SL650 Fuel Delivery Issue?

[timepar7]

Hello,

I have a Polaris SL650. It is my first Jetski and is quite a bit of fun. My fun however ended a few weeks ago when the fuel line from the selector switch to fuel filter kinked and failed to get the motor primed again. I dont have a great deal of experience with small engines but as a kid I did my fair share of carb teardowns and finding lost springs in mystery liquid (carb soak) along the way.

I cut out and replaced all the fuel lines one by one from the fuel tank to the fuel pump outlet. (I didnt replace from the fuel pump to carb since they looked ok.
My top speed after replacing these was only around 30 MPH though. It seems that I can get to about 1/2 to 2/3 throttle and the jetski tops out for motor RPM and speed. My girlfriend has a SLT750 from the same person we purchased these from (older gentleman getting rid of 2 trailers and 4 jetskis this era). The SLT750 runs laps around the 650, but that might be from the extra 100cc. The 650 just seems to have more power left in it that isnt being utilized?

-I tested compression last night and I get around 70 PSI on each cylinder cold. Seems a bit low, but all are fairly even to another.
-Impeller and stator look to be in good shape as well. Ride plate is sealed well and no weeds or plastic are in the impeller area.
-I just replaced the spark plugs from BR7ES to BPR7ES. Rear cylinder was clean, middle and front were a tan color. I can adjust the first cylinder a little bit probably.
-Fuel pump is the blue single in, single out style and seems to be in good condition. I took it apart and there was no junk caught in it.
-I am using premix gas 32:1 no ethanol with Amsoil


What is the next step? Do I dig into the carb and mess with my high idle or do I go into the carb and start that project?

Thanks!

[Beernutz]

Did you retain the fuel line restrictor in the return line? That is needed to maintain fuel pressure.

FUEL:

Please refer to this link when looking for a picture of the autocock that is to be removed, or the restrictor located inside the return hose. Post #2 http://www.greenhulk.net/show...urndown-Basics

Please refer to this link when looking for pictures of the fuel system or carburetor manual.

http://www.greenhulk.net/showthread.php?15433-Fuel-Fuji-Carbureted

Due to their age alone, the fuel system should be updated or upgraded.

1992-1995 most models had fuel hoses that were inside the fuel tank that are notorious for rotting and falling off.


Fuel hoses may look fine on the exterior, however, they tend to fail from the inside-out. Clogging and restricting the fuel passages that can lead to major engine damage.

Your fuel hoses are 1/4" I.D. and 20' usually takes care of a 2 seater ski. (about $20) They should be of good quality, not the cheap clear hose you buy off Ebay. I personally prefer the braided reinforced fuel hoses you get from an auto parts store, (DO NOT buy the $5 ft hose for fuel injection) but many others like to use a quality clear fuel line from a reputable supplier. Keep in mind that there is a hose that goes from the engine pulse fitting to the fuel pump, and that should be replaced as well. Keep that hose as short as possible (no longer than 12") and making sure there are no kinks or bends in any of the lines.

In the 1994 and 1995 650 and 750 PWC, there is a small brass restrictor found inside the return hose going from the carbs back to the fuel tank. Also in that pic above (link posted earlier) is the Autocock, and it is to be removed per a Polaris bulletin, and the hose capped air tight. They were prone to failure and causing piston damage.

The brass restrictor is located approxiamtely 1" past the last carburetor inside the fuel hose. This MUST be re-installed in order to create fuel pressure. If you do not have 1, one can easily be made from a carburetor jet and a brass hose connector. Post #4 http://www.greenhulk.net/show...highlight=made

If your ski came with external fuel filters, just replace them. They are cheap enough and it's good insurance. (about $8 ea)

The petcock or fuel shut off valve should be inspected/rebuilt/or replaced all together. There are rubber parts and O rings inside that get brittle, swell, or physically move which can cause fuel starvation and lead to damage. A Sea Doo selector valve ($15) will fit fine, it's just the arrow direction will be off.

