White smoke

[MikeinNJ13]

I have a 1994 Polaris 750SLT. I just rebuilt the carbs and it started right up. Now there is alot of white smoke coming out of the exhaust. is there a way to tell where its a blown head gasket another quick way of detmining the problem. All cylinders have spark. no one seems hotter the 2 and 3.

 

[Rob454]

Re: White smoke

Are you starting it on a flush kit or just starting it dry? Blown headgaskets on jet skis isnt liek a blown headgasklet on a car. Is the white stuff smoke or steam? If its smoke then thats just oil and its normal. 2 strokes smoke a lot and it seems like its excessive especially if youre doing it on a trailer in a garage or street
Rob

 

[MikeinNJ13]

Re: White smoke

Rob,

I am starting and using the flush kit. I hope and don't think I let the hose run when the jet was not running. It's white smoke not steam. Cylinder 1 seems hotter then 2 and 3. Hotter to the touch. The other two were cool.
What do you think.
1) bad gas or water in gas
2) to much oil in the crank case.
3) bad piston and rings.
4) water in the crank
5) blown head gaskets.
6) I didn't set the carbs right. even though I did exactly what the manual said.
I'm thinking of putting in the water and running but don't want to blow the engine.

 

[Rob454]

Re: White smoke

Rob,

I am starting and using the flush kit. I hope and don't think I let the hose run when the jet was not running. It's white smoke not steam. Cylinder 1 seems hotter then 2 and 3. Hotter to the touch. The other two were cool.
What do you think.
1) bad gas or water in gas
2) to much oil in the crank case.
3) bad piston and rings.
4) water in the crank
5) blown head gaskets.
6) I didn't set the carbs right. even though I did exactly what the manual said.
I'm thinking of putting in the water and running but don't want to blow the engine.

Sounds liek #1 is running leaner since its getting hotter.
the gas woudlnt make it smoke white. it woudl be darker black or grayish.
there is no oil in the crankcase cause there isnt a crankcase on a two stroke. Well there is but not the way youre thinking. there is no oil pan on a 2 stroke jet ski motor.
bad piston or rings woudlnt make it smoke liek that
Water in the crank woudl make it run like s**t
Polaris has some finicky carbs. You didnt remove the stainless steel plate on the base of the three carbs you put it back on right?
What are your settings for the high and low screws.
Youll do more damage to the motor running it on a flush kit in the long run than in the water. You pump needs to cool off also.
Check your high and low speed adjustments. Check your plugs and see what color youre getting on them YOure looking for a dark brown color on the rim of the plug. that tells you youre running right. if its all white like its brand new after running a couple of minutes then youre lean. if its black then youre rich.
if youre anywhere in Orange county California i can meet you in long beach this weekend and see what its doing
Rob

 

[Aquaman]

Re: White smoke

When you say #1 do you mean the one closest to the front? If so it's called the MAG cylinder because it is closest to the magneto. It will run the hottest of the three, especially on the hose.

Finicky carbs? They're Mikuni 38 mm's, nothing finicky about them. Early Polaris ski's had a lean issue related to both the fuel pump and selector valves .

If you're still running the oil injection they're known for leaking alot of oil into the system when left sitting which causes excessive smoking on start up...excessive smoking can appear to be white smoke.

Here's what I'd do if I were you.

Replace all fuel lines, don't forget restrictor in return line.
Replace fuel selector switch.
Upgrade to a triple outlet fuel pump.
Convert to premix.
Pull heads and check piston wash.

 

[Rob454]

Re: White smoke

He has a 94. those carbs were finicky. believe me ive worked on a lot of polaris skis. the carbs themselves are fine its the fuel delivery that was bad in that design. Either way liek i said before he will do more damage to the ski in the long run by trying to TUNE it on a hose than in the actual water. I usually start by running really rich and work my way back to a good fuel air mix
Hope it all works well.

One other thing you can do is T tap between your fuel feed lines and then use a Y from the single fuel feed from the fuel pump to feed the Ts fuel to your carbs. Plug up the old single feed where the fuel pump used to feed the #3 carb. Not sure how much triple outlet fuel pumps run these days.
Aquaman is right abotu probably replacing the fuel lines. The selector switch its a option but since your there might as well replace it. Buy a new one dont bother with a used one. I dont think you need to pull the heads off but if you do youll need new headgaskets. make sure they get installed the correct way. Dont reuse the old ones cause they are a crush one time use only IMO. ive used the old ones but that was usually at the river or lake when we had no spares. Polaris are good skis but parts are harder to come by due to the fact they are no longer making skis.
its too bad their latest designs were incredible both in the visual aspect and the mechanical aspect IMO

Carb T carb T carb
Y
l
fuel pump

That was a cheap trick I did before the triple feed pumps were available
Rob

 

[Aquaman]

Re: White smoke

Rob,looks like we basically agree on most points. I must admit I'm a little confused when you say the carbs are finicky but then you say the carbs themselves are fine it's the fuel delivery that was a bad design. I agree though, the early (pre '96) fuel delivery system left a lot to be desired.

I also agree, he'll NEVER get it dialed in on a hose...just ain't gonna happen. One thing to keep in mind is how the low and high speed circuits overlap. I'm a lousy typist so I'll cut & paste a tuning procedure from another site:

Start with the high speed screws set at 1 turn out, and tune with the tachometer for peak Rpm, then stop there and count the number of turns on the high speed screws. Write this down on a piece of paper.. Then turn the high speed screws in all the way and open them to 1/4 turn open. (Now you will be testing starts only, so no more big high rpm trips around the course). You are only turning in the high speeds to allow you to easily tune the low speeds.

Now check the low speed screws and set them at 1 turn and do a practice start; To test the low speed setting pretend that you just jumped the start and you have to start with no holder. Hold the ski by yourself and hold as many Rpm as you can (don't blow it out first for testing) and then nail the throttle hard.... NO FARTHER THAN 50 KILOMETERS, as you are only testing the start response

If it blubbers like a schoolgirl trying to guzzle a quart of beer, then it's too rich on the low speed screws..
If it falls flat on the line (like someone punched you in the stomach).. It's too lean on the low speed screws.

When you like the acceleration off the line, stop there and count the number of turns on the low speed screws. Write this down on a piece of paper.. Then re-set your high speed screw where they show the best peak Rpm earlier and try both a start and a peak Rpm run...
It will probably "blubber" a little off the line... DO NOT turn in the low speed screws... Instead, go back out on the course and fine tune for peak Rpm again.. The blubbering off the line is caused by having too much fuel in the high speed circuit... Write down your new high speed setting on the piece of paper along with the best low speed setting that you found earlier, this will be your base-line carburetor settings.
If the high or low speed screws are open more than 11/4 turns, then you need to swap to the next bigger jet.
If the high or low speed screws are closed all the way, then you need to change to the next size smaller jet.


*** If no matter what you try, it still won’t leave the line without falling on its face "lean bog"... Then try the next size lower pop-off spring in the carbs... Don't be afraid to try #95 or even #80 gram springs..

Tapping the lines is also a good idea but Mikuni triple outlet pumps are less than $30.00 and worth their weight in gold if you've ever melted or holed a piston because you ran it lean.

I guess we can also agree to disagree on headgaskets. I reuse them 5-6 times, just clean them in a parts washer and apply copper gasket spray in between use. I'll do this to check piston wash when tuning...after tuning I may use new if I have them but I've never had a problem (knock on wood) reusing gaskets.

Like Rob said, parts are harder to come by since Polaris opted out of the PWC market but an Ebay search just turned up 471 parts auctions. While most of the Ebay auctions are used parts companies like WSM, Mikuni, Boyesen, Solas, and R&D still sell oem and performance parts. Polaris parts are also interchangeable from year to year and ski to ski, not all parts and not all years but still better than most manufactures.

Bottom line....Tune it and enjoy it.

 

[Aquaman]

Re: White smoke

Almost forgot to add....I don't troll forums pointing members to other sites so I won't post it here but if you shoot me a PM I'll link you to arguably the best site for Polaris info on the web.

 

[Rob454]

Re: White smoke

I guess we can also agree to disagree on headgaskets. I reuse them 5-6 times, just clean them in a parts washer and apply copper gasket spray in between use.
Bottom line....Tune it and enjoy it.

Ive used them on the rare occasion when i had to. I also used that copper spray a gasket stuff. But I tend not to like doing that but yeah they can be reused I jsut prefer to install new ones. Usually if you pull the head there is enough damage to warrant pulling it.

its too bad because polaris really started to come on strong with their motors and designs for skis. I remember one of my buddies bought a 1050 pro and that thing was fing FAST right off the showroom floor
ROb

 

[MikeinNJ13]

Re: White smoke

Rob454 and Aquaman,

I put the ski in the water. I think the white smoke went mostly away after running fast. It seems to come back alot more when idling slow. there is a 1/4 5mile hr no wake zone before I can open it up.

I seems to have no top end speed. 30-40Mph. My other polaris 1995 SLT is atleast 10-20MPH faster. (both displays don't work and have not popped open the electrical box yet to check the fuse).

I think it might be the high speed screws. It like there no power band. I will print out your long response (thanks alot)

I set the screws like the manuel said front 1 1/4 out, middle 3/8 out and aft 7/8 out. Low speed jets all 1/2 out. (Also there may have been a broken end in the middle carbs low speed jet. I can see if the is. I think I sprayed carb cleaner in it when I was rebuilding and it went through).

So should I turn them all out one turn or start just with the front one.

I have not done a compression but will. maybe its just bad rings ??

 

[Rob454]

Re: White smoke

Completely stock ski? stock air box or aftermarket flame arresters? I woudl start with the lows at 3/4 out and the highs at 1 1/4. tune your low end then go from there. Start with new plugs. youre better off running rich and changing plugs than running lean and burning up a piston. ive done before is this . Gofind a little cove and tie the ski to a tree and then i go in about 4 feet of water. then tune it there.
I had access to a water tank so I usually used that for the main tuning then fine tuned it on the water running. the jets basically go like this
the low speed jets control your fuel from idle to about 30-40% throttle then the high speed open up from 40% to 100% providing the main fuel but the low speed jets also priovide fuel. the transition is whats sometimes hard to get tuned. I usually start working on the low end to get it to jump out of the hole then tune the top end. Depending on how the ski acts you may need to turn the lows and highs in or out. Thats why its important to pull the plugs and make sure youre not lean.
it would be a good idea to check your compression before you do anythign else. ground the plug wires and zip tie the throttle all the way open. open the chokes nd then do your compression. on a 3 cylinder youre looking for a optimal 125-130 PSI. If they all read the same youre ok. anything lower than 110 youre due tfor a rering IMO. Soem gauges can be off by 20-30 LB so make sure you either use a good guage or if theire all the same compression then most likely the guage reads wrong.
Rob

 

[Aquaman]

Re: White smoke

Rob454 and Aquaman,
I seems to have no top end speed. 30-40Mph. My other polaris 1995 SLT is atleast 10-20MPH faster. (both displays don't work and have not popped open the electrical box yet to check the fuse).
I have not done a compression but will. maybe its just bad rings ??

Check the fuse....knowing RPM at WOT would be a big help. Also check compression. If you're low on compression you're wasting you time and patience on the carbs.

How is it running at top end? Does it run smooth or seem like it's cutting out?


I reuse head gaskets when tuning...lost my bore scope so I pull the heads to look at piston wash...I try to use new after I'm through tuning.

Ever hear of guys popping the rivets and only using a single layer of the headgasket? Brings up compression in the neighborhood of 10-12 psi. I haven't tried it yet but it sounds interesting.

 

[Rob454]

Re: White smoke

Ever hear of guys popping the rivets and only using a single layer of the headgasket? Brings up compression in the neighborhood of 10-12 psi. I haven't tried it yet but it sounds interesting.

I havent heard that one but it wold be like milling the head. thinner headgasket more compression. only thing is how much more compression 10-12 PSI no big deal. Worth a shot I guess but I would watch it real close while riding the first time out
Rob