Sleds cuts out at 7000 rpm

peaceofwork · Dec 10, 2017

I'm fishing for ideas here, I got out riding to discover the sled runs strong up to about 7000 then it just bogs , not outright stalling but just bogging and Is not geting to any higher rpm. It's like someone hit the kill button but then it's idling fine and ready to do it again. I'm thinking the fuel is not getting their - it got a new fuel filter this fall.
It had top end zip last weekend but vforce low idle ,then for this this weekend I had it apart and installed boyesen reeds and it starts and idles consistently great - but when I get it out to the snow she won't turn on. I checked all the electrical conections and threw in different spark plugs but no change.

richeyrich · Dec 10, 2017

Have you checked the tps?

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TRS · Dec 10, 2017

If everything you removed and replaced is in order. Check your EValve hoses and the bellows. If the EV port is plugged in the cylinder it will do this also.

Octanee · Dec 10, 2017

I'd check into the exhaust valves, from what I've read if they don't work how they should they can cause the sled to fall on its face in higher rpm. If the sled was leaning out from a fuel issue, you'd probably have lots of back firing and probably throwing a detonation code.

peaceofwork · Dec 10, 2017

TRS said:
If everything you removed and replaced is in order. Check your EValve hoses and the bellows. If the EV port is plugged in the cylinder it will do this also.

I did look for wet exhaust valve housings indicating a torn billow, but great thought on plunged port.
Hoses and wire conections looked good around the power valves no leakage so I assumed it was all good,
Besides eyeballing the billows what's a good test n check method on the ev port?

peaceofwork · Dec 10, 2017

Octanee said:
I'd check into the exhaust valves, from what I've read if they don't work how they should they can cause the sled to fall on its face in higher rpm. If the sled was leaning out from a fuel issue, you'd probably have lots of back firing and probably throwing a detonation code.[/QUOTE
it just ran beautifully untill 7000 no backfiring no code .

richeyrich · Dec 10, 2017

Put the tps back into spec. It can cause erratic idle, and can cause problems on top end.

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peaceofwork · Dec 10, 2017

richeyrich said:
Put the tps back into spec. It can cause erratic idle, and can cause problems on top end.

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Thinking about this, if the TPS was out of adjustment wouldn't the sled be
tough starting, reverse hard to get, poor idle quality ?

richeyrich · Dec 10, 2017

peaceofwork said:
Thinking about this, if the TPS was out of adjustment wouldn't the sled be

tough starting, reverse hard to get, poor idle quality ?

Exactly. Those are the most common. But if it’s not set right and the computer thinks it’s positioned some other place, it can cause it to have lean or rich characteristics

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TRS · Dec 11, 2017

peaceofwork said:
I did look for wet exhaust valve housings indicating a torn billow, but great thought on plunged port.
Hoses and wire conections looked good around the power valves no leakage so I assumed it was all good,
Besides eyeballing the billows what's a good test n check method on the ev port?

You need to remove the EVs and run a piece of mechanics wire through EV the port in each cylinder. Make sure your piston is close to bottom dead center.

peaceofwork · Dec 11, 2017

i first thought maybe I missed recouping an electrical conection when I replaced the reeds, or one of the new spark plugs I had just put in was crap, and I had ruled out power valves because I did not see any black drool weeping and hoses and electrical all looked good to me.
the plunged pv ports idea makes a lot of sense to me because I did have vforce reeds in it that made the bottom end extremely rich .
TPS did not concern me because reverse was right their every time I hit the button and it idled well and started quick.
Thanks for the ideas guys I was down to guessing digital wrench time

stormrider3 · Dec 11, 2017

It' s the reeds. Put the old ones back in.

peaceofwork · Dec 11, 2017

stormrider3 said:
It' s the reeds. Put the old ones back in.

Not a chance lol , I tryed to like them but intermitant low idle was not my thing. do a search on vf3 and vf3R for cfi motors I did not think I wanted to buy a controller to pull fuel out of the bottom end just to possibly make them work.

peaceofwork · Dec 14, 2017

Today is a shop day, I got a digital multimeter, power valve gaskets, and a fuel pressure tester. I 58-60 lbs and when I shut it down it drops to 52/54 lbs and hangs their for a long time.
Perhaps I should be seeing what the pressure is at about 7000 rpm when it gets the big bogg?
Al least it's warmed up and pleasant to work on now so power valves are coming out and getting checked as are the ports in the cylinders then it's TPS check time.

peaceofwork · Dec 14, 2017

It tested at .695 and I put it to .700 ,was this enough of a difference to cause the kind of problems I was experiencing ?

RoostinRyan · Dec 14, 2017

peaceofwork said:
It tested at .695 and I put it to .700 ,was this enough of a difference to cause the kind of problems I was experiencing ?

I doubt it. Mine was out about that much and I hardly noticed anything if anything at all. Have you looked in to the tss? Mine would cut out intermittently (mainly when I was standing) while wot. The tss wasn't fully depressing and causing it to fall off.

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TRS · Dec 14, 2017

peaceofwork said:
It tested at .695 and I put it to .700 ,was this enough of a difference to cause the kind of problems I was experiencing ?

Nope, we set all of them to .698.

peaceofwork · Dec 14, 2017

ryanlinger said:
I doubt it. Mine was out about that much and I hardly noticed anything if anything at all. Have you looked in to the tss? Mine would cut out intermittently (mainly when I was standing) while wot. The tss wasn't fully depressing and causing it to fall off.

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I hear it's got a bypass or its taped up or both ... What do I need to know when looking over the TSS?

RoostinRyan · Dec 14, 2017

peaceofwork said:
I hear it's got a bypass or its taped up or both ... What do I need to know when looking over the TSS?

If it's taped up I would assume it's good. That's essentially what I did with mine and it did the trick. Just made the switch pushed in all the time.

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peaceofwork · Dec 15, 2017

I found a cracked power valve diaphragm so now it all makes sense

Sleds cuts out at 7000 rpm

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