- Location
- Braapp factory
Piston crown collapsing
- Thread starter keith t
- Start date
- Location
- South Africa
Lean fuel mixture
- Location
- Riverside, CA
That is Pre-ignition, most failures begin with detonation and after they have
seized several times, a piston will develop a sharp edge on the piston crown.
When the sharp edge becomes hot enough, it will cause the engine to preignite,
and melt the piston crown and expose the rings.
Preignition melts, detonation destroys. But there is no obvious signs of detonation
or water damage.
The water droplets on top of the cylinders is curious? Did the head gasket blow
on the front cylinder?
Because it is the front cylinder, an air leak is possible, and since it was caused by
preignition it is very possible that the engine was lean. The middle cylinder may
have ran hot because of the increased load, or it had something in common with
the front cylinder.
My question is: Why is there relatively new Wiesco pistons in the top end? Has it
seized before? How many hours are on that top end or engine?
Did the spark plugs have extended tips, or multiple bridges, or maybe Split Fire
spark plugs? Some types of Automotive spark plugs will reduce peak HP, and
create a hot spot to preignite from, especially if they were the wrong heat range.
What type of carbs and size are on it? Impeller size? Is there an aftermarket ignition,
what was the compression, and gas/oil mixture? Please fill any gaps in your set-up.
One last thing, did you change out the stock pump. The blaster hull will put a larger
load on the engine than a stand up hull (certainly true with X2's).
Bill M.
Have you modified the hull to allow more air into the engine compartment?
seized several times, a piston will develop a sharp edge on the piston crown.
When the sharp edge becomes hot enough, it will cause the engine to preignite,
and melt the piston crown and expose the rings.
Preignition melts, detonation destroys. But there is no obvious signs of detonation
or water damage.
The water droplets on top of the cylinders is curious? Did the head gasket blow
on the front cylinder?
Because it is the front cylinder, an air leak is possible, and since it was caused by
preignition it is very possible that the engine was lean. The middle cylinder may
have ran hot because of the increased load, or it had something in common with
the front cylinder.
My question is: Why is there relatively new Wiesco pistons in the top end? Has it
seized before? How many hours are on that top end or engine?
Did the spark plugs have extended tips, or multiple bridges, or maybe Split Fire
spark plugs? Some types of Automotive spark plugs will reduce peak HP, and
create a hot spot to preignite from, especially if they were the wrong heat range.
What type of carbs and size are on it? Impeller size? Is there an aftermarket ignition,
what was the compression, and gas/oil mixture? Please fill any gaps in your set-up.
One last thing, did you change out the stock pump. The blaster hull will put a larger
load on the engine than a stand up hull (certainly true with X2's).
Bill M.
Have you modified the hull to allow more air into the engine compartment?
- Location
- Braapp factory
Lots of questions, here goes
The water droplets on top of the cylinders is curious? Did the head gasket blow
on the front cylinder?
ADA girdled head, o rings all look fine
Because it is the front cylinder, an air leak is possible, and since it was caused by
preignition it is very possible that the engine was lean. The middle cylinder may
have ran hot because of the increased load, or it had something in common with
the front cylinder.
OK
My question is: Why is there relatively new Wiesco pistons in the top end? Has it
seized before? How many hours are on that top end or engine?
Engine was built by me, i rebuilt it when i removed it from couch as a precaution. That was 4 years ago and the ski is used around 20 times a year, and mostly full throttle .
Did the spark plugs have extended tips, or multiple bridges, or maybe Split Fire
spark plugs? Some types of Automotive spark plugs will reduce peak HP, and
create a hot spot to preignite from, especially if they were the wrong heat range.
NGK BR8ES
What type of carbs and size are on it?
Mikuni 44s of a GP1200 sat on an o ringed quick release plate
Impeller size?
16/23
Is there an aftermarket ignition,
Wiring mod and advance plate (from day it was built)
what was the compression,
150psi
and gas/oil mixture?
SHell V power 99RON with 500mls oil per 20 litres fuel
Please fill any gaps in your set-up.
