I have owned the first model year after the introduction of EFI...which of course was an MM (Ultra Classic) system. I have owned three (and now 4 EVO and TC) versons of bikes equipped with this older managemt system. I have seen (not experienced) ONE failure on any bike that wore the MM system and that was a defective head temperature sensor. Thousands and thousands of miles on bike-after-bike and never had a serious problem, save the stupid fuel line connections (which are easily corrected).

All these bikes have ran wonderfully, got great fuel mileage and hauled me and my baggage (including the wife) all over the lower 48 and two foreign countries.

My question for anyone that cares to answer or remark on....what spare components do you/would you pack in your tool box on extended cross-country trips? What is your source for these spares? Do most Stealerships still stock MM parts? I see head temperature sensors listed all the time on e-bay, but usually listed for the 99 and newer. Mine is a 98 RK.

I'm thinking crank position, ignition pick-up and a head temperature sensor? The bike simply runs too good at the moment for me to justify gutting it and converting to a carbureator. It does all I want it to do and I am completely satisfied with it's performance. About the only thing that would force me to convert is a failed ECM module.

All comments, questions and suggestions are welcome.

 

I own a 98 road king with the m & M fuel injection.
About 4 years ago i started to carry the Goodridge brand replacement fuel lines that are specific for these bikes.
The cam sensor (in timer cone) usually starts to melt and gives warning when it is starting to give-up the ghost so i do not carry an old one any more.
I am considering a spare temp sensor at this time.
I do have a cheap 150 ohm resistor (under $1) in the tool bag as a Hail Mary but i have not tested it. Seems the engine temp sensor reads about 150 ohm when the engine is hot and my theory is that maybe the resistor can be used in place of the temp sensor if the sensor started to swing widely during an extended trip.
That is it for M & M specifically.
I do carry a large assortment of tools,digital meter, 12 volt pump, slime, home made jumper cables and lots of other stuff but that is not M & M specific.
A well maintained vehicle and some tools can sometimes make a road side break down a slight delay instead of a wasted day.

 

Thanks....this is the sort of input I was seeking. Seems like most folks can't wait to do the carb-swap...and that's fine, but if one is satisfied with the MM system and it's performance, I see no reason to change. I have been thru the "snotty nose" cam timing sensor thingy. I did not count that as a failure as it never stopped working....just melted puke all over the place. I have a newer version installed now that has a blackish filler and maybe it will hold-up, if not...I simply cleaned all the gook from the other one and sealed it with epoxy. I know it works, so that's my spare. I had developed an emergency fix for the stock HD lines, but this bike had Goodridges on it when I purchased it. I still carry my emergency fix becase the Goodridge lines have metric o-rings in them...oh....I carry a spare set of those o-rings as well. The 150 ohm resistor is a good idea. I'll trust your measurement on a hot sensor and may pick one up. I'd like to just get a new sensor, but all the ones I see seem to specify from 99 thru whatever year. The 99 and 00 TC had the MM system, but the sensor screws into the side of the head and not the top like the pre-99's do. That may be why they are specified as 99 and newer. I have not even asked the dealer if they had one or what it cost, but I'd like one for mine. Maybe somebody will read this and come up with a PN?

I have only known one cam position sensor to fail and that was on a newer bike with the Delphi system.

When you get right down to it, most carb converters (people) still use some sort of electronic pick-up for timing, or an aftermarket electronic ignition system. I had one of those fail, so you have not made the bike totally reliable until you go back to points, mechanical advance and fall-back to the single-fire system. If I ever converted mine for reliability reasons....I'd go all way back to points.

I've put well over 150,000 miles on MM equiped bikes and have yet to have a failure that parked it. Knock-on-wood....I plan to continue to trust it until the cost to fix any issue will equal or exceed a carb conversion.

