polaris sl 650 question

Need help, while towing in my blown 750 kaw, my sl 650 melted a hole in piston #3 (rearmost). I've heard people mention about adding a second fuel pump on these models (riden WOT most of the time) anyone know about this mod, or how to do it. also istead of checking plugs for the correct mixture, am I supposed to be looking at the piston tops instead? (bare alum-OK, black top=lean?) thanks

I don't have the info on the fuel pump mods, but some other ideas... You're right on the piston wash. On the Polaris, mine seem happiest with a slight wash (bare aluminum) about the size of a dime at the 10 o'clock and 8 o'clock positions if you're looking standing at the rear of the engine. A larger wash should be noticeable at the 3 o'clock position as well. In other words, the intake transfer ports cause the wash as the bared aluminum is next to the ports mentioned. You're right about the fuel pump mod, but check that crank for twist as well. Put one cylinder on top dead center and measure the other 2. They should be even. Put another on top, and measure the remaining 2... This will give the best results in a shade tree environment. Zoltan will have the info on the fuel pump mods and I'm sure he will post here as well.

On the Polari' I have redone...I replaced the older round body pump with the newer dual output Mikuni pump. Plug the OEM inlet nipple on the rear carb and route the fuel supply from the pump, down and up between the carbs and install 2 'T' unions (one between both carbs) for the fuel supply. You will most likely have to rejet your carbs since they were originally designed for fuel supply only from one side/carb.

And if you want to be a little more precise, have one fuel return on the front carb and one on the rear going to another 'T' before returning to the tank.

The fuel pump mod is described in detail at
http://www.sbtontheweb.com/techpolhole.htm

I have never done this nor did I ever experience any problems related to not getting enough fuel from the stock pump on my SL750. On my 96 SLX with 44's bolted on I am using a single high output fuel pump. Even the stock fuel pump for the stock 38's had 3 lines out of the pump and not one being distributed to all the carbs like 95 and older Polaris'. Maybe Polaris went with an upgraded fuel pump for a reason?

Sounds similar to what my 96 SLX came with stock.

'Carolina Watercraft Works, Inc.' wrote:

What year sl650, if its a sl650std, which I believe came out in 95, then you may have a problem. They originally came out with an aluminum impeller instead of stainless, and a spacer ring on the tail cone, this setup over loaded the motors and would frequently melt holes in #3, this is the cyl that runs the hottest, partially due to the fact that the rear cyl of a 3 cyl runs with advanced timing due to crank flex. If you were towing, you were just putting that much more load on the crank. If it is in fact the sl650std, there was a factory update. LOL

SIZE DOES MATTER!!

Bruce Wolford Wet Wolf Tech

it is a 93 sl650 and it already had the cooling mods performed.

In that case, Polaris had a service bulletin (PWC-95-03) to remove the auto cock fuel valve. Did you have this done along with the cooling mods? Check into this because it might be the cause of the hole? Also, I could be wrong but I remember only the 92 model needing the cooling upgrade and not the 93.

anyone have info on this fuel cock mod? being a 93 Iknow the cooling mod was done, I figured after it was sold, but probably from the factory.

mod was done, I figured after it was sold, but probably from the factory.

If you have the vacuum petcock, it would be a little round thing hanging next to the fuel pumpwith three hoses going to it, one for gas in, one for gas out, and one for vacuum to open the valve. Just pull it out of the system, (Bypass it) and be sure to plug the vacuum fitting on the case. You might also want to check the fuel petcock, there is a rubber seal between the hub and the casing, and they have been known to shift around and partially plug the fuel passage. Make sure that the fuel tank vent going into the tank isnt plugged or kinked. The 93 650 had single feed to the carbs, its better to dual feed them from the center like Laszlo says. If you havent done any mods to the thing, then the stock fuel pump should do the job. BTW while you are messing around with the fuel system, make sure that the cap that holds all of the fuel lines to the tank is aluminum, not plastic, the plastic ones break, and there was a recall. LOL

SIZE DOES MATTER!!

Bruce Wolford Wet Wolf Tech

I have the anti-siphon valve, what is the purpose of diconnecting it. Will the thing flood if the fuel isn't shut off? thanks again