2010 M8 HCR WOT Sputter

[Doof]

Made a new thread as I kinda hijacked the other thread (2011 Crossfire 800 WOT Bog) So we've had this problem for a while now on my dad's 2010 M8 HCR. Has about 2400km on it, brand new primary with arctic cat gold spring put in late January. Brand new Boyesen reeds put in at the same time as new clutch. The problem actually started just before the rollers on the old clutch starting sticking and needed replacing.

The sled won't hit full RPM's when you open it up, whether it be from no throttle, 1/4 throttle, or 3/4 throttle, just sits around 7700rpm and spits and sputters until you let off the throttle. If you ease into the throttle steadily it will be able to go up and hit 8100rpm and hold it there. If you have it at 8100+rpm and let off the throttle slightly and try hammering it again, it starts sputtering again.

We've cleaned exhaust valves as well as adjusted exhaust valve cables. We've replaced all 4 plugs. We've tried pulling the ECU off of my 2011 M8, nothing changed. Tried putting stock can back on instead of Jaws can, nothing. We've tested fuel pressure at idle 3 different times, got 47psi every time.

Should we be lifting up the track and testing fuel pressure at different RPM's and throttle positions? Or are one of the fuel pickups possibly plugged up?

Is there a problem with injectors that's not popping up as an engine code?

Is there possibly something wrong with the exhaust valves or servomotor that we couldn't tell was wrong?

Or is there something buggered with electrical, throttle position sensor on the throttle body? Or TSS?

Any input would be greatly appreciated as we have a trip planned to go to McBride this upcoming weekend.

Thanks in advance!

 

[Uptown]

Hmm thats an interesting problem. I have a 10 m8 with 3600km. Primary just ate my weights! Only have i seen powder bogs, and rich low rpm burble\smoke. I think 47psi is in spec but it is at the high end of the spec. Dont think 47psi will cause your problem, it should rip at WOT. One thing to check is all the spark plug caps, they are resister caps, can unscrew them and test resistance ect. I could look up the spec, also the coil packs, maybe 1 is faulty but doubt that is it.
I agree with the fuel psi under load test. It is dangerous to have the track spinning at WOT in the air.
If the gauge was by the handlebars a guy might be able to read it at WOT but thats tricky to get an accurate reading.
If the pump is putting out 47psi at idle then the pump will be ok. the pump creates flow, the regulator causes a restriction which creates the pressure. if the pump can flow enough to create 47psi the pump is working ok at that time. maybe a intermittent regulator but the problem seems consistant so probly not the regulator. I downloaded a manual and will take a look at it. Good Luck!

 

[sled_wrangler]

from what your saying im thinking power valve servo have you tried putting your survo on it ??

 

[Uptown]

Read a few things.
Fuel injector resistance: 2.1-2.9 ohms
fuel pump is 12v DC, can plug in to a car battery for testing by itself
If the APV power valves are not opening would cause low power ect. Said every time the engine is started the ecm cycles the apv motor for a self check. IF the valves are too heavy to pull or too light they will try 2 more times then stop all together.
Sounding more like power valve issue to me now.

 

[Doof]

Ya I'm thinking fuel pump and regulator are fine. But I will check out the spark plug caps in the morning and swap out the servomotor from my '11 and see what happens. Thanks for the info guys.

 

[Doof]

Swapped out the servomotor off my '11 this morning and is still acting up. While I was riding it around I found that if I didn't quite crack it open all the way it would hit 8100rpm and hold, but if you applied anymore throttle it started sputtering again. The throttle cable is set to the right length, so this has me thinking it's the throttle sensor on the throttle body. Could it be reading the throttle position wrong and injecting the wrong amount of fuel at WOT?

Anyone know anything about these throttle sensors that could chime in on this?


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[sled_wrangler]

do the cables for the power valves move freely ? when it starts to sputter after wot whats the rpm at ???

 

[Doof]

When I was swapping out the servomotors I checked the cables and they open and close freely without binding. When it starts to sputter it doesn't go over 7640rpm.

 

[sled_wrangler]

well the last thing i have got for ya is maybe the TORS at the bars ... do you have a tether on the sled if so maybe try taking that out and see if that cleans it up ...im going to talk with a buddy today and i will run your problem past him and see what he says

 

[Doof]

Is that override the switch the throttle safety switch or is it something else? I heard someone else say something about it and I don't know exactly where it would be. There's no tether on the sled either


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[sled_wrangler]

If there is no tether then don't play with it ... it is the throttle over ride in case the throttle is wot it will put it into an over ride so it doesn't go thru fences like mine did lol

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[Doof]

Sounds like an interesting story lol! So if the TORS is buggered, is that the little sensor/switch under the kill switch?


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[sled_wrangler]

Yeah its in that housing

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[tchriste]

I had the same issue on my 09 and it turned out to be shorted out spark plug leads. They had rubbed together and were shorting between the leads.

 

[DR.STEEP'N'DEEP]

I would try swapping fuel pumps it only takes about ten minutes. I had a fuel pressure problem on my 09 m1000 the pressure when up to 80 psi all on its own and it did not run proper i turned it back down to 43 psi but it still sputtered until i change the pump. I dont know if it was the pump, regulator or smart valves cause i just changed all of them at the same time. Does your sled hold fuel pressure for a while after its shut off or does it drop off right away? I dont think its your throttle safety switch but you could try and unplug it.

 

[Doof]

Well we phoned around to a couple dealers earlier today and they figured it had to be fuel pickups.

Right as I seen your reply christe, we were actually looking at these. We were in the middle of pulling the fuel pump off and noticed one of the spark plug boots was all cut up and had a chunk missing out of it. It was the spark plug right underneath the pipe on the PTO side, I'm thinking it might have been arcing out? Also the lead on that same plug looked like it had been rubbing up against the steering post as well. So we halted our fuel pickup operation, put everything back together and going to put a new lead and boot on and see how it runs in the morning!

Hopefully that's the fix!


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