Newer models have a fuel filter built into the water seperator. They also have an orange ring that floats as an indicator if water is present inside the fuel. Older models have just the water seperator with no ring or fuel filter, so you must actually look for water in the bottom of the bowl. Inspect both of the them periodically. (water is heavier than gas, therefore it sinks to the bottom of the bowl)

Your 650 and 750's used a round (35L per hr) single outlet fuel pump. The internals get worn and cause you to lose fuel pressure leading to piston failure. I recommend you install a new triple outlet fuel pump. What that does is restores lost fuel pressure due to age, and also supplies each carburetor individually VS. the single that feeds the first carb, then the second, and finally the third. The new round triple outlet (35L per hr) can be bought for around $35. See above link for new hose routing.

The 780 engines came standard with a pentagon shaped High Output (65L per hr) triple outlet fuel pump. Anyone with a 780 should just rebuild VS. replace their fuel pump. A rebuild kit costs around $20 while a new pump runs around $65. Please note that you should only use GENUINE MINKUI parts when rebuilding. It's quality stuff that's lasted for many years. Now is not the time to try and save a few dollars on cheaper aftermarket parts.

Pro 785's use 44mm carbs that have the fuel pumps integrated in the end carburetors. The surplus fuel from both carbs then feed the CEN and the excess returns back to the fuel tank. The Super BN 38/44mm rebuild kits (same as the 650/750/780 use) will have the parts for the fuel pumps included with them.


Carburetors at this age should be rebuilt. Them looking clean inside, or pouring carb cleaner in the fuel tank isn't going to do squat. You need to open up the carbs, replace the old parts, clean the fuel passages, and replace the internal filters on the back side. Yes, there are filters INSIDE the carbs as well. You will need 3 genuine Mikuni carb rebuild kits for a Super BN 38/44mm carburetor, (around $45 ea) which is what you have. 1 kit handles 1 carb, and you have 3 carbs. Not included in the kit is the needle and seat, of which you will again need to buy 3 of. They are a size 2.0 "push in" type for a Mikuni Super BN. (around $15 ea)

Finally there are 2 fuel tank vents that located just below the steering console or hood. 1 allows air INTO the fuel tank and is "T" into the vent hose. Almost looks as if there should be a hose attached to it, but there isn't. And the other is mounted directly into the rubber grommet inside the console that vents out to the atmosphere. It should release any excess pressure built up inside the fuel tank. (opens at 1.5 PSI) If this valve fails to open, you can have excess pressure inside the fuel tank that will force fuel into the engine if you fail to turn the petcock (fuel selector valve) to the off position.

OIL:

You should only use a good quality TCW III 2 stroke oil or a fully synthetic oil specific for your application in your PWC. Not all oils can be used in oil injection units, so pay attention to what you buy.

If you use the stock oil injection system, make sure to replace the 1/8" I.D. oil hose and clamps. Many costly engine failures occur because of a $.06 hose clamp broke or the hose cracked/kinked/fell off.

You should replace the oil filter just because of age as well. (about $8 ea)

If you choose to remove the oil pump and go with premix, you should remove the oil pump and the internal gears. You can buy a block off plate, or make one just as easy from a piece of aluminum laying around the house. Just be sure it's sealed air tight after you install it.

You will want to run the premix at a ratio of 40:1 under normal conditions and 32:1 using regular (non synthetic) oil when breaking in new piston rings. Synthetic is too slick to properly seat the rings.

Then you have 3 choices of what to do to prevent the MFD from warning of low oil.
1. Leave the oil tank full and clamp off the oil hose.
2. Tie the oil sender float in the "up" position and store it out of the way.
3. Install a 40 ohm resistor between the oil sender wires. This works great if you do it inside the elec. box.

I would highly recommend changing your plugs again to the next one cooler, BPR8ES, as unless you can guarantee there are absolutely no air leaks in the crankcase or fuel system, it is far too easy to have a lean burn down.

Also, your compression is quite low, however that could be the tester you're using. You are correct in both cylinders being even being the important part.

