Can My Bike Timing Be Advanced?

[va_blue_stang]

Wanted to see it could be advanced and how to do it?




Thanks for all the help, Mitch

[FJ111200]

Judging by the replies i suppose that's a no.
But maybe if the bolt holes on the pick up plate were slightly elongated then maybe it could be moved just enough to give a bit of advance.
I think the advance is programmed into the igniter unit and the pressure sensor helps control it.
I don't really know that much about the XJ set up, even though i've put it on one of my XS's, minus the pressure sensor, which i've just bought from ebay USA. Just waiting for it to arrive so that i can play about with it a bit more.
One thing i've noticed with just the igniter unit and pick ups being used on the XS is that it's a bit hesitant from the off, and doesn't like to go over a 100mph, but it's still on standard XS jetting and minus the pressure sensor, so as i say, i've still got a bit of playing to do.

[DGXSER]

Yes, the 81 XS and the XJ both wre made without the ability to change the timing. In 81 Yamaha built the mechanical advance into the 4RO TCI, but kept the vac advance intact.

In 82, on the XJ, they built the vac advance into the 10M TCI as well as the mech advance. So no moving parts in the timing setup. To have the TCI repsond to vacuum, the put a vacuum sensor in that attaches to the same #2 Carb Nipple as the actual vac advance on the XS models. It converts the vac to an electronic signal it gives to the TCI.

The assumption is this was the answer to the pick-up coil wires breaking down over time.

[crazy steve]

I'm curious, does anybody know just how the 'vacuum advance' on the 10M TCI works? I've seen this sort of set-up on other bikes, and on those it basically 'toggles' between two advance curves. Above a certain set point, you get one curve, below another, both controlled by rpm. Not quite the same thing as the 'true' vacuum advance that's on the XS; the 'vacuum sensor' is just a on/off switch. If the XJ is different (variable output), then it would have to be calibrated...

[DGXSER]

Steve, variable would take variable signal from the sensor, and to the TCI.

I do not know for sure, but that kind of tech in 1982 was very rare at best. Not something I suspect would be found on these bikes.

[crazy steve]

Steve, variable would take variable signal from the sensor, and to the TCI.

I do not know for sure, but that kind of tech in 1982 was very rare at best. Not something I suspect would be found on these bikes.

Yeah, I'd be surprised if it were that type, but ya never know...

[BA80]

No.................................

[cywelchjr]

I'm curious, does anybody know just how the 'vacuum advance' on the 10M TCI works? I've seen this sort of set-up on other bikes, and on those it basically 'toggles' between two advance curves. Above a certain set point, you get one curve, below another, both controlled by rpm. Not quite the same thing as the 'true' vacuum advance that's on the XS; the 'vacuum sensor' is just a on/off switch. If the XJ is different (variable output), then it would have to be calibrated...

My understanding is that it's a true variable advance that actually replaces the mechanical vacuum advance pot. I'm sure there was some sore of calibration that was done on it in the factory when they were built, but I'm not aware of an out of the factory calibration routine, just as there isn't a routine for calibrating the mechanical unit either.

[crazy steve]

I shouldn't have been lazy and actually went and looked....

According the XJ manual (page 7-12), it's a simple 'toggle' system; you get one curve if vacuum is 50 mmhg, another if it's 100 mmhg. The lower curve is only slightly different from the 'mechanical' advance, while the other has a pretty big advance up to about 2000 rpm, a drop for the next 1K, then a slow climb as it gets up to 5K.

One reason I was curious is there's a number of fully-programmable bike ignitions available that might be a workable alternative to the hard-to-find XJ box. I'm sure they won't be particularly cheap, and I'm also sure some custom work would be needed to fit them, but JAT....