Why am I losing rpm's?

JSTYER

JSTYER

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Mar 19, 2013
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114
Age
47
Location
WI
I have an 02 SRX with the loaded 8dn-20's WWW primary, green secondary with a Dalton 54/46 helix set at 60. Today was the first time I got her on the lake and opened it up, she pulls like a banshee at 8500 rpm's up to 100mph, but then it drops down to 8000 and seems to quit pulling 105 was the best I can get. My buddy with a 99 SRX walked right by me and kept getting farther ahead. What should I look into? My 02 should keep up to a 99
 
what else is done to the sled? jetting, gearing, belt age, track,how many studs, and when was the last time the powervalves were adjusted and the likely the biggy, how loose is the track at rest?

I say "biggy" because if it hits 8500rpm up to 100mph and then loses it, the track rubbing under the gastank will definitely do that! most people think a loose track is fast but not on topend it balloons up and scrubs off speed and rpm because its loading the rear clutch. Look under the back of your sled by flipping up snowflap with a flashlight shine it up to see under the gastank from back, think youll find the tunnel protectors are black from rubbing the track.
 
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Jetting and gearing is all stock, just put a new 00 belt on it, I cleaned the valves just before winter and adjusted them, I just tighten the track before the ride, cause I had a wheel to replace. 144 studs
 
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I had the same problem with my stock viper a couple of years ago. I played with track tension, cleaned and replaced belt, and cleaned and adjusted power valves with no luck. Several members suggested I replace my clutch springs as they were original with 7000 miles on them and it solved my problem.

I agree with mrviper about the track rubbing, I ran mine loose for years to save on the slides and ended up with a giant hole in my tunnel. The plastic tunnel protectors don't last forever. I may have been losing a little top end mph but I was able to maintain 8500 rpm for miles until the springs got old and week.
 
put the sled up on the stand and tighten the track until it only hangs down a 1/2" from the hyfax in the middle, go out and try it again and see what it does, pay paticular attention to the rpm and mph if it falls back it will help tell the story of whats going on.
If it hits 8500rpm and goes up to 100mph at 8500rpm its not likely the clutching, something else is pulling it back, the track rubbing is usually the culprit.

you need to be a little more detail specific with the information in order to help.
 
Ok I will try that and my springs are new, I won't get to a lake again for awhile, and geez I apologize I was just looking for some advice and that you gave me.
 
let us know when you look under the flap and look at the tunnel protectors.
BTW_nobodys bustin on you, so dont take it the wrong way, its just print on a screen. Just need information to solve a problem, remember nobody here can see or hear your sled to see whats happening, only reading print on a screen and trying to solve a issue, its alot like guess work without specific info to follow.
 
I just looked at my tunnel protectors and they look fine no sign of rubbing and the track is tight. What else should I look for? Pull the valves again and check them?
 
nothing else really would explain it, i highly doubt its the valves if you cleaned them and set them, and for what it sounds like not really the clutching if it runs right up to 8500rpm till you get to 100mph, that sure sounds like track rub to me.

The part i am talking about looking at is right under the gastank area of the sled, so you kinda have to get your head up in the back between the falp and bumper area to see, thats where they balloon up, right before the track goes over the drivers, most people never know because its not easy to see.

what does the tach do when you pin it, can you describe what the rpm does?

take a close pic of the side view of your track while its up on a jackstand.
 
My 99 does the exact same thing. I just didn't know that wasn't right. I just looked under mine and did see rub marks on the tunnel protectors and the track. Don't know if that's my issue or not. The track has been on it for a while but maybe it is still rubbing. Could this happen if the track is too tight? I have about a quarter inch of sag from my hyfax. Interested to see what this ends up being.
 
I looked all the way up inside of tunnel and it looks fine. When I pin it rpms shoot to just under 8500 then climbs to 8500 all the way too 100 mph then drops off to 8000 and has no more pull. Buddy with the 99 has stock secondary and helix looks like he has 89-10 weights and I can't see a color code on primary spring.
 
Definitely sounds like we have the same problem. Here is my setup: 8dn-20 primary weights with 4.5 both holes, y-w-y primary spring, 51/45 helix, green secondary spring at 70. 1 1/4" track with 132 studs, stock gearing and 8 tooth drivers. Brand new Yamaha belt, the newer style. Freshly cleaned and adjusted valves and new rings. Mine jumps to 8500 for a second then drops to in between 8300 and 8400 (where it is supposed to be for a 99) then when I get to 80 or so it starts dropping and goes to 8000. Unfortunately for me I cannot test it because we lost all of our snow here and we are going north next weekend so I hope whatever this ends up being will be the same fix for me.
 
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hay jstyer have you checked the clutchs for aliment?.that little bit can hurt top end.just my 2 cents.& how many studs do you have.something is robbing your topend power some where:o|?.:2strokes:
 
144 studs, no I haven't checked clutch alignment I don't have that tool. Sure it doesn't have anything to do with the secondary set up?
 
if you think your problem is in the clutching put your stock parts back in and see if it holds 8500rpm.
 
Ok, I just went out and pulled my valves and the 2 outer ones were almost stuck and the center was stuck. I had cleaned and set them to spec before winter, I got 500 miles on why are they so gummed up? Another thing I switched to Amsoil interceptor this year would that have anything to do with it?
 
There is a thread from a couple days ago about power valves gumming up. I ran amsoil dominator last year and it took a lot of effort to get my valves out. I ran 600 miles last year. I just went and got 2 gallons of yamalube.
 
Sounds like the amsoil does a good job of dirtying up powervalves. I checked my pv's after almost 900 miles of running yamalube and they still looked clean.
 
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