How do I know were to put the different rocker arms????

[RainCityRider]

I am rebuilding my 78 CB750 and didn't mark the rocker arms when I took them out. So it seems like they aren't hitting right on the cam shaft.

Is the an order for the A & B rocker arms?

There are different numbers on some of them:
3 X A 61
1 X A 82
2 X B 36
1 X B 37
1 X B 68

 

I'm lost?

Also what is the firing order for the engine? Do 1&4 and 2&3 fire at the same time?

[RainCityRider]

"ok, so this is a simple question for any one that has taken the head off the top of the engine........the two outside pistons move at the same time with each other.....the two inside pistons move at the same time opposite the outside......."now"........if you look at your points plate you will see that the points fire at the same time for 1and 4 and opposite for 2 and 3....so you would think the firing order was 1-4 and then 2-3...back and forth like that......."but"........"nope"......... if you really dig deep, take out your plugs to watch the rise and fall of the pistons....remove the valve cover to watch the movement of the valves.....you will see that the firing order is not...."why" because if you watch your point as the engine is turned over slow you will see that the spark plugs fire during the "compression and exhaust" phase........."Why"...........because its just easier in the design of the engine, you have 4 cylinders and only two sets of point!

The Winner is.................................................................Houndog 1 2 4 3

To be honest........I never really thougt about it, just not a big deal......get a cb750 shop manual and you will be fine and yes...your coils are working twice as hard"

found on: http://www.hondachopper.yuku.com/topic/7651

Is the 750sergant right is the firing order 1234? Does that mean both 1&4 fire but only say 1 has gas in it?

Or is it 1-2-4-3 as found here, http://www.salocal.com/sohc/tech/fire4-lcnt.gif

[Bryanj]

(1) Rocker arms will only fit between cam lobe and valve one way round the cast numbers mean nothing

(2) 1 & 4  SPARK together but do not FIRE together as one is on TDC compression (bang) the other on TDC exhaust (blow)

similarly 2 & 3

[SteveD CB500K0]

It is 1-2-4-3

Your posting times and IP indicate that you may be in North America?  You might find some more local help on our sister forum www.sohc4.net - use the same username so that we recognise you.

[Yoshi823]

From what I remember there are some numbers on the rockers,but they are not relevant.But there are two types of rocker arm and will only fit in one place or the other.In the ideal case,for the wear surfaces to be the same,the correct rocker should be mated with the same cam lobe.When I install the rocker shafts and the rockers,I always turn the engine over until the cam lobes for say the inlet 1 and 2 are pointing down, then I slide the shaft through both rockers at the same time...with plenty of fresh oil.I always tension the cam chain when there are no rockers fitted,rather than 15 degrees after 1 & 4  timing mark with #1 on compression.

The markings that are relevant are the cam carrier caps as they are line bored at the factory during manufacturing.

Most 4 cylinder Jap bikes do run with was it commonly termed as a wasted spark system.This is normally recognised as those with only two coils for 4 cylinders.
Any coil has a certain rise time during which energy is transferred from the primary coil,which is that energy stored in the condenser on a standard SOHC 4,into the secondary wiring via an EMF,that being induced energy.The amount of time required for the transfer to fully energise the secondary windings is the rise time.As the output of standard Honda coils is relatively weak ie.about 6000 volts or 6kv,this is why a worthwhile modification is to install uprated Dyna coils.
Cars used to have a single coil together with a distributor system so would not utilise the wasted spark system.
Some more recent Jap fours utilise the 'coil-in-the-cap' system so as to save space in the frame for a bigger airbox.This is where the primary signal,derived from the ECU,is delivered to the coil on the top of the spark plug.
I had Andrews coils fitted to my 750/823 F2 and together with NGK D8EV plugs it made it very worthwhile.

The firing sequence on the Honda fours is the same as for the majority of modern Jap fours...as in 1-2-4-3. The bike that comes to mind that does not fire in this order is the new R1 that has the 'cross-plane' crankshaft.