Early (2005 and older) vs Late (2006+) Crankshafts

[Sea Dood]

With some of the talk about diffs between early and late cranks, I thought I would take a photo to show the difference in pin locations. I learned something new in the process:

The counterbalancer marks are different too!

See the attached photo. The early crank is on the left, late on the right. Both are sitting with #3 cyl at TDC. The early crank pin is at 11 o'clock, the late is at 7 o'clock.

Notice that the CB mark on the late crank is shifted by one tooth counter-clockwise relative to the early one. Does anyone know why this is? I assume that the CB shafts are different to match the marks. The early and late CB shafts have different part numbers as well.....I wonder if they are different weights between early and late, too?

I guess I am going to make sure I matching crank and CB's between early and late just to be safe.

[beerdart]

It is possible that the crank on the right has slipped the gear. The CB mark should be dead 3:00 o'clock with #3 at TDC.

http://www.greenhulk.net/forums/show...hit&highlight=

[Sea Dood]

It is possible that the crank on the right has slipped the gear. The CB mark should be dead 3:00 o'clock with #3 at TDC.

http://www.greenhulk.net/forums/show...hit&highlight=

No; take a close look at the relation of the marks to the bolt holes on the crank gear. It is clearly one tooth earlier on the late crank.

I went back to the shop and did some more checking. You are right that the tooth is at 3 o'clock when #3 is at TDC, for both cranks. But as you can see, the difference between cranks is not two bolt holes; it is two bolt holes PLUS one tooth! This means that if you use the wrong crank in relation to the PTO cover, your static ignition timing will be off by one tooth, or 9 degrees.....note that the 4-tec adjusts dynamic timing using the knock sensor, but if you are using a Rotax Racing ECU without the knock sensor, you could be in trouble.

[beerdart]

Thats odd here is the manual for 05 and 06 both show the mark third tooth from the bolt hole.

[Sea Dood]

Thats odd here is the manual for 05 and 06 both show the mark third tooth from the bolt hole.

I learned long ago never trust the photos or drawings in the manuals!

[beerdart]

I learned long ago never trust the photos or drawings in the manuals!

Very true but with the crank pinned the CB mark should be 90deg to TDC.

[Sea Dood]

Yep; note in my post above, I carefully set the cranks with #3 trued up, and the marks on both are at 90 deg to TDC. But the bolt holes are not even between the two.

To sum up, by just removing the pin and moving the encoder wheel two bolt holes, you are not where you should be. It still will be 9 degrees off...

[R88ory RXP]

I can't see that a motor would start/run if the timing was that far out, 9 degrees is a lot, Idle would be very bad, and revs would be well down assuming it retarded it by 9, if it advanced it that far then, yes you could get deto problems.

[Sea Dood]

If you put a 2006+ crank in an earlier engine by pulling the pin and moving the encoder CW two flywheel bolts, the ignition timing ends up being retarded 9 degrees. Retarding 9 degrees at idle would only affect RPM. But the 4-TEC system adjusts airflow through the idle bypass valve to keep RPM at 1800. At high RPM, the ignition system is dynamic; it pushes the timing until it finds knock and backs it off a few degrees. It just might not be able to push it enough to maximize power in certain ranges. And mid-range probably does suffer.

Unless the 2007 crank I have was manufactured wrong! Anyone else have a late crank they can inspect and report back?

[R88ory RXP]

If you put a 2006+ crank in an earlier engine by pulling the pin and moving the encoder CCW two flywheel bolts, the ignition timing ends up being retarded 9 degrees. Retarding 9 degrees at idle would only affect RPM. But the 4-TEC system adjusts airflow through the idle bypass valve to keep RPM at 1800. At high RPM, the ignition system is dynamic; it pushes the timing until it finds knock and backs it off a few degrees. It just might not be able to push it enough to maximize power in certain ranges. And mid-range probably does suffer.

Unless the 2007 crank I have was manufactured wrong! Anyone else have a late crank they can inspect and report back?

Im intrigued coz I have a 06 crank in my 04 engine, It shouldnt effect me too much coz I have a stand alone so can set my timing where ever I want but I maybe able to help tell if it does effect anything.

R88