Should Cam Bolts First Be Torque To Specs, Before Trying To Get Accurate Valve Shim Clearance Readin

Hi, need some good advice!

If the above subject heading is true, what are the torque specs for all the cam cap bearings, before trying to check accurate valve clearances for proper shim sizes?
Next; Valve Shim Replacements:
If the valve shim replacement chart shows you need a 2.75mm shim on one valve, and you only have a 2.70 and a 2.80, would it be better to use the smaller thickness size of 2.70, since the valves clearances have a tendency to tighten up, rather than loosen up?
Also meaning, if I understand it correctly, a little extra clearance will kept from getting burt valves, as the only cooing they get is from the valve seats.
If true, does that happen more so on the exhaust side, do to the hot exhaust gases that constantly flow around these valves?
However, is this also becoming a catch22 in the sense that:
If the valves don't open far enough, then they won't take in enough fuel on the intake side, nor exhaust enough fuel on the exhaust side.
Which may effect the restarting of the engine after a hot ride on a hot day?

OK, bottom line:
Considering all this, how crucial is a .05mm difference in replacing shim sizes?
Thanks a lot for any knowledgeable and experienced advise on these subjects.
As I think understanding the reason why, is just as important.

 

?, it's in the book
if it says 275 then use a 275, if it's right, it's right. if it's not right, it's wrong.

see above

 

I can't speak to torque specs, although I know they are listed in the manuals. However, I will tell you what Dave (Hogfiddles) told me regarding shims. He stated (more than once - I can be a little thick sometimes) that in spec is in spec and out of spec is out of spec. Therefore, if it were me, as long as they are within the listed tolerance, your good. If not, go ahead and swap it with one that will bring it within spec.

 

one would hope that the cam bolts were in spec to start with if you are going to disturb the bolts you should remove them and do a plasti guage clearance check on the cam shaft.
quite a can of worms to open up just to do a shim check. also would hate to snap one.
torquing the bolts is not mentioned in the procedure for checking valves, so by omission it is not needed unless you have a reason to belive that the cap bolts are not properly torqued.

Yamahas spec for clearances for the valves is just what it states
intake .11 to .15 mm
exhaust .16 to.20 mm

what you adjust them to depends on your thoughts of the spec.
Yamaha states on initial check to do it at 3000 miles (or 7 months) then 5ooo miles (or 12 months) after that.
largest gap less valve opens
minimal gap more the valve opens.

you should look into BMW valve shims example 2.625 as opposed to Yamaha 2.60 and 2.65 shims gives you finer control of the gap and a closer tolerance to stated numbers.

running your valves tight would also require you to check them more often.

the xj 550 motor has a seca and maxim version of cams with the seca cam having more lift of 1mm. this gives the impression that you could run the maxim tight and not bend your valves.

but bottom line is in spec is in spec.
you could buy a bunch of shims and hand pick them, measure them to find shims closest to stated size but that gets costly

edit.
I wondered a little from your question .
if you need a 2.75 a 270 or 280 would still put you out of spec
280 would be tight 270 would be loose

is your question because you do not have the correct shim?
we do have a shim pool going on here

 

You're thinking too hard. Unless the cams were removed, and reinstalled without torquing the cap bolts to spec, there is no reason to re-check the cap bolts. In order to re-check the torque values you would have to remove the cam cap bolts entirely, clean them, measure them for stretch, re-oil them, and then re-torque them to spec. That procedure is unnecessary.

 

your other thread explains the problem with tight valves


HARD TO RESTART AFTER RIDE, UNTIL IT COOLS DOWN.

 

One bike, one thread.
(I am one with the force. The force is with me.)

One bike, one thread.
(I am one with the force. The force is with me.)

One bike, one thread.
(I am one with the force. The force is with me.)

One bike, one thread.
(I am one with the force. The force is with me.)

 

THANKS TO ALL for the replies and the reasons why!

And thanks for the offer on the shim pool.

Must be my lucky day, as the shim that appeared to be marked 270,
(as the marking was partially unreadable), was actually a 275 when miked with a dial caliper with a mm scale.

So funny how some shims are harder to read than others.
Being that all shim numbers are face down in the buckets any ways.

Ok, all's well that ends well.
Enjoy the ride!

 

keep the numbers down that side is supposed to be down if they were up the cam lobes would wear the ink off

write the shim numbers down in a notebook and you can use a sharpie to mark the numbers on the cam shaft caps

 

FOR SURE, every tip, idea and bit of info is always helpful.
Especially from the ones that can truly state from past experience;
Been There, Done That!

Have a good one!

 

How about an answer for this? Let's say I wanted to run intake cam for the exhaust as well.
Do you shim it the same as the actual intake cam, or like normal exhaust specs?

 

if you are asking about the 550. a maxim runs the same cam intake and exhaust
the seca has an intake and an exhaust cam with different lobe heights it is still shimed as to intake and to exhaust specs as maxim

max cams

seca cams

there is more info on cam swaps in the info overload thread
The Information Overload Hour

the thing to consider is if you will bend a valve by hitting the piston
running the shims to the tightest clearance pushes the valve open more
but I think yamaha wants you to go with the largest clearances

 

Well actuality, I will be using 1988 FZ600 intake cams for my project re-build.

 

Valve clearances are set for the purpose of the cam. Exhaust valves run hotter, expand more, and therefore need a larger cold clearance in order to be in working-spec when hot.