Results 1 to 4 of 4
  1. #1

    Join Date
    Jun 2015
    Posts
    2

    Opinion on engine rebuild

    Good day gents,

    I have been lurking here and there for small bits on information. This time I need opinions from the pro and decided to sign up. Long story short, I have a Polaris 750 slt with the Fuji engine, (thanks to this site this is how I know), when I purchased it a few years back the engine was new but it had a bad stator. fixed it up and ran very good for the last 4-5 years. I don't use it that much, maybe 1hr per week end when I am at the cottage. Anyway, at the end of last summer, after my brother in law rode it in a way that would make anyone what to punch him, after the engine stalled on him. I think it seize from the heat. well it didn't work like it used to. I put in new plugs to get some reading on what was going on inside. From there I found out I was burning a hole thru the mag and mid cylinder.

    Now that I am at the point of a rebuild, I had the following questions.

    - are those cylinders salvageable since they don't have a thru hole in them? minor lost of compression?
    - If I replace them should I put new rings on the PTO cylinder too? it had 120 psi after the engine seized
    - Do you thing aluminum particle entered the crank case and would need to be cleaned?

    I found a leaking mag seal by doing a pressure test. I haven't had a chance to see if I can just pull them out or if I need to split the base.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	IMG_20150623_180806.jpg 
Views:	33 
Size:	69.1 KB 
ID:	363218   Click image for larger version. 

Name:	IMG_20150623_180831.jpg 
Views:	35 
Size:	67.9 KB 
ID:	363219  


  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    46,547
    +1
    2,711
    Welcome

    What model year is your SLT750? Last two digits of the HIN number plate on the rear deck.

    The leaking crankcase seal needs to be fixed. In addition I suggest you remove and rebuild the carburetors. Use genuine OEM Mikuni rebuild kits, available from Watcon.

    The partial craters in the pistons is typical of lean burn, not enough fuel for the amount of air being burned. You may be able to get away with using the pistons as is. The better approach is to replace with new pistons and rings, of course.

    At the same time as the carburetors are rebuilt, freshen the rest of the fuel system. New fuel hoses throughout, new fuel filter. And a new fuel selector valve (shut-off valve). Replace the o-rings inside the fuel/water separator. All this will ensure the fuel delivery to the carburetors is consistent and does not have air leaks.

    See my signature links for even more recommended maintenance on these older Polaris watercraft.

  3. #3

    Join Date
    Jun 2015
    Posts
    2
    Hi K447

    thanks for the quick reply

    for sure I will be changing the seal. It is a 1995.

    Being proactive, a have already rebuilt the whole fuel system after I purchased it. New fuel line, bypass fuel selector and installed inline valve, no autocock, inline primer to help start at the beginning of the season, new carb kit about 1 year ago, fuel restrictor is in place and I do have a sled fuel pump with 2 outlets. I will do maintenance on the fuel separator as you say since I never thought of it.

    I am in Canada do you know if parts are readily available in here, our currency is junk compare to US right now and usualy shipping is more expensive than the part itself.

  4. #4
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    46,547
    +1
    2,711
    Quote Originally Posted by beerfart View Post
    ... It is a 1995.

    Being proactive, a have already rebuilt the whole fuel system after I purchased it. New fuel line, bypass fuel selector and installed inline valve, no autocock, inline primer to help start at the beginning of the season, new carb kit about 1 year ago, fuel restrictor is in place and I do have a sled fuel pump with 2 outlets. I will do maintenance on the fuel separator as you say since I never thought of it.

    I am in Canada do you know if parts are readily available in here, our currency is junk compare to US right now and usualy shipping is more expensive than the part itself.
    Where in Canada?

    John at Watcon is familiar with international shipping so delivery to Canada is generally not a problem.

    The inline primer, if installed in the fuel feed hose, has the potential to reduce fuel flow or introduce air bubbles. Remember, the fuel system from tank to fuel pump is under suction, not pressure, when the engine is running.

    If you must retain the primer, a better method may be to install it in the fuel return hose. Loop the return hose low in the hull and plumb the primer tee at the low point. There will be fuel there when the engine is off, and there is no potential for interference with the fuel supply to the fuel pump.

    Many people successfully use these engines without any primer. A primer means additional hoses and hose connections with fuel inside, plus the primer itself. Each extra thing with fuel inside is a potential point of failure or fuel leak. Fuel leaks, even small ones, are dangerous inside the enclosed hull of a PWC.

    The fuel shut-off valve is a safety item. If the sun heats the fuel tank and the tank vent does not release pressure the result can be liquid fuel forced through the carburetors and accumulate inside the engine. This can and does happen, I have seen reports of engines filled with gasoline right up to the choke plates. Even small amounts of forced gasoline can create an explosive fume cloud within the hull while sitting in the sun.

    The recommended fuel pump upgrade is the three outlet Mikuni fuel pump, which was stock on the Polaris Fuji 780 engine model. It has sufficient flow capacity to ensure proper fuel delivery.

    Was the carb rebuild kit aftermarket or genuine Mikuni? We have seen issues with the aftermarket kits.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. How far does a 3.5oz tube of 1211 go on an engine rebuild?
    By lemon4879 in forum 4-Tec Performance
    Replies: 2
    Last Post: 06-24-2012, 04:16 PM
  2. Top 5 "don't forgets" on engine rebuild/install
    By rev114 in forum 4-Tec Performance
    Replies: 34
    Last Post: 03-22-2012, 07:02 PM
  3. engine rebuild on 750 in need of torque spes
    By cody_davidson in forum Polaris Open Discussion
    Replies: 3
    Last Post: 08-14-2011, 10:22 PM
  4. Need opinions on rebuild 65u
    By bbanks in forum Yamaha Old School Skis
    Replies: 10
    Last Post: 05-11-2010, 03:09 PM
  5. 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

Posting Permissions

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