Introduction to Bigger Motors

[Woody]

Hi All,

I wanted to know what the different options available are to increase motor size. I currently have a 701 std. bore motor with ada girdled head, b-pipe, msd enhancer, stock lightened flywheel, stock 08 SJ prop...and am sick of the unreliablility of it.

I am a noob at this so I'm hoping you guys can give me an idea of what each thing would be. Yes...I know you should consult your individual builder on your specific build, but I want to have a basic idea of what the different options are. Some common things that i hear about but have no idea what they are include:

-What is a Stroker Motor (what is 3mm 5mm 8mm etc. stroker, rad stroker)
-What are powervalves
-What is a trued crankshaft?
-What is resleeving?
-What is a flat dome vs. a normal dome? I currently have the 35cc ada domes...how do they differ?
-What is the purpose of the reeds? What is the difference between the aftermarket reeds
-Who are the different manufacturers of different aftermarket motors and what options does each manufacturer have. Also, if you can give approximate costs (round numbers) of each motor (not one manu. specific, moreso like...an 800cc motor goes for about $X, a 900 goes for about $y, etc.)
-What is DASA "Thrust" Engine
-Does porting a stock motor cause extra stress on parts of the motor ie. crank, etc.

I am looking to upgrade in the future (who knows when that will be)...but I want a motor that will be super reliable, even if it means sacrificing some power. I am not a mechanic, I only know what is taught to me....so I want to be riding my ski and not wrenching it. I'll compensate for this powerloss by putting in a bigger motor. I do mostly Freestyle Riding (obvi since I'm on this board) but occasionally ride the tracks through the marsh.

What are suggestions for putting together an ubber-reliable motor?

 

[cleetus]

Built right your motor should be ubber-reliable...
This will answer some of your questions...
http://en.wikipedia.org/wiki/2-stroke_power_valve_system

trued driveshaft = (to true is to make something as close to perfect as possible, in this case perfectly straight)

your cylinders are aluminum (soft) and have steel sleves in which the pistons travel up and down in. In some cases (like a crack, want to fit maximum sized pistons in cylinder) you remove the sleve and replace it with another one

the rest og the stuff you can easily search

Your motor should have lots of power, and has some very good mods. If they werent done correctly, or havent been maintained they will lead to problems... I would say your next step would be bigger pistons and some porting (porting is improving airflow, airflow makes power)... But first you need to get you boat running right.

 

[Woody]

thanks cleetus. why do some people specifically choose not to use powervalves?

 

[Woody]

as far as searching for other manufacturers and stuff, i wasn't able to find one specific thread that listed all of the major names that do porting and/or machining of bigger motors...which is why i'm creating this thread...hopefully to get it all in one place so when the next noob comes along searching for it, he/she finds it all in one place instead of cluttering up the forums like i'm doing lol

 

[Speedfreak]

There are some basic options to increase power but if you have an unreliable motor now then I wouldn't suggest anything but tuning yours correctly and then learn how to ride with what you have.

All the power in the world won't make you a better rider. YES it is fun to play on but it won't increase your skills. In fact a big motor before your ready for it can hinder your riding ability. I went from a limited ski (like you have) to a 850 in a new hull and it is just plain hard to get used to.

Every builder has a different price but porting can be had for 400 or so if you build the motor and tune the motor.

Jetworks sells a 3 or 4mm stroker kit that fits in the stock cases. A great bang for the buck for 2 grand-ish

Some other peopel can chime in on bigger motors. I have one but don't know what they cost I got mine in a package deal with the ski.

 

[wsuwrhr]

I would love to answer your questions, one by one. You have to understand, what you are asking would take hours to complete.

I will try and do a little at a time, I am sure others will chime in as well.

Brian

Hi All,

I wanted to know what the different options available are to increase motor size. I currently have a 701 std. bore motor with ada girdled head, b-pipe, msd enhancer, stock lightened flywheel, stock 08 SJ prop...and am sick of the unreliablility of it.

I am a noob at this so I'm hoping you guys can give me an idea of what each thing would be. Yes...I know you should consult your individual builder on your specific build, but I want to have a basic idea of what the different options are. Some common things that i hear about but have no idea what they are include:

-What is a Stroker Motor (what is 3mm 5mm 8mm etc. stroker, rad stroker)
-What are powervalves
-What is a trued crankshaft?
-What is resleeving?
-What is a flat dome vs. a normal dome? I currently have the 35cc ada domes...how do they differ?
-What is the purpose of the reeds? What is the difference between the aftermarket reeds
-Who are the different manufacturers of different aftermarket motors and what options does each manufacturer have. Also, if you can give approximate costs (round numbers) of each motor (not one manu. specific, moreso like...an 800cc motor goes for about $X, a 900 goes for about $y, etc.)
-What is DASA "Thrust" Engine
-Does porting a stock motor cause extra stress on parts of the motor ie. crank, etc.

