Author Topic: Frustrated with setting valves - CB750  (Read 3153 times)

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Offline Tugboat

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Frustrated with setting valves - CB750
« on: September 08, 2012, 04:18:33 PM »
OK, so maybe (probably) I'm just dense, but.....

With the tappet covers off, I turn the crankshaft and watch the #1 valve open (go down) and close (come back up). Then I advance the crank until the 1-4 lines line up, right?




I can then set the #1 intake & exhaust valves.. but then supposedly you're supposed to be able to check #2 intake, #3 exhaust, right?

Here's the deal: it seems like #2 intake valve is open at this position.. note that #2 intake adjuster nut is below the threads while #1 intake adjuster nut is above that.



Am I missing something?
« Last Edit: September 10, 2012, 09:03:15 AM by Tugboat »
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Offline Tugboat

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Re: Frustrated with setting valves - CB750
« Reply #1 on: September 08, 2012, 04:24:16 PM »
DUH!!! Just rechecked the manual and was reading it wrong.. #1 In & Ex, #2 Ex, #3 IN

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Offline CrankyOldGuy

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Re: Frustrated with setting valves - CB750
« Reply #2 on: September 08, 2012, 04:36:28 PM »
The valve tappets should be adjusted using the "T" mark line, which is left of the "F" mark line.  The parallel double lines "II" are the advance timing marks.

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Offline 70CB750

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Re: Frustrated with setting valves - CB750
« Reply #3 on: September 08, 2012, 04:45:08 PM »
DUH!!! Just rechecked the manual and was reading it wrong.. #1 In & Ex, #2 Ex, #3 IN

Happened to me few times too.  The table in manual makes me think the top line is exhaust and the bottom line is intake - i.e. I take it more as a map of the engine and not as a table.
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Offline david 750F

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Re: Frustrated with setting valves - CB750
« Reply #4 on: September 08, 2012, 04:51:43 PM »
+1 with CrankyOldGuy..
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Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #5 on: September 08, 2012, 05:21:15 PM »
Hi Tug.... when I stopped by earlier, I presumed you had the crank turned to the 'T' mark 1-4   ::).
Need to be @ T for valve lash adj.
See if I can clear it up..... Turn motor to T 1-4 mark then either no. 1 or no. 4 piston will be at the top and on it's compression stroke. If the no.1 valves are loose and can be moved slightly with your fingers then that is the cyl. to adjust. If no.1 valves are tight and no.4 are loose, then obviously adjust no.4.
Then rotate 360 deg to T mark 1-4 again and do the other cyl. ( 1 or 4 ).
Repeat process for 2-3 using the 2-3 'T' mark .. :)
« Last Edit: September 08, 2012, 05:23:01 PM by Spanner 1 »

Offline lucky

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Re: Frustrated with setting valves - CB750
« Reply #6 on: September 08, 2012, 06:34:42 PM »
Forget all that stuff.

Turn the crank to 1-4 mark See if one or 4 rocker arms are both moveable.
Adjust those on that cylinder.

Turn the crank one rotation do the other cylinder.
Same for 2 and 3.

Basically when a cylinder has both cam lobes facing downwards on 45º angles ,THAT cylinder is on the compression stroke and you can adjust its valves.

IF you have small LED flash light you can peek through the valve cap and see the cam lobes.

Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #7 on: September 08, 2012, 06:45:06 PM »
Don't forget, reply #5 and reply #6 are exactly the same thing  ::)

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Re: Frustrated with setting valves - CB750
« Reply #8 on: September 08, 2012, 08:25:35 PM »
Forget all that stuff.

Turn the crank to 1-4 mark See if one or 4 rocker arms are both moveable.
Adjust those on that cylinder.

Turn the crank one rotation do the other cylinder.
Same for 2 and 3.

Basically when a cylinder has both cam lobes facing downwards on 45º angles ,THAT cylinder is on the compression stroke and you can adjust its valves.

IF you have small LED flash light you can peek through the valve cap and see the cam lobes.
Lucky that sounds like what Spanner said. So which part do we forget? I don't understand
Ken

Offline lucky

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Re: Frustrated with setting valves - CB750
« Reply #9 on: September 08, 2012, 09:44:56 PM »
Forget all that stuff.

Turn the crank to 1-4 mark See if one or 4 rocker arms are both moveable.
Adjust those on that cylinder.

Turn the crank one rotation do the other cylinder.
Same for 2 and 3.

Basically when a cylinder has both cam lobes facing downwards on 45º angles ,THAT cylinder is on the compression stroke and you can adjust its valves.

IF you have small LED flash light you can peek through the valve cap and see the cam lobes.
Lucky that sounds like what Spanner said. So which part do we forget? I don't understand
Ken

Never mind I was just in a hurry and did not read everyone else's answer.
I am sure the OP will figure it out.
I mean't that instead of trying to use the method in the book about setting the valves, to just set them all on the compression stroke. Otherwise forget the books instructions in this case.
« Last Edit: September 08, 2012, 09:50:03 PM by lucky »

Offline shinyribs

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Re: Frustrated with setting valves - CB750
« Reply #10 on: September 08, 2012, 11:16:18 PM »
Seems overly complicated to me. Just watch whatever valve you want to adjust next,turn the crank until it closes,then turn the crank a smidge more to be sure-adjust-rinse and repeat.

