Points Timing

[js4016pk]

Hi all, running into an issue with timing my 75 xs. I am currently trying to time the right cylinder points at the fire mark. i have the plugs out and valve covers off and am just rotating the motor counterclockwise with a wrench on the flywheel to see when the points spark..i believe this is called "static timing" but correct me if Im wrong. The issue Im having is it isnt firing until about 15 degrees after TDC which it should be 15 degrees before. Now i have my points base plate set as far as it can go to the right or clockwise to try and fix this but i need more! what else could be the problem? there is some Free play in the advance unit rod which im wondering if that could be the issue or is that normal??

 

[js4016pk]

I have read in other threads its best to check with a light to see when points start to open and this got it closer so now opening right at TDC which still isnt correct but its a step in the right direction. I also tried holding my advance weights open which takes up that "Play" in the advance rod and the points are then opening right at the fire mark where they should be....so is the play in that advance governor unit my issue?

 

[5twins]

I don't think so. When the advance weights fling out, that rotates the advance rod about 1/8 turn or so, and that advances the timing for running at higher RPMs. With the weights flung out and the rod turned, you should be firing on the full advance mark.

 

[js4016pk]

Thanks for the response 5twins.. bike is starting on first kick and running relatively well but with timing light on rotor at an idle it still seems to be hitting at TDC instead of at the fire mark and im all out of room to turn my points backing plate. any ideas on what could be the issue??

 

[5twins]

Is this a new-to-you bike and the first time running it? The timing chain could be all stretched out and in need of replacement. Point gap can also have an effect. You may have to play with that to get it timed right, especially if you're dealing with used points and an old timing chain that you don't know the condition of.

 

[js4016pk]

No first time rebuilding it though,I have new cam chain and new points, gaps are set at .012-.015...and im almost certain im not a tooth off on the cam since i checked cam timing with a degree wheel. I feel im missing something stupid but im out of ideas. i just need a tad more movement out of the points back plate to get it set where i need it...but im all out of movement in the plate.

 

[retiredgentleman]

No first time rebuilding it though,I have new cam chain and new points, gaps are set at .012-.015...and im almost certain im not a tooth off on the cam since i checked cam timing with a degree wheel. I feel im missing something stupid but im out of ideas. i just need a tad more movement out of the points back plate to get it set where i need it...but im all out of movement in the plate.

Did you aline the 2 reference marks on the camshaft (slot at 12:00 on one side and punch mark,even with head surface, on the other side) with the crank set at TDC mark?

 

[5twins]

Besides rotating, sometimes the points backing plate also has some side to side slop. It can get pushed off center and that can limit the adjustment amount. Try loosening it's two mounting screws way up, rotate it back and forth a few times through it's adjustment range, snug the mount screws back up, and try the timing set again. This may center the plate again for you and give you back the adjustment you need.

You could also open the points gaps up to the max. To get a larger points gap, you move the points set closer to the cam so it pushes them open more. This also makes the points cam contact the rubbing block a little sooner as it's rotating and that advances your timing a little.

 

[js4016pk]

Retiredgentleman yes i set everything just as the manual said while instaling the cam chain. 5twins thanks for the tip ill give that a try when i get home

 

[js4016pk]

I am human and do make mistakes...if Everything else seems right is the only logical answer that the cam would be off 1 tooth then??

 

[5twins]

I guess it's possible. Your 447 cam sprocket has 36 teeth so each one would make a 10° difference. That seems to be about what you're off the timing marks by. You can check without disassembling too much. The pin hole in the cam that locates the advance unit on the right side should point straight up or straight down when you have the motor set on the TDC mark. Here's some instructions .....

http://www.650motorcycles.com/CamTiming2.html

You may not need to pull the advance unit off to check this. It has a little retainer pin on the back above the pin in the cam to keep it in place. This shows through to the front side .....

If you can spot that on the front of your unit, you won't have to remove it. But, it may be covered by that notched ring that holds the unit on. That may have to come off, or at least be loosened so you can see the pin in one of it's notches .....

 

[js4016pk]

Appreciate the info Ill be sure to look into this later today! Thanks alot

 

[retiredgentleman]

I am human and do make mistakes...if Everything else seems right is the only logical answer that the cam would be off 1 tooth then??

Every so often guys question themselves, as to whether they have assembled the camshaft and crank alinement correctly. Personally I don't see how it could be assembled wrong. If the crank was at TDC and the camshaft punch mark was even with the head surface, that's 100% accurate.

I think I checked that alinement about 10 times, when I last did a top end re-build.