need some help!

[mattymac]

helped a buddy out last year, installed an SLP single/can, VF reeds, clutching, & jetting, to his gen 2 800 rmk. first ride out he calls and says his sled has never ran better! Second ride out first half of the day same thing, sled runs great... he is climbing an average hill when half way up it just starts spitting and sputtering??? everything looks OK, new set of plugs and the sled BARELY can make it to the truck under its own power. He brings it to me saying that he is sure the motor has blown in some form. 150lbs in both cyls?

If you can get it started it does not wanna idle, you can work the throttle but the motor cant even get up to where the clutch will engauge, its kinda like the RPM's hit a wall and will not advance and just plain runs rough? choke/no choke doesnt seem to make a diffrence and its getting alot of fuel back into the airbox, obviously since the motor will not pick up on RPM's no matter how you work the throttle.

Now heres what I have done/checked:

started with the basics...

plugs
went through the carbs inside and out
kill switches, unplugged the black/white wire
checked out all the chassis harnes wires for bare spots/shorts, unplugged hood harness, taillight wire under fuel tank/seat
unplugged yellow brown plug from stator
checked reeds, intake boots
checked pipe/silencer for any kind of obstructions broken baffle?
fuel seems to be fine (and since it was instant I thought no way but still)

I also changed it out with 2 diffrent CDI boxes
changed coil and spark plug wires/caps
tried a diffrent stator and ignition trigger sensor!!!!!
it has a brand new temp sensor on it, and I even tried another one from a diffrent sled as well


It is not lean! its rich if anything so im not thinkin crank seals or cracked cases or something outta the ordinary like that

150lbs compression dead on in both cyls!

I dont have a TPS sensor tester but I have another set of rackslides im gunna swap just to see tomarrow

I dont think the crank is twisted, I have only seen one around here that did it and it would still make RPM's and run just not top out and it was dead on top. It twisted about 1/8" outta phase

guys im at a loss here anything im missing???

TIA!!!

 

[mountainhorse]

How did you check the Reeds?
Did you remove both reed blocks and look at them carefully?

 

[clutch man]

My guess is that the crank walk out of time.
you need to have crank timing checked then see where you our!!
If you have check every thing you have listed oh here
check tps too the crank is more my guess i had one that was just 22% out and did the same. so check crank, crank seal, tps, then see where you our.

helped a buddy out last year, installed an SLP single/can, VF reeds, clutching, & jetting, to his gen 2 800 rmk. first ride out he calls and says his sled has never ran better! Second ride out first half of the day same thing, sled runs great... he is climbing an average hill when half way up it just starts spitting and sputtering??? everything looks OK, new set of plugs and the sled BARELY can make it to the truck under its own power. He brings it to me saying that he is sure the motor has blown in some form. 150lbs in both cyls?

If you can get it started it does not wanna idle, you can work the throttle but the motor cant even get up to where the clutch will engauge, its kinda like the RPM's hit a wall and will not advance and just plain runs rough? choke/no choke doesnt seem to make a diffrence and its getting alot of fuel back into the airbox, obviously since the motor will not pick up on RPM's no matter how you work the throttle.

Now heres what I have done/checked:

started with the basics...

plugs
went through the carbs inside and out
kill switches, unplugged the black/white wire
checked out all the chassis harnes wires for bare spots/shorts, unplugged hood harness, taillight wire under fuel tank/seat
unplugged yellow brown plug from stator
checked reeds, intake boots
checked pipe/silencer for any kind of obstructions broken baffle?
fuel seems to be fine (and since it was instant I thought no way but still)

I also changed it out with 2 diffrent CDI boxes
changed coil and spark plug wires/caps
tried a diffrent stator and ignition trigger sensor!!!!!
it has a brand new temp sensor on it, and I even tried another one from a diffrent sled as well


It is not lean! its rich if anything so im not thinkin crank seals or cracked cases or something outta the ordinary like that

150lbs compression dead on in both cyls!

