head bolt retorque.

[Ron Wandler]

Rebuilt my 1977 650 engine, however after completion I noticed I had a small oil leak and some puddling on the upper right side of the head. I removed the gas tank and upper motor mounts, removed all the head bolts - these next few steps are very important- replace the rubber washers with brass, put PERMATEX Hi-Temp Gasket Maker ( or an equivalent) on all your head bolts and torque to 35-40 ft. Pds. ( I did 40 ft. Pds. ). This corrected the oil leak, NOW the VALVE CLEARANCE needs to be rechecked as retightening or upping the torque on the head bolts can throw your valve gap settings off, which will cause the bike to be harder to start, stalls when hot ect. Hope this helps and eliminates further performance pitfalls.

Enjoy the Ride! Live and let live.

 

[retiredgentleman]

Rebuilt my 1977 650 engine, however after completion I noticed I had a small oil leak and some puddling on the upper right side of the head. I removed the gas tank and upper motor mounts, removed all the head bolts - these next few steps are very important- replace the rubber washers with brass, put PERMATEX Hi-Temp Gasket Maker ( or an equivalent) on all your head bolts and torque to 35-40 ft. Pds. ( I did 40 ft. Pds. ). This corrected the oil leak, NOW the VALVE CLEARANCE needs to be rechecked as retightening or upping the torque on the head bolts can throw your valve gap settings off, which will cause the bike to be harder to start, stalls when hot ect. Hope this helps and eliminates further performance pitfalls.

Enjoy the Ride! Live and let live.

I don't know where you got the 35 to 40 ft-lbs numbers from, but those are much too high. 40 ft-lbs.....................that may cause you problems. The common number used is 30 ft-lbs, because its a safe amount, and there will be no oil leakage, or problems with the head gasket.

Brass may work OK but copper is the preferred washer for the outer large studs.

There's no need to use any gasket sealer type goop on head bolts.

 

[Ron Wandler]

XS Direct offers copper or brass; I happened to choose Brass. The point I was essentially attempting to emphasize is that the valve adjustment needed attention after re torquing the head bolts; ( as at no time was this mentioned within this forum ). I have attempted to attach a snap shot of the info regarding 35-40 ft pds of head bolt torque. The diagram shows 25 ft Pds. But the last paragraph states this to be too light and makes the 40 pd. recommendation.

 

[TwoManyXS1Bs]

That 40 ft-lbs is for full-diameter race studs...

 

[gggGary]

Per the Yamaha service bulletin, loosen or remove and re-torque the nuts one at a time and use oil or anti seize. I made some changes to my original post way up at the top to reflect what I have learned in the shop and on this forum in the 4 years I have been hanging here.

 

[Ron Wandler]

Thanks Gary. Please clarify what the recommended re-torque foot pounds should be for the head bolts; 25, 30, 35 or 40 ft. Pds.? All these numbers have been recommended by a variety of sources. I apologize for any and all confusion.

 

[retiredgentleman]

Thanks Gary. Please clarify what the recommended re-torque foot pounds should be for the head bolts; 25, 30, 35 or 40 ft. Pds.? All these numbers have been recommended by a variety of sources. I apologize for any and all confusion.

No need to apologize.This is the wild internet, and information flys around from many sources. Some of that information may be false.

The 10 mm head nuts had different specs at different years. Yamaha specd them as low as 22 to 25 ft-lbs. in early years. In later years such as 1978 and into the 1980's, the Yamaha Service Manual lists 27 ft-lbs.

The general concurrance is that 30 ft-lbs is more than enough to get the job done, and is a safe amount to not over stress the studs.

I used 30 ft-lbs on my top-end re-build about 7 years ago. One a year I check that they are still at 30 ft-lbs. My engine continues to run very well, and I have no oil leakage from the engine.

 

[xs650dreamer]

Should I loosen starting with number 15, then tighten starting at number 1 ?

 

[650performance]

Even on race engines with much higher cylinder pressures you don't have to torque the head bolts any more than 29 lbs. Bud Aksland, who built Kenny Robert's engines, used narrow, 1/8" thick steel pressure "spreaders" instead of washers under the head bolts and noted that if the bolts were torqued to 30+ pounds it would cause distortion to the casting which obviously isn't a good thing.

