Results 1 to 6 of 6
  1. #1

    Questions on a frankenstein Engine

    I am fixing up a '96 SLX 780 that had a hole in the PTO piston. I procured a 750 bored to 766 that had a bad crank and took the heads, exhaust manifold and piston from it and installed on the 780 engine. First, do I use the factory settings for the carbs? Second, will I have a problem with the muffler as the part numbers are different?

    Thanks.


  2. #2
    thester71's Avatar
    Join Date
    Jun 2009
    Location
    central ma.
    Posts
    1,698
    I don't know how you got the 750 parts to fit, they are totally different.

  3. #3
    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
    The 750 cyl will fit on the crankcase, but has a TOTALLY different exh manifold bolt pattern. Also has different port timing than a 780, you'll never get a good running engine with that set up. Just buy another 780 cyl, or have your old one bored oversize.

  4. #4
    Canadian Beaver Inspector jkindt's Avatar
    Join Date
    Sep 2009
    Location
    Lethbridge, AB, Canada
    Posts
    1,721
    Quote Originally Posted by xlint89 View Post
    The 750 cyl will fit on the crankcase, but has a TOTALLY different exh manifold bolt pattern. Also has different port timing than a 780, you'll never get a good running engine with that set up. Just buy another 780 cyl, or have your old one bored oversize.
    The OP stated that he got the cylinders, heads, pistons, AND the exhaust manifold from the 750. Essentially he has changed his engine to a 750, why wouldn't he be able to have a good running engine this way. It will just be a 750 instead of a 780.

  5. #5
    I used the magneto and CDI of of this engine for my 750 and the timing seemed to work fine. Everything physically fits in the ski. The only real thing left of the slx 780 engine is the muffler and carbs. Do I need to make the carbs a little leaner because of the loss of 4cc per cylinder? Will the slx muffler make the ski run different that I will have to compensate for?

    Thanks.

  6. #6
    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
    OHHHHH, so he installed the 750 top end on the 780 bottom end.... I got you.

    It can work, but you'll want to install the 750 jets in the carbs, and most likely want to use the 750 CDI.

    Waterbox is the same for both skis.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. question on painting engine
    By tenjuna in forum Polaris Open Discussion
    Replies: 5
    Last Post: 11-14-2009, 12:14 AM
  2. question on ported 1300...idle surges after having water in engine...i
    By MJE in forum Yamaha PWC Performance (2-stroke)
    Replies: 1
    Last Post: 07-23-2009, 09:06 AM
  3. Question on submerged engine
    By gkecorp in forum Yamaha PWC Performance (2-stroke)
    Replies: 6
    Last Post: 05-08-2009, 11:42 PM
  4. Quick question on RXP engine rebuild
    By 8 is enough in forum 4-Tec Performance
    Replies: 1
    Last Post: 01-08-2009, 09:58 PM
  5. question on difference in engine internals
    By 8 is enough in forum 4-Tec Performance
    Replies: 0
    Last Post: 12-07-2008, 08:32 PM

Posting Permissions

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