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Exhaust/Power valves

Octanee

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Hey guys, does anybody have any experience with them exhaust valves and when they don't work what happens? I have tried searching and haven't come up with much. does the sled ever cut out/fall on its face after starting a pull? I had that happen a few times. I stumbled across this video, exact sound at 3:56 https://youtu.be/C6U2KPGbmpA?t=3m50s same as the sound my sled made last ride however it still pulled rpm ~8k or so, probably due to the turbo helping it. I also noticed my air fuel fluctuated oddly between 12:1-15 ish really fast while the bog/stutter happened.

I have checked my valves and the diaphragm and the ports, all is clean and no blockages/ issues I can see.

any way to test the solenoid that controls the valves? when the sled is off should the solenoid be closed off or open? Do they stick? I read on the older 900cfi sled some guys were drilling out that small hole under the diaphragm. (although mines not plugged but while im at it?)


Thanks!
 
Last edited:
T
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I didn't watch the link you posted, but I did just have power valve issues.

2016 Turboed 800 - ~8psi boost.

My sled went from pulling 8450 to ~8000 instantly. Ended up being a broken cable for the power valves.
 

AKFULLTHROTTLE

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What were your symptoms with the egt? I had swapped mine a few weeks ago with my spare sled but you never know....

Well mine would bog off an on. The other issue I always had with the Pro was the reeds which were the same symptoms. Bogs a lot, falling on its face.

Not that you dont have a EV issue but i never had any on my boosted pro.
 

Octanee

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Well mine would bog off an on. The other issue I always had with the Pro was the reeds which were the same symptoms. Bogs a lot, falling on its face.

Not that you dont have a EV issue but i never had any on my boosted pro.

Good info. Did your exhaust sensor ever throw a code? I will re-swap my exhaust sensors for the heck of it. Reeds wise I don't have much first hand experience yet. The sled starts great every time, last ride it would Rev up just fine and no backfires nor any bogs per say, it rev'd up and wound out then fell on its face once or twice then after that it did that weird stutter like in the video, I could also boost it in and out of the throttle down the trail and it was ok doing that, wide open was acting up. They are also new and it's been mostly trail miles, sled hasn't wanted to run for me all winter so I haven't had much of a winter lol but that doesn't mean the reeds are still good.
 

AKFULLTHROTTLE

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I went through reeds about 400-700 miles on the Pro. Mine never through a code but was stored in there only viewable with a digital wrench.

Also make sure you gap your plugs to a .018. To large of a gap will cause the spark to be blow out and cause a pop/cut out.
 

Octanee

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I went through reeds about 400-700 miles on the Pro. Mine never through a code but was stored in there only viewable with a digital wrench.

Also make sure you gap your plugs to a .018. To large of a gap will cause the spark to be blow out and cause a pop/cut out.


Good info, I'll swap my exhaust sensor for this weekend, clean the power valves anyways, verify the solenoid is not bleeding air, put new plugs in again, I have them gapped to 20 though, ran great all this time otherwise but you never know. New fuel filter again just because lol, I think ill check my turbo injectors again since it's not a big deal. Going to verify my vacuum lines off the carbs are fine, (boost gauge was reading just fine). And hope between all that, that it will run good.
 

Octanee

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Got out today with it, I tried plugging my exhaust valves, coincidentally it ran great did about 2-3 pulls then sat and had a snack, fired it up and it ran like crap, it was leaning out,

However the very weird thing I found was if I was at about 3/4 throttle, it ran fine, play that throttle the last 1/4 wide open it'll stutter and bog, back it off it was fine. Then other times it damn near didn't matter if I rolled the throttle or stabbed it, it just didn't want to go.
 

Octanee

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You try a new MAP sensor yet?

After that maybe TPS? Or Fuel Pump/filter


Thanks for the suggestions, I appreciate them. I appear to have it sorted now... gosh the things been a lemon, So this time I did 3 things, swapped fuel pumps with my spare pro, new fuel pressure regulator... I noticed this am while putting the sled together that there was a brass like dust around 1 of my spark plugs, turns out the cap was loose/worn out?, I just replaced it this past season and has 500 km on it tops, replaced that as well. Hard to say whats what, but I know yesterdays ride It was showing it wanted to run lean at times, and the issue was sporatic, like completely falling on it's face for a second like somebody hit the kill switch or the stutter, or just running good. I can't see 1 cylinder going down causing the falling on it's face, or the lean readings? you'd think you'd read richer with a cylinder not firing all the time., May have caused the stutter sound though. let it sit for a bit it was fine, then not so fine. ran great up to 7k rpm or so and or 3/4 throttle ish.....


In either case it ran good today so hopefully it keeps it that way.
 

ez-ryder

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"you'd think you'd read richer with a cylinder not firing all the time"

It will show lean if it misfires.

This was posted on a car forum.

lambda sensors are oxygen partial pressure sensors, so if the quantity of oxygen in the exhaust gas increases as a result of a misfire, the appearance AFR from the wideband would indicate lean. This effect can also be seen with retarded timing, light up too late and you have incomplete combustion by the time the charge is exhausted, ergo sensor reading will be leaner than true AFR. This was a big problem in the early days of 2.5 litre conversions which were quite intolerant of timing on medium to high boost, the retarded timing used to keep it safe unfortunately also made the appearance AFR leaner than the true AFR, which in some cases resulted in large carbon deposits on piston crowns, exacerbating the problem even further.

If you want the full picture you need a proper lambda meter, which will show you the exhaust gas composition; a misfire would show a big increase on O2 and a big increase in HC, and depending on the meter it will either let you decide what that means, or sometimes even correct the appearance AFR based on those two, otherwise mutually exclusive, readings (how can you ordinarily have unburnt fuel left, and still have oxygen to burn it ?).
 
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Octanee

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Nov 15, 2010
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Cranbrook Bc
"you'd think you'd read richer with a cylinder not firing all the time"

It will show lean if it misfires.

This was posted on a car forum.

lambda sensors are oxygen partial pressure sensors, so if the quantity of oxygen in the exhaust gas increases as a result of a misfire, the appearance AFR from the wideband would indicate lean. This effect can also be seen with retarded timing, light up too late and you have incomplete combustion by the time the charge is exhausted, ergo sensor reading will be leaner than true AFR. This was a big problem in the early days of 2.5 litre conversions which were quite intolerant of timing on medium to high boost, the retarded timing used to keep it safe unfortunately also made the appearance AFR leaner than the true AFR, which in some cases resulted in large carbon deposits on piston crowns, exacerbating the problem even further.

If you want the full picture you need a proper lambda meter, which will show you the exhaust gas composition; a misfire would show a big increase on O2 and a big increase in HC, and depending on the meter it will either let you decide what that means, or sometimes even correct the appearance AFR based on those two, otherwise mutually exclusive, readings (how can you ordinarily have unburnt fuel left, and still have oxygen to burn it ?).


Great info!, I learned something new today!, I did try googling the subject but I never got info like this which is what i needed. I think I understand it now, as un-burnt fuel is not the same as burned fuel in regards to the hydrocarbons and such, so the o2 sensor will read leaner as its looking to read something else. Explains the readings I had being at times fluctuating between OK 12:1 or all the way up to 15:1 1 then back to 12. So it had totally threw me off and I was looking in the wrong direction, Live and learn hey, I've had enough issues with this sled though that the least it can do is run for the rest of what little season we have now :/

At least in that regard I can feel good that I shouldn't of had any detonation occur. I did scope my pistons and they looked fine.
 
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