SL 1050 Performance

[awolverton42]

I have the stock carbs from the 97 SL1050, the 40mm 2 jet carbs without accelerator pump. I would really like to find a rack with accelerator pump to fix the lack of low end acceleration.

I have not reassembled my top end yet, just shipped my crankshaft out to Northern Crankshaft yesterday to get rebuilt.

wmazz, are you referring to the carbs with the accelerator pump or without? And would you happen to know which years had the carbs you're talking about?

[wmazz]

The SLTX carbs have 3 jets, and these carbs are the hi-performance Keihin
carbs. The accelerator pump is not necessary with the mod.


Bill M.

While you have your engine apart, calculate your geometric compression ratio (CR),
or find a spec for it (CR), deck height, and stock squish clearance.


I think you would be very happy with the carb mod and a tighter squish.

What impeller do you have?

[K447]

If you have the right Keihin carbs, you can add some real arm jerking acceleration
with a simple carb mod. ...

Bill M.

...

Welcome to Greenhulk.

Your replies to posts from others are excellent.

If you would be interested in collecting your thoughts, experience and advice into a set of posts and threads, I expect many others would find that informative and quite useful. We can help make the info you provide findable and searchable.

We have a separate web site that links and organizes some of the useful info found on GreenHulk.net
It started out as a set of notes mostly pertaining to Polaris PWC, but is not exclusionary.

Some things on each PWC brand are unique to that brand or model but these machines also have a lot in common across the makes. Including common problems and the ways to diagnose and fix them.

http://polarispwcknowledge.shorturl....t-things-to-do

[awolverton42]

The SLTX carbs have 3 jets, and these carbs are the hi-performance Keihin
carbs. The accelerator pump is not necessary with the mod.


Bill M.

While you have your engine apart, calculate your geometric compression ratio (CR),
or find a spec for it (CR), deck height, and stock squish clearance.


I think you would be very happy with the carb mod and a tighter squish.

What impeller do you have?

Would the 40mm vs 38mm carbs from an SLTX make a difference? Or should I stay with the 40mm set up? I know the SLTX's had 38's with accelerator pump. I believe later SLX models had 40's with accelerator pump? Please correct me if I'm wrong. Would be nice to know for sure.

A different carb rack is not a must for me at the moment, but maybe after I get it tuned in next summer with my current carbs I'll look into it.

I had my pump apart when installing my 6 vane stator, and it's the pump is out right now because I pulled the engine. When I had the impeller out separately it said Polaris on it with the part number that I don't recall, but I'm sure its the factory impeller. I bought the machine with low hours. So I don't know what pitch it is or anything, but its stock.

How do I calculate geometric compression ratio?

[casey67]

Would the 40mm vs 38mm carbs from an SLTX make a difference? Or should I stay with the 40mm set up? I know the SLTX's had 38's with accelerator pump. I believe later SLX models had 40's with accelerator pump? Please correct me if I'm wrong. Would be nice to know for sure.

The 96-97 SLTX had 38mm w/accel
98-99 SLTX had 40mm w/accel same as SLX/SLXH. All 1200 carb models had 40mm w/accel (other then 1999 X45/SLTX-B) jets were different nearly every year/model.



Most of my experimenting was with 40mm w/accel.
They have a dead spot at steady throttle on the mid jets (IIRC 3500 rpm) If held steady they seem to run out of fuel.
I had increased mid jets as big as possible, like 50 on a 1050. Any higher would cause a rich missfire/gurgle when accelerating, at and around that 3500 rpm. I had the low and high jets at a great mixture, I didnt experiment with smaller low/high jets and larger mid.

I'm interested in this mid circuit modification.
Did you have to change low/high jets because of the mod ?
Was accell pump TOO much fuel because of the mod ?

[wmazz]

How do I calculate geometric compression ratio?

The service manual lists the compression ratio as 12:1.

Have you ever tested your 1050's compression before? Or have you tested the
compression of a ski, and you didn't know what the spec was?

There is an easy way to find out what the spec is @ sea level, or to determine
what the spec for your location (compression changes depending on where you
live).

SL1050 compression ratio as 12:1.
Air pressure @ sea level 14.7psi or ~15psi.

12 * 15 = 180psi with a Snap-On compression gauge.

I am mentioning the Snap-On compression gauge because it is the only brand I
know that can be trusted. Many other brands are hit or miss, and lots of compression
testers (even name brands) read 30psi low.

If you want a good estimate based on where you live, use a weather station from a
local race track (NOT an Airport). Try Air Density Online (list of tracks in U.S.)
I picked Clovis, New Mexico as an example. The uncorrected barometric pressure in
in-hg was a very low 25.92in-hg. Then go to Google and use an in-hg to psi converter.
->12.73psi. Then multiply the local air pressure with your compression ratio
-> 12.73*12 (CR) = 152psi.

Another example: Near Dallas Texas, is Paris Drag Strip. The uncorrected barometric pressure
at that drag strip is 29.64 in-hg (inches of mercury). Convert to psi = 14.55psi. Times geometric
compression ratio of 12:1 = 174.6psi cranking compression.

Would the 40mm vs 38mm carbs from an SLTX make a difference?
Or should I stay with the 40mm set up?

The 38's with the mid range jet (if you do the mod) will make a bigger difference
Than dual stage reeds, increased compression, +ignition timing, an accelerator pump
combined

I know the SLTX's had 38's with accelerator pump. I believe later SLX models had 40's with accelerator pump? Please correct me if I'm wrong.
Would be nice to know for sure.

I do not know, but accelerator pumps are not intended for performance gains, as
I think Casey67 found out.

Most of my experimenting was with 40mm w/accel.
They have a dead spot at steady throttle on the mid jets (IIRC 3500 rpm) If held steady they seem to run out of fuel.

They are there because the carburetor has a lean low speed circuit for the smog laws.
They test emission standards at an idle, and the accelerator pump is just there to prevent a bog.

I'm interested in this mid circuit modification.
Did you have to change low/high jets because of the mod ?
Was accell pump TOO much fuel because of the mod ?

I eliminated the accelerator pump. The stock jetting may work, you might need to increase the
low jets 2 sizes.

A different carb rack is not a must for me at the moment, but maybe after I get it tuned in next summer with my current carbs I'll look into it.

I purchased a 1050 rack on an Ebay auction for dirt cheap. But to properly rebuild
with Japanese Keihin carb kits will cost ~$200.00.

If you are planning on rebuilding the carbs, and not buy cheapo Chinese kits I recommend
getting a used rack.

Especially if you are having issues like this thread:

I am a new jet ski owner. My 99 Polaris 1050 SLX runs great when given throttle but stalls out at idle.
It is very hard to start and run at low speed.

He is describing a vacuum leak, and I have some recommendations for rebuilding Keihin
carbs.

Like I said, if you need to rebuild your carbs, find a rack with the mid-range jet. Why
spend the money to rebuild your set, and another set, down the road.



Bill M.

[savageman69]

40mm with accel pump work real well when jetted correctly....im not sure you can make a stock bore 1050 pull much harder than i have it setup....altho mine is not setup for all out speed its for rough water...it pulled away from my 2000 slx 1200...from start to finish, i love this ski and sold the slx to keep it instead because i feel its the best setup 2 seater...the 97 hull was amazing...i have no bog, hesitation or flat spots.

[awolverton42]

The service manual lists the compression ratio as 12:1.

Have you ever tested your 1050's compression before? Or have you tested the
compression of a ski, and you didn't know what the spec was?

I have tested my compression, it was 125-130 across the board when I bought it last may, and I checked it every 5 or 6 rides and it stayed there all summer, until I blew a lower rod bearing lol. I have a Bosch compression tester that i tested next to a family member's Snap On tester on 3 different motors and they were within 3 psi of each other every time.

savageman69, your SL1050 setup is what I'm looking for lol. Do you remember the jetting for your current setup? I wouldn't copy it exactly obviously I would tune it on my own, I'm just curious. I would like to find a 40mm w/accel rack somewhere.

[awolverton42]

Also I've been reading up on jet works flow control valves. Would it be a good idea to add one for acceleration? I can always wait and test without first.