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MPI SC surging from just above idle to 7000 rpm

mtnxr

Veteran
Joined
Feb 2, 2004
Messages
48
Location
Colorado
OK second trip out. Things were closer than the first trip. However I did have this really annoying problem of the sled surging or missing from just off of idle to about 7000 rpm it would miss hard enough to about throw you over the bars and then take off again. A/F was 13ish at idle and would drop to high 10s to 12s during the problem area. Ran decent above 8000 rpm and at WOT.

I tried to search and came up with checking the boots and for vacum leaks and checking electrical connections etc. I am also wondering, since I just bought the sled, how you know if the MPI controller has been updated or not. It is the old style and not GEMS. I tried to call MPI last week but they are closed till next week.
 

Fuel Controller

Mine has version 13 writen on the back of it and I believe this is the latest version. Mine does not have GEMS on it either, mine has: "Mountain Performance Inc." and "Apex fuel controller".
 
same problem but below 8000 is ok above 8000 is bad. problem got progressively worse by the third day. Iwas told to change plugs first. have't got to it yet but I will. keep you posted.
 
Installation issues , or controller ,2007 apex rtx
my sled has 5500 km on it and runs PERFECT .
Try these fuel settings ,
and you must have a bov.
5 lbs, for traveling ,
can't always buy premium fuel ,
sled goes 228km / 128 miles on fuel , 130 mph

1 / 2.0 / 2 / 4.5 / 1 / 8

Sled runs on the numbers a/f , no miss , no hesitation, no sputter , zero , runs great!

We also have a 2006 RTX set up the same , runs perfect also , ( both version 13 )
 
Thanks for the replys. I am running 50/50 race and Premium fuel. We ride 8-11,000' elevation. I was told when I bought it that they put new plugs in prior to selling it to me. I bought it with 650 miles on the sled.

Where I really noticed it was boondocking yesterday trying to ride slow and pick through the trees. It was constantly either trying to throw you over the bars from stalling or off the back of the sled when it would take off.

I tried settings from HA Boost to MPI settings but everything I tried resulted in the same results for this problem. I ride with a guy on a SC Nytro and it runs flawless so I have seen the light....just want to get it to work like that.
 
You can use the fuel controller to eliminate fueling possibilities just like the old 2-Stroke trick of quickly flipping the choke on-off to check for a lean condition ... I've had the exact same surging symptoms you describe below 8000rpm on two occasions ... once the cause was a lean fuel controller condition in the transition from idle/cruise to acceleration ... the other was not enough weight it the clutch which caused a lean condition at part throttle positions (too much rpm and not enough fuel) ... the two modes you should be most concerned with when troubleshooting this are the idle/cruise and altitude compensation ... add fuel one click at a time and see how it responds ... example ... if you started with idle/cruise at 0.5 and altitude compensation at 2.5 like the instructions state (mine will not even run on these settings, it's too lean, and dies as soon as the fuel controller comes out of its diagnostic mode) you would increase fuel in idle/cruise to 1.5 and increase fuel in altitude compensation to 3.5 ... at 5500-to-8500ft elevation 20F-to-30F and the non-GEMS controller I found setting 2 idle/cruise and setting 7 altitude compensation to work the best for me on my setup with the cold air intake ... >> NOTE: If you do not have a cold air intake you are sucking HOT air into your engine boondocking and MUCH cooler air on the trail where you have higher airflow through the engine bay which means your engines fuel requirements are all over the place which means you WILL end up chasing your tail trying to get it to run correctly in both conditions << ... my final settings were 2-4-4-4-2-7 ... for your elevation you might try these settings ... it should be a bit rich ... but if it eliminates the surge you have found your problem ... if it doesn't ... you will have to look for another cause ... that's troubleshooting ... logical determination by elimination of possibilities.
 
Thanks Hammer and I hope you are getting better! Without good health not much else matters. My 39 year old wife had a tumor inside her heart 3 1/2 years ago, had open heart surgery and ended up with a high performance titanium heart valve out of the deal (we tease her about the valve some). She is doing well but that kind of experience makes you rethink some things.

Back to the sled, I should be close on my clutch weights but could not come up with the spring that I wanted so I engaged somewhat high and would over rev at WOT so I controlled the RPM all day with my thumb with a few exceptions of course.

I tried settings from MPI settings of .5, 5, 7, 5,5, 2.5,2.5 and then I tried Trey's settings of 2,1,3,4,1.5,3....In my 40 plus miles of playing with this between 9500 ft and 11,000+ft elevation I played with numbers between these ranges. I could get a noticeable difference in how it ran above 7,000 rpm but nothing seemed to change at all in the problem area. I felt that the #1 and #6 settings should be where I could make a difference but I could not get it to act any different with those settings. The only time I saw a difference was on the way back to the truck it mellowed out (the surging that is). That was around 6500-7000ft

I am suspicious of the controller maybe because it was installed in January 06 as far as I know and the previous owner does not seem to know if it has been replaced or updated in any way. I have read about problems with them. There is no aparent version number on the controller that I could find.
 
I engaged somewhat high and would over rev at WOT so I controlled the RPM all day with my thumb
If you mean over-rev as in Rev-Limiter ... Been-There-Done-That ... ADD WEIGHT to the primary until it under-revs no matter what the elevation or throttle position ... then try adjusting the fuel again ... I found the Tachometer to be WAY behind the actual RPM if you're too light in the primary ... This is because the Rev-Limiter cuts ignition pulses and the Tachometer displays RPM by reading and buffering ignition pulses (so Tachometer reads slower and lower than actual).
 
Ok I will work on that. By over rev I mean I could hit 10500 and I was shooting for closer to 10000 max. I am running the 26/22 combo for my SC pulleys and trying to live by your warning about over reving the SC. I am working with Trey at HA Boost on the clutching, he gave me the setup with weights, springs, secondary etc... But the dealers in western colorado did not have a yellow pink yellow spring so I ran a stiffer one. My weights are maxed out with the rivets that Yamaha offers so I gotta get that softer spring to try it.
 
The subject of the stock fuel mapping or C/O adjustment came up and I was curious if there is any chance that it could have been changed along the way and be contributing to the problem? Just a thought. I am not exactly sure what the previous owners had done so I am trying to nail down the variables.
 
The CO settings are a very fine adjustment whereas the fuel controller is a relatively course adjustment in comparison ... Unlikely to be the cause of the surging problem ... I staggered the cylinders to make all four plugs look the same on my SC setup.

Cylinder #1 at 0
Cylinder #2 at -6
Cylinder #3 at -8
Cylinder #4 at -10
 
Thanks Hammer...I was just searching the posiblities. I sent the controller to MPI because it appears it was installed in January 06 and there is no indication that it was ever updated with the new versions. Once I get it back I will work at getting the settings right.
 
Update, Sled works great with the new controller...Just rode again yesterday and it is just a blast to ride.
 
Update, Sled works great with the new controller...Just rode again yesterday and it is just a blast to ride.
 


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