motor quit not too long ago....for some reason, I've gone through them about one every 20,000 miles. Harley wanted nearly $100 just for the ISC motor. I ended up buying a new MM throttle body including all the sensors/motor/injectors for $75 on Ebay.
Have already installed the new throttle body and got everything adjusted per the manual instructions. Used the Scanalyzer for nearly all the adjustments except the TPS. Even the new throttle body, the TPS was not adjusted correctly. Got everything adjusted per the 2001 shop manual (not the 1998 manual) and the bike has never run this good. The 2001 touring bikes had the same system, just different procedures when it came to adjustments.
Without a scanalyzer and breakout box....nearly impossible to get the MM system properly setup.
After that I picked up a factory shop manual and quickly discovered several things were wrong with it. Finally got everything in right order or at least close to it. I still had cold/hot idle issues from time to time.
I recently came across the Harley Scanalyzer.....I then discovered things were still out of adjustment including the TPS which was set from the factory. Got everything adjusted to factory spec. and it ran pretty well. Everything in the MM system must be adjusted deadon or you'll have problems. Close enough or good enough.....really doesn't work very well here.
The ISC motor quit not too long ago....for some reason, I've gone through them about one every 20,000 miles. Harley wanted nearly $100 just for the ISC motor. I ended up buying a new MM throttle body including all the sensors/motor/injectors for $75 on Ebay.
Have already installed the new throttle body and got everything adjusted per the manual instructions. Used the Scanalyzer for nearly all the adjustments except the TPS. Even the new throttle body, the TPS was not adjusted correctly. Got everything adjusted per the 2001 shop manual (not the 1998 manual) and the bike has never run this good. The 2001 touring bikes had the same system, just different procedures when it came to adjustments.
Without a scanalyzer and breakout box....nearly impossible to get the MM system properly setup.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
Works well when all is fine but only as good as the guy repairing it when it has some hiccups, usually gets a bad rap because it is only as good as the guy repairing it but a very repairable system.
Has a ceiling on engine mods and needs some major work to deliver higher HP engines and been there, done that. Ran a modded MM system for years and currently have a carb on it with both monitored by a AFR reading system, the carb out performs the MM hands down and way cheaper than trying aftermarket EFI systems for the Evo and easy to convert. Big picture is the MM does what it is designed for but hard to find techs that want to tackle repairs and a flat rate tech will just hang parts at a dealership but many, many 100,000 mile machines out there
Has a ceiling on engine mods and needs some major work to deliver higher HP engines and been there, done that. Ran a modded MM system for years and currently have a carb on it with both monitored by a AFR reading system, the carb out performs the MM hands down and way cheaper than trying aftermarket EFI systems for the Evo and easy to convert. Big picture is the MM does what it is designed for but hard to find techs that want to tackle repairs and a flat rate tech will just hang parts at a dealership but many, many 100,000 mile machines out there
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
The FI has too many special tools and parts adjust it correctly.
The carb needs a screwdriver.
I always like the KISS theory.
The carb needs a screwdriver.
I always like the KISS theory.
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Joined: Mar 2010
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From: Pocatello
Just stay away from the "early" MM FI. That was '95-'96. Ask me how I know. The aftermarket supports '97 and up. The MM was used well into the Twinkie years.
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Stellar HDF Member
Joined: Feb 2007
Posts: 2,558
Likes: 280
From: Russellville, Arkansas
There were several design changes over the years though.....in 1997, the ISC motor plus the bracket was changed. The cold/hot idle set screw was changed from allen to torx.
In 1999, starting with the Twin Cam.....the injectors went from black to red. The red injectors push alot more fuel. Also, of the four bolt holes that secures the air cleaner housing....the bottom left hole was smaller, so now all the four holes were the same size.
Screamn Eagle also had high performance throttle body for the EVO and Twin Cam. This came late and was pretty much a flop. By this time, folks were already cursing this system all together and began switching to a carburetor. However, they did have somewhat sucess with the Stage 2 kit being fairly inexpensive and worked rather well.
Having said all that....it is not a terrible system. It will be increasingly difficult to maintain this system though as it's been over 10 years since the last HD Magneti-Marelli rolled off the factory line. There will be fewer and fewer HD tech's that know this system.
If it were not for owning a scanalyzer or breakout box.....I probably would have switched to carburetor.
Sorry for being so long and winded.....
Elite HDF Member
Joined: Dec 2009
Posts: 4,598
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From: navarre ohio
touring bikes used MM injection till 01... i ride a 01 EGC with 50k miles. it runs great. the only time you have a problem with FI is when you change it around and have to tune it..they make tuners for them though.. good cold starts, smooth running, starts every time, doesn't flood, you don't need a carb clean every spring