Stroking your crank (Retards the timing)

[Dust Devil]

Needing to retard back to original setting.....

If they can move the con-rod pin on the crank, Than why don't they re-position the (Key) groove on the (Crankshaft) to re-establish the (BTDC)
For Spark timing, Valve Timing and counter-balancers fulcrum position.

Refer; to Chapter 9-4 Crankshaft/transmission (exploded view)
service manual.

http://files.me.com/bauman43/tl8ntm

and Chapter 5-18 (engine top-end)

The picture show the (Key) slot for the gear positioning on the Crankshaft which needs to be filled-in and ground-smooth and grind a new slot in the proper position using a degree wheel.

And measure a new (TDC) with the piston at the top its Stroke and the degree wheel on crankshaft establishing the new slot location for the (Key).

(See attachment) An example of a degree wheel.

[Duster]

Good question...

I'll have to look at the amount of stroke and think about it when I am less tired.


With what I am thinking now, I would think you would have to have an entire new stroked crank, and timing should be right... same as normal.... yeah I know not optimal at all because it's not right now I'm sure.

I don't think they modify the stock crank though... and a new one should be properly indexed.

Ask Maxpower about it... they have a stroker kit.

Someone here has had a stroker too already I believe.

I haven't looked into it that much though.

[Dust Devil]

Quote: Originally Posted by Duster

Good question...

I'll have to look at the amount of stroke and think about it when I am less tired.


With what I am thinking now, I would think you would have to have an entire new stroked crank, and timing should be right... same as normal.... yeah I know not optimal at all because it's not right now I'm sure.

I don't think they modify the stock crank though... and a new one should be properly indexed.

Ask Maxpower about it... they have a stroker kit.

Someone here has had a stroker too already I believe.

I haven't looked into it that much though.

Will bend rods and break a crankshaft pin. With-out the proper timing advance. That's why many gave upon a stroke kit for the KFX450R.

For example: Hot-Rod +3 you would have to have it welded. Even so?
many complain about slower acceleration.

Car motors spark around 7 degrees (BTDC) at Idle speed....And advance from there,
4 additional degrees more (BTDC) with a +3 stroker. (Not sure of KFX450R Ignition timing specs) to a total of around 11 or 12 degrees before (TDC)
(Which explains for motor damage and poor performance)...
IGNITION TIMING

Not even Falicon crankshafts mention any modification to crankshafts to bring it back to around 7 degrees (BTDC).

Big Bore/ Stroker Kits/ Falicon Crankshaft Components, Inc.

[Dust Devil]

Quote: Originally Posted by Duster

Good question...

I'll have to look at the amount of stroke and think about it when I am less tired.


With what I am thinking now, I would think you would have to have an entire new stroked crank, and timing should be right... same as normal.... yeah I know not optimal at all because it's not right now I'm sure.

I don't think they modify the stock crank though... and a new one should be properly indexed.

Ask Maxpower about it... they have a stroker kit.

Someone here has had a stroker too already I believe.

I haven't looked into it that much though.

...(retards crankshafts pin position in rotation)

Shorter stroke-Faster crank rotation (Advances crankshafts pin position in rotation...)

A "Stroker" engine is one which uses an aftermarket or modified crankshaft, connecting rods, and/or pistons to increase the stroke of the motor, which is the linear distance traveled by the pistons.
"Stroking" an engine increases the displacement. Most stroker engines use kits which contain components much stronger than stock, making the completed engine more durable as well as more powerful.



You have to (Re-Adjust the Speedometer) with larger or smaller tire size???
Because you are increasing or decreasing the circumference or distance traveled...


Greater linear distance travel.....

File:GearBoxRotRotVar.gif - Wikipedia, the free encyclopedia

Larger (outer) distance traveled slower (inner) axle rotation yet the timing spark is set to a fixed stock Bore x stroke 96 x (62.1mm)...+stroke increases the circumference of the rotation with no change to the Crankshaft sensor location or CDI timing) holding the ignition set timing to (62.1mm)...

[Duster]

I believe you have that all wrong... I'm just too tired to explain it to you.


Best I can do now is to say an RPM is an RPM regardless of stroke distance.
TDC is TDC regardless of stroke distance.
Timing is spark timing in relation to TDC.

In my mind, a stroker crank would have to somehow be "INDEXED" to work with the rest of the stock stuff. Otherwise if it did not it would just be a nightmare mess... cam timing and ignition timing... everything.

If it were not somehow indexed to stock everything would be off.

See what I mean?

If ignition timing were retarded because of a stroker crank, the valve timing would be too... and you'd end up with the piston hitting the valves.