One last thing, did you change out the stock pump. The blaster hull will put a larger
load on the engine than a stand up hull (certainly true with X2's).
Running Solas mag
Ski also runs 701 industries air down kit
Carbs seat as follows
160 mains, 115 pilots
High screws 2 turns out
Lows 1 turn out
Interested to hear thoughts
Thanks, Keith
The water droplets on top of the cylinders is curious? Did the head gasket blow
on the front cylinder?
ADA girdled head, o rings all look fine
Because it is the front cylinder, an air leak is possible, and since it was caused by
preignition it is very possible that the engine was lean. The middle cylinder may
have ran hot because of the increased load, or it had something in common with
the front cylinder.
OK
My question is: Why is there relatively new Wiesco pistons in the top end? Has it
seized before? How many hours are on that top end or engine?
Engine was built by me, i rebuilt it when i removed it from couch as a precaution. That was 4 years ago and the ski is used around 20 times a year, and mostly full throttle .
Did the spark plugs have extended tips, or multiple bridges, or maybe Split Fire
spark plugs? Some types of Automotive spark plugs will reduce peak HP, and
create a hot spot to preignite from, especially if they were the wrong heat range.
NGK BR8ES
What type of carbs and size are on it?
Mikuni 44s of a GP1200 sat on an o ringed quick release plate
Impeller size?
16/23
Is there an aftermarket ignition,
Wiring mod and advance plate (from day it was built)
what was the compression,
150psi
and gas/oil mixture?
SHell V power 99RON with 500mls oil per 20 litres fuel
Please fill any gaps in your set-up.
One last thing, did you change out the stock pump. The blaster hull will put a larger
load on the engine than a stand up hull (certainly true with X2's).
Running Solas mag
Ski also runs 701 industries air down kit
Carbs seat as follows
160 mains, 115 pilots
High screws 2 turns out
Lows 1 turn out
Interested to hear thoughts
Thanks, Keith
- Location
- Riverside, CA
I am not very good at short answers, and I am no expert with the 1100. I used
to own a 900, but they are very different. Since the mid 80's I have enjoyed
repairing blown up engines, building pipes, and tuning. But not engine
building.
Was there something different about the air temp, or where you were riding?
I like the hot weather in the desert, The pictures on Facebook look cold
When you rebuilt the engine, did you use oem Kawasaki main seals,
or did you purchase less expensive aftermarket main seals.
They may look the same, but often there is a difference on the vacuum
side of the main seal. That difference will cause the seal to leak vacuum,
but still hold pressure.
Has the engine back fired recently, have you used starting fluid? A front
main seal that has been partially pushed out of the cases would be a real
problem.
Did you disassemble the carbs yet? Any signs of rust or water in the gas?
Has the engine been hard to start after sitting for at least a week? I define
hard starting as trying to start the engine for more than 60 seconds, when
all the fuel has drained from the float chamber. Hard starting, after it
had been running earlier that day is a red flag.
I don't know what the jetting on the 1100, with Yamaha carbs should be. Those
Yamaha 44's are not the same as an aftermarket Mikuni 44sbn. That said, your
jetting seems to be on the rich side. If you account for the high speed screw position
@2 turns, that will equal approximately 8 jet sizes ( I use 1/4 turn per jet size). Your
160 mains with the hi speed screw set @closed would equal 180 mains.
What seat diameter and spring do they use?
Has the carbs been modified (no bomb sight).
Your total fuel (low jet + main jet = x number) seems to be high. An aftermarket
Mikuni will run a total of 260 as a single carb, and dual and triple carbs are normally
less. Maybe ~230 on duals, and ~230 ~220 or so for a triple. Your jet total is 275 to
295 depending on your high speed screw position.
If the impeller size is on the steep side for the application, one of the warning signs
is the main jets are richer than normal, or a tuner may never be satisfied with the jetting.
Bill M.
