Factory directives

[mack]

Anyone know if Yamaha sent out factory directives changing the intake shim tolerances for inline air cooled fours, affecting the XS and XJ series?

[Bonz]

My factory manual (1980 edition) has updates that tighten the allowable valve clearance to help reduce valve noise.

[motoman]

Ammendmant dealer sent only that 81H valve clearances be set at upper clearance specs.

[Bonz]

In other words, to set the 81H on the loose side, correct? And the info was given to dealers, not included in any service manual available to the public, per se, correct?

Do you think the bikes began to have valve issues with the tighter clearances Yamaha retroactively stated, so Yamaha upped it for the 81H (Venturer) because of the higher sustained speeds that bike might encounter?

[motoman]

In other words, to set the 81H on the loose side, correct? And the info was given to dealers, not included in any service manual available to the public, per se, correct?

Do you think the bikes began to have valve issues with the tighter clearances Yamaha retroactively stated, so Yamaha upped it for the 81H (Venturer) because of the higher sustained speeds that bike might encounter?

Correct Bonz. That info came from a long time friend who now has his own shop and ironicly was factory trsained on these ole' XS series. He mentioned that to me when he re-shimmed the valves on my Venturer He had it as seperate sheet memo sent to dealers way back when.. Let him do it as he had all necessary shims and does it without removing cam journel caps. And for the $40 labor charge, he can keep doing it.

I believe that looser end of spec. on the two inner cyl. somewhat corresponds with the center cyl. being 2steps richer mains than outers. Theoretically more heat center two cyl., top-side of center two are slightly blocked from smooth non-restrictive air flow from the oil cooler, extra load pushin' a barn door through mother nature and the more expected constant rpm's on LD rides which naturally exibits towards a leaner burn anyways.

Back in the day there wasn't any real sustained high speeds with the double-nickel speed limits, but I remember pushin' it that 'five over' rolling long distances for hours @60mph/4K which is still feeding a lean burn at those constant rpms. But was also consistantly getting 46-48mpg two-up rolling 210-230mi. before switching to reserve and afuel stop Attribute that to lower speeds and fuel back then that gave gave more bang for the buck.

[Bonz]

Cool, that's good perspective on the center two cylinders.

I don't remove the cam journal caps though, just use the do-hickey tool and it's a pretty easy chore to get the shims out. Heck, it's only 8 of them and usually a only few of them need to be removed at that.

How much faster is it by removing the cam caps, and what do you see as the cost/benefit to messing with the cam caps and what could get boogered?

[jetmechmarty]

Bonz, are you bored? You appear to be opening a can of worms.

[Bonz]

Rotflmfao!

[mack]

question

The reason for my question is that I've been working on this little XJ 650 and both the factory manual and the haynes both state that for the US model J the clearances for both intake and exhaust were to be .16-.20 mm. It singles this particular model out from all the others.
However I remember when I was restoring the LH that Crazy Steve had mentioned that the 81 series's shim spec's had been changed to the .11-.15 numbers to allow them to run quieter. I had assumed at the time the cams had been altered as well. Since the XJ is an 82 I was wondering if the J series cams hadn't been altered.
I asked this question on the XJ site and the only response I got back was that all air cooled inline four spec's had been changed for the intake tolerance values and that both the OEM and Haynes manuals were incorrect. I have the supplement for the XJ and it makes no mention of any deviation from ther factory manual in this regard.

[mack]

directives

Back a few years when you brought up the Yamaha parts fiche, on the bottom was a tab that had all the factory service directives listed. I can't find that anymore now that they have deleted a number of models.

[MindWebs]

micro

not sure if this helps or makes things more confuzzing

1981 Yamaha Seca XJ750RH-(B)/(R)

Intake valve clearance: 0.11mm-0.15mm
Exhaust valve clearance: 0.16mm-0.20mm

(directly from micro fische)

Now..

There is a "page" talking about
XJ550/XJ650/XJ750
Camshaft side play

Some owners of an affected model may complain of a tapping noise in the top end.
this may be caused by excessive clearence between the thrust surface of the
camshaft and the camshaft cap.
if this is the case, there will be excessive camshaft side play, and the camshaft will
rattle in the cylinder head.

The tapping gererally occurs at idle and diminishes around 1800 rpm.
It is particularly evident when an affected model with this problem is placed on it's sidestand.

Blah, blah, blah.

check camshaft sideplay (0.025mm-0.076mm)

Replace camshaft caps closest to the cam chain tower, the "new" cap are machined to a wider spec to eliminate this issue

[mack]

Thanx

Thanx everyone. I have decided to go with the original spec on this bike. Those engineers in Japan knew what they were doing when they built this bike. Why they singled out the J model shim clearances to be different is a mystery but they did. So I will stick with what both manuals say.
I shim my SF to the wider spec as well and it has never given me any trouble and still runs like they day I bought it so.... it's my benchmark.