Higher Compression and Advanced Timing 94 750 SSXI Reliabilty - Page 2
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 2 of 2 FirstFirst 12
Results 11 to 20 of 20
  1. #11
    PWCToday Newbie
    Join Date
    Jun 2013
    Location
    USA
    Age
    34
    Posts
    12

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Quote Originally Posted by jetman624 View Post
    If Newmiller is cutting your head to run 92 octane gas, and you understand how advancing your ignition-- especially THAT much on the top end-- creates ADDITIONAL heat in the combustion chamber, the answer is an obvious "no, don't run it".

    If Newmiller is cutting your head to run 92 octane, and you want to run a HIGHER octane than that, than maybe you could get away with the fixed advance. But running compression that necessitates 92 octane and then adding a fixed advance on top of that is probably not wise.
    Thanks for all you guys help!

  2. #12
    PWCToday.com Is My Home Away From Home mcn6's Avatar
    Join Date
    Apr 2006
    Location
    Oregon
    Age
    64
    Posts
    3,285

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    All I can tell you is... 19 deg advance at 7200+ rpm on pump gas is not safe. I will also tell you that I fit new pistons to 750's and 800's with advance plates all the time and even with the top ends that have not actually seized, the cylinders and pistons have had the crap beat out of them from the high rpm deto. If you don't plan to run at high rpm for more than a split second the plates are great as they do give a decent improvement in throttle response, good luck training your trigger finger to stay out of the throttle though )



    Home of Newmiller Machine

  3. #13
    PWCToday Newbie
    Join Date
    Jun 2013
    Location
    USA
    Age
    34
    Posts
    12

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Quote Originally Posted by mcn6 View Post
    All I can tell you is... 19 deg advance at 7200+ rpm on pump gas is not safe. I will also tell you that I fit new pistons to 750's and 800's with advance plates all the time and even with the top ends that have not actually seized, the cylinders and pistons have had the crap beat out of them from the high rpm deto. If you don't plan to run at high rpm for more than a split second the plates are great as they do give a decent improvement in throttle response, good luck training your trigger finger to stay out of the throttle though )
    Right, I'm aware of the risk of detonation from using the wrong octane and that's what I came here looking for to see if there is a risk of detonation with the combination of advanced timing and the higher comp head. I do a lot of wide open lake riding and I'm not looking to get into needing race fuel so I'll be leaving the plate off the ski and be happy with the rest of my add-ons. Again, I appreciate all of you helping out.
    Last edited by Nickefer; 03-23-2015 at 03:55 PM.

  4. #14
    PWCToday.com Is My Home Away From Home mcn6's Avatar
    Join Date
    Apr 2006
    Location
    Oregon
    Age
    64
    Posts
    3,285

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Your best option if you want the throttle response provided by the timing advance is to install an Advent ignition or a programmable total loss. With either one you can set static timing at 30 deg and still ramp it back down to 13 deg at max rpm. Second and less preferable option would be to simply run higher octane gasoline (97+/- octane). High octane gas, especially without the compression bump to go with it, has the same effect as retarding ignition timing in that maximum combustion chamber pressures are reached at a later degree of crankshaft rotation.



    Home of Newmiller Machine

  5. #15
    PWCToday.com Is My Home Away From Home bandit88's Avatar
    Join Date
    May 2014
    Location
    Green Bay WI
    Age
    34
    Posts
    2,236

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Quote Originally Posted by mcn6 View Post
    All I can tell you is... 19 deg advance at 7200+ rpm on pump gas is not safe.)
    Chris, I am a bit confused by this. I know you recommend advancing the 650 motor 3 degrees when you recut the head for 93 octane. This would bring the advance to 20 degrees at 6000rpm. Does it retard after that making it safe, or is there something special about the 650s that makes you recommend this? Also I thought I heard on the 650 ignition that the timing was static throughout the RPM range...? Am I missing something here?

    Thanks

  6. #16
    PWCToday.com Is My Home Away From Home jetman624's Avatar
    Join Date
    Nov 2003
    Location
    South OC, CA
    Age
    38
    Posts
    2,683

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Quote Originally Posted by bandit88 View Post
    Chris, I am a bit confused by this. I know you recommend advancing the 650 motor 3 degrees when you recut the head for 93 octane. This would bring the advance to 20 degrees at 6000rpm. Does it retard after that making it safe, or is there something special about the 650s that makes you recommend this? Also I thought I heard on the 650 ignition that the timing was static throughout the RPM range...? Am I missing something here?

    Thanks
    In case he doesn't see this-- I would consider the RPM range he said it was not safe for pump gas, and consider the RPM range your 650 is running at. Probably not 7200+...
    '02 SXi Pro: Factory Limited pipe, ported SXR cyl, SSP stearing system, WORX ride plate, skat trak intake grate, blowsion tubbie II, 3DR SS hull extensions, 3DR trued hull, 3DR pump shoe mod, bored pump nozzle

    '92 X2: Mostly stock, except for the 750

    '91 X2: #718

  7. #17
    PWCToday.com Is My Home Away From Home bandit88's Avatar
    Join Date
    May 2014
    Location
    Green Bay WI
    Age
    34
    Posts
    2,236

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Quote Originally Posted by jetman624 View Post
    In case he doesn't see this-- I would consider the RPM range he said it was not safe for pump gas, and consider the RPM range your 650 is running at. Probably not 7200+...
    Not 7200+ but 7000 is a good max. Some of the 650 pipes dont make max power until 6750. Cant see that couple hundered rpm making that big of a dif, maybe im wrong. Also I would think a 650 would rev higher than a 750 seeing that it has quite a bit less rotating mass and a shorter stroke.
    Last edited by bandit88; 03-24-2015 at 05:14 PM.

  8. #18
    PWCToday.com Is My Home Away From Home mcn6's Avatar
    Join Date
    Apr 2006
    Location
    Oregon
    Age
    64
    Posts
    3,285

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Keep in mind that these numbers are my own that I noted while running timeing curves trying to diagnose other issues, they are not official Kawi numbers...

    Stock 650 timing curve:
    12* at idle
    18* at 4500 rpm
    12* at 6800rpm

    Basically the curve ramps up to 18*. At 4500 rpm it starts ramping back down to 12 degrees at 6800 rpm which equals about 3* per thousand rpm. This will put advance at apx. 13 to 14* at 6000 rpm. At this point simply add the 3* to everything.

    Clear as mud?



    Home of Newmiller Machine

  9. #19
    PWCToday.com Is My Home Away From Home Cleatusjo's Avatar
    Join Date
    Aug 2014
    Location
    Chesapeake Bay, Anne Arundel co.
    Age
    64
    Posts
    2,404

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    Great thread

  10. #20
    Resident Guru runrider's Avatar
    Join Date
    Jul 2010
    Location
    PA
    Age
    38
    Posts
    836

    Re: Higher Compression and Advanced Timing 94 750 SSXI Reliabilty

    I thought 650s use a fixed timing across the whole rpm range?

Page 2 of 2 FirstFirst 12

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0