I am looking to upgrade in the future (who knows when that will be)...but I want a motor that will be super reliable, even if it means sacrificing some power. I am not a mechanic, I only know what is taught to me....so I want to be riding my ski and not wrenching it. I'll compensate for this powerloss by putting in a bigger motor. I do mostly Freestyle Riding (obvi since I'm on this board) but occasionally ride the tracks through the marsh.

What are suggestions for putting together an ubber-reliable motor?

 

[wsuwrhr]

-What is a Stroker Motor (what is 3mm 5mm 8mm etc. stroker, rad stroker)
-What are powervalves
-What is a trued crankshaft?


-What is DASA "Thrust" Engine

Stroker motor refers to any motor that has had the stroke altered from stock, usually made larger of course.

701/760 Super jet motors, or GP motors as they are also called, start out stock at 68MM stroke. The GP motor is used in 90% of the twin cylinder sitdown models and 100% of the standup models. Many of the 701/760 parts are interchangable. I don't know when they stated production, but they are still made new, making it a pretty popular platform and cheap availabilty of used parts.

GP strokers are made 4-6-8-10-12-16MM ending(for now) at 82 MM stroke.

4MM is a "drop in" to a factory case, anything bigger will need the case "trenched", meaning the case needs to be cut larger for clearance for the big end of the rod.

4-6-8-10 will work in a factory case, 12MM is pretty far out there and needs great care to work in a factory case, but it is still possible. 16MM no doubt will need an aftermarket case.

Powervalves are a gate, for lack of a better word, they restrict the exhaust area at low RPMs and move out of the way to unrestrict the exhaust area at higher RPMs, like having a smaller AND larger cam in a four stroke engine. Gives you the best of both worlds in a way, good bottom end with good power in upper end.

A "trued" crankshaft is a crankshaft who's rod journals are perfectly indexed to be a "true" 90 degrees(or 180 degrees in this case) apart and then usually welded so as not to move. The crank runs truer and with less vibration, all for more power and better bearing life.

I don't know what DASA -thrust is...

But a "DASA engine" refers to an engine builder, DASA Racing, who in the past has also used the name Racer's Edge, builder of the "Lamey" cylinder.

As far as cost, there are many options available to be able to quote.

But I can say as far as our company, our aftermarket cylinders are all the same price, since they all cost the same to produce, same with billet cranks up to 12MM. They are all the same price as well.

Factory cranks maybe cheaper to modify for strokers, but we exclusively only use billets from a company called "Crankworks".

Brian

 

[SUPERTUNE]

Hi All,

I wanted to know what the different options available are to increase motor size. I currently have a 701 std. bore motor with ada girdled head, b-pipe, msd enhancer, stock lightened flywheel, stock 08 SJ prop...and am sick of the unreliability of it.

I am a noob at this so I'm hoping you guys can give me an idea of what each thing would be. Yes...I know you should consult your individual builder on your specific build, but I want to have a basic idea of what the different options are. Some common things that i hear about but have no idea what they are include:

-What is a Stroker Motor (what is 3mm 5mm 8mm etc. stroker, rad stroker)
-What are powervalves
-What is a trued crankshaft?
-What is resleeving?
-What is a flat dome vs. a normal dome? I currently have the 35cc ada domes...how do they differ?
-What is the purpose of the reeds? What is the difference between the aftermarket reeds
-Who are the different manufacturers of different aftermarket motors and what options does each manufacturer have. Also, if you can give approximate costs (round numbers) of each motor (not one manu. specific, moreso like...an 800cc motor goes for about $X, a 900 goes for about $y, etc.)
-What is DASA "Thrust" Engine
-Does porting a stock motor cause extra stress on parts of the motor ie. crank, etc.

I am looking to upgrade in the future (who knows when that will be)...but I want a motor that will be super reliable, even if it means sacrificing some power. I am not a mechanic, I only know what is taught to me....so I want to be riding my ski and not wrenching it. I'll compensate for this powerloss by putting in a bigger motor. I do mostly Freestyle Riding (obvi since I'm on this board) but occasionally ride the tracks through the marsh.

What are suggestions for putting together an ubber-reliable motor?

