School me a strokers kit and cubs

[yfz450]

I'm looking to build a duner for the summer and ice racer for the winter. I already have a YFZ450 for trails and all the other stuff I get into.

 

I'm a little lost when it comes to stroker kits and porting / cylinders for each kit. Things I've heard from different shops are:

1.) If you port for a stock stroke and then decide to upgrade to a stroker, your stock cylinders are worthless because all the porting done for stock stroke will no longer match up.

2.) Cub cylinders are better out of the box than most ported stock cylinders.

3.) You purchase cub cylinder based upon your stock - ie there's a set for stock stroke, 4-mil, 7-mil, 10-mil, etc.

4.) 7-mil is more "dependable" and "reliable" than a 4-mil.

5.) 4-mil requires no case mods, but 7-mil does.

6.) If you purchase cub cylinders for stock stroke, you will need new ones if you go 4-mil, 7-mil, etc.

 

So of my 6 questions, which ones are fact and which ones are myth?

[Bansh-eman]

I'm looking to build a duner for the summer and ice racer for the winter. I already have a YFZ450 for trails and all the other stuff I get into.

 

I'm a little lost when it comes to stroker kits and porting / cylinders for each kit. Things I've heard from different shops are:

1.) If you port for a stock stroke and then decide to upgrade to a stroker, your stock cylinders are worthless because all the porting done for stock stroke will no longer match up.

2.) Cub cylinders are better out of the box than most ported stock cylinders.

3.) You purchase cub cylinder based upon your stock - ie there's a set for stock stroke, 4-mil, 7-mil, 10-mil, etc.

4.) 7-mil is more "dependable" and "reliable" than a 4-mil.

5.) 4-mil requires no case mods, but 7-mil does.

6.) If you purchase cub cylinders for stock stroke, you will need new ones if you go 4-mil, 7-mil, etc.

 

So of my 6 questions, which ones are fact and which ones are myth?

ok 1. is correct, your prot timings will not match,how ever you can have your jugs ported to accomedate the stroker

 

2. not true... a cub is a drag setup, if your racing mx or tight trails then its a polar opposite of what your looking for so it wouldnt be better...

 

3. true there is a setupup for each stroke...

 

4. not true a 4mil 7 mil 10mil are all as reliable motor as long as you build them that way and dont cut corners.. spend the money to put quality products to insure your build is reliable.

 

5. true 4mil does not require case mods... 7mil and more requires the cases to be trenched

 

6. ummm not true but is smarter... you can always port your jugs to have the timings changed but a cub setup for a 4mil 7 mil what ever the case is ,, can be used right out of the box... most have the castings cleaned up but they are ready to go when u get them...

[FireHead]

ok 1. is correct, your prot timings will not match,how ever you can have your jugs ported to accomedate the stroker

 

2. not true... a cub is a drag setup, if your racing mx or tight trails then its a polar opposite of what your looking for so it wouldnt be better...

 

3. true there is a setupup for each stroke...

 

4. not true a 4mil 7 mil 10mil are all as reliable motor as long as you build them that way and dont cut corners.. spend the money to put quality products to insure your build is reliable.

 

5. true 4mil does not require case mods... 7mil and more requires the cases to be trenched

 

6. ummm not true but is smarter... you can always port your jugs to have the timings changed but a cub setup for a 4mil 7 mil what ever the case is ,, can be used right out of the box... most have the castings cleaned up but they are ready to go when u get them...

 

I agree............ :thumbsup:

[dajogejr]

Very nice explanation, Greg....

 

I would add:

Unless you get a steal on parts for a 7, build a 10 mil.

It's the same price....same work.

 

I'd also add be prepared to do the WHOLE bike. It is not a drop in motor.

I'm talking longer swingarm, dunable override and lockup clutch.

I only had a 4 mil on gas last year, my tranny and clutch were perfect and adjusted properly and it still shifted like shit.

 

If I would've done my homework, I would've went straight to 10 mil...but, lesson learned...DOLLARS spent.

 

I am in the same boat as you. I picked up a 400EX for trails, poking around...and when my cub blows up...LOL.

In my opinion a 400EX is the perfect trail bike....reliable all day long, and fun to ride.

I'm not taking ANYTHING away from a 450. I ride with a Ton of them...but since 400's are now more forgotten due to the 450's....you can get a steal on one for the price.

If money wasn't an issue, I would pick up a 450 and a big old 4X4....but, I could only buy one, and spending thousands on a second bike wasn't an option.

 

I think you're crossed up with longer stroke vs. longer rod (the 7 mil more reliable....)

