impeller has 1/8" rotational slop, please advise.

[wmazz]

(it wont idle or start easy) i assumed it needed to be rebuilt and rejetted.

I am concerned that there maybe something else causing your problems.

If you don't find any obvious problems inside the carb like a stiff, or leaking diaphragm,
and obvious vacuum leaks (wet gaskets). Maybe there is another problem with the engine
ability to produce manifold vacuum (top end and/or main seal problems).


Bill M.

It would be great if it was something as simple as the spark plug wires

 

[kevbo]

I always power tune WOT 20 rpm rich of peak on glass, have not stuck a piston since. My main jets usually end up larger than what is posted on the internet. Sometimes by a lot!

 

[Project101]

I am concerned that there maybe something else causing your problems.

If you don't find any obvious problems inside the carb like a stiff, or leaking diaphragm,
and obvious vacuum leaks (wet gaskets). Maybe there is another problem with the engine
ability to produce manifold vacuum (top end and/or main seal problems).


Bill M.

It would be great if it was something as simple as the spark plug wires

Thanks bill for the good info and positive feed back.
I can’t wait to work on it. And dig in , though I have a bit more time left in San Diego before I move back up north with my wife and our toys . I’m pretty knew to stand ups , I have built/ restored one , I’m a recovering car builder turned to 2T dirt bikes and skis. They are way more rewarding to work on and build and take way less space in the garage and less money and way more fun to ride. I wish I had made the switch 10yrs ago.
But with that in mind I’m certain with the pro tips I’m getting here I will do just fine .

 

[wmazz]

I always power tune WOT 20 rpm rich of peak on glass, have not stuck a piston since. My main jets usually end up larger than what is posted on the internet. Sometimes by a lot!

The Mikuni sbn and Keihin cdk 2 carbs have a really wide range, when it comes
to acceptable main jets.

A 5/16" or 8mm id insert swedged & glued into the SBN main jet booster will
make it easier to find the correct main jet size because it is easy to find the point
where the main is rich. So reducing main jets until it smoothly transitions is much
easier.

For me, I can't recommend how I used to develop my main jet sizing because it
is to easy to settle on a main jet that is too lean. So I end up having to recommend
safe alternatives to find a main jet size. Unfortunately trying to find a main jet size
is time consuming and most people want it to be a quick process. Most people
just don't have the patience to develop good specs.

But with the idle drop test, you can develop a low speed jet, needle & seat, spring,
and pilot screw setting rather quickly. And by having a properly adjusted low &
pilot circuit you will not have problems with that circuit affect the high speed
circuit. A rich pilot (low speed) screw will kill peak rpm.

When jetting I try to achieve 3/4 pilot (low) screw and 3/4 on the hi speed screw.
I also use 1/4 turn = 1 jet size. That is always the goal whether it is standard or
reverse jetting.

When I am calculating Reverse jet specs, I incorporate the 1/4 turn = 1 jet size into
the original jet specs (so long as they are not frivolous adjustments made for
goon clearance, like some pipe specs).


Bill M.

The capabilities to make a home made data acquisition system to collect rpm
and exhaust gas temp is easy these days with an Arduino, and EGT modules
from "Playing with Fusion." On the dyno, Kawasaki used ~900 degrees for the
main jets.

 

[wmazz]

A method for developing your own specs with a sbn 44 or 46. Begin
with good jet specs. For a single 46, it is: 120 low, 160 main, 2.0 seat,
80gr spring.

Jet specs that include an 80gr spring work very well, when converting
to reverse specs.

Sometimes jet specs get carried away with the low jet size. In order to
test the low speed circuit, you can use the Idle drop test in my Blog.
After the Idle drop, if the low speed (pilot) screw ends up at 3/4 to 1
turn out, the conversion to reverse specs will go nicely.

If the low speed (pilot) screw ends up between +1 and 2 1/2, the low
jet is lean. If the low speed (pilot) screw ends less than 3/4 to closed,
the low jet is too rich.

Always start with the low speed and pilot circuits first.

A rich pilot (low) screw setting will kill peak rpm.

(1) Calculate peak HP rpm using the tuned length of the pipe using :
ED x 39484 / TL = Peak HP rpm. Popular exhaust duration ED is 180,
186,192. Popular tuned lengths (TL) are 1095 & 1050 (wet pipes).

Keep in mind that where you test and the weather are important factors.
As close to sea level and ~70 degrees is best.

During the summer your jetting will trend leaner, and during winter it
will require richer settings.

Altitude kills HP, and peak HP determines impeller size. At altitude your
only good option may be an impeller with less pitch to reach your rpm
goals.

