valve timing and cam specs

[Christian Raith]

That could even be painful

[steptoe]

                 



                             DANGEROUS,  yes,


                              but very rewarding 

[petejw1966]

hey steptoe,
ive got those cheap vac guages,
i always callibrate them b4 use,
but saying that they are crap, out of the 4 guages
only 2 work properly, still its enough to sync.

i was just going thru some old mechanical text books from tech
and came across a vacuum guage performance chart and got to thinking
which can be dangerous.   lol   

[steptoe]

if I can add my 5 cents here Pete,, make sure your vacuum gauges are synced,,it sounds dumb but there you have it,,
                                            this is how I do it
hook the gauges { 1 @ a time } up to the same cylinder so you can adjust til they read the same,,they have a small adjustment screw on the face

then you know they're breathing the same,,, like they said doesn't matter what numbers there sitting on,,,,,,, as long as they read the same,, can't adjust #2, so line 1 & 2 up first, then 3 & 4 , then adjust 2 & 3

 I also sync mine on idle,,,,,,mainly because an opening of 1/2 to 1 mm needs to be exact were as wide open doesn't need to be as close

I didn't know so maybe some else doesn't know 

[petejw1966]

i agree with you there Christian,
i just thought they may have detuned the later
models for emission purposes.

for a clapped out motor, ive finally got it running
pretty good, so atm cant really complain.  :-)

[Christian Raith]

Yamaha spent a lot of time and money getting the XS1100 right, many runs in the Aussie outback trying to blow them up.

Even the original exhaust people replace is hard to beat for all round performance.

Now Carbs and ignition, that's another matter.
A few other things like spin on oil filters, Led lights etc make a big difference and put it up there with modern bikes

LONG LIVE THE XS1100

[petejw1966]

yeah, was thinking the same thing,
its running well, just thought it might add
sum oommf down low, but i dont want that
at the expense of the top end.

[pgnz]

Those markings on vac gauges aren't anything to take  notice off,   as long as the bikes cam dots are aligned,  timing plate sitting on 'F' at idle,  valve clearances all in spec, and vac readings all equal,  then she's sweet.    Degreeing the cams with slotted sprockets and all that garbage just moves the powerband around and where you gain in one area you lose in another,  the stock timing is setup nicely as is with grunt spread right across the rev range

[petejw1966]

hey pgnz,
good to have you on board.

i dont know if thats helped me or confused me.   lol

its got the peak lift at .346 for the inlet/ .326 for the exhaust, i t need to know at what degrees that hits at,  at the crankshaft.


mines the 81 model, i think the exhaust cam is the same but the intakes
are different from memory.

300 - 350 is still low according to the guages, youve got the big bore kit in yours from memory?,
i dont know if that would make a difference or not.

i read somewhere a while back that manufactures back in the 70s- 80s
timed the valves late for emissions, i dont know if thats true or not,
so i thought if i could get the specs id check it out.

[pgnz]

Pete , mine sit on 300 - 350 mm vacuum at idle,  here's some specs from some cams,  they were run off a fancy gadget from the oufit that ported the cylinder head on my bike.  I'm not too clued up as to what it all means but here's some of the printout anyway

inlet

78e       lift    duration        open           close           area

           .002     440.8      215.8 btdc      45.0 abdc     30.30
           .020     263.7      129.4 btdc      45.6 bbdc     29.65
           .050     241.1      118.3 btdc      57.2 bbdc     29.27
           .250     133.3      64.4  btdc      111.1 bbdc    20.94
           .300     92.5       43.9  btdc      131.5 bbdc    15.30

           peak lift- .346
 
           peak open acc - .000745
           peak nose acc - .000187
           peak close acc - .000718
           lift@ tdc - .3463

exhaust

78e        lift      duration      open             close         area

           .002      438.9       41.1 bbdc      217.8 atdc    28.66
           .020      263.3       45.7 abdc      129.0 atdc    28.01
           .050      240.2       57.2 abdc      117.4 atdc    27.63
           .250      122.6       116.0 abdc     58.6  atdc    18.44
           .300      72.2        141.3 abdc     33.5  atdc    11.46

           peak lift - .326

           peak open acc - .000699
           peak nose acc - .000172
           peak close acc - .000690
           lift@ tdc - .3263



inlet

80sg      lift       duration      open            close         area

           .002       423.4         217.7 btdc   25.7 abdc    28.44
           .020       250.8         124.7 btdc   53.8 bbdc    27.82
           .050       229.2         113.7 btdc   64.5 bbdc    27.46
           .250       123.7         60.9 btdc    117.3 bbdc   19.36
           .300       84.7          41.50btdc    136.8 bbdc   13.97

           peak lift - .345
           
           peak open acc - .000767
           peak nose acc - .000216
           peak close acc - .000770
           lift@ tdc - .3448


exhaust

80sg        lift        duration        open          close              area

           .002        417.1           24.3 bbdc    212.7 atdc    28.32
           .020        250.5           53.7 abdc    124.2 atdc    27.58
           .050        228.8           64.4 abdc    113.2 atdc    27.38
           .250        123.1           117.2 abdc   60.4  atdc    19.24
           .300        84.2            136.8 abdc   41.0  atdc    13.86

           peak lift - .344

           peak open acc - .000736
           peak nose acc - .000217
           peak close acc - .000741
           lift@ tdc - .3439

[petejw1966]

hey guys,
ive been syncing my carbs and noticed that the
needle on the vac guage reads low  around 10, this has been on both engines
ive had.
any manual or guage that ive read, a reading of 10 would indicate
late valve timing.

im wanting to check the valve timing on my bike but i cant find any
specs on the cams,
i need to kno what the degree is btdc at maximum lift on the cam?
(i hope that makes sense)

also was wondering what reading you guys are  getting on a vac guage at idle?

tia