Page 1 of 2 1 2 LastLast
Results 1 to 10 of 14
  1. #1
    TopCop931's Avatar
    Join Date
    Apr 2010
    Location
    Nutley, NJ
    Posts
    520

    New Compression Numbers

    Well guys, after running my SLT 780 for the first time this weekend I decided to spring for a brand new compression gauge and do another test. Since it had been years since my ski had been out there I did not go WOT. I kept it around 5000 rpm. All went well.

    Anyway, my first test when I was getting it up and running was 120 PTO, 118 Center, and 124 MAG.

    Today with my brand new gauge I got 124 PTO, 122 Center, and 132 MAG. Everything seems well within range and going well. Any thoughts on my new numbers? I am thinking I got better readings because of the nice new gauge.

    Either way, I am ahead of the game with a ski that has not been running for over 4 years.


  2. #2

    Join Date
    Sep 2009
    Location
    St. Louis, MO
    Posts
    220
    When you got these numbers was the ski hot or cold? Have the throttle wide open?

    Numbers aren't all that bad, but rule of thumb is you want them all within 10% of each other. Could be that might just need new rings.

    How well did it run though once you got it out on the water?

  3. #3
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
    Join Date
    Jul 2007
    Location
    Cedar Rapids,Iowa
    Posts
    6,381
    +1
    23
    Actually in the 120's is good for a Fuji tripple that If the ski is stock. Alot can change #'s with even the same gauge. If the ski is hot,how wet the cylinder is from fuel,how long ago it was ran. The 10% factor is the best mark. My '94 SLT runs in the 115 range and runs strong and hard. I'd say you have a solid ski, make sure you do any upgrades and maintance. Personally I'd rebuild the carbs and clean the fuel system completely.

  4. #4
    TopCop931's Avatar
    Join Date
    Apr 2010
    Location
    Nutley, NJ
    Posts
    520
    Quote Originally Posted by stl_sl650 View Post
    When you got these numbers was the ski hot or cold? Have the throttle wide open?

    Numbers aren't all that bad, but rule of thumb is you want them all within 10% of each other. Could be that might just need new rings.

    How well did it run though once you got it out on the water?
    The ski was cold WOT all plugs out.

    The thing ran very well for a ski that hasn't seen any action in years. No bogging or sputtering. Good idle in the water at about 1250. The entire rear end was redone and it never hit the water until this weekend. They are all within 10% with what I just came up with although the MAG was a few points higher than the first time I checked the pressure really they only came up about 4 points on each cylinder.

  5. #5
    TopCop931's Avatar
    Join Date
    Apr 2010
    Location
    Nutley, NJ
    Posts
    520
    Quote Originally Posted by Keddano View Post
    Actually in the 120's is good for a Fuji tripple that If the ski is stock. Alot can change #'s with even the same gauge. If the ski is hot,how wet the cylinder is from fuel,how long ago it was ran. The 10% factor is the best mark. My '94 SLT runs in the 115 range and runs strong and hard. I'd say you have a solid ski, make sure you do any upgrades and maintance. Personally I'd rebuild the carbs and clean the fuel system completely.
    The ski is all stock. The gas lines were in good shape and had already been upgraded. Me and my brother did the carbs and surprisingly they were in good shape too. I changed all the filters, cleaned the gas tank (got lucky there too, the thing was just about bone dry) checked out the fuel pump and it checked okay. I also replaced the fuel water separator because I didn't know whether you could just change the element in there or not. I went for $80.00 for a new one. The only thing in the fuel system I had a problem with was the on-off switch. At first it wouldn't start if it was turned off for a day or so. So I disconnected it and blew through it with compressed air and now it is fine.

    I did notice that the PTO and Center cylinders seem to be a little wetter with fuel than the MAG though. Right now I am writing it off to the MAG getting a little hotter than the other two when running on the hose but I know I am bulls*itting myself. My brother doesn't see it as a problem but he fails to realize that this thing is nothing like the Audi's he works on all day long.

    I think this woman that gave me the thing had it maintained at a marina every time she took it out. I don't know why she couldn't find anyone that would check to see if the CDI was bad because that is what the problem was.

    Oh yeah. I didn't fog it yesterday because I was in fresh water and to be truthful, couldn't get a hold of any fogging oil. I have read here that you should fog after every ride.