I am concerned that you may have built the ski for mainly top speed, and the impeller
was chosen for top speed, and that it was possibly 1 size to steep (for your set-up). That
would explain the jetting (unless the carbs are modified), and possibly why it has been
a reliable ski up to this point.
to own a 900, but they are very different. Since the mid 80's I have enjoyed
repairing blown up engines, building pipes, and tuning. But not engine
building.
Was there something different about the air temp, or where you were riding?
I like the hot weather in the desert, The pictures on Facebook look cold
When you rebuilt the engine, did you use oem Kawasaki main seals,
or did you purchase less expensive aftermarket main seals.
They may look the same, but often there is a difference on the vacuum
side of the main seal. That difference will cause the seal to leak vacuum,
but still hold pressure.
Has the engine back fired recently, have you used starting fluid? A front
main seal that has been partially pushed out of the cases would be a real
problem.
Did you disassemble the carbs yet? Any signs of rust or water in the gas?
Has the engine been hard to start after sitting for at least a week? I define
hard starting as trying to start the engine for more than 60 seconds, when
all the fuel has drained from the float chamber. Hard starting, after it
had been running earlier that day is a red flag.
I don't know what the jetting on the 1100, with Yamaha carbs should be. Those
Yamaha 44's are not the same as an aftermarket Mikuni 44sbn. That said, your
jetting seems to be on the rich side. If you account for the high speed screw position
@2 turns, that will equal approximately 8 jet sizes ( I use 1/4 turn per jet size). Your
160 mains with the hi speed screw set @closed would equal 180 mains.
What seat diameter and spring do they use?
Has the carbs been modified (no bomb sight).
Your total fuel (low jet + main jet = x number) seems to be high. An aftermarket
Mikuni will run a total of 260 as a single carb, and dual and triple carbs are normally
less. Maybe ~230 on duals, and ~230 ~220 or so for a triple. Your jet total is 275 to
295 depending on your high speed screw position.
If the impeller size is on the steep side for the application, one of the warning signs
is the main jets are richer than normal, or a tuner may never be satisfied with the jetting.
Bill M.
I am concerned that you may have built the ski for mainly top speed, and the impeller
was chosen for top speed, and that it was possibly 1 size to steep (for your set-up). That
would explain the jetting (unless the carbs are modified), and possibly why it has been
a reliable ski up to this point.
Here is what I see as odd in this? Its #1&2 cyls that are effected?? Normally it would be the output or pto side of the motor showing deto? The output side normally does more work. This leads me to believe some sort of mechanical issue is causing an air leak?? Or timing pre ignition? Bill M has shown many of the mechanical reasons for deto. The only other point to speculate is the crank has moved out of phase? Being that the motor has seen mainly high speed operation, its not unreasonable to assume, the phasisng change on #1&2? In any case, a full teardown and assesment will need to be in order to fully identify the root cause. Did you happen to do a leakdown test before disassmbly?? That should have been the initial starting point.
Ill try and keep an eye on this thread and see how you progress.
Ski ya, Paul
Ill try and keep an eye on this thread and see how you progress.
Ski ya, Paul
- Location
- Braapp factory
Guys, thanks for the inputs so far. CArbs were checked over today and found to be absolutely clean, no blockages, pops holding pressure and popping cleanly at 24psi across all 3. Its is worth adding that the returns are all drilled and a 110 main jet is added into the return line. The Only "issue" noted is that when put under pressure some small bubbles were escaping through threads on jet in return line, this will be double checked and sorted tomorrow.
It also may be of note that the pump bearings collapsed spectaculary ( the week before engine blew ) not sure if this could have added strain into the motor ?
Crank will be checked when my builder is back in UK in next week or two.
Keep the advice and pointers coming please , its very much appreciated
Keith
It also may be of note that the pump bearings collapsed spectaculary ( the week before engine blew ) not sure if this could have added strain into the motor ?
Crank will be checked when my builder is back in UK in next week or two.
