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Cant get WOT rpms up!

Discussion in 'SR Viper Talk' started by Sno-Xr, Feb 22, 2021 at 6:49 PM.


  1. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    From what Im seeing, wot rpms should be up around 8900-9000 on the Vipers? I picked up a 16 RTX that had Bikeman perf clutch weights already installed, and supposedly stock otherwise. When I grab a handful of the flipper, it will spike to about 8250(after Ive unloaded several tip and center magnets), but will steadily drop to the low 7's as speed increases.
    Decided to pull both the primary and secondary(and belt) from my 15 STX DX with the Big Venom clutching and install them on the RTX, as it hits 8900+ right from the git go and stays there on the 15. But I'll be damned if it doesnt run approximately the same as it did with the Bikeman weights in the stock clutches. It will barely get into the 8's, and drops back to the low 7's.
    Any thoughts? Motor seems to be running fine otherwise, just wont keep the R's up during hard pulls.

    Thanks
     
  2.  

  3. mbarryracing

    mbarryracing TY 4 Stroke God

    Messages:
    1,849
    Location:
    Springville NY
    Country:
    USA
    Snowmobile:
    2006 Yamaha Attak Turbo
    2015 SR Viper RTX-DX
    1996 Vmax 600XT
    It's absolutely making less power for some reason. It's not the clutching.
    Possibly the fuel pump is not supplying enough fuel for adequate AFR at WOT?
     
  4. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    Hmmm, thats what I was afraid of. Now to figure out exactly what the issue is
     
  5. 2015ViperMTX

    2015ViperMTX Pro

    Messages:
    137
    Location:
    Iowa
    Country:
    USA
    Snowmobile:
    2015 viper mtx
    How many miles on the sled? Does it have fresh fuel? I’d change plugs and fuel filter.
     
  6. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    Ive run about 700 miles on it this year, had 3000 when I bought it. Plugs will definitely be on the list, but seems to start and idle fine. May end up swapping fuel pumps since the 15 is waiting for a new chain case, jackshaft and related parts! Lol
     
  7. super1c

    super1c Moderator Moderator VIP Member

    Messages:
    682
    Location:
    Freeland - Otsego lake, MI
    Country:
    USA
    Snowmobile:
    16 viper LTX-SE/17 viper LTX-LE
    When I couldn’t get proper RPMs after exhausting clutching, plugs ect it ended up needing a valve job. Got all my power back and RPMs after.
     
  8. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    What was involved? Pulling top end and replacing the valves? Or lashing/shimming?
    Also, was compression low?
     
  9. super1c

    super1c Moderator Moderator VIP Member

    Messages:
    682
    Location:
    Freeland - Otsego lake, MI
    Country:
    USA
    Snowmobile:
    16 viper LTX-SE/17 viper LTX-LE
    I was fortunate enough to be under warranty. The valves were too tight. Shimmed best I know and he followed cannondales post here as he had not done one yet. Sorry not more help on that but there are some great posts here about it. Was like a new sled after.
     
  10. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    Thanks for the info, I will look into whats all involved.
     
  11. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    It seems most are having issues with idling and start-ups when the valves are too tight. Is that what your issue was? Or did you lack top end rpms?
     
  12. super1c

    super1c Moderator Moderator VIP Member

    Messages:
    682
    Location:
    Freeland - Otsego lake, MI
    Country:
    USA
    Snowmobile:
    16 viper LTX-SE/17 viper LTX-LE
    Starting issues and top rpm. No idle problems. And starting issues were hot start issues.
     
    Sno-Xr likes this.
  13. cannondale27

    cannondale27 Moderator Staff Member Moderator Vendor Lifetime VIP Member VIP Member

    Messages:
    20,084
    Location:
    Manitowoc,WI
    Valve cover removal is easy so yes check the valve clearance. But pull the plugs first. Look at them. If fuel they will be white and would think it would missfire.
     
  14. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    Sounds good. Thanks Steve
     
  15. Thunder Products

    Thunder Products Making your sled the best! Advertiser Vendor

    Messages:
    406
    Location:
    Cedarville, MI
    Country:
    USA
    Snowmobile:
    Yamaha, Polaris, AC and Ski-Doo
    LOCATION:
    Cedarville, MI
    WEBSITE:
    www.thunderproductsclutching.com
    Hey bud, hope you get your sled figured out.
     
  16. Sno-Xr

    Sno-Xr VIP Member VIP Member

    Messages:
    1,018
    Location:
    Clio (Flint), MI
    Country:
    USA
    Snowmobile:
    Nytro
    Thanks Terry, you and me both!! Been a crazy sled year for me. Still havent figured out my elec gremlin haunting my Nytro. Picked this sled up so Id have 2 good running sleds and find this issue, and then jackshaft bearing went out in the Viper I bought from Krissy, and it took out the chain case. "I love Snowmobiling, I love Snowmobiling I love Snowmobiling I love Snowmobiling"!!!! Hahaha
     
    Last edited: Feb 25, 2021 at 7:18 PM
    cannondale27 likes this.

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