Timing curve?

[Lou_TX]

Howdy,

my question is: what is the timing curve for this 650 motor?

To elaborate:
My 1975 XS650 seems to be lacking power until I hit about 4,000rpm and then it wakes up and pretty suddenly. So it is not a gradual power increase.
Carbs are good and she runs like a raped ape above 4k.

I just checked timing. At idle, the timing mark aligns with the F maks and when I increase RPM, the timing does not advance until close to 4k when it quickly goes to full advance. I wonder if that's the culprit.

Hence my question above: what is the timing curve for this 650 motor?
The MM gives me specs on base timing and full timing but does not mention at what RPM the timing should be fully advanced, nor does it show any timing curves/graphs. I did not find anything here on this forum or in online searches either.

Naturally, I will be removing and cleaning the centrifugal weights in the timing advance system but I would still like to know the spec so that I can make sure that the advance kicks in correctly.

Thanks a lot in advance (pun sure as heck intended! )
Lou

 

[Its been a long time]

Don't forget to clean and grease the advance rod that runs inside the camshaft.

 

[Lou_TX]

Don't forget to clean and grease the advance rod that runs inside the camshaft.

Absolutely!

 

[Its been a long time]

Absolutely!

 

[Lou_TX]

Update: Disassembled and cleaned the weights, pulled the shaft out and it sure had a lot of dry grime on it, making it hard to turn. Also cleaned the points but could not gap them because I cannot find my feeler gauges. I know which toolbox they are always in but they are not there. Strange.
I'd like to gap the points before I adjust the timing (it is advanced at idle now which it should not be).
Gotta find the feeler gauges first.
It's always something. No project can go perfectly smoothly.

 

[Lou_TX]

Still looking for the information on timing advance. If not a curve, at least an RPM spec when the motor should hit full timing advance.
TYIA

 

[Paul Sutton]

The following thread about halfway down the page is the XS1B timing curve. Several prefer the feel of their XS650s with a few degrees knocked off the full advance as drawn in red on the diagram by jpdevol. I certainly preferred about 5 degrees knocked off.

https://www.xs650.com/threads/what-have-i-gotten-myself-into-xs650-with-ignitech-ignition.63675/

In the days of the XS650 Yamaha generally only reported the degrees advance at idle rpm and the degrees full advance at 3200 rpm.

 

[Paul Sutton]

Here is some info from the XS650 Manual on "thexscafedotcom" website:

The timing curve usually gets shown as a straight line from approx. 1500 rpm up to about 3200 rpm because the mechanical advance is approximately linear with rpm due to the nature of springs.

 

[gggGary]

cleaned the points but could not gap them because I cannot find my feeler gauges

Guess you youngsters don't know a matchbook cover is .014"?
At a swap meet today I was watching a vender light a propane lantern with matches from a matchbook wasn't sure which was older the vender, the lantern, or the matchbook. Another way to tighten the idle/full advance spread; https://www.xs650.com/threads/home-market-tx650-going-to-soir.66443/post-853004
Since it's springs yeah whatever rate the springs give you. Some aftermarket springs sold as replacements are too stiff making for a funky, late, abrupt "curve".

 

[Lou_TX]

Gentlemen, thank you all, that is exactly what I was looking for!