 

The engine temp sensor on the 1998 is a long one and is located in the front cylinder chimney (center of head).
It is different from the twin cam engine temp sensor
The part number is 32446-95 as per link i use for part numbers.
That is the EVO engine temp sensor in the head used from 1995 to 1998 EVO M & M fuel injected touring bikes.
http://www.shopronniesharleydavidson...partfinder.htm
I have found no substitute for temp sensor but it seems to be nothing more than a threaded thermal-resistor.
Figured some other air cooled motor might use similar but had no luck.
I have been unable to find resistance values of the twin cam sensor either.
The service book for my 1998 evo road king EFI has a small table in section 9 with resistance values showing a hot motor being about 150 ohm and cold (under 30 F) was something like 2500 ohm.
The system works in a range of 0.4 volts to 5 volts.
I really do not understand how resistance works but a total guess on my part would be that a resistor of the correct value, would act in a similar fashion, at the same resistance measurement of a functioning sensor, at a single specific point.
The temp sensor has two wires going to it and again i would guess that a resistor would be attached at those two wires.
My understanding is that a resistor has no polarity so inverse connection at sensor wires would make no difference.
Again, that is a lot of guessing and i would appreciate someone with electrical knowledge to confirm. For reference the resistor i have is 1 watt 150 ohm.

 

Actually....I can help you out with the understanding of what a resistor actually is. A resistor of any certain value "stays" at that certain value and dosen't change. In other words....a 150-ohm resistor will always be a 150-ohm resistor....no matter what potential is applied or what the ambient temperature is. 150-ohms seems to be the value I find for a hot-motor and closer to 2500-ohms for a cold motor. BTW....I have also confirmed the PN: 32446-95a. That component is a "thermistor" or at least carries thermistor characteristics. As the temperature rises, the resistance of a thermistor drops. That's why you may see comments concerning voltages of .4 to 5. As the resistance in the sensor gets lower more current will flow thru the circuit causing these voltage-reading changes.

The 99 and newer will not work due to the thread size and possibly other parameters. I think sticking that 150-ohm resistor in the tool-pouch sounds like a good idea. An alternative would be a variable resistor within the range of 100 to 2500-ohms. Nothing but a wire-wound resistor with a **** on it, but chances of finding one close to that would be a real trick. The same principal is employed with the fuel gauge. It has a contact-arm that rubs across a resistive element, changing the voltage and moving the needle in the gauge based on current flow thru the pointer (contact).

Best/worst case seems to be to install that 150-ohm resistor across the two pin-plugs and go for it. I do know that close to 0-ohms will make one run very rich at idle. Me and a friend triked his Ultra some years ago and managed to crush the sensor lead wires under a bolt-head....which would have resulted in a very low resistance.....a straight wire. It was hell to crank and once it got started, it ran very, very rich. Luckily, we figued out what we had done before he left the parking lot of his shop with it.

I'm a degreed Electronics Engineer, but my degree was obtained in 1969. Basic electronics hasn't, but IT and computing has way outran me since then.

 

Thank you for the detailed explanation and real life example !
Are the watts of significance in this application ?
I have the 1 watt 150 ohm for the hot motor.
Maybe i can spend another $1 and get something in the much higher "0000" ohm range to simulate cold.

 

Without taking you thru the math and acting like a rocket scientist, power in watts is dependent on the curret flow in amps and the potential in volts in a DC circuit. Using 14V as the normal case (engine running and a good battery) for the potentianl applied and the 150-ohms of resistance....the power (watts) would be a tad over 1-watt depending on wire resistance....etc. I don't know what potential the ECU is applying to the sensor and it may be well below 14V. I'd grab a little larger wattage resistor, but don't get carried away. The wattage rating has nothing to do with the actual resistance. A 150-ohm 1-watt resistor and a 10-watt 150-ohm resistor do exactly the same thing. The higher the wattage, the more heat it can stand.....at's about all that means. The 1-watt would likely be enough, but it would not hurt to use a larger (wattage) one to be safe.

 

After looking around and finding places that offered them (32446 95a)....but "was not available" or "out of stock". I bit the bullet and purchased one for $77 when I found it. I'm pretty sure the Stealership price would be well above that.....if they had one. At least that's one more thing I hope I will never have to use and if I don't....I'd be willing to bet I could sell it one day.

I've been broke-down in northern Utah on a holiday (for other reasons having nothing to do with EFI) and I don't like being broke-down in the middle of nowhere. You Utah folks don't get your feathers ruffled...I LUV Utah.

Now I guess I will consider what else I need to consider. This bike simply runs too good to butcher. It's a 1998 95th. Annivesary Classic and I don't relish the thought of grinding-up an expensive fuel tank to convert it. After doing the math, I can get about one of every major problem-prone sensor and even an ECU for the price of a carb-conversion.