Stroker Selection Question

[Shonuff]

So I was just wondering how does one decide whether to go to a 5mm stroker like Gil or longer . . . say an 8mm stroker?

Are there advantages to the 5mm? Does the 8mm not show enough of an improvement over the 5 to justify the drop in reliability (if there is one)?

What's the story?

 

[keefer]

I think after 5 or 6 mil you have to machine the cases for clearance. All of the 5 & 6 mils I have ridden make great power and are very ridable. The 8 mils I have ridden are more like rocket ships, monster power, maybe too much for some. But then again, is there such a thing as too much power? If I ever get around to building a stroker I think I will go with 5 or 6 mil because it makes sweet power and should retain good reliability if built & maintained properly.

 

[crammit442]

So I was just wondering how does one decide whether to go to a 5mm stroker like Gil or longer . . . say an 8mm stroker?

Are there advantages to the 5mm? Does the 8mm not show enough of an improvement over the 5 to justify the drop in reliability (if there is one)?

What's the story?

There are VERY differing opinions on this. Some builders think it's hardly worth going past 6mm because of the reduction in case integrity. Others think it's not worth going LESS than 8mm. I believe a well setup 6mm will run as hard or harder than most longer stroke motors without having to thin the cases as far. Since most of us are not concerned with displacement limits like the mod racers were, displacement can be made up with bore. Joe Kelly's(njfl) new ADA big motor at 7mm(he went with 7mm because he found a cheap 7mm crank) runs WAY harder than most 8 and 10mm motors on the same bore size. IMO, it's all in the complete package.

 

[crammit442]

One other thing I thought about. Jetworks builds a 4mm motor on the OEM cylinder that runs better and harder than most 5mm and 6mm Lamey packages.:burnout:

 

[Idok]

One other thing I thought about. Jetworks builds a 4mm motor on the OEM cylinder that runs better and harder than most 5mm and 6mm Lamey packages.:burnout:

this is the route that I woudl take....Pretty sure this crank requires no case mods as well!

 

[HBCwatercraft]

7 and up use 133 rods to help rod angle,the more the stroke the more the angle it opposes on the cylinder wall this will effect run time and maint..5mm you can still get away with full throttle runs,6mm and up u need bursts due to strain(6mm depends on rod selection i think u can go both ways on that long and reg.

 

[crammit442]

7 and up use 133 rods to help rod angle,the more the stroke the more the angle it opposes on the cylinder wall this will effect run time and maint..5mm you can still get away with full throttle runs,6mm and up u need bursts due to strain(6mm depends on rod selection i think u can go both ways on that long and reg.

Who told you that?:thinking: I guess Tricky and all the mod class racers didn't get the word.:scratchchin:

 

[HBCwatercraft]

more mm=more angle=more wear?thus everyone saying 8 and 10mm being not reliable?correct me if im wrong.is critical rod angle not a factor in your eyes.rod angle and cases getting thin are the major prob no?

 

[crammit442]

more mm=more angle=more wear?thus everyone saying 8 and 10mm being not reliable?correct me if im wrong.is critical rod angle not a factor in your eyes.rod angle and cases getting thin are the major prob no?

What??? That reads like a text message. Anyway, yes rod angle matters, but motors longer than 6mm NOT BEING ABLE TO BE RUN WIDE OPEN was what you posted. That's not an across the board fact. Plenty of 8mm motors run WOT all the time. Also, most builders like to run long rods on 6mm and bigger strokes, not just 7mm. I was just pointing out that you made an all encompassing statement that was not exactly accurate. That's all! Hope that helps!

 

[SUPERTUNE]

Not all 5mm cranks will clear cases, only 5mm stroker cranks with stock OEM rods from Yamaha will just about clear most of the time, a few times the casting in the crankcase does hit in a couple of spots. All 5mm and rebuilt cranks using HOT RODS will not clear the cases and will need about .040-.045 to clear the bigger big end of the HOT RODS as they are beefier rods.
Not true about stroker cranks being run wot for extended time.
8mm strokers must use 133mm or 134mm length rods as it won't work with 125mm stock length rods.
Wide open throttle running is built into the engine build spec's itself and is Never a problem by itself. (port mapping for target rpms, compression ratios, squish design, ignition timing, and overall carb efficiency)
I do believe that the 5mm cranks that do use stock OEM rods MAY suffer a little more wear over time, I still get 3 years or more beating them to death here in Florida with our extended riding seasons and salt water to boot. (more care must be taken in salt water riding)
Proper case preparation is always needed for any modified engines including strokers and type of running use.
And Yes, I do believe one can have too much power, look at me with my low level ride skill with my VERY high skill at making lots of HP. I most of the time cannot ride/tune what I can build!
As these 992/1014 1000cc monsters are way too much for most riders, and definitely includes me!
Engine setups must also follow cc rules if competing in certain classes and fit customer $$ buget.
By far it's best to build a 8mm stroker/long rod/small bore/Lamey PV cylinder engine over a big bore/stock stroke/lamey or stock cylinder engine.

 

[Speedfreak]

Can you explain why length is more important than bore? Since I know NOTHING about large motor building I would think that a 880cc motor is a 880cc motor regardless of how the cc's are reached.

 

[kevbo]

The engines design is more imortant than its size. The shops that use longer rods and aftermarket cylinders are effectively making a whole new engine using only Stock crankcases. This the best way to do it and its expensive. Going +5 while using stock rods and cylinders is much cheaper but have never been much more powerful than stock stroke engines. Don't get too caught up with size, many strokers have disapointed their owners.

 

[SUPERTUNE]

The major differences between same cc engines with different bores, smaller bores are always easier to fill with more fuel charge than bigger bores, thus a lot more efficient and will make more power.
Look at 2 stroke school of motocross 125 cc engines vs. 400cc engines HP per cc's, The 125cc engines always made more power per cc.
A longer stroke will favor freestyle/freeride type power as we want power right off the bottom of the rpms vs. higher rpms.

 

[yamaboy2000]

Chuckie aka Supertune is truely an asset to our sport and this site, his knowledge is world class:bananajump:

 

[Shonuff]

Agreed.

 

[scottie mac]

A 6mm long rod is a pretty tough motor to beat. It makes close to 8mm power and you don't have to bore the cases quite so thin. Having said that, I have had 6mm short rods, long rods and 8mm long rods and the 8mm do make more power.

Just remember, like Chucky said, power is the result of the total package.

Scottie

 

[cdubb]

Long rod,stock rod,off set pin,stock pin,stock piston,off set piston:thinking:

So with all this Im lost as to which route to build my motor. This should be more cut and dry,all the options to achieve the same result have me confused. I want a reliable stroker on a budget. So what are my options,where to get rods,what pistons/cylinders.

Can some one make a list of what parts to get what stroke with all the options Im lost. Thanks