Super Jet Stroker Cranks

[KTM434]

You have to consider a stock Yamaha engine has 155psi compression. Do you know anyone running a stroker with that low of compression? Side loading is influenced by rod length/angle and compression as well as stroke. Most people running a stroker have huge mag pumps, total loss, high enough compression for race gas/av gas and ride harder than someone with a stock 650/701. If you ran a stroker with 165psi and stock pump it would last longer. Not necessarily the same as a stock 650/701 but it would be a lot more comparable.

 

[Tommygunz]

What makes you say, "And my two years of riding equates to a normal riders 5-8 years"? That is a guess AND a 2 year range. You blew out brand new OEM Yamaha cranks (plural) faster than you blew 4mil cranks (plural)?

I guess I meant that compared to most of the guys I know and ride with I ride as much in two years as they would ride in 5+ . Sorry for any confusion.

And yes I have blown multiple Yamaha cranks. And my 4 mil was just torn apart for inspection and figured it could use new bearings.

Again sorry for any confusion Madmat. If you have any questions feel free to call or text me at 262-689-4063. I will gladly clear up any confusion

 

[MADMAT]

....195psi stock crank.....with a mag (define huge...that is relative to what is pushing it, no?)....and total loss....I bet it will outlive its stroker counterpart by 400% with identical conditions/riders. Hell even 205psi on race gas and stock crank I bet!

 

[MADMAT]

No Tpain I have no questions....just discussing. I realize you have blown multiple cranks...I would like to know over what period of time I guess......and why?

 

[Tommygunz]

What makes you say, "And my two years of riding equates to a normal riders 5-8 years"? That is a guess AND a 2 year range. You blew out brand new OEM Yamaha cranks (plural) faster than you blew 4mil cranks (plural)?

I guess I meant that compared to most of the guys I know and ride with I ride as much in two years as they would ride in 5+ . Sorry for any confusion.

And yes I have blown multiple Yamaha cranks. And my 4 mil was just torn apart for inspection and figured it could use new bearings.

Again sorry for any confusion Madmat. If you have any questions feel free to call or text me at 262-689-4063. I will gladly clear up any confusion

 

[Tommygunz]

Sorry double posted somehow.

Yamaha crank lasted about a year before losing bearings and blowing up. Then built a 760 @225 comp built by PHP Zack. Made it year and a half before it died and went to stroker. All were just pushing 144 stock pumps blueprinted by Zack. For the last 6months my motor has been pushing a 148 mag.

 

[KTM434]

Large mag pump being a 148-160mm puts more load on an engine and higher compression makes the side loading worse. I wasn't saying total loss influences engine life just pointing out the extremes that people running a stroker go through to get the most power. Usually they are less concerned about longevity and that's going to affect the average lifespan of a stroker since they appeal to that type of rider more than a rec rider. Strokers can be setup to have a good lifespan with very little issues. Matt_E had his 10mil for 1-2 seasons and he said it looked brand new when he inspected it

 

[Philip Clemmons]

More power equals more maintenance and shorter life. Look at top fuel cars that are rebuilt after every 3.85 second run. They have the best equipment in the world, but are pushing it to its limit. As has been mentioned, most don't invest in a stroker crank and leave everything else stock. The power and performance is increased significantly once that commitment has been made. It's not for everyone..........the power vs dollars vs maintenance relationship is something that must be evaluated and considered on an individual basis for each person and their intended riding style and the level of maintenance they are willing to perform.

On a side note, stock stroke engines have limitations as well. Even though the rod ratio is kept stock, the added piston weight, and corresponding added combustion force (added power) from a 850-964 SS motor will require more maintenance, even though its "still a stock crank". You don't go from 701 power to 850-964 power (using the same rotating assembly parts) without some sacrifice in longevity...........

 

[chadman154]

What makes you say, "And my two years of riding equates to a normal riders 5-8 years"? That is a guess AND a 2 year range. You blew out brand new OEM Yamaha cranks (plural) faster than you blew 4mil cranks (plural)?

Tommy rides ALOT. Im pretty sure thats what he means

 

[phreeride215]

I think Yamaha recommends a (stock engine) crank rebuild at 250 hours on a 701. I know plenty of people with 800-900cc range strokers getting well beyond that time out of a crank.

 

[Matt_E]

I'd like to point out that you can't really compare the life of an OEM crank with a stroker. Why?
Because you don't check the health of the OEM crank every season or every other season. You just run it until it breaks. And you get lucky for seven years.
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The stroker crank you consciously check after every season of riding because it was freaking expensive. So you find you should probably replace the bearings after two seasons, just to be safe.

I really don't think you can say that the OEM crank lasted 7 years while the stroker lasted 2 years, and I am pretty sure you can see why.

 

[NVJAY775]

Good point

 

[227]

What I'm getting from this thread is anytime time you increase HP by tweaking your motor, you do so at the cost of reliability or longevity. I guess my question between the lines has been answered- Thank you every one for your input.

 

[Matt_E]

Gotta pay to play. Power ain't free.

 

[loictahiti]

I've one old style OEM+6 crank stroker (with std rod) with 82 mm Piston , 61X ported cylinder , 175 psi on both Cyl with custom OEM head , Protec EX , WRX style on my 3 Y Flat deck :
http://www.x-h2o.com/threads/68349-funny-project-Yamaha-Flat-deck

run almost 2 WE/month since my project is finished ...... never seen water intrusion and still running with good oil

Stroker it's like fixed steering , when you taste it , you keep it :Banane01::Banane01:

 

[mthomps]

What I'm getting from this thread is anytime time you increase HP by tweaking your motor, you do so at the cost of reliability or longevity. I guess my question between the lines has been answered- Thank you every one for your input.

This has been a really great thread. Thanks for making it.

I have a question I didn't see an answer to, so if you don't mind:

Is it possible to engineer a completely new engine with more power that rivals the lifetime of an OEM yamaha? Or is what yamaha came up with close to the best trade off possible by physics?

 

[wanderer1]

This has been a really great thread. Thanks for making it.

I have a question I didn't see an answer to, so if you don't mind:

Is it possible to engineer a completely new engine with more power that rivals the lifetime of an OEM yamaha? Or is what yamaha came up with close to the best trade off possible by physics?

Yamaha did that,its called the 66E

 

[Matt_E]

Yamaha did that,its called the 66E

It's unfortunate they ed up the reliability part of the equation with their brainless powervalves.

 

[sportfish258]

What I'm getting from this thread is anytime time you increase HP by tweaking your motor, you do so at the cost of reliability or longevity. I guess my question between the lines has been answered- Thank you every one for your input.

John , Generally speaking the 4 mill cranks wear about the same as a sock crank , but takes a small amount of case work it install . The cost to rebuild a stock crank is about 500, you can rebuild it to a 4 mill for ....... 500. It's a no brainer if you're building a new motor. If you build a super bore set up with a 4 mill it puts you at 830 ish cc and change . IMO it will give you years of longevity and service . I think crazy timing curves and neglect cause most of the X'ers failures with regard to strokers .


Power House Performance is making a new design that sounds fantastic . Maybe Zach will chime in ......

 

[wanderer1]

It's unfortunate they ed up the reliability part of the equation with their brainless powervalves.

True, easy fix