 

[gggGary]

Remember this little guy, it's a pain to get to, often isn't even hand tight, it is the only fastener for a long thin section of the head gasket. It's 6mm, use ONLY 7 foot pounds, that's just snug on a short 1/4" ratchet handle, go super man here and you'll break it or strip out the head!

 

[Willy D]

I have a 79 my head bolts aren't 10,8, and 6mm
They're 17,12, and 10 do they go by the same ft.lbs for tightening?

 

[DanielBlack]

I believe that's a 17mm head on a 10mm bolt. Etc.

 

[timbeck]

Hey Willy---17,12and 10 are the mm size of the bolt heads. 10,8 and 6 mm are the size of the bolts. Torque away , your 79 is no different.
tim

 

[kshansen]

I have a 79 my head bolts aren't 10,8, and 6mm
They're 17,12, and 10 do they go by the same ft.lbs for tightening?

I think the mistake you are making is book would be referring to the diameter of the stud/bolt not what size the socket that fits the nut or bolt head!

You might want to double check but off the top of my head a 10 mm stud/bolt would take a 17 mm wrench, 8 mm stud/bolt would take a 12 mm wrench and a 6 mm stud/bolt would take the 10 mm wrench. Now this is not a 100% positive formula as in some cases a stud/bolt might have a larger or smaller size for the wrench. The majority of times when a size is given for a fastener when referring to torque they are talking the diameter of the stud or bolt. Now if you are working on some old British bikes.....all bets are of with Whitworth fasteners!

 

[Willy D]

Cool thanks!

 

[yamageddon]

Well, as promised my results from the retorque: '82 5V4, apprx 25000 miles, never been rebuilt. Base-and head gasket was 'sweating' some oil. Did a retorque of the heads, as described in this thread, yesterday. Went riding even though it was freezing but it was dry for an hour. Result: The sweating stopped indeed, but now it was leaking as never before...both sides... bummer! Next day, with gggGary's retorque result in mind, went for another short ride, enough to get the oil on temp. Let the bike warm up slowly. Result: No leaks...whut? No leaks?...So far so good! Waiting for some nice weather to see if it holds on longer trips.

 

[MaxPete]

Hi All:

I just skipped through this thread and it really IS a goldmine of great info. The one contribution I might make is to reinforce the importance of backing each fastener off BEFORE applying your torque wrench.

One of the reasons the XS650 engine is such a robust unit and that it is relatively oil-tight, is that the fastening scheme is well designed and was mainly well-executed at the factory back when the bike was built. However, that was 35 to almost 50 years ago and so it is time to do it again, and do it properly.

In particular, it is essential to ensure that the head of the fastener and the threads are not stuck - because that would give a false torque reading on your wrench.

Remember that the purpose of these fasteners is to squeeze the head down onto the cylinder barrel and the barrel down onto the engine case. Fastener tightening torque is a highly IN-direct means of measuring that squeezing force. However, it is all we've got - and so it is important that the torque we apply actually goes into turning the fastener rather than over-coming resistance due to friction and/or crap seizing the fastener threads and head.

I know I have posted it before in another thread, but because this old thread and topic have come up again and the material is germane, I am attaching a slide deck that I prepared for a dinner meeting of our local chapter of the Can. Vintage MC Group (www.cvmg.ca). If you look at slides 17 and 19 - you will see the importance of lubricating the threads and under-head area of fasteners to ensuring true torque readings.

Other than that, I would read the thread carefully, be methodical and follow the advice of the Gurus on maximum torque and the tightening pattern (and don't forget that little hidden fastener that is snuggled down between the carburetors - 7 ft-lb ONLY on that one because it is just a little 6mm diameter machine screw).

Pete

PS - if you do not have a good torque wrench - don't even think of trying this little job on your bike.

 

[Paul Sutton]

I am still thinking of a design for a socket/spanner for tightening that 6mm bolt between the intake ports when the bike is fully assembled. Any suggestions?

 

[MaxPete]

A wobble extension (the kind that can take a small angle) for a socket might do it - but you’d want to be careful about over-torquing that little 6mm bolt.

 

[yamageddon]

It certainly was a b*tch to get to that small bolt. Could reach it with a wobble extension but that will change the reading on the torque wrench. So I carefully gave it a little 1/8 of a turn.