[timepar7]

This was where I left it last night. Red plugged end is the fuel delivery rail and from the fuel pump the fuel out, goes underneath the carb where it is teed and then runs up into the header in two spots between the two carbs. The fuel return line from this photo and from what I remember just goes back to the tank. I will look tonight to see where it goes once I get to the fuel tank cap. I want to say that it had a restrictor on the end of it, but I could be wrong. This might be part of my problem if there is no restrictor - aka all my fuel pressure is gone if that is the case.
The machine runs good, it just runs out of power.
The front cylinder head has a bit of oil/water mixture on the screw portion in the photo you can see it on the bottom bolt. I am unsure what would cause this other than the cylinder head gasket failing? I ordered a new one to replace but I would like to just sort out one problem at a time....

[xlint89]

I didn't take the time to read through the post, sorry.

But just looking at the pic provided, you still have the autocock installed.

That should have been deleted many years ago per Polaris bulletins.

That small blue part that attaches to the fuel pump, needs to be removed.

I'd also suggest getting a new fuel pump and hoses due to age alone.

While you're at it, you should rebuild the carbs.

[timepar7]

I didn't take the time to read through the post, sorry.

But just looking at the pic provided, you still have the autocock installed.

That should have been deleted many years ago per Polaris bulletins.

That small blue part that attaches to the fuel pump, needs to be removed.

I'd also suggest getting a new fuel pump and hoses due to age alone.

While you're at it, you should rebuild the carbs.

Well its been quite a week. I went through the carbs and reset popoff to around 25 psi across the 3 carbs. I had two of the three high speed jets about half closed off with junk - so a good carb rebuild was needed. I also found a post on here to check out the exhaust orifice screen and sure enough it was full of leaves and junk. My thermostat was the next thing inline that I wanted to check out and when I dropped the two allen screws, it gave me a prize.... the inner copper post that the thermostat spring/plug assembly came out with the thermostat body. Thermostat was filled with rocks along with a bad seal ring. The white plug on the other water flow pathway only had what looked to be a teflon washer and spring (the remainder I assume is long gone). I ordered a new bypass plug and will install when it arrives. -Would the second white plug in the thermostat being missing cause my speed issues?

I got onto the lake and tuned in my carb for the low speed setting and set the high to 1.25 turns out factory setting. I think I might need to go a little more out than this. Will check out the plugs. It took most of the day to mess with the low speed setting and get that proper. At the end of the day with a empty tank and just myself on the jetski I still can only reach about 30-32 MPH on a clear stretch of water. The jetski runs out of punch when turning and getting off the gate, engine rips but doesnt lock up. I think the next project to go into is the impeller.... intake grate is the stock 3 bar style. I am unsure if an alternative would make much difference. Feeler gauge showed an equal 0.020" gap around the impeller. Wear ring looked ok, will just touch up some of the dings from the last owner. Impeller has some chips out of the face. I bought a impeller puller tool and will try to clean up the edges and ensure it is as equal as I can get it.
-Is there a certain model/pitch of impeller you would suggest? Polaris manual just calls out a progressive impeller.

[ZMANN]

when you went thru the carbs did you rebuild with OEM mikuni parts ? Specially the diaphragms?

I would get that pump replaced with the octagon style as suggested

your picture of the 650 brought back a lot of memories of what mine looked like when I bought it

[timepar7]

when you went thru the carbs did you rebuild with OEM mikuni parts ? Specially the diaphragms?

I would get that pump replaced with the octagon style as suggested

your picture of the 650 brought back a lot of memories of what mine looked like when I bought it

Yes I forgot that I purchased the 3x output pump and removed the autocock in addition. Installed per the directions and ensured the fuel return had the restriction orifice installed. I saw a moist (I assumed loose) bolt on the water block and within a quarter turn by hand the bolt snapped. Along the way of trying to get the other bolts off from being sized on, I snapped two more... So my Saturday night consisted of drilling and re-tapping those bolts. I am a bit worried of replacing the head gasket and having the same luck....
Do you by chance know if the RTD or temp sensor in the cooling block exit (near the thermostat) has any effect on the motor rpm? I dont think the 94 model SL650 had a function to limit rpm. I cant seem to see where this goes back to the main control board other than just for a sanity check to enable the motor

[ZMANN]

I don't think those issues would limit RPM

to reiterate, did you use OEM mikuni kits ?

did the ski perform better until you had the crimped hose issues, and you replaced a few fuel lines ?

if it was mine I would try to see if the 70 psi test was flawed before I did more work

[xlint89]

Please explain with better description what's going on.