Let's just start with some basics with YOUR engine for now,
You shouldn't have reliability problems with a few basic bolt-ons like you described unless your trying to run too much compression, carbs are not working properly or not jetted correctly, to much timing, and possibly a little over propped with 35cc domes.
Here's the reason why you need the setup just right...
Take the increased compression ratio for example on what you did...
A stock 61x 701 Superjet engine uses a cast one piece head and a gasket.
Let's break it down to cc's, the stock uncut head is 34 cc's. the .052 thick head gasket adds 6 cc's to the head volume for a total of 40 cc's is what the engine has for cylinder combustion chamber volume.
Now you buy and use a ADA head and get 35cc domes and this design has eliminated the oem headgasket, so 35 cc's would be your NEW combustion chamber volume that the engine has.
With that stated, you changed the combustion chamber 5 cc's smaller for increased compression ratio.

So let's do the math with figuring the compression ratio of your engine.
Just off the top of my head here as I'm at home and don't have exact stock compression ratio, I know it's close to 11.9:1 full stroke method.
Now let's figure out displacement of your engine...stock bore at 81mm, stock stroke at 68mm.
Bore x Bore x Stroke x .7854 divided by 1000 will equal displacement of one cylinder, then x 2 will equal total displacement of engine.
This would come out to 700.8 cc's. (Yamaha 701)
One cylinder would be 350.4 cc's
In order to measure compression ratio you need to know what your fill volume (FV) is on the total combustion chamber with the engine assembled and the piston dome top protruding into the total cc's of the head volume.

The easy method for this is to set the piston to TDC and a light coat of white grease creamed into the top to seal piston to cylinder, a light coat on top of the sleeve and bolt down the head (and gasket if using one).
Use a CC buret and fill combustion chamber with light fluid (I use mineral spirits), fill up 3 to 4 threads up the sparkplug hole, this measurement you give you your FV number.
Now that you have these fact's on you engine, let's do the compression ratio calculations.
Let's say the FV is 32cc for a stock engine...
350.4 + 32 divided by 32 = 11.9:1 compression ratio.
Now let's use you new head numbers, with 5 cc's less...
350.4 + 27 divided by 27 = 13.9:1 is your new compression ratio.
2 full points in compression ratio!
This IS a BIG change in compression ratio for today's premium fuel with all of the bad additives + ethanol made for cars to use in our ski's.
Add in the increased heat from a tigher squish clearances with the aftermarket head can add even more danger for detonation to occur.
Now over prop it a little too much and a little too lean on carbureation using stock lean burn emission standard carbs can and does spell disaster if not setup just right.
Read, read, and did I say read? about racing two stroke engines and will take some time to understand how modifying a two stroke in a watercraft, with some hands on experience.
Or just go to a reputable shop and pay them for a modifying your engine for your needs.

 

[steveyz250fpilot]

I searched for some posts where you would have found a reference to a DASA Thrust motor, and most of them were referring to motors utilizing a DASA (Lamey) Cylinder setup and offered by a company named Thrust Innovations.

 

[Woody]

Thank you all very much for your help. This is exactly what I am looking for...a little more insight into the bigger motors so when I do decide if and when to go to a bigger motor, I can at least talk the talk with my builder.

 

[Idok]

Let's just start with some basics with YOUR engine for now,
You shouldn't have reliability problems with a few basic bolt-ons like you described unless your trying to run too much compression, carbs are not working properly or not jetted correctly, to much timing, and possibly a little over propped with 35cc domes.
Here's the reason why you need the setup just right...
Take the increased compression ratio for example on what you did...
A stock 61x 701 Superjet engine uses a cast one piece head and a gasket.
Let's break it down to cc's, the stock uncut head is 34 cc's. the .052 thick head gasket adds 6 cc's to the head volume for a total of 40 cc's is what the engine has for cylinder combustion chamber volume.
Now you buy and use a ADA head and get 35cc domes and this design has eliminated the oem headgasket, so 35 cc's would be your NEW combustion chamber volume that the engine has.
With that stated, you changed the combustion chamber 5 cc's smaller for increased compression ratio.

So let's do the math with figuring the compression ratio of your engine.
Just off the top of my head here as I'm at home and don't have exact stock compression ratio, I know it's close to 11.9:1 full stroke method.
Now let's figure out displacement of your engine...stock bore at 81mm, stock stroke at 68mm.
Bore x Bore x Stroke x .7854 divided by 1000 will equal displacement of one cylinder, then x 2 will equal total displacement of engine.
This would come out to 700.8 cc's. (Yamaha 701)
One cylinder would be 350.4 cc's
In order to measure compression ratio you need to know what your fill volume (FV) is on the total combustion chamber with the engine assembled and the piston dome top protruding into the total cc's of the head volume.