A longer stroke gives you more HP, torque...etc.

 

A longer rod lessens the rod angle, which in effect lessens the stress of the rod trying to push the pistons through the walls of the cylinder. A longer rod adds reliability, no more power or torque...the longer stroke adds the power.

 

You can always run cut domes and run the pistons up into the head further...or "eek" use a spacer plate. But, if you can...it's always best to get the casting for the stroke you're intending to run...

 

Hope this helps...

[FireHead]

A longer rod lessens the rod angle, which in effect lessens the stress of the rod trying to push the pistons through the walls of the cylinder. A longer rod adds reliability, no more power or torque...the longer stroke adds the power.

 

A longer rod will also give you a longer compression moment as the piston moves through TDC. This can be desireable or not depending on what fuel you are using, :thumbsup:

[SoCalinIt]

I'd also add be prepared to do the WHOLE bike. It is not a drop in motor.

I'm talking longer swingarm, dunable override and lockup clutch.

I only had a 4 mil on gas last year, my tranny and clutch were perfect and adjusted properly and it still shifted like shit.

 

I agree totally Dave! You know how much chit I did to my bike...

[Bansh-eman]

Very nice explanation, Greg....

 

what you mean im not going to get slammed by you??? humm maybe its cause im speaking of a topic im knowlegable about...oj you might want to look into this...

 

sorry i couldnt resist :thumbsup: let not bring it to this post hehehe

[FireHead]

what you mean im not going to get slammed by you??? humm maybe its cause im speaking of a topic im knowlegable about...oj you might want to look into this...

 

sorry i couldnt resist :thumbsup: let not bring it to this post hehehe

 

I take it that you think ojcool is going to be out from under his "Guess my Dyno" thread sometime soon, or atleast enough to get time to read another thread................... :biggrin:

[dajogejr]

I take it that you think ojcool is going to be out from under his "Guess my Dyno" thread sometime soon, or atleast enough to get time to read another thread................... :biggrin:

 

I think he ran out of Crayola Crayons, back to the dollar store for mommy and daddy...

 

That dickbag will be posting again soon...some stupid question like here's what I found out from dyno tuning two different mustangs.

 

:shoothead:

[FireHead]

I think he ran out of Crayola Crayons, back to the dollar store for mommy and daddy...

 

That dickbag will be posting again soon...some stupid question like here's what I found out from dyno tuning two different mustangs.

 

:shoothead:

 

Have you looked at the "Guess My Dyno" thread lately? He's got a video.

[Animalman294]

Good explainations all...................... :thumbsup:

[yamaha04]

does a stock stroke banshee rev faster then say a 7mil. because of the distance it has to travel being less iv always wonderd this

[dajogejr]

does a stock stroke banshee rev faster then say a 7mil. because of the distance it has to travel being less iv always wonderd this

 

Typically yes....

However, there are more factors involved. Intake, carb size, port work/layout/durations, and probably the most important one, exhaust pipe type.

[yamaha04]

Typically yes....

However, there are more factors involved. Intake, carb size, port work/layout/durations, and probably the most important one, exhaust pipe type.

 

 

hmmm so me and my buddy are getting the same setp from FAST other then im not getting a 4mil and he is. hes running CPI's and i will have T5's so im guessing i will beat him out of the whole and he will gain on me up top because of the longer stroke?

[cam2]

I'd also add be prepared to do the WHOLE bike. It is not a drop in motor.

I'm talking longer swingarm, dunable override and lockup clutch.

I only had a 4 mil on gas last year, my tranny and clutch were perfect and adjusted properly and it still shifted like shit.

 

If I would've done my homework, I would've went straight to 10 mil...but, lesson learned...DOLLARS spent.

i agree as well. i like my 421 cub (+4mm), but to me it's a tweener motor. it's no good for the trails, so in order to get it set up properly in order to enjoy all of the power, you'll need an overide tranny and lock up clutch, like dave said. in my mind if you're going to need the OR and LC, along with the other goodies you might as well spend the extra for the +10mil and be done with it. i know that the +4mils run strong, but if you have the rest of the bike set up properly you might as well get the larger engine IMHO. i knew this when i put my +4mil together but because i don't race it i wasn't concerned with it at the time. but, i sometimes think to myself that i should have went big, or stayed with a set of stock ported jugs for the +4mil crank in order to have a bike that was more ridable overall. which wouldn't require a OR or LC. because i don't race and i don't have a lot open space to let the cub eat i'm concidering selling my cub top end and getting a set of ported stock jugs in order enjoy the bike again. i would like to have another bike, but that's out of the question for now. IMHO, go big if you can.