  6. #6
    Tony's Avatar
    Join Date
    May 2007
    Location
    North Carolina
    Posts
    1,760
    +1
    38
    Your numbers sound good. Different gauges will usually give different readings. What's important is the numbers be within 10% of each other and measured with the same gauge.

  7. #7
    TopCop931's Avatar
    Join Date
    Apr 2010
    Location
    Nutley, NJ
    Posts
    520
    Quote Originally Posted by Tony View Post
    Your numbers sound good. Different gauges will usually give different readings. What's important is the numbers be within 10% of each other and measured with the same gauge.
    Let's see if I can make it through the summer without any major problems.

    I am going on vacation the second week of July and will be running it every day weather permitting. All salt water too.

  8. #8
    TopCop931's Avatar
    Join Date
    Apr 2010
    Location
    Nutley, NJ
    Posts
    520
    Quote Originally Posted by TopCop931 View Post
    Well guys, after running my SLT 780 for the first time this weekend I decided to spring for a brand new compression gauge and do another test. Since it had been years since my ski had been out there I did not go WOT. I kept it around 5000 rpm. All went well.

    Anyway, my first test when I was getting it up and running was 120 PTO, 118 Center, and 124 MAG.

    Today with my brand new gauge I got 124 PTO, 122 Center, and 132 MAG. Everything seems well within range and going well. Any thoughts on my new numbers? I am thinking I got better readings because of the nice new gauge.

    Either way, I am ahead of the game with a ski that has not been running for over 4 years.
    After having such a good run on Friday I decided to check my piston wash today using the LED light as Xlint suggested. Wash looks good. (I am still going to use that bore scope when my brother brings it home to me tomorrow.) I figured since I had the plugs out why not do another compression test also. These are the numbers I got with the exact same gauge that I used last time. 135-PTO, 130-Center, 135-MAG. The gauge is brand new and only the second time I used it. The ski was cold at WOT. Now, I know these numbers are very good but I am wondering why they are much better then the first time I checked it. (I will point out that I flooded it the day before the first test trying to start it without the lanyard in so maybe it was still a little wet in there.)

    I had another great day today. This thing is awesome. I wish there were more fresh water spots in Jersey to go. If anyone else from Jersey knows anywhere else besides Lake Hopatcong please let me know. I will be down the Jersey Shore the second week of July so the old girl is going to be in the salt everyday. I already stocked up on the fogging oil and protectant from Amsoil.

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Location
    Cleveland OH
    Posts
    17,327
    +1
    29
    Compression sounds good.

    Piston wash looked good? Something like this?



    If you're going to be in the salt, make sure to flush the engine. Salt isn't all that bad if you take care of the engine afterwards. All the Cali guys ride the ocean.

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    36,570
    +1
    1,272
    Quote Originally Posted by TopCop931 View Post
    ...This thing is awesome.

    ...the old girl is going to be in the salt everyday. I already stocked up on the fogging oil and protectant from Amsoil.
    Will you be storing it in the water?

    Make sure the sacrificial anode puck is in place.

    It needs to have a solid metal to metal contact to the jet pump body, or it will not do its job of protecting against salt water corrosion.

    I don't recall exactly where it would be located on your jet pump, but I expect it to be bolted right to the pump base up inside the pump tunnel.

    Take your grease gun, and give the through-hull bearing a squeeze of high quality [COLOR=rgb(0, 0, 0)]Lithium base waterproof marine bearing grease[/COLOR] every day after riding

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. New GPR Numbers
    By night022 in forum Yamaha PWC Performance (2-stroke)
    Replies: 10
    Last Post: 08-25-2009, 11:32 PM
  2. 96 xp water in the hull and compression numbers
    By snoopy'sbitch in forum 2-Stroke Performance
    Replies: 10
    Last Post: 08-16-2009, 08:43 PM
  3. Compression Numbers
    By David_HX_RXP in forum 4-Tec Performance
    Replies: 11
    Last Post: 05-30-2009, 08:28 PM
  4. chk out these compression numbers for the kawi
    By dav_dman in forum Honda Open Discussion
    Replies: 0
    Last Post: 07-02-2007, 08:47 AM
  5. New Speed Numbers!
    By 2fast4u in forum Yamaha PWC Performance (2-stroke)
    Replies: 11
    Last Post: 12-12-2006, 01:02 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •