NC24 camshaft installation.

[Old Painless]

I just want to check the camshaft arrangement before i start putting things back together again finally over the next few days.

The NC30 manual gives the following information.

A: Cylinder 4 @ TDC compression stroke - fit front camshaft

turn crank 630 degrees

B: Cylinder 1 @ TDC compression stroke - fit rear camshaft

Where it says fit front camshaft i fitted both cams in the front head, where it says fit rear camshaft i fitted both cams in the rear head. Is this correct or should i have fitted the front cam in the front head and back head @ A and the rear cam in the front head and back head @ B ?

I have a slight tapping noise which i presume is valve clearances rather than valves hitting pistons but i want to be safe.

I followed the instructions to the letter but self-doubt has crept in.

[CMSMJ1]

Right to be doubtful I think - the NC24 does not have the same timing as the 30

The crank throws are different



I would be wary of the Haynes book of lies for this...

[Old Painless]

Well that confused the hell out of me. lol

I assumed the NC30 were the same setup as the NC24 as the marks on the timing indicator and cam ends lined up properly on my engine as if they were correct.

[Neosophist]

Well that confused the hell out of me. lol

I assumed the NC30 were the same setup as the NC24 as the marks on the timing indicator and cam ends lined up properly on my engine as if they were correct.

There totally different.

The NC24 has a 180 degree firing order and the NC30 has a 360 firing order.

Thats why the cams don't line up the same way that they do in the 'valve clearnace guide' on here as it was written for an NC30.

All the timing marks are there to line it up if you know general engine principles chuck the haynes book away, hardly anything in there is relevant to an NC24 apart from the specs on the last page.. and even some of those are wrong.

If your still having trouble you'll need to follow one of the VFR750 guides on installing cam-shafts as they fire the same order as the NC24. You'll also find one in English too :)

Unlike the NC24 service manual thats in Japanese

[Old Painless]

The VFR 750 manual uses marks on the cam gear themselves to align everything for timing, these align with the top of the cylinder head much the same as any other 4T bike would, the NC24 cam gears do not have marks, the end of each cam is marked with a line and a punched dot.

With a firing order 1,4,3,2

Mark 1 is cylinder 1 @ TDC
Mark 2 is cylinder 4 @ TDC
Mark 3 is cylinder 3 @ TDC
Mark 4 is cylinder 2 @ TDC

Is this correct ? I will do some googling in the meantime concerning firing orders, always more to learn.

[Old Painless]

Found this:

It's because, being a 90 degree vee with a 180 degree crankshaft, the firing intervals are 180/270/180/90 (as opposed to the 180 degrees for an inline four).

No. 1 fires at 0º
No. 2 fires at 0º + 180º = 180º
No. 3 fires at 180º + 270º = 450º
No. 4 fires at 450º + 180º = 630º
No. 1 fires again at 630º + 90º = 720º

I think this carries an error in that it lists the firing order as 1,2,3,4 rather than how it should be, out of numerical sequence.

and amusingly, this:

BANG space BANG space space BANG space BANG BANG space BANG space space BANG space BANG

[Neosophist]

Found this:

It's because, being a 90 degree vee with a 180 degree crankshaft, the firing intervals are 180/270/180/90 (as opposed to the 180 degrees for an inline four).

No. 1 fires at 0º
No. 2 fires at 0º + 180º = 180º
No. 3 fires at 180º + 270º = 450º
No. 4 fires at 450º + 180º = 630º
No. 1 fires again at 630º + 90º = 720º

I think this carries an error in that it lists the firing order as 1,2,3,4 rather than how it should be, out of numerical sequence.

and amusingly, this:

BANG space BANG space space BANG space BANG BANG space BANG space space BANG space BANG

Look at that picture Mark posted, all of the information is in there...Including the firing order and @ how many degrees it fires, compared to the NC30 crank.

1,4,3,2 (NC30)

1,3,2,4 (NC24)

NC24:

Cylinder 1 Fires [0 deg]
Space [90 deg]
Cylinder 3 Fires [180 deg]
Space [270 deg]
Space [0 deg]
Cylinder 2 Fires [90 deg]
Space [180 deg]


And so on and so on :)

[Old Painless]

According to the VFR750F manual, you set #1 to TDC, install the rear head camshafts with the lines on the cam ends lined up with the lines on the cam guides then spin the engine 450 degrees and do the same with the front heads.

WTF does 450 degrees come from ? The uneven firing order on these engines wrecks my head.

[Neosophist]

According to the VFR750F manual, you set #1 to TDC, install the rear head camshafts with the lines on the cam ends lined up with the lines on the cam guides then spin the engine 450 degrees and do the same with the front heads.

WTF does 450 degrees come from ? The uneven firing order on these engines wrecks my head.

270 degrees + 180 degrees :)

Look at the picture Mark posted at the top of the thread.. on the right-hand column it has the NC24 column.

It shows you what cylinders are firing at what degrees. :)

If your still having trouble I could take you some pictures of the cam positions relative to crank position :)

[Old Painless]

I now completely understand the firing order and how to get the crank in the right place to put the front cams on, its just which cylinder should be at TDC for it to go on properly. I've put the rear cams on with #1 at TDC and the front cams on with #2 at TDC as per the above VFR750 manual now and it sounds okay, better than before anyway.