Loosing rpm's @ WOT.........AGAIN!!!!!!!!!!!!!!!!!!!!!!!!!!!

[ranger1]

Last spring my sled started losing rpms when running wide open, it would start out at only 10,300 then creep even lower the longer you held it to the bar ( below 10,000!). I posted a thread on this in the fall & actually thought I had fixed the problem as I found that the two into one pipe was cracked almost all the way around. Welded the pipe, put it back together, went for a burn down the lake & came back a happy man because the rpm's were up to 10,700 & held there!!
Unfortunately, that was short lived, the next time out it was doing the same damn thing!!
My Excell muffler was leaking a little bit so I took that apart, checked the packing, put it back together with copper gasket maker & some stainless clamps, no leaks what so ever.....no fix what so ever either!
Only 2,500 miles on the speedo bearing, changed it anyway, that wasn't the problem. Took both clutches off, cleaned them & replaced both springs just in case one was week & allowing it to shift out to far, that didn't do anything. Took the sled apart last night to check the copper donuts that I replaced last year & those as well as the flex pipes & the y pipes were in perfect condition.( except there wasn't much of the copper high temp silicone left, lol, not worth using it there).
I am now at wits end on this, I have logged in many hours trouble shooting, checking things that I thought could have effect on the rpm's & replacing parts that didn't fix the problem.
I really need some help here, does anyone have any idea what the heck the problem can be, any & all help would be greatly appreciated

 

[tomanytoyz]

Ok i would check plugs to see howz it burning .

Check track tension ,ballooning of track will do it .

Was this a long lake run .? approx how long

 

[ranger1]

Ok i would check plugs to see howz it burning .

Check track tension ,ballooning of track will do it .

Was this a long lake run .? approx how long

My track has 5/8 to 3/4" free hang like always.
The rpm's drop down to 10,000 after holding the throttle open for ten seconds or so.
Kind of hard to check the plugs because it would have to be after a wide open run & check them right on the lake. The plug reading would be buggard if I drive it home then check, wouldn't it?

 

[Shiek]

rpm

How many miles on your clutches? primary spring and secondary spring they could be sacked out, i would look at your clutches--rollers, bushings, slider ramps..etc

 

[ranger1]

Re: rpm

How many miles on your clutches? primary spring and secondary spring they could be sacked out, i would look at your clutches--rollers, bushings, slider ramps..etc

I just had them both off, changed both springs, cleaned them, checked the pins & rollers, the clutches are in perfect shape.

 

[Shiek]

rpm

snow conditions? your belt in specs? cluthes aligned? how many miles on sled, ever change the plugs? plug caps maybe dirty ?

 

[ranger1]

Re: rpm

snow conditions? your belt in specs? cluthes aligned? how many miles on sled, ever change the plugs? plug caps maybe dirty ?

Yo Shiek, the snow conditions don't make any difference, whether it be wide open run on hard pack or two feet of powder. Brand new belt last spring as well, I borrowed the alignment bar from my local dealer, alignment is bang on & the clutches stay nice & cool.
Just changed plugs this past fall in part of my "process of elimination", lol
I think I have covered all the mechanical basis....I think, lol! Wonder if it could be fuel or electrical?

 

[tomanytoyz]

Ok i would check plugs to see howz it burning .

Check track tension ,ballooning of track will do it .

Was this a long lake run .? approx how long

My track has 5/8 to 3/4" free hang like always.
The rpm's drop down to 10,000 after holding the throttle open for ten seconds or so.
Kind of hard to check the plugs because it would have to be after a wide open run & check them right on the lake. The plug reading would be buggard if I drive it home then check, wouldn't it?

Ok yes the plugs would have to be checked after a hard run.

Go back out there and do another run and when it starts to drop rpms again let off a little and give it wide open again and see if it will reach the rpm.

Strange cause you fixed the problem with the exhaust and now its back and nothing leaks?

Check your chain tension also,

And is your throttle bodies wide open when you squeeze it out.

