Topic: Valve adjustments on a CB400f

[JonasP]

Hi guys!

I've assambled my engine after a rebuild. The chain and sprocket in the engine is alligned with TDC of the pistons on 1 and 4 and I installed the camshaft with the lopes down (45 degrees) on piston 1.

I've been reading what feels like all posts and comments on valve adjustment, but i can't seem to get it right. From what I have gathered, you can check for compression stroke by feeling the  rocker arms. They should be i tiny bit loose (give a little noise). If they are tight I should rotate the engine to the next 1.4 T. Mine must have been adjustes completely wrong, because mine was loose either way.

On compression stroke, the valve should be closed, right? Which mean lobes should be facing down 45 degrees to not make the rockerarm push down and open the valve? So as most of the comments stated, i could rotate the engine, watch the intake valve and see it go down (open) and come back up (close) and then watch for the 1.4T mark.

My manual says I now should be able to set IN1 EX1 IN2 and EX3 and then rotate engine and do the rest. But the IN2 and EX3 was tight and couldnt be adjusted As a last a resort I loosened alle the valve adjuster screws. Rotated the engine and looked at which TDC 1.4T I had loose rockerarms on IN1 EX1 IN2 and EX3 at the same time. I then adjusted all the valves, rotated the engine and adjustes the rest.

The thing thats confuses me now, is that IN1 and EX1 now are even more loose on the second rotation timing mark (not where i adjusted the valves) than on the "first" timing mark where i adjusted them. This teels me that I actually adjustes the valves on 1 with the lobes up and when I rotate the engine the lobes are then down, right? Wouldn't i have closed valves or at least really close to closed valves at both TDC 1.4 then? Im not quite sure if this is right. But when i try to set the valve clearence at the other 1.4T (when the lobes are down?) I can't adjust IN2 and EX3 as the manual states - even with the screws alle the way out on all cylinders.

Hope this make sense ans you can clear this up for me. Thanks!

//Jonas

[jonda500]

I hate the X's & O's method in the manual - this is my preferred valve adjustment method.

First take out the sparkplugs so the engine will be safe to rotate using the 23mm nut under the points cover(-do not use this nut to rotate the engine with the plugs in as it is actually only as strong as the 10mm (M6) bolt holding it on!).

 If the adjusters have been backed out temporarily tighten the adjusters on the two #4 cylinder valves to eliminate all play.

Rotate the engine until you see the T / F 1.4 marking through the inspection hole in the points plate, now whilst closely watching #4's tappets (look into the two closest adjusting holes) rock the engine back and forth either side of the 1.4 timing mark (~10 o'clock to 2 o'clock) - If you are not seeing the tappets move rotate the engine one full turn back to where you see the 1.4 again and repeat - what you need to see is the exhaust tappet coming up just as the inlet tappet is going down for #4 cylinder- this indicates that #1 cylinder is on compression stroke so line up the T mark and you can go ahead and adjust #1's tappets.

Rotate the engine clockwise half a turn only till the T 2.3 timing mark lines up and adjust #2's tappets.

Rotate the engine clockwise half a turn only till the T 1.4 timing mark lines up and adjust #4's tappets.

Rotate the engine clockwise half a turn only till the T 2.3 timing mark lines up and adjust #3's tappets.

John

[Keith]

Agree! Less confusing, probably more accurate.

[JonasP]

Thanks! I'd much rather adjust the valves separately! But is there a specific mark i should tighten the adjusters at, then?

Since its the camshaft and rocker arms that 'decides' which cylinder is on the compression stroke. Its quite important if the lobes are up or down right?

I tried to test this by looking for the 1.4T mark with the most play. But since I could'nt adjust the IN2 and EX3 where IN1 and EX2 had the most play. So now when adjustes the other way around, I have 0,05 mm at the adjusted TTDC and a lot of play at the rotated 1.4T mark.

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[JonasP]

EDIT; a specific mark to tightedln the adjuster before i rotate back ans forth at the 1.4T mark.

