Supercharged Nytro MTX, Cuts at 6000rpm?

[comp]

Hi there, i recently bought myself a 2012 Nytro MTX 153" witch a 220hk compressor kit from MPI (i think?) with a GEMS fuel box.
Dno if I need to mention it, but it runs at sealevel in northern Norway.

Problems seemed to arrive quite quickly, i`ve had a testrun for about 5km, then for my next ride when the real snow arrived i got about 1km before the problem showed up.
In the middle of a wheelie i sensed that the power seemed to be fadeing, dropped it down and tried to hit the throttle again, then it started to cut off at around 6000-6500rpm.
The sled cut`s with or without resistance to the belt.
Cold or hot, it starts just fine, seems to run smoothly like it should from 1400-6000rpm but after that it cut`s off, as if you remove the ignition.
It "can" sometimes after driving a short distance stop, when then reduceing to idle after 5-15sek, but then start again just as if nothing was wrong.
I`ve tried replaceing the sparkplugs but with no result.
Checked the wiering for ground sources, the connections for the gems box etc, no positive results.

Anyone that have any suggestion as to why this is happening?
Or even what i can look for?
I`ve got one week before im returning it to the seller (it`s a long drive, that`s why i haven`t done it yet).

Thanks alot for any answers.

 

[Einar74]

Sorry about a little off-topic.

But what weights are you running with this setup in Norway?

I am in Iceland and run from 0-4000ft. I am having problems dialing in a MPI stage 1 supercharger setup.

I am running now like 82grams and it is spinning to like 9100rpm and overboosting and running to lean.
Running stock injectors and fuel pump and should be seeing 6-7psi with the pulley setup.
But pro-logger gauge is saying 10psi , I am a little bit puzzled about what I should do next other then try to add clutch weight and get the rpm down and see what that will do to the air/fuel radio. Now I am seeing like 14,5/1 on wot.

 

[stingray719]

Check the pulleys. Yeah I know it sounds stupid but I had the exact thing happen to my old supercharged Phazer, the pulley was spinning on the shaft but catching enough to still produce some boost. Amazing thing is it ran that way for about 80 miles before it finally blew the belt.

Side note, if you do not install the pulleys exactly as instructed by MPI they WILL come loose.

 

[comp]

Einar74, ill check the weights the next time im at my snowmobile, bought it like it is so i dont rly know what weights im running.

Ill check the pulleys aswell, seems weird but at the same time very logical.
If the boost drops when you get you around 6k rpm the sled will get way too rich mixture and cut, but then again, after several testruns, one would think this would be happening at lower and lower rpm at it would slip more and more?

Thanks.

 

[SRXSRULE]

Check and make sure it didn't blow the throttle bodies off the intake. Seen it happen more then once. Eric

 

[BigFish BC]

so are you just losing boost or is the sled just shutting off?

 

[comp]

Its like its cutting off the ignition, if i dont give alittle throttle again after releasing it after the cut, it will stop.
If i were to take a guess, i would say maybe its a safety switch that releases a ton of gasoline cus its unsure of the mixture or something?
I dont have a boost gauge or even an AF display.. its preset so there shouldn`t be necessary to adjust anything, and this problem came just suddenly, worked just fine a moment before and on my first trip.

 

[stingray719]

Einar74, ill check the weights the next time im at my snowmobile, bought it like it is so i dont rly know what weights im running.

Ill check the pulleys aswell, seems weird but at the same time very logical.
If the boost drops when you get you around 6k rpm the sled will get way too rich mixture and cut, but then again, after several testruns, one would think this would be happening at lower and lower rpm at it would slip more and more?

Thanks.

That was what drove me nuts, when cold boost would work and after a few minutes it would drop to 2 lbs boost and fueling would go nuts. Adjusted the gems so many times it was maddening. Bright spot though was after replacing the belt and pulley the sled ran like a scalded cat....was a lot of fun.

Then again maybe you have a different problem.

 

[christopher]

Hi there, i recently bought myself a 2012 Nytro MTX 153" witch a 220hk compressor kit from MPI (i think?) with a GEMS fuel box..

I have reached out to MATT at MPI to come and read this thread and offer you a solution.

 

[Matt@MPI]

Did this come set-up for a different altitude? If it was clutched for a higher altitude and taken to a lower one it will hit the rev limiter so fast that it will only read 6-7k on the gauge.

 

[comp]

Nope, according to the weatherstation, the city i bought it from where it ran just perfectly is only 60meters over sea level.
And where i drive its from 5 to like 600meters above sea level.
But if it was that, it would happen instantly wouldn't it?
On my first ride we were only at about 70meters, but everything worked just fine, same as the last time i drove it until it just suddenly started failing, with no error codes or anything :/

 

[BigFish BC]

so does it idle fine?does it only do it when you let of throttle.

 

[comp]

The snowmobile works as if nothing was wrong as long as i keep it under 6000rpm. idle is fine, however if I have been over 6000rpm and gotten cutt`d off and then let off the throttle to idle, it will shut off after about 5-10sek, but then again it can start up and idle just fine momentarily after.

I guess you can compare it to switching off the key everytime you give enough throttle to bypass 6000rpm, if i keep full throttle it will just die, but if i let off and then give alittle throttle again it runs just fine without shutting off aslong as its under 6000rpm

 

[BigFish BC]

this sound to me like a fueling issue,could be low fuel pressure or it could be fuel box.since it kinda just started out of nowhere i would suspect the fuel box,they are known problem spot sometimes.
the reason i suspect fuel box is under 6ooorpm it not doing much,as boost builds box adds fuel, if it doesnt it starts to lose power or die from no fuel.

 

[comp]

DING DING DING.
BigFish BC, you were right, it was the gems fuel box that was acting up.
Disconnected the box and ran the snowmobile on stock supply just to test the theory, and it worked, no more cutting and ran smoothly, tho kinda need a new one if i want to be riding for more than 5minutes don`t i?
Talked to the dealer who sold me the sled and he will send me a new gems box

Thanks to all who tried to help, i really appreciate it

-Kevin from Northern Norway

 

[bholmlate]

good deal!!!
I was just about to say maybe the box got moisture in it. that is a common problem with that box that i have read about in the forums and why a lot of people don't like to run them and end up running other fuel controls. Either that or put them in a water tight case

A lot of knowledgeable people in this forum and knew someone one would come up with the answer. have a safe season on the other side of the pond.

 

[comp]

Yeah, i had the same thought, the box was placed right behind some sprinkles where it will be filled up quite fast on huge pow days, like the day that this fault appeared
Gonna put the new gems box in a waterproof case or something like that just to be safe

Have a safe season you guys aswell

 

[BigFish BC]

glad you got it figured out.

 

[SRXSRULE]

On my GEMS box I always took masking tape and taped the front and back, then applied a good gasket sealer around the edge where the seam is and then also work it into all the wires that come into the box. I mounted mine on the riders side of the steering post riser. Its where you can reach it, doesn't get hit with snow, is out of the heat and never holds any water there. Eric