first time valve shim

[bcknblkbird]

i'm going to shim to the max. limits on both intake & exhaust. so it will be many miles before i shim again. all the intakes are 0.15mm (0.20 wont go in) all exhaust are 0.25 (0.30 wont go in) will this work? thanks for your input. all this is in mm.

[crazy steve]

Your exhaust should be fine at .25 mm. Your intakes should be OK too if a .15 mm feeler will go in but a .20 mm won't. That's on the tight end of the scale, but still good.

[bcknblkbird]

so you are saying that 0.15mm is tight for the intake and 0.11mm is loose?

[crazy steve]

No, .15 mm is the low end of the scale for the intakes. Acceptable clearance is .16 to .20 mm for the intakes, if you can get a .15 mm feeler in there you have more than .15mm. Going up a shim size will put you over .20 mm...

[bcknblkbird]

intake specs 0.11~0.15 0.15 loose right?

[bcknblkbird]

so what are the specs for a xj1100 ?

[bcknblkbird]

for an xj1100 valve specs intake 0.11~0.15 exhaust 0.21~0.25 i thought i had messed up big time!

[crazy steve]

intake specs 0.11~0.15 0.15 loose right?

No, anything under .16 mm is tight if using the early spec. The '78-79 bikes were .16-.20 mm intake, .21-.25 mm exhaust. Yamaha tightened the intake clearance to .11-.15 mm starting in '80 to reduce valvetrain noise (leaving the exhaust alone) and used this spec to the end of production. You can run either intake spec, but using the late spec just means you have less 'room' before you need to adjust the valve as it wears.

The thing to remember here is the XS/XJ valve clearances get smaller with wear, not larger. Too little clearance means the valves spend less time on the valve seat and can't disappate heat as well. Eventually if the clearances get small enough, the valves don't close all the way and loss of compression will result and you'll see a risk of burned valves.

I much prefer to use inch measurements for this; each shim size equals .002" change in clearance, far easier to calculate shim sizes...

[bcknblkbird]

see what your talking about now thank you steve.

[bcknblkbird]

valve shim done. intake at 0.15 exhaust at 0.25 mm plug wires right, cams were not loosened, turned the crank several times to make sure nothing was hitting, done it by the book. now it won't start and backfiring thru the exhaust. any ideas? thanks!

[bikerphil]

Check to make sure you haven't mixed up your spark plug wires when putting all back together, JAT. 1+4 go to the coil with the orange trigger wire, 2+3 go to the coil with the gray wire.

[bcknblkbird]

boy i feel like a dumbass! i knew better than that, or i thought i did lol
. i was wondering why my plug wires look so funky. now it runs fine ! thanks a bunch phil!

[bikerphil]

now it runs fine

Sweeet. Yep, I've made the same mistake too my friend.