Keep the advice and pointers coming please , its very much appreciated
Keith
- Location
- Braapp factory
No leakdown check done, with hindsight that should have been done, but once plug was pulled and aluminium grey colour, the head was whipped off to i vestigate further
- Location
- Riverside, CA
Did you drill out our low speed bypass holes? or is the low speed circuit and butterfly stock?
Bill M.
Thee low speed bypass holes and butterfly angle are different than a std Mikuni.
3 Fuel pumps?
- Location
- Braapp Factory
I'm the one who's been checking over keiths carbs, like mentioned they are popping perfectly across the 3 at 24psi, fuel lines holding pressure (over 10psi), no leaks in
carb assemblies at all.
3 fuel pumps yes, all functioning, no creases or leaks. holding pressure.
the tiny fuel return restriction holes within the carbs have been drilled out and the restriction gained by running a 110 main jet immediately after last carb in return spur....
that is where there was slight leakage through the threaded part of the jet into the carb spur... possibly causing loss of fuel pressure??? (not leaking through there anymore)
it is a weird one this, my 1100 kwak blaster was built at the same time, motor similarly was rebuilt before it went into the blaster, same prop, same advance plate, same ignition wire mod. only differences are his solas pump vs my stock with pump core and i'm running A/M mikuni 44's (jetting totals the same within 5 or 10 points although mine is jetted 130 lows 150 mains 1+1/2 out on bottoms, 1 out on tops.
both skis have been absolutely spanked for the last 4 years, mine is still like new???
- Location
- Riverside, CA
Kev T.
I like your low speed jetting but not Keith T's low speed jetting, his appears to
be lean.
There are 3 basic jetting scenarios: 1) oem or what most people consider normal
with a smaller low jet than the main jet. 2) Reverse jetting with low pop-off. The
low jet is normally larger than the main jet and the seat diameter is larger than
necessary, and the pop-off is low ~18 psi. 3) Reverse jetting with a high pop-
off. The low jet is normally larger than the main jet, but they use 1.2 to 1.5 seats
on multi carb manifolds, 2.0 seats on single carbs (but a 1.5 would probably work)
with 115gr springs, and no specific pop-off is required. 3b) I suppose you can use
the rules configure a jetting with a 95gr spring too.
The return line has two functions: 1) prevent fuel pressure at idle (and maybe low
rpm) from influencing the needle and seat. If the seat is incapable of closing under
high fuel pressure, the engine will run rich. (just like a very low pop-off). 2) The
return line will also separate the air out of the fuel line and returns the air back to the
tank. That way only fuel makes its way to the needle and seat, and prevents engine
failures.
On a SeaDoo (or any other engine that uses a side draft manifold) the air separator
no longer works because the carbs are horizontal and the air bubbles can not float to
the top (return lines are always mounted above the incoming fuel line so the air can
float to the top). When carbs are mounted vertically (like on Kawasaki's) there is no
need to air bubble separator tanks before the carb.
IMO, Keith's return line only functions to reduce the fuel pressure! Standard fuel
pressure is **7.5 psi @wot. The fuel pressure is the same for a weed whacker engine as
it is on Mikuni's largest fuel pump. Only volume is different.
According to the Mikuni manual the 1.5 seat is capable of supplying the carb with
all the fuel it requires, and that larger seats are unnecessary unless you are using
them to achieve a specific pop-off. Which is why Reverse jetting with a high pop-
off works for both recreation and racing.
Now I have wandered off subject.
The only reason I know to use a drilled out return line is to support jetting scenario
#2. With a drilled out return line you can regulate the fuel pressure so that a large low
jet and low pop-off will not run rich, and cause a problem on a start line. Jetting
scenario #2 also affects the low speed (pilot) screw function. It becomes more of a
low speed screw than a pilot circuit adjustment.
One last thing.
Have you or Keith worked on street bikes that are carbureted? Most street bikes are
equipped with a fuel screw that controls the pilot circuit. The pilot circuit is the starting
and idling circuit and it is supplied by the low jet, just like in a Mikuni sbn & Keihin CDK2.