Adjust the IN2 qnd EX3 where IN1 and EX1 (not EX2)

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[Bodi]

Don't follow the manual's procedure. Jonda explained the easiest way to not screw this up. You adjust the tappet clearance to spec (0.004" as I recall: a feeler should drag but not be immovable when done, remember the locknut will pull the screw back up a bit when tightened) with the rocker at the cam's base circle... which is definitely the case at TDC on compression stroke.
The firing order is 1-2-4-3, so confirm that 1 is at TDC compression stroke - to find that, turning the engine slowly you will see/feel the #1 rockers moving near TDC (where the 1-4 line on the crank is at the pointer) exhaust stroke, you then turn the engine one more full turn for TDC compression stroke.
Honda's method saves some crank turning and a few minutes for an experienced mechanic, with the stock cam. Jonda's is less confusing and safer in general - and it works with "hot" cams that may not be at the base circle for either valve when at TDC exhaust stroke

[JonasP]

Perfect! Thanks guys. So I tried to look at #4, found the mark where the EX was coming up and IN was going down and then rotated the engine to the next 1.4T mark. I have set all the clearences and now i got no play and #1 after rotating half a turn drom TTDC. It feels right, but ia there a way to check if its done right?

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[Bodi]

Just check for a bit of play on both valves of each cylinder when it's at compression stroke TDC. Turning the crank then, the exhaust valve will open around BDC on the power stroke, close around TDC on the exhaust stroke, the intake valve also opens around TDC exhaust stroke, stays open until around BDC of the intake stroke, then both stay closed through the compression stroke and most of the power stroke. 

[jonda500]

Just to clarify - (with T1.4 mark lined up (#1 & #4 at TDC)) to find out whether #1 is on compression and ready to adjust, rotate back and forth and look for overlap in the rocker movement of #4, OR(harder as it's on the opposite side to the points), look for rocker overlap in #1(which means #4 is on compression) and then rotate the engine 1 full turn to make #1 be on compression and ready to adjust.

Another way is to turn the engine clockwise with a finger stuck in the spark plug hole of the cylinder whose valves you want to adjust, when you feel air pressure with your finger, continue slowly turning until the timing mark lines up for that cylinder (T1.4 for #1 or #4,  T2.3 for #2 or #3) and you're ready to check the valves on that cylinder!
John

   

[Keith]

You can double check your work. Start with cylinder 1 as an example. Ensure clearance on both valves. It's possible the lock nut is not tight because your wrench could hit the edge of the opening, so double check. Now, I assume your intake clearance is 2mm. A 3mm feeler gauge should not go, but a 1.5mm should slide with no resistance. Next, check exhaust side, nut tight, 4mm will not go, but 2mm should have no resistance. (Spec should be 3mm)Do all valves the same way. Done. Always double check your work.

[Chachi]

I just did this for the first time last night on my 750 (with the help of a Honda mechanic friend).

He showed me this method:
"Another way is to turn the engine clockwise with a finger stuck in the spark plug hole of the cylinder whose valves you want to adjust, when you feel air pressure with your finger, continue slowly turning until the timing mark lines up for that cylinder (T1.4 for #1 or #4,  T2.3 for #2 or #3) and you're ready to check the valves on that cylinder!"

We used that as the first check, then felt the rest based on the X's and O's to confirm. Used X and O pattern from shop manual to adjust. Biggest help was him having his 'drop style' 10mm (?) wrench to use on lock nut.

[NobleHops]

Many great tips, thanks to all.

[Bodi]

Just in case someone tries it, note that the 2mm clearance listed above is completely wrong and around 10x too big.
Running the engine with the 8 tappets set to 2mm would sound like an army of dwarves simultaneously bashing at the engine with their pickaxes.

Check the service manual or owners manual for the correct clearance, I don't have the answer just now and random online sources are very unreliable.

Aftermarket cams usually specify non stock tappet clearance btw.

[Keith]

You are correct...should have been 2 thousandths intake and 3 thousandth exhaust. Not mm! My apologies.

[JonasP]

Thanks you guys. This was a huge help. Got them all adjusted correctly and doublechecket. Great tips in this thread! (y)

[Perseo]

The manual for CB350F - available on this site - says .002 INCHES for BOTH intake and exhaust.  In mm, that is .05 for each.

If anyone knows why the posts above seemed to want to say .003 inches for the exhaust of a CB400F, please post.  My understanding is that the CB350F adjustment is correct for the CB400F as well. 

I suspect that many (most) of the SOHC4's have .002 inches intake and .003 inches exhaust, but not the CB350F and CB400F.

[Perseo]

.002 inches intake and same exhaust.

http://manuals.sohc4.net/cb400/technical_reference/TS400.pdf