A simple way for simple minds such as I.
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Offline Nymotorcyclerepair

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Re: Frustrated with setting valves - CB750
« Reply #11 on: September 09, 2012, 07:17:51 AM »
Pull first plug out. Put finger over hole turn motor until u feel pressure this is combustion stroke 1piston top dead center. Line your marks,up on crank to "t" 1-4. Your first cylinder should be tdc and rocker Arms on intake and exhaust should be free.as well as 2intake and 3 exhaust. Set your clearance, rotate 360 back to t" 1.4 piston 4 should be tdc and valves for fouth cylinder should be free as well as 2exhaust and 3intake. Set cleaancez and yur done.

Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #12 on: September 09, 2012, 10:14:49 AM »
Reply #5 = reply #6 = reply #11..... just sayin'  ;D

Offline 754

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Re: Frustrated with setting valves - CB750
« Reply #13 on: September 09, 2012, 10:33:58 AM »
 Pulling plug is a waste of time, just wiggle the rockers..

 If setting valves is a problem, dont tackle carbs, forks, swingarm, and dont even think of removing parts off the engine.. let alone going inside... Ok well maybe pulling 750 sprocket cover would be OK..
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Offline Lamp

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Re: Frustrated with setting valves - CB750
« Reply #14 on: September 09, 2012, 12:24:15 PM »
I haven't read the thread but your a little off on your timing mark. Get the timing mark lined up with the . Between the 1 and 4 (1 . 4) then see if number 1 it 4 valves are loose and adjust them. Then roll the engine over 1 time which will turn the cam 1/2 turn and adjust the rest. There's only 1/1000 of an inch talorance so if you're off even a little you'll never get the bike started.
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Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #15 on: September 09, 2012, 12:40:58 PM »
Sorry Mr. Lamp :o but that's plain wrong !!.... there is only one correct mark to adjust your valve lash and that is exactly @ the 'T' mark ( Top Dead Center ) for either 1-4 or 2-3 AND the motor turned only in a clockwise direction to arrive at the mark ( to ensure cam chain slack is zero ).. :)

Offline lucky

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Re: Frustrated with setting valves - CB750
« Reply #16 on: September 09, 2012, 12:44:55 PM »
Pulling plug is a waste of time, just wiggle the rockers..

 If setting valves is a problem, dont tackle carbs, forks, swingarm, and dont even think of removing parts off the engine.. let alone going inside... Ok well maybe pulling 750 sprocket cover would be OK..

I agree, just wiggle the rockers.

Offline shinyribs

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Re: Frustrated with setting valves - CB750
« Reply #17 on: September 09, 2012, 01:54:00 PM »
Yep,cant go wrong like that. Absolutely the simplest way possible. Its not a fluc capacitor,just a simple enginesickle   ;)
The darn fool didn't know it couldn't be done...so he went ahead and did it anyway.

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Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #18 on: September 09, 2012, 05:04:52 PM »
Ya can wiggle away guys, but you still need a reference point to adjust the lash at, which happens to be the 'T' mark.... what if your valves are set tight and don't wiggle?? Just keep turning the crank/cam until they loosen up and ya can wiggle 'em ?, is that what ya do?..... ::) ::)

Offline 754

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Re: Frustrated with setting valves - CB750
« Reply #19 on: September 09, 2012, 09:38:04 PM »
 Re  #11, I did mean at the T mark.
Myself I dont think a few degrees off should matter, any cam I put a dial indicator to, has a lot of degrees of base circle..which is what you are at when setting valves..
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Offline shinyribs

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Re: Frustrated with setting valves - CB750
« Reply #20 on: September 09, 2012, 09:50:06 PM »
Ya can wiggle away guys, but you still need a reference point to adjust the lash at, which happens to be the 'T' mark.... what if your valves are set tight and don't wiggle?? Just keep turning the crank/cam until they loosen up and ya can wiggle 'em ?, is that what ya do?..... ::) ::)

Wiggling is just a simplified way of putting it. Rotate the crank until a valve closes. Any valve you  chose to adjust at that particular time. You should able to tell when it closes as it rises to a point furthest away from the head. 99.99% of the time it'll wiggle. A closed valve is a GREAT ''reference point'' to indicate when a valve is closed. Nearly fool proof!

Of course,if you have plenty of time on your hands and enjoy laying beside the bike to hunt for the timing mark,thats a fine way to do it ,too. My old Martek ignition makes it nearly impossible to see that mark,and I've been adjusting valves this way for years on more than just bikes. A closed valve is always a closed valve. Regardless of stretched timing chains,mis-indexed cams...etc...a closed valve never lies.

Never said it was the only way,just a simpler way.
The darn fool didn't know it couldn't be done...so he went ahead and did it anyway.

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Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #21 on: September 09, 2012, 10:30:54 PM »
A closed valve is GREAT.... but I'll take Honda's clearances @ TDC any day over any other quickie method.... what should the valve lash be at your 'whatever' point on the cam ??

Offline Spanner 1

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Re: Frustrated with setting valves - CB750
« Reply #22 on: September 09, 2012, 10:36:33 PM »
Do you fcuk with your timing 'by ear' too?
Geez, I for one don't want anything to do with your bike.... g'luck  :D

Offline 754

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Re: Frustrated with setting valves - CB750
« Reply #23 on: September 09, 2012, 11:30:28 PM »
 I used to static time by eye, no light..worked well.. Dont think my eyes are as good now..
My brother calls that using the "EYEcrometer". He can set car timing quite well by ear..
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My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

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Lost quite a few CB 750's along the way
69 z50
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Offline ChuckG750f1

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Re: Frustrated with setting valves - CB750
« Reply #24 on: September 10, 2012, 09:02:27 AM »
Well I've taken my sprocket cover off.  Is there a video I can watch to help me get it back on?  ;)
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