That means the Mikuni & Keihin low speed screw is actually a pilot circuit for starting and
idling, and the low speed circuit is controlled by the fixed low jet and what ever the overlap
of the pilot circuit occurs.
There are tuning methods to determine the proper low speed (pilot) screw setting and
determine if your low jet is lean or rich. If the pilot circuit is rich, after you adjust it, the
engine will gain peak rpm.
Bill M.
Pop-off is how we test the springs preload. But atmospheric pressure opens the needle
and seat.
** I measured flowing pressure, not static pressure. If there was no return line, the static
fuel pressure would be significantly higher at starting and idle. As an example a house
in the USA may have only 4 psi of flowing water pressure (at a faucet) and over 40 psi of
static pressure.
I like your low speed jetting but not Keith T's low speed jetting, his appears to
be lean.
There are 3 basic jetting scenarios: 1) oem or what most people consider normal
with a smaller low jet than the main jet. 2) Reverse jetting with low pop-off. The
low jet is normally larger than the main jet and the seat diameter is larger than
necessary, and the pop-off is low ~18 psi. 3) Reverse jetting with a high pop-
off. The low jet is normally larger than the main jet, but they use 1.2 to 1.5 seats
on multi carb manifolds, 2.0 seats on single carbs (but a 1.5 would probably work)
with 115gr springs, and no specific pop-off is required. 3b) I suppose you can use
the rules configure a jetting with a 95gr spring too.
The return line has two functions: 1) prevent fuel pressure at idle (and maybe low
rpm) from influencing the needle and seat. If the seat is incapable of closing under
high fuel pressure, the engine will run rich. (just like a very low pop-off). 2) The
return line will also separate the air out of the fuel line and returns the air back to the
tank. That way only fuel makes its way to the needle and seat, and prevents engine
failures.
On a SeaDoo (or any other engine that uses a side draft manifold) the air separator
no longer works because the carbs are horizontal and the air bubbles can not float to
the top (return lines are always mounted above the incoming fuel line so the air can
float to the top). When carbs are mounted vertically (like on Kawasaki's) there is no
need to air bubble separator tanks before the carb.
IMO, Keith's return line only functions to reduce the fuel pressure! Standard fuel
pressure is **7.5 psi @wot. The fuel pressure is the same for a weed whacker engine as
it is on Mikuni's largest fuel pump. Only volume is different.
According to the Mikuni manual the 1.5 seat is capable of supplying the carb with
all the fuel it requires, and that larger seats are unnecessary unless you are using
them to achieve a specific pop-off. Which is why Reverse jetting with a high pop-
off works for both recreation and racing.
Now I have wandered off subject.
The only reason I know to use a drilled out return line is to support jetting scenario
#2. With a drilled out return line you can regulate the fuel pressure so that a large low
jet and low pop-off will not run rich, and cause a problem on a start line. Jetting
scenario #2 also affects the low speed (pilot) screw function. It becomes more of a
low speed screw than a pilot circuit adjustment.
One last thing.
Have you or Keith worked on street bikes that are carbureted? Most street bikes are
equipped with a fuel screw that controls the pilot circuit. The pilot circuit is the starting
and idling circuit and it is supplied by the low jet, just like in a Mikuni sbn & Keihin CDK2.
That means the Mikuni & Keihin low speed screw is actually a pilot circuit for starting and
idling, and the low speed circuit is controlled by the fixed low jet and what ever the overlap
of the pilot circuit occurs.
There are tuning methods to determine the proper low speed (pilot) screw setting and
determine if your low jet is lean or rich. If the pilot circuit is rich, after you adjust it, the
engine will gain peak rpm.
Bill M.
Pop-off is how we test the springs preload. But atmospheric pressure opens the needle
and seat.
** I measured flowing pressure, not static pressure. If there was no return line, the static
fuel pressure would be significantly higher at starting and idle. As an example a house
in the USA may have only 4 psi of flowing water pressure (at a faucet) and over 40 psi of
static pressure.
Last edited:
Quinc
Buy a Superjet
- Location
- California