I do not know what getting off the gate means.

Engine rips, but doesn't lock up. What does that mean?

Pretty sure .020" is the service limit for the impeller to wear ring clearance. Not that it will severely hold you back on speed, but it's at the limit.

What is the number stamped on the impeller?

With this being a 650, I assume you don't have a tachometer. You can buy a cheap tach and install it for testing purposes. Just make sure it works with 2 strokes. Engine RPM can help in determining if it's engine or drive line related.

[timepar7]

The impeller is PN 5131056.

Compression I tested again with MAG = 80 PSI, Mid = 75 PSI, PTO = 70 PSI. I tested the 95 750 SLT that we own (for a direct comparison) and MAG on that one for my harbor freight compression tester justification was 80 PSI. I am am using premix, 32:1 with 91 no ethanol gas.
-Yes the jetski preforms awful now even after going through all of the fuel system items - AFTER the event where my kinked fuel line left me stranded with no start.

Something is wrong and I just don't know what. I rode the 750 around and it is a whole different beast. Even at idle they dont feel similar; both have basically the same engine with just a little bigger piston in the 750 to 650. The 750 has the normal level of "pop" or liveliness that I have experienced from all 2 stroke snowmobiles ect that I have ridden. The 650 rides and runs more like a 4 stroke with its feel of powerband.
-I took off the silencer and it was caked in black oiley soot which seems to be normal. I am unsure if I need to start digging into the engine timing or shaft coupler.

-As far as "doesnt hook up", the jetski seems to do poorly with high torque operations. Going from a dead stop to half speed and it hardly planned out with a heavier rider onboard. Instead of 30 MPH top speed with a heavier rider it only would go 15-20 MPH. It almost seems like my engine coupler is slipping somehow even though I dont believe this style of shaft connector can "slip" like some of the centrifugal pumps I have worked on in the past. The style on the SL650 has a threaded portion connecting to a splined junction piece. (Woods couplers with square keyways).

I am just at a loss. I don't think I have experienced disappointment in a long time as to when I rode the same year of SLT750... Any help or direction is greatly appreciated. I think next thing I will research into is the timing and spark.

Please explain with better description what's going on.

I do not know what getting off the gate means.

Engine rips, but doesn't lock up. What does that mean?

Pretty sure .020" is the service limit for the impeller to wear ring clearance. Not that it will severely hold you back on speed, but it's at the limit.

What is the number stamped on the impeller?

With this being a 650, I assume you don't have a tachometer. You can buy a cheap tach and install it for testing purposes. Just make sure it works with 2 strokes. Engine RPM can help in determining if it's engine or drive line related.

[xlint89]

056 would be the correct impeller. Did you get that off the impeller, or just look it up? Not being a dick, just verifying that IS the impeller you have installed.

Compression looks low. Did you test with the throttle held open? PTO needs to be good since it drives the fuel pump. (120 psi is generally normal)

32:1 premix is quite a bit oil. That's normally what people run when breaking in new rings. 40:1 is more common. What brand oil are you using?

What spark plugs are you using? NGK BPR8ES is what you should be using with .028" gap

Did you replace the fuel hoses? If so, did you install the fuel restrictor in the return hose?

Are your carbs in sync? If you were making adjustments did you make sure they all open the same amount at the same time?

What are the carb adjustment screws set at?

No, it's not normal for black oily goo to be coming out the exhaust. That's usually unburnt fuel collecting. You have something going on causing a rich condition.

1. When the ski is idling and the flame arrestor is off, it's normal for a little bit of fuel to spit out the top of the carbs. If you have 1 spitting more than the others, you prob have a broken reed valve.

2. Your carbs are out of sync, mis-adjusted, or not jetted properly.

3. You are not running on all 3 cyls.

4. Water intrusion into the combustion chamber.

5. Ignition timing can be off

After running the ski, are all 3 cyls warm to the touch? If 1 is cold, that cyl should be looked at for a non-running condition.

Look in the tech section for how to read piston wash. Get yourself a small flexible flashlight that can fit down the spark plug hole and compare what you have to what it's supposed to look like.

Engine couplers can strip out. You should have the old SS splined type. The splines do get worn and can slip. The newer rubber version can slip also.

Then you can have stripped splines in the impeller as well.

CAUTION: DO NOT put your finger in the engine coupler. If you have any shards in there, you will find out the hard way.

It's not engine related, but if your ride plate and/or intake grate is not sealed properly to the hull, you can get air in the jet propulsion that causes performance issues. Some signs of this can be exhaust soot found in the pump tunnel.

There's something you can try. Sometimes the spark plug wires get poor connections and trimming the wires back about 1/4" can expose clean wire for a better connection. Unscrew the plug boots off. (yes they thread on) cut the wire 1/4" shorter, re-screw the boots back on. See if that helps

[timepar7]

Here is my list of response. I was trying to just list them within your reply but I haven't figured out how this forum works fully yet.

-I got the part number from online since I didn't take a photo of the impeller PN when I had it out. I checked however and it matched the factory OEM last week when I was cleaning some of the edge burrs.

-Yes compression was done with the throttle full open. I have only gotten 80 PSI max out of the tester even on two other jetski so I am leaning on the tester cable not sealing very well to over 80 PSI. I will check around work to see if I can borrow another model.

-I have seen mixed reposes for what mix to use. I believe the manual calls out 40:1 and I think that might be a good switch to make even though it will probably require some carb re-tuning. I am using Amsoil Marine HP Synthetic with 91 No Ethanol.

-I am using NGK BPR7ES Plugs since that is what the manual stated. I have seen on here however since then that the BPR8ES are suggested to switch to. I used the 8ES from the other jetski when I had initial engine problems with fuel lines and these plugs made the machine run even worse. I think that was just from the heat range and carb being not tuned to another. I will order some 8ES plugs.

-Yes I have a restrictor and yes I have replaced all fuel lines with new, removing the autocock and using the PTO lower side pulse into the 3 output fuel pump.

-Carbs are in sync. I checked this when I re-installed my carb. All carbs equally open and close to another per throttle position. I tested all of the popits to 25 PSI to the manual suggested. These might be a bit light. My idle is such that I cant hold onto the dock alone without moving forward.

-Carb screws are set at 1.5 turns out on the low and 1.5 turns on the high. I set to the suggested initially but found I had to open up a little bit to help my idle and low end response. Suggested were 1.25 turns on the low and 1 turn on the high out from fully tight.

-I cut back the spark plug wires last night. They were a bit crusty so this might help.

I guess the next thing to look at is the ignition timing and determining if all cylinders are running. I checked camshaft position and seemed to be equal when center cylinder was highest the two outside cylinders were equal and and their lowest.

I have a bit of oil on the MAG cylinder bolt nuts on top. I have a new head gasket but I dont want to tear into this until the other items are checked off. So far any bolt I have tried to remove has just sheared off.

056 would be the correct impeller. Did you get that off the impeller, or just look it up? Not being a dick, just verifying that IS the impeller you have installed.

Compression looks low. Did you test with the throttle held open? PTO needs to be good since it drives the fuel pump. (120 psi is generally normal)

32:1 premix is quite a bit oil. That's normally what people run when breaking in new rings. 40:1 is more common. What brand oil are you using?

What spark plugs are you using? NGK BPR8ES is what you should be using with .028" gap

Did you replace the fuel hoses? If so, did you install the fuel restrictor in the return hose?

Are your carbs in sync? If you were making adjustments did you make sure they all open the same amount at the same time?

What are the carb adjustment screws set at?

No, it's not normal for black oily goo to be coming out the exhaust. That's usually unburnt fuel collecting. You have something going on causing a rich condition.

1. When the ski is idling and the flame arrestor is off, it's normal for a little bit of fuel to spit out the top of the carbs. If you have 1 spitting more than the others, you prob have a broken reed valve.