 

[ranger1]

Tomanytoys, I haven't checked chain tension this year, I will check today, (finger tighten then back off 1/4 turn I believe?) I will take off the air box & check the throttle bodies also.
.....strange, after it ran perfect for one day, ya got that right, lol!!

 

[Redbeard]

Ok i would check plugs to see howz it burning .

Check track tension ,ballooning of track will do it .

Was this a long lake run .? approx how long

My track has 5/8 to 3/4" free hang like always.
The rpm's drop down to 10,000 after holding the throttle open for ten seconds or so.
Kind of hard to check the plugs because it would have to be after a wide open run & check them right on the lake. The plug reading would be buggard if I drive it home then check, wouldn't it?

Ok yes the plugs would have to be checked after a hard run.

Go back out there and do another run and when it starts to drop rpms again let off a little and give it wide open again and see if it will reach the rpm.

Strange cause you fixed the problem with the exhaust and now its back and nothing leaks?

Check your chain tension also,

And is your throttle bodies wide open when you squeeze it out.

Ranger, is there anything that could be obstructing the exhaust internally? Also, have you opened the airbox and checked the internal foam to make sure there is not an obstruction?
Hopefully I'm not repeating something you've already covered.

 

[kviper]

Apex will show WOT RPM loss in anything but good hard pack, usually not as much as you are seeing though, (200 RPM?) I didn't see that you have checked fuel filter in tank? It can be hooked out with a piece of wire from the filler. Check fuel pressure at WOT,hook a gauge in line. If you do a plug check that would be a good time to do a leak down test or at least a compression test.

 

[ranger1]

Ok i would check plugs to see howz it burning .

Check track tension ,ballooning of track will do it .

Was this a long lake run .? approx how long

My track has 5/8 to 3/4" free hang like always.
The rpm's drop down to 10,000 after holding the throttle open for ten seconds or so.
Kind of hard to check the plugs because it would have to be after a wide open run & check them right on the lake. The plug reading would be buggard if I drive it home then check, wouldn't it?

Ok yes the plugs would have to be checked after a hard run.

Go back out there and do another run and when it starts to drop rpms again let off a little and give it wide open again and see if it will reach the rpm.

Strange cause you fixed the problem with the exhaust and now its back and nothing leaks?

Check your chain tension also,

And is your throttle bodies wide open when you squeeze it out.

Ranger, is there anything that could be obstructing the exhaust internally? Also, have you opened the airbox and checked the internal foam to make sure there is not an obstruction?
Hopefully I'm not repeating something you've already covered.

Hahaha, ya I had the exhaust apart, the packing everything out of it, then put it back together. Airbox is clear as well. I have checked a lot of things so no worries if you suggest something that I already checked. Thanks for the help just the same

 

[ranger1]

Apex will show WOT RPM loss in anything but good hard pack, usually not as much as you are seeing though, (200 RPM?) I didn't see that you have checked fuel filter in tank? It can be hooked out with a piece of wire from the filler. Check fuel pressure at WOT,hook a gauge in line. If you do a plug check that would be a good time to do a leak down test or at least a compression test.

Check the fuel filter.....K, didn't do that, if you figure there is a possibility that could be the culprit then, check the fuel filter it is,lol! I did a compression test when I got the sled used & one of the cylinders was 6-7lbs less than the other three. It is the same now but it ran perfect & like a bat outta hell when I first found out the one cylinder was a little low. I have been running ring free in it all this season just in case it could be caused by carbon build up, maybe the valves not seated right. I am looking into buying a leak down tester, more accurate way to test.

 

[kviper]

Fuel pump weak, running short of fuel at WOT? How does it run compared to another sled you have raced before?

 

[tomanytoyz]

Are you using oil? seems to hit its mark then fall off..you fixed then was fine then it fell again,,

hmmm.how many km or mi ?

Make sure your fuel vent hose is ok

Maybe engine is getting a little warm too.