The easy method for this is to set the piston to TDC and a light coat of white grease creamed into the top to seal piston to cylinder, a light coat on top of the sleeve and bolt down the head (and gasket if using one).
Use a CC buret and fill combustion chamber with light fluid (I use mineral spirits), fill up 3 to 4 threads up the sparkplug hole, this measurement you give you your FV number.
Now that you have these fact's on you engine, let's do the compression ratio calculations.
Let's say the FV is 32cc for a stock engine...
350.4 + 32 divided by 32 = 11.9:1 compression ratio.
Now let's use you new head numbers, with 5 cc's less...
350.4 + 27 divided by 27 = 13.9:1 is your new compression ratio.
2 full points in compression ratio!
This IS a BIG change in compression ratio for today's premium fuel with all of the bad additives + ethanol made for cars to use in our ski's.
Add in the increased heat from a tigher squish clearances with the aftermarket head can add even more danger for detonation to occur.
Now over prop it a little too much and a little too lean on carbureation using stock lean burn emission standard carbs can and does spell disaster if not setup just right.
Read, read, and did I say read? about racing two stroke engines and will take some time to understand how modifying a two stroke in a watercraft, with some hands on experience.
Or just go to a reputable shop and pay them for a modifying your engine for your needs.

Thank you all very much for your help. This is exactly what I am looking for...a little more insight into the bigger motors so when I do decide if and when to go to a bigger motor, I can at least talk the talk with my builder.

he is already talking to you!
:bump:

 

[FyrHazard]

Subscribing - Because knowledge is POWA!!

 

[tor*p*do]

me too, I have outgronw my 6M6 and need more of that powa!!!! :fingersx:

:Banane26:

 

[Magnum Mike]

It would be great to have a chart that goes something like this (wild guesses on these numbers):

name cc cylinder case engine cost estimated HP
------------------------------------------------------------------------------------------
OEM 650cc $400 used
OEM 701cc 61X $500 used
OEM 760cc 62T
OEM 800cc $1500
DASA 800cc
groupk 851cc 62T 62T+$2200
Seadoo 951cc
DASA 1000cc DASA


Crap... no matter what I do I can't keep the columns aligned... I guess something like Google Docs would the the best place for multiple people to edit a chart with the specs.



a

 

[chasingdaylight]

It would be great to have a chart that goes something like this (wild guesses on these numbers):

name cc cylinder case engine cost estimated HP
------------------------------------------------------------------------------------------
OEM 650cc $400 used
OEM 701cc 61X $500 used
OEM 760cc 62T
OEM 800cc $1500
DASA 800cc
groupk 851cc 62T 62T+$2200
Seadoo 951cc
DASA 1000cc DASA


Crap... no matter what I do I can't keep the columns aligned... I guess something like Google Docs would the the best place for multiple people to edit a chart with the specs.



a

That would be cool but, there are so many combinations and builders that it would be a very difficult list to make..

Plus this site DYNO IS STILL MIA... OR BROKEN i think :deadhorse:

Make/ get a relationship with a known engine builder and do your research on what you think you want and need... Do not overlook your pump set up too
a lot of power can be lost from the wrong pump, engine weight combo


my guess on engine power would be stock around 80..

A limited ski (stock pistons crank) with all the add ons in the 100 range.

Aftermarket cylinder with add ons 125 hp stroker with the same add ons a little more

full big bore, strokers, light flywheel, good ignition maybe up to 190??

making any combo work to it's full output is the key to any ski build

Just my 2 cents

 

[Woody]

yeah i need to get my ski tuned properly. its not as BAD as I made it out to be...I guess I was just frustrated.

i stuck a piston the first ride of the season cause it was too lean...then I increased jet sizes and stuck it again...luckily i was able to free this one up.

anyhow...back on topic. i like all the ideas of motors available, different makers, etc. as far as price goes...thats hard because as mentioned there are a lot of different combinations...but ballpark numbers work well too for us noobs (ie. 800cc motor is anywhere from x-y....927 is from....etc.).

and thank you all mechanic gurus that are helping us laymen out lol

 

[Aircraftsalz]

Most Engines shops aren't going to post prices, Every motor package is different so its hard to give you #'s. Best thing is to call some engine builders & ask. I personally like Xscream & the after service I can't say enough about. Give Radney a call & you will be happy!. Me & my riding buddies all ride Xscream motor packages, motors just run & we never wrench on them!!!!

I got another Xscream motor in the oven now!

 

[CoreyLKN]

x2 for XSCREAM! I talked to Radney the other day and got me started on the right track to a rippin motor and explained everything. Definitly give them a call!

(727)442-7700

 

[retroicon]

The most important question for you is ... what's your budget?

Once we know that, we can give you some options.

Your options for $1,000 are a hell of a lot different than your options would be at $10,000 ... so what are you lookin to drop?

G

 

[Polish jet pilot]

The most important question for you is ... what's your budget?

Once we know that, we can give you some options.

Your options for $1,000 are a hell of a lot different than your options would be at $10,000 ... so what are you lookin to drop?

G

......reality strikes back!