2. Your carbs are out of sync, mis-adjusted, or not jetted properly.

3. You are not running on all 3 cyls.

4. Water intrusion into the combustion chamber.

5. Ignition timing can be off

After running the ski, are all 3 cyls warm to the touch? If 1 is cold, that cyl should be looked at for a non-running condition.

Look in the tech section for how to read piston wash. Get yourself a small flexible flashlight that can fit down the spark plug hole and compare what you have to what it's supposed to look like.

Engine couplers can strip out. You should have the old SS splined type. The splines do get worn and can slip. The newer rubber version can slip also.

Then you can have stripped splines in the impeller as well.

CAUTION: DO NOT put your finger in the engine coupler. If you have any shards in there, you will find out the hard way.

It's not engine related, but if your ride plate and/or intake grate is not sealed properly to the hull, you can get air in the jet propulsion that causes performance issues. Some signs of this can be exhaust soot found in the pump tunnel.

There's something you can try. Sometimes the spark plug wires get poor connections and trimming the wires back about 1/4" can expose clean wire for a better connection. Unscrew the plug boots off. (yes they thread on) cut the wire 1/4" shorter, re-screw the boots back on. See if that helps

[Beernutz]

Carb pop-off pressure is to be between 10-18psi.

Your high speed settings are all set too rich. Each carb is to be set differently, based on which cylinder it is.

[xlint89]

Here is my list of response. I was trying to just list them within your reply but I haven't figured out how this forum works fully yet.

-I got the part number from online since I didn't take a photo of the impeller PN when I had it out. I checked however and it matched the factory OEM last week when I was cleaning some of the edge burrs.

-Yes compression was done with the throttle full open. I have only gotten 80 PSI max out of the tester even on two other jetski so I am leaning on the tester cable not sealing very well to over 80 PSI. I will check around work to see if I can borrow another model. Most auto repair stores will lend a compression tester for free.

-I have seen mixed reposes for what mix to use. I believe the manual calls out 40:1 and I think that might be a good switch to make even though it will probably require some carb re-tuning. I am using Amsoil Marine HP Synthetic with 91 No Ethanol. If you're using Amsoil you can prob use 50:1

-I am using NGK BPR7ES Plugs since that is what the manual stated. I have seen on here however since then that the BPR8ES are suggested to switch to. I used the 8ES from the other jetski when I had initial engine problems with fuel lines and these plugs made the machine run even worse. I think that was just from the heat range and carb being not tuned to another. I will order some 8ES plugs. The #7 plugs are hotter and is prob why they ran better if you're running rich. The reason we suggest using the 8's is because they are cooler and will help in preventing the holed piston when ran lean on fuel.

-Yes I have a restrictor and yes I have replaced all fuel lines with new, removing the autocock and using the PTO lower side pulse into the 3 output fuel pump.

-Carbs are in sync. I checked this when I re-installed my carb. All carbs equally open and close to another per throttle position. I tested all of the popits to 25 PSI to the manual suggested. These might be a bit light. My idle is such that I cant hold onto the dock alone without moving forward. As noted above, pop off pressure should be between 10-18

-Carb screws are set at 1.5 turns out on the low and 1.5 turns on the high. I set to the suggested initially but found I had to open up a little bit to help my idle and low end response. Suggested were 1.25 turns on the low and 1 turn on the high out from fully tight. Again, see the chart provided by Beernutz

-I cut back the spark plug wires last night. They were a bit crusty so this might help.

I guess the next thing to look at is the ignition timing and determining if all cylinders are running. I checked camshaft position and seemed to be equal when center cylinder was highest the two outside cylinders were equal and and their lowest. I was going to suggest a crank phase test.

I have a bit of oil on the MAG cylinder bolt nuts on top. I have a new head gasket but I dont want to tear into this until the other items are checked off. So far any bolt I have tried to remove has just sheared off.

No need to tear the head off. Use the flashlight down the spark plug hole I suggested.


Check the cyls and feel if they are all warm.

Check the fuel spitting out the top of the carbs for possible broken reeds.

Look at your piston wash. It will tell you cyl or cyls are having problems.