1st Gen Timing Info

[oldfaithful]

Hey Guys,

 

This is just a learning exercise today.

 

I've been searching for specific info on the timing of the 1st Gen, particulary the 84 since that's what I've got. If I understand correctly, our V4 is an odd fire engine, meaning that the cylinders are not evenly spaced 180 deg apart like the typical inline 4. However, when looking at the pickup coils on the inside of the left cover (see the pic I found and re-attached) it appears that not only are the banks separated by a prescribed angle, but each cylinder within the bank appears to also be separted by a smaller angle. My search leads me to a 70 deg angle between banks, but what is the separation angle between cylinders on each bank? Why would the mfg have chosen that timing, and is there some benefit that escapes me? Thanks all!

[oldfaithful]

Sorry, I forgot the pic.

[MiCarl]

Here is your firing information (taken from MKII book, but should be the same for MKI. I believe you'll find it at about page 150 in the service manual).

 

1 - 0 deg.

3 - 180 deg.

2 - 430 deg.

4 - 610 deg.

 

The whole reason to rotate the 2 & 4 cylinders away from the 1 & 3 cylinders is to get a narrower engine. I suspect 70 degrees is the minimum angle they could use and get the package they needed.

 

In other words, it's a compromise between acceptable smoothness and the packaging requirements to get the engine in the motorcycle.

 

The angles between the cylinders in each bank is 0. The angles you see in the pick up coils are to package the coils. You'll notice the inboard/outboard offset on the pick ups. There are two protrusions on the flywheel. One triggers the inboard pick ups and the other the outboard pick ups.

[dingy]

Also, there is a balance shaft in front of the crankshaft that smooths the motor out.

 

Left shaft in attached picture.

 

Gary

[icebrrg3rd]

...My search leads me to a 70 deg angle between banks, but what is the separation angle between cylinders on each bank? Why would the mfg have chosen that timing, and is there some benefit that escapes me? Thanks all!

 

There is only the 70° "V" between the front and back banks, the banks within themselves have no separation between them. Not sure how/why those pick-ups are like that in your pic. Here's my pic of the cylinders, you can see they are in line and not at an angle to each other.

 

 

-Andrew

 

edit - I see MiCarl explained the offset of the coil pick-ups, I missed that...

[dingy]

FYI.

 

The front and rear bank are offset by the width of a connecting rod, from right to left, about an inch. This is due to the pistons on each side share a common journal on the crank.

 

Gary

[oldfaithful]

Thank you. I just couldn't find the specifics.

 

Now, as I try to wrap my mind around this, lets see if I've got it right. The firing order is 1-3-2-4 but the order in which pistons hit TDC is 1-4-3-2, and crank rotation is clockwise when viewed from the left. In a graph of position vs angle of rotation (ranging from 0 to 720 deg), #1 would fire at 0 deg, #3 at 180 deg, #2 at 290 deg and #4 at 470.

 

Now, thinking about the pickups in the previous pic. Rotation should be as attached and the TCI must trigger #1 & #2 on the voltage rise of the induced spike, while #3 & #4 must trigger on the voltage drop of the induced voltage. Is that right?

 

Please let me know if I've gone astray, and thanks!

[dingy]

Attached is a graph from the service manual showing timing & combustion sequencing.

 

Gary

[MiCarl]

You've gone astray.

 

Crankshaft turns counter clockwise when viewed from the left.

 

TDC of each compression stroke is the angles I gave you and Dingy posted the chart of.

 

What is it exactly you're trying to figure out? The only reason I see for knowing these angles is in checking the valve lash, and it doesn't seem that's what you're trying to do.

[oldfaithful]

Is it just me or does that section of the manual say the timing sequence is 1-3-4-2, while the chart below it shows 1-3-2-4?

[dingy]

Is it just me or does that section of the manual say the timing sequence is 1-3-4-2, while the chart below it shows 1-3-2-4?

 

This is not the only error by far in the manual. One I hadn't noticed before though.

 

Gary

[oldfaithful]

As to what im up to...nothing in particular. The bike really doesnt need anything serious at the moment. Shes running fine. Im a design engineer, i guess i just like to know how things work. And i really dont want to tear it apart to examine the internals.