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Discussion Starter #1
Hey guys!


I am new to the forum and am hoping you could help me with a wierd problem.
I have a 2008 (most possibly made in 2007) 800 model max xt efi 4x4.
When my rpm goes over 6000, somethimes the cpu thinks its in reverse and stops the trottle or the power. It's like it cut's my throttle for a quick sec. I can see the R in the display, so the cpu is maby acting right, but what is the orgin of this? When I have over 7000 rpm it constantly cuts rythmicly. So lying with full thottle on the freeway is impossible because of the atv cut's power frequently.

I had a theory about the sensors on the tranny, but I have tighten those, and watched that there was no vibrational difference from 5000 to 7000, yet the power is constant without "cut's" on 5000.

I think it's something inside the engine that is wrong.

I have a "maintenance soon" error message followed by "High Tor Mulen". Tryed googling it but, nothing. I also tried getting out error codes (p-codes) but there werent any.

I might at some point overfilled with oil. Because the other day a lot of oil were gone without any lekage.
I also may have damaged the bearings in the cranck case while I was trying to get the clutch out without a clutch puller.
I also fully had apart the tranny and changed some bearings after runnig it dry and half totaled the tranny. The tranny is now working very good, and I can't understand how rpm controlled cut's can have anything to do with the tranny. It gotta be something inside the engine that is wrong...

Any Ideas? I'm out on my deapth here x)
 

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I thinks it has to do with the gear position sensor, that is what tells the ECU what gear the bike is in. As far as why it indicates reverse at 6000 RPM, must be something in the sensor module that is intermittent and sensitive to vibration.
 

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After the maintenace message it should show whatever the dealer has programmed it to say. I have seen dealers put Hi and then the owner's name, but that's pretty cheesy.

I t sounds like the certain RPM is causing a bad contact in a wire or in one of the gear position sensors.
 

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ECM may be seeing a different RPM than you are actually running and hitting the rev limiter before it actually should. Sounds like a trip to the dealer to put in on buds is in order.
 

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That's the previous owners name I'd bet. As for your gear position problem I'd say its in the ECM. Something is probably messed up in there and bit communicating properly. Would sure be handy if you had a friend or neighbour with the same quad that you could swap parts from just to try it. I'd say either way you'll probably end up at the dealers for programming. Make sure to bring a valid bill of sale or title with you as they may not work on it without proof of ownership.
 

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Discussion Starter #7 (Edited)
I thinks it has to do with the gear position sensor, that is what tells the ECU what gear the bike is in. As far as why it indicates reverse at 6000 RPM, must be something in the sensor module that is intermittent and sensitive to vibration.
I also taught about this solution, but I rev'd the atv on a standstill and, there was very little vibrational difference from 4/5 to 7k rpm. Yet it still happened.

After the maintenace message it should show whatever the dealer has programmed it to say. I have seen dealers put Hi and then the owner's name, but that's pretty cheesy.
I did not know, that's cheesy yes!

ECM may be seeing a different RPM than you are actually running and hitting the rev limiter before it actually should. Sounds like a trip to the dealer to put in on buds is in order.
Well a trip to the dealer is what I am trying to avoid, but it seems inevitable.
Actually the rev limiter shows "-" rpm as in minus, so gotta fix that anyway.
But if this was the case shouldn't it see the same rpm as not good, every time? Because it can vary from eks. 6100 to 7300 sometimes before it starts.
 

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Discussion Starter #8 (Edited)
An update on analysis:

Drove home last night and avoided highways to keep the rpm low.
Suddenly at 5200 ish it cut's.. It was dark so I used my extra 10k lumen lightbar.
I drove into a area with more lightning and switched off the light's. Then there were no cut's.

I tried this a couple of times, it stopped the cut's, but not every time (at high rpm).

When I came home I had a low batt warning.

So I got this theory: The fuel pump is electric. And more rpm = more fuel = more electrical consumption? Then with a low battery/high load of consumption there is not enough energy for all, and the fuel pump cut's.
But then, how come the R?

Anyway I will buy a batterycharger and charge the battery, and then we'll see if it's that.

However I need to go to the dealer anyway, will keep you updated :)

Thanks for all the answers! :thumbsmilie:
 

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Sounding like a power issue now. Test charging voltage and have the battery load tested after you get it fully charged. Any auto parts store should do the load test for free if you bring the battery in. With a volt meter on the battery you should see 13.5-14.5V at idle and it shouldn't go over 15 at any RPM when revved up. If it's lower then you have a stator issue. Higher, voltage regulator and possible stator.
 

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Discussion Starter #11
Check your battery connections for tightness and corrosion also check the 3 phases on your stator.
Sounding like a power issue now. Test charging voltage and have the battery load tested after you get it fully charged. Any auto parts store should do the load test for free if you bring the battery in. With a volt meter on the battery you should see 13.5-14.5V at idle and it shouldn't go over 15 at any RPM when revved up. If it's lower then you have a stator issue. Higher, voltage regulator and possible stator.
Wow!

I logged in just to update on the problem, that "mysteriously" fixed itself after I tighten the loose "+" end on the battery. Here is the explanation, Thank You!
I shortened unfortunately the plus to earth a couple of times by trying to tighten the bolt, so my theory was that the ECU needed some "shocking" ;)
But I see now that your theory is the right, of curse! :)

Now it rides fine at any rpm, no cut's at all (except for annoying rev limiter).

This was really a tricky one..
Thank you for great answers! :th_smiliethumbsup:
 
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