Question about head bolt washers on for 81' special

[RVA804]

Previous owner did some top end work (cam chain tensioner arm, new cam chain guide and replaced the cam chain). He also painted everything black. I'm a little confused by the head bolt washers though. These came stock with rubber-coated washers, correct? I scraped a little paint off of the top of one washer and it's definitely not rubber. My immediate thought was, "fuck yes, he swapped out the rubber washers for copper washers" because the color under the paint looked copper. Well, I scraped a little more paint off the side of the washer and it looks steel. The top was just rust. But, I thought these came stock with the rubber coated washers?

 

[RVA804]

the reason why I mentioned the top end work that the previous owner did is because he obviously had this pulled apart - sorry if that first part seems irrelevant.

 

[5twins]

The 4 outside washers under the large acorn nuts were a rubber/metal combo type. The 4 inner ones were plain steel. If you do change them out, only those 4 outers need switching. Those studs have oil flowing down them, that's why they need a sealing washer. The 4 inner studs are dry so a plain steel washer is fine there.

 

[angus67]

But for sake of asthetics, the three enginenes i have ha bronze washers on all eight.

 

[Paul Sutton]

Of all the head washers it is the rubber coated ones that need to be re-torqued more frequently. There seems to be very little if any settling with the steel ones. For this reason I will change over to copper/bronze washers at some point to replace the rubber coated.

 

[fredintoon]

Of all the head washers it is the rubber coated ones that need to be re-torqued more frequently. There seems to be very little if any settling with the steel ones. For this reason I will change over to copper/bronze washers at some point to replace the rubber coated.

Hi Paul,
I keep posting this, Yamaha used the wrong washers.
Their composite washers are layered like a Bassett's Liquorice Allsort so of course the rubber layer squishes out to lessen the torque.
Copper or aluminum plain washers are a workable substitute but what would really work is to use Dowty Sealing Washers instead.

 

[xjwmx]

The four outer ones are the ones that seem to loosen no matter what they are made of. It's not the fault of the rubber. Who knows. But I advise you not to repeatedly torque the head nuts unless there is some actual problem you're trying to fix. I.e. don't torque them simply to try to keep them torqued to spec.... My theory is the gasket will eventually crush down into something that no longer functions well as a gasket, leading to actual problems.

I have a feeling that the four sealing washers were a "finishing touch" rather than something that was actually necessary in this particular design. If your washers are plain steel and there's no sign of a leak around them it helps confirm it.

 

[Paul Sutton]

Thank you for that Fred and Xjwmx. I think it will be easier for me to make up Aluminium washers to the correct thickness than Copper. There was a thread recently regarding thickness so I must dig that up. Xjwmx, should I just stick to the correct torque at rebuild and then recheck after perhaps 40 miles then forget any further adjustment?

Thanks Guys.

 

[xjwmx]

^Aluminum washers might be a different matter. When I was in school I remember my mechanical engineering friend talking about how aluminum would not hold torque, it used to be used in house wiring but over time the screws holding the aluminum wire would become loose against the aluminum leading to fires... I have Mike's brass washers. A Suzuki copper washer will work, search here for part no. Knowing what I know now I'd just reuse the stock washers.

As for what to do with the nuts. Here's what I did. When I put the motor together I torqued all the fasteners coming out of the head to spec. The next day I put it in the frame and before I did the top mount I torqued everything again. I haven't torqued it since. I'm sure if I torqued it now I would find at least those four outer ones are loose. I have lots of miles on it and no sign of a leak yet. Do you have your gaskets already?

 

[Paul Sutton]

Thank you Xjwmx regarding the Aluminium issue - will go with Copper. When I had my XS1b rebored in the 80's I set the torque on the bench and never re-adjusted it. I must have done about 6000 miles on it and everything was fine, then sold it. I found an earlier thread suggesting to re-torque on assembly, again after heat up on idle and then a final check after 75 - 100 miles. With my RDs I only ever set them on the bench so I think I will stick to setting the torqe on assembly and make one re-check after 10 - 20 miles and leave it at that.

Thank you for the feedback on Aluminium.

 

[5twins]

Several torque checks within the first 1000 miles or so is common practice on many different motors after a rebuild. The new gaskets will compress down due to the initial torque applied and after several heat cycles (expansion and contraction due to heating and cooling). Eventually, after a few checks, you won't find the fasteners loose any more. That tells you the gasket compressing is done. I find the biggest culprits to be the 8 acorn nuts on top of the head, the little M6 bolt at the rear, and the 2 smaller bolts under the spark plugs. These are the ones applying pressure to the head gasket. All the rest are just holding the top cover on and usually stay tight. There's no gasket used there, just sealer, and I guess it does pretty much all it's compressing and squeezing out on the initial tightening.

 

[xjwmx]

^That might be your experience, but with my original gasket, before the rebuild, no amount of tightening would keep the nuts tight, and there is no doubt "gasket compressing was done"! If it ain't broke, don't fix it, unless you just want to fix it. You will eventually kill the gasket with compulsive tightening.