I dont have a TPS sensor tester but I have another set of rackslides im gunna swap just to see tomarrow

I dont think the crank is twisted, I have only seen one around here that did it and it would still make RPM's and run just not top out and it was dead on top. It twisted about 1/8" outta phase

guys im at a loss here anything im missing???

TIA!!!

 

[mattymac]

put a new set of carbs on today from another 800 in my shop im doing a torque master on, mainly for the TPS and same thing no change?

As far as reeds go yeah I had them out today and they look 100% perfect???? still plenty of tension on the pedals none broken, missing, damaged and a good seat to the cage itself.

At this point im leaning toward the crack being twisted and outta phase, ive checked/swaped everything else that it could be.

it simply starts up like its running on one cyl (thermal gun tells me both are firing and making almost identical heat) while working the throttle the engine will barely get as high to try and engauge the primary. It acts like there is zero timing advance and the motor just wont pick up, alot of fuel getting blown back into the airbox as well.

 

[turbolq4]

maybe it sheared the timing key?

 

[mattymac]

maybe it sheared the timing key?

swapped in a diffrent stator, the timing key on the crank was fine along with the flywheel itself.

 

[rmkrazi]

Where along the line did you give the fuel pump green light? I don't know how that would correlate to excessive fuel in the air box but who knows?

 

[rmk4ever]

You dont state what kind of milage, theese things r notorius for twisting out of phase @ about 2800 - 3500 miles. I'd also check the fuel pump for it sounds like you got way to much fuel in there, i've seen the diaphram go bad on these & fill the crank case with fuel. Real easy to "blow" a crank seal that way... dont ask me how I know.

 

[mattymac]

the sled has 1900 miles on it.

as far as the fuel pump I did ponder the idea of checking it but to me the typical signs of it leaking into the crankcase isnt there. there is no excess fuel in the crankcase, the sled has sat for days on end and doesnt have any hard starting issues other than it seems like it idles like its only hitting on 1 cylinder. It will "run" for extended period of time, just obviously not well. Im not gunna rule it out since at this point ive checked almost everything else, and I have seen stranger things, just IMO not all the signs lead me to think the fuel pump is bad.

thanks for all the ideas guys! I aint givin up on this thing yet!!

 

[dvav]

i had the crank break on my 7oo and it still ran just wanted to die then i saw the clutch spinning out of balance thats how i noticed what happened grab the clutch and lift up and down might help or not .

 

[AirForceSledder]

May sound dumb but have you checked the motor mounts? Doesnt sound like thats the problem according to your info, but worth a check either way. Since you said it happened all of a sudden while climbing a hill...who knows

 

[mattymac]

i had the crank break on my 7oo and it still ran just wanted to die then i saw the clutch spinning out of balance thats how i noticed what happened grab the clutch and lift up and down might help or not .

I have another RMK in my shop right next to this gen2 that had that same thing happen to it, typical 800 rod pin breakage. Still would run on its own power, split the cases and the crank fell out in 2 pieces!

Its getting the torquemaster bottom end from indydan!!

the gen2 does sound and run similar though but definatly isnt the problem.

 

[mattymac]

May sound dumb but have you checked the motor mounts? Doesnt sound like thats the problem according to your info, but worth a check either way. Since you said it happened all of a sudden while climbing a hill...who knows

everything is bolted down where it needs to be as far as motor mounting goes, even with the track in the air the sled cant even spin the track under its own power.

Waiting for some dial indicators to check crank phase in the sled, im still leaning toward a twisted crank.

thanks agin guys for all the ideas!!

 

[dvav]

another way to tell if the crank is broke inside is if you can get it started with the clutch cover up and watch the primary as you blurp the throttle till the clutch grabs the belt and you can see it flex in toward the secondary . if it is broken and you run it too much it will start to smear part of the cases i caught mine just in time and towed it out rather than pushing it to death

 

[westerdoll]

We all ride RMK 800's and two of my friends cranks went out with the exact same symptoms last year. That was a good tip on checking the primary to prevent killing your bottom end. It was still a pricey fix!