Head bolt washers?

[avenue]

Quick Q,

I'm getting ready to put my top end back together after buying my project in pieces and refreshing the engine.

Do the bolts and acorn nuts on the head require washers? I would think so but the PO was pretty meticulous about ziplocking every single part on the bike during disassembly and I'm not seeing washers with the headbolts (especially the two bolts below the spark plugs and single one above the cam chain tensioner). If they're needed, can I pick some up at the hardware store or should I be ordering specialty washers? A spec on the washers is appreciated, if they are indeed specific for the application.

Thanks for the help,
avenue.

 

[retiredgentleman]

There are 8 large studs (10 mm) that use acorn nuts. You want to use copper washers on the 4 outside studs, because they are exposed to oil pressure that oils the rocker arms. The 4 inner large studs are fine with just steel washers. The other 4 (8 mm) on the top and the 2 under the plugs, plus the 1 at the back can just use steel washers.

Very important to use the correct torque:
10 mm studs use 30 ft-lbs
8 mm use 14 ft-lbs
6 mm use 7 ft-lbs ( the 1 at the back of motor)

Also be sure to re-torque after putting on some kms..................leave the top motor mount off while doing the re-torques.

I bought the copper washers at www.650central.com.

 

[avenue]

Thank you.

Very helpful.

avenue.

 

[scabber]

The washers are thicker than hardware store make shure that the acorn nuts don't bottom out before you get the head tightend properly.

 

[retiredgentleman]

The washers are thicker than hardware store make shure that the acorn nuts don't bottom out before you get the head tightend properly.

Actually the thicker the washer, the less chance of bottoming the acorn nut.

If you look in my picture, you will see that I used the copper washer and I also used a metal washer for increased thickness. I added the metal washer just as a precaution to bottoming, but after some careful measurements, I realized you don't need to use an extra washer.

The stock washers were 0.124". The copper washer is 0.071". The metal washer is 0.031".
From my measurements, you can use the copper washer by itself. In fact you could use the 0.031" metal washer by itself, such as for the 4 inner studs. If you want to have extra clearance, use 2 metal washers on each inner stud.

Another varible could be if some of the studs are not fully screwed into the engine block. So each engine could be a little different.

Perhaps Yamaha used 0.124" washers as stock, as extra insurance that the acorn nuts could not bottom out, even with the odd stud that was not fully screwed in.

 

[scabber]

The washers spread the load on the casting over a greater surface area than the nut. Since the combustion process takes place under the head a stronger washer might be required or not since they use that rubber piece of shit under the other 4. Head gaskets come in different thickness. As retired said lots of varibles.

 

[angus67]

i replaced all eight with brass from mikesxs. looks spiffy.

 

[CoastsideXS650]

+1 on the thick brass washers from MikesXS. They really help to freshen up the top of the motor and don't leak.

 

[blackbetty]

i replaced all eight with brass from mikesxs. looks spiffy.

Hell yea!

 

[TeeCat]

Me three... just replaced mine during a re-torque very recently. My outer four appeared to have been the original rubber-coated ones... gack!

TC

 

[angus67]

your engine looks spiffy, too, blackbetty!!

 

[weekendrider]

Those that have used the brass washers do you think they are a hard or soft brass?
Would annealing make them too soft?

 

[XSLeo]

You can use the brass washers on the inner studs , but once the engine is in the frame you won't see them anyway, so why spend the cash?
Leo

 

[azman857]

I did all 8 studs. I've never annealed them when I rebuilt my top end and no leaks! Well, at least from them....I did all 8 to keep things uniform.