(2) If your peak rpm is 300rpm less than the estimated peak HP rpm,
install a smaller impeller. Do not use a Tiny Tach. If there is a better
tach available and it is not water proof, put it inside a zip-loc and seal
the wire with a piece of duct tape.

(3) Install a 80 gr spring with a 2.0 or 1.5 (for duals) needle and seat.

(4) Perform the idle drop test. Repeat until you have a screw adjustment
of 3/4 to 1 turn out.

If the engine starts and idles with the screw closed, the low speed jet
is too rich. Decrease low jet 3 sizes, reset screw to 3/4 and continue testing.

(5) Use short 50 yard sprints with a tach, out from shore and back to shore
to determine high speed circuit.

Adjust the HS screw in or out for peak rpm. Don't be afraid to close the low
or hi speed screws if that is the direction your testing leads you.

(6) Use 1/4 turn = 1 jet size. Calculate for 1 turn out on HS screw, and
install new main jets. For example if you are at 2 1/2 turns out, subtract
1 turn from 2 1/2 = 1 1/2 and add 6 main jet sizes and retest. If the HS
screw is closed, subtract 4 sizes and reset the HS screw to 1 turn out.

(7) if you are 500rpm or greater above the estimated peak HP rpm, install
a larger impeller, and retest steps 2 thru 6.


Bill M.

 

[Project101]

A method for developing your own specs with a sbn 44 or 46. Begin
with the Mikuni oem jetting. For a single 46, it is: 120 low, 160 main,
2.0 seat, 115gr spring

Always start with the low speed and pilot circuits first.

A rich pilot (low) screw setting will kill peak rpm.

(1) Calculate peak HP rpm using the tuned length of the pipe using :
ED x 39484 / TL = Peak HP rpm. Popular exhaust duration ED is 180,
186,192. Popular tuned lengths (TL) are 1095 & 1050 (wet pipes).

Keep in mind that where you test and the weather are important factors.
As close to sea level and ~70 degrees is best.

During the summer your jetting will trend leaner, and during winter it
will require richer settings.

Altitude kills HP, and peak HP determines impeller size. At altitude your
only good option may be an impeller with less pitch to reach your rpm
goals.

(2) If your peak rpm is 300rpm less than the estimated peak HP rpm,
install a smaller impeller. Do not use a Tiny Tach. If there is a better
tach available and it is not water proof, put it inside a zip-loc and seal
the wire with a piece of duct tape.

(3) Install a 80 gr spring with a 2.0 or 1.5 (for duals) needle and seat.

(4) Perform the idle drop test. Repeat until you have a screw adjustment
of 3/4 to 1 turn out.

If the engine starts and idles with the screw closed, the low speed jet
is too rich. Decrease low jet 3 sizes, reset screw to 3/4 and continue testing.

(5) Use short 50 yard sprints with a tach, out from shore and back to shore
to determine high speed circuit.

Adjust the HS screw in or out for peak rpm. Don't be afraid to close the low
or hi speed screws if that is the direction your testing leads you.

(6) Use 1/4 turn = 1 jet size. Calculate for 1 turn out on HS screw, and
install new main jets. For example if you are at 2 1/2 turns out, subtract
1 turn from 2 1/2 = 1 1/2 and add 6 main jet sizes and retest. If the HS
screw is closed, subtract 4 sizes and reset the HS screw to 1 turn out.

(7) if you are 500rpm or greater above the estimated peak HP rpm, install
a larger impeller, and retest steps 2 thru 6.


Bill M.

Thanks this is a great info! I feel like I just got some great knowledge that I may have never learned on my own. Seriously thanks this is priceless to me. I’m definitely going to give it a shot. I know my 1100 ski could be jetted better aswell. But I need to build a better expansion chamber first . Which will be right after I get my wife’s ski dialed.
What are guys using for TACs ?
How are they data logging , how are you guys keeping track of engine temp?
I have plans for both of those but I’m not trying to reinvent the wheel here if I don’t have too.
This thread has really shifted but I love it.

 

[kevbo]

Im using an (now) old PET tach, the $5 ebay tachs do not update fast enough but there has to be an affordable pulse tach that does. I don't worry about temps as long as the compression and timing are below widely accepted maximums. Of course, no one is happy until they stick a piston. Combustion temps will be plenty low if the fuel mixture is on the rich side of peak RPM. I use an air separator mounted above the engine to make sure it stays that way on anything that is in the meltdown zone . Carb tuning goes very quickly compared to all the time I spend finding the best impeller and nozzle combo.

 

[wmazz]

know my 1100 ski could be jetted better aswell. But I need to build a better expansion chamber first.

Which 1100? and how is it set-up?

Is it the SXI with the 1100 engine? What carburetor brand? and we need to talk
about pipes.


Bill M.

 

[wmazz]

After taking a second look at this paragraph, I wish that I explained
it better. So I edited it. It needed to "start with good specs" Many
good specs for sbn carbs use 80 gr springs. In fact a spec that includes
an 80gr springs generally work out very well.

A method for developing your own specs with a sbn 44 or 46. Begin with the
Mikuni oem jetting. For a single 46, it is: 120 low, 160 main, 2.0 seat, 115gr spring

(3) Install a 80 gr spring with a 2.0 or 1.5 (for duals) needle and seat.

Rewritten: A method for developing your own specs with a sbn 44 or
46. Begin with good jet specs. For a single 46, it is: 120 low, 160 main,
2.0 seat, 80gr spring.

Jet specs that include an 80gr spring work very well, when converting
to reverse specs.

Sometimes jet specs get carried away with the low jet size. In order to
test the low speed circuit, you can use the Idle drop test in my Blog.
After the Idle drop, if the low speed (pilot) screw ends up at 3/4 to 1
turn out, the conversion to reverse specs will go nicely.

If the low speed (pilot) screw ends up between +1 and 2 1/2, the low
jet is lean. If the low speed (pilot) screw ends less than 3/4 to closed,
the low jet is too rich.


Bill M.

 

[Project101]

Which 1100? and how is it set-up?

Is it the SXI with the 1100 engine? What carburetor brand? and we need to talk
about pipes.


Bill M.[/QUOTE
Yes it’s an sxi with an 1100zxi 1mm over bore stock 010 milled head (it was warped ) CDK2 carbs no accelerator pump. I bought it as a basket case and did my best to put it back together. It runs pretty good on a basic level , starts right up idles nice . But I know there is more in there. First known problem Was Pipe was cut to fit the hull. (Not by me) so I know there at a min is a loss of volume . Second for sure problem. The water jacks on the pipe were not welded once modified . 100% of jacketEd exspansion chamber Water was getting into the exhaust . Found out later that’s why the engine had water in it. I made a quick 50% solution. And 3D printed plugs and plugged the exspansion chamber water ports On the Copper gasket and just left 1 open . I now know it’s still to much water.
My plan was to build a pipe / water box or resonator. Not sure which yet. Then go from there . As of now ski has about 7ish hours of run time and is a blast . But winter is coming and I want to sort it out more. Best speed from my friend on a couch was 55mph .
I want to dial the impeller and pump/cone. But I like doing 1 step at a time as to Keep to the KISS method.
This is my first ski so I’m still learning but it’s way more fun than cars
I made a youtube of it. Kinda goofy.
I just bought it built it and wanted to learn
And have fun.
Here’s the link

 

[Project101]

Bill ,

Im using an (now) old PET tach, the $5 ebay tachs do not update fast enough but there has to be an affordable pulse tach that does. I don't worry about temps as long as the compression and timing are below widely accepted maximums. Of course, no one is happy until they stick a piston. Combustion temps will be plenty low if the fuel mixture is on the rich side of peak RPM. I use an air separator mounted above the engine to make sure it stays that way on anything that is in the meltdown zone . Carb tuning goes very quickly compared to all the time I spend finding the best impeller and nozzle combo.

Can you explain the air separator more I’m not trackin ?


Bill, did you get my last post?
I’m interested to hear your knowledge on the expansion chamber And carbs and my set up.
Thanks

 

[kevbo]

Air in the fuel line can increase combustion temps. Its good to prevent this on anything that does long full throttle runs. Basically I pump fuel into a small header tank and return excess fuel and any air back to the main tank. The carbs never get air and the fuel mixture stays consistent.

 

[wmazz]

The best single pipe for a 900/1100 Kawi is a copy of a Rotax 1/2 pipe used
on ultralights. But no one makes one.

The stock 900 and 1100 pipes look like a regular pipe, but it doesn't function
as a normal pipe because it only scavenges. Any return wave is wasted.

On the dyno, a dried out stock pipe with a water injection solenoid worked really
well.


Bill M.

I never got around to make reverse jet specs for Keihin CDK2 carbs, but for a
few years Keihin manufactured carbs with a mid-range jet, and these carbs
are better (when opened up) than most Mikuni carbs for acceleration.

If you want a project, convert a set of Polaris 1050 carbs for your 1100.

The downside is they don't bolt on, and oem carb kits for Keihin are expensive.

That is the reason why Mikuni's may be a better option, IDK.

 

[Project101]

my goal is to lose some weight gain usable hp fit better, look cool and have fun doing something I haven't done before. The plan was to find a junk 1100 lower expansion chamber and do 1 of 4 ideas, idea #1 block off all port fill full of water and copy the same volume and length and dimensions and make my own pipe out of aluminum /try hydroforming(sounds fun) or make cones and weld together #2 coat inner a pipe with PVA fill full with spray foam and cut in half, make a plug and try carbon fiber. #3 school my self up on 2 stroke pipe theory and make my own pipe to better suit the triple and fit well.
I'm leaning toward option 1. seem least difficult and should give decent results, and check most boxes, should be lighter, fit better, look cooler and well it should perform better than what I have with that big plate welded on the side, I hope just getting all the water out should help as well.

Bill,
what water injection system are you specifically talking about? model make?
I'm gonna wait on the carbs for a while. they are something I will re-attack at a later time once my ski is more sorted.
and on that my carbs are just about jetted stock, out of the hole it seems to soft, mid seems super strong top feels pretty good too. but I'm just an amateur so I'm how this engine should feel. plugs look rich. but right now she fires right up idles nice and rips pretty good. i think next on my list will be the pipe, then pump and impeller, then jetting. or a combo of the two.

 

[kevbo]

You may have a tough time getting keihin jetting numbers to reverse. The mains are sized the same as mikuni but the pilots are not. A keihin 85 is like a mikuni 130. A carbon or thin sheetmetal lower pipe would be the ticket for weight savings. Make sure to keep it round and make a flange for flexible mounting. Working with stainless is easier unless you have a lot of composite experience.

 

[wmazz]

3 into 1 Expansion chambers don't work on triples!

The stock 900 and 1100 pipes look like a regular pipe, but it doesn't function
as a normal pipe because it only scavenges. Any return wave is wasted.

On the dyno, a dried out stock pipe with a water injection solenoid worked really
well.

Who cares about lost volume
I care about the design.

Dry out the stock pipe, incorporate a FPP/MSD/Advent (ECWI) Electronically Controlled
Water Injection

Good porting (not Group K porting, or DASA), and impeller.


Bill M.

Make sure to keep it round

Round doesn't matter, neither do dents. Pipes take a lot of punishment before they
loose HP.

 

[Project101]

3 into 1 Expansion chambers don't work on triples!



Who cares about lost volume
I care about the design.

Dry out the stock pipe, incorporate a FPP/MSD/Advent (ECWI) Electronically Controlled
Water Injection

Good porting (not Group K porting, or DASA), and impeller.


Bill M.



Round doesn't matter, neither do dents. Pipes take a lot of punishment before they
loose HP.

ok , so I may be better off just cutting my welded plate repairing all the leaks that let water in uncontrollably drying the pipe and and adding water injection. . I may try this first. Due to it just costing time to fix the leaks .
I still may make a lower pipe . Out of alum or stainless for kicks.
Thanks for all the info guys. I have a lot of research to do.

 

[kevbo]

I was thinking about the fatigue life of thin material. Stainless isn't too bad. Composites have limited pressure capacity with flat sides. Thin aluminum will quickly crack since the flats will always be flexing. Square waterboxes are a very bad choice because they have to be overly heavy to resist cracking or bursting. I have made realy quiet 3 chamber boxes under 2lbs that could take an afterfire. They have to be round though.

 

[wmazz]

Pipe building for watercraft has many challenges (pitfalls) compared to
building a pipe for a MX bike.

The first challenge is to not raise the inside temperature of the engine compartment
from heat (ECH) radiated by the pipe. Increased ECH decreases HP because it lowers
the air density to the engine. In other words you could be at a 800' lake and because
of the ECH the density altitude will be something like 5500'.

The next challenge is water jackets. There are 2 main problems, (1) is pin hole leaks
caused from lifting the torch to fast. The fix for this is to pressure test the pipe before
you build water jackets, find and repair the leaks before you continue. (2) Cracking
caused by 2 layers of metal expanding at different rates. Very few production pipes
have included the features necessary to prevent cracking.

Nearly all OEM watercraft use a version of an outboard exhaust system. Kawasaki and
Yamaha have used some version of this system on nearly all of their product. These
exhaust systems all try to scavenge more fuel.

The ultralite style exhaust does a much better job of scavenging than an outboard
style. My ultralite pipe I made for GoPeds (Tin Can) made more HP on the dyno than
a popular torque pipe.

I have dyno tested several triples and twins. One of the things the triples liked was
a free flowing waterbox and an enlarged exhaust outlet.

I don't have any pictures of my watercraft pipes, except the production version of
the 770 Tigershark, but I do have a few pictures of my GoPed pipes and no pictures
of my "Tin Can."

 

[kevbo]

You can get a remarkable amount of "tuning" at half and even quarter wave lengths.