[jeffskfx450]

Aftermarket rods(longer or shorter) or pistons do not change the stroke of an engine. I know it seems like it would, but stroke is only determined by the crankshaft. Rod length does not change stroke, the advantage to a longer rod is it increases leverage, think of it as a handle on a cherry picker on the jack, the shorter the handle the more you have to put out to lift something and the longer the handle the less energy you have to put out to lift an object.
Stroker motors do not decrease acceleration. Strokers a good for increased bottom to mid(which it would accelerate quicker) you will probably lose some top end power, Big bores are good for mid to top end power.
I think you are correct though on the timing change, it would change but I'm sure it could be accomadated for, or else they would not make strokers for as many applications as they do. I think the ignition timing would have to be changed(maybe not for sure)
Is a stroker a bad idea, it depends on the riding you do, if you would like some increased torque and more acceleration, and could sacrifice a little top end, then I think it would be a great idea
Just depends on you riding style!!!!!!!!
For reliability I think it would be very reliable, as long as everything was balanced correctly and assembled right. Crank Works would be able to answer your questions on everything, and give you a better idea on things.

[Duster]

My brain is real tired right now... but nah boys... I think all that changes is the total distance the piston travels up/down in one RPM.

I still say your cam chain gear only rotates the same one RPM and your stator hub only turns the same one RPM.

Cam timing would be the same and ignition timing would be the same degrees.

Timing advance would probably be an added benefit to go along with a stroker though to ignite the larger volume air/fuel charge sooner and get a better burn at the right time.



As far as the delivery effects of a stroker kit... well I think that would be dependent upon the individual stock engine geometry, head design and also the timing. Same goes for a big bore kit. This can be easily proven to you in-person... all you have to do is go ride the KTM engines.

It's pretty remarkable how quick revving and responsive their long stroke SOHC engine are... here are some bores x strokes to consider....

KTM 450XC = 89x72

KTM 525XC = 95x72

KTM 450SX = 97x60.8

KTM 505SX = 100x60.8

KFX450R = 96x62.1

TRX400EX = 85x70

[jeffskfx450]

I have never done a stroker engine, so I'm not sure on the timing being different, but I think I remember hearing somewhere that it does change a little(that was on a car engine) As for basing where the power comes in on a stroker, I was just going by what my local dyno shop has told me. I was thinking about getting a hotrods stroker when it came out, but the dyno shop told me it would probably, due to my riding style, be best to go with the big bore instead. They claimed that they have done some strokers in some engines and it hurt the top end power, but gained on the bottom. I beleive they said they did an ltr stroker, and it lost some top end but the guy loved the bottom in gain, because he like to climb dunes. Gave it a lot more torque
Conclusion, I have never installed one, so I would not know, just going on hear say

[Dust Devil]

Quote: Originally Posted by Duster

My brain is real tired right now... but nah boys... I think all that changes is the total distance the piston travels up/down in one RPM.

I still say your cam chain gear only rotates the same one RPM and your stator hub only turns the same one RPM.

Cam timing would be the same and ignition timing would be the same degrees.

Timing advance would probably be an added benefit to go along with a stroker though to ignite the larger volume air/fuel charge sooner and get a better burn at the right time.



As far as the delivery effects of a stroker kit... well I think that would be dependent upon the individual stock engine geometry, head design and also the timing. Same goes for a big bore kit. This can be easily proven to you in-person... all you have to do is go ride the KTM engines.

It's pretty remarkable how quick revving and responsive their long stroke SOHC engine are... here are some bores x strokes to consider....

KTM 450XC = 89x72

KTM 525XC = 95x72

KTM 450SX = 97x60.8

KTM 505SX = 100x60.8

KFX450R = 96x62.1

TRX400EX = 85x70

You move the (pin) .010 +1 out from the center of the shaft increases the Circumference of the pins center of rotation.

Center of crankshaft-to the center of the (con-rod Pin) "timing" Ratio changes... (Like using a .010 or +1 Larger gear...) and the KFX450R has a Fix timing Crankshaft sensor so the timing can't be adjusted (Like the good ol' days)

Any change to the circumference (Center -center) changes the speed Ratio....Slower of faster.
Shorter stroke faster ratio.(Quicker) (- stroke) Less Fuel/air for combustion
longer stroke slower ratio.(Faster) (+ stroke) more Fuel/air for combustion

What happens when you change tooth size on a sprocket....???? Faster or slower results... A change in timing to complete the rotation of the Axle...

Stroke Any Engine - How To - Hot Rod Magazine

[Duster]

On the timing it should be that you just need a little more advance to get a better burn on the now larger air/fuel charge drawn into the larger displacement... a tweaking the most out of it advance....


And yeah, it is no telling how a KFX engine would respond to stroking alone.

I do know though that the big 3 (FuelATV & PC3 & plain Jardine RT5) coupled with a +2 mm bore, 13.5:1 piston, and +5 mm stroke is worth more Torque than the stock KFX has in Horsepower.... 37 ft lbs.... and everything together is worth a 21hp gain... And that's just with a stock head, port/polish + hotcams only.

Flows enough to actually benefit from a +2 mm throttle body bore instead of loosing if that tells you anything.

(no mention at all on an ignition module for either by the way)

I'll let you have a look at the KFX507 and LTR527 curves compared to stock in this clipping.
You can judge for yourself.....


(NOTE: the LTR527 has a LOT more done to it than the KFX)