Camshaft timing - Is my engine timed one crankshaft tooth out?

I

Its been a long time

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Well, since doing the static ignition timing the other day and finding I had to rotate the points back plate right across anti clockwise - I have been wondering if there's an issue here that I wasn't looking for?

The engine in the XS650D has clearly been apart before my ownership. It obviously hasn't run since being assembled and I haven't yet run it (auto advance unit was found to be fitted 180 degrees out, no way the engine ran like that).

What is concerning me now is - With the points backplate set in the middle of its range, the top set of points are maybe 25 to 30 degrees advanced. By turning the backing plate fully anti clockwise, the static timing comes in at the very left of the F timing mark. In fact, still a bit too advanced. The points backplate cannot rotate any further, it's screw bound.

Here's my worry. If the camshaft was timed one crankshaft sprocket tooth incorrectly, that is exactly what you would find when you try to set the ignition timing? Please see picture below.

Do I have a camshaft timing issue here?

1000001795.jpg
 
Signal said:
A quick check. On a stock bike with #1 at TDC the mechanical advance drive pin hole in the cam should be a 6 o'clock. If it isn't your cam timing is out.
I cant advice about points plate position.
Click to expand...
Thanks for that. I'll check that out before I go any further. Was planning on maybe starting the bike for the first time next week. But I need to do this before doing anything else now.
 
Yes, with the engine at TDC, the locating pin hole in the cam for the advance unit should face straight up or straight down (depending which cylinder is on it's compression stroke).

AdvancePinHole2.jpg


It's also possible the cam chain is badly stretched and should have been replaced during that rebuild but wasn't. Running out of timing plate adjustment is the classic sign of a worn out chain.
 
5twins said:
Yes, with the engine at TDC, the locating pin hole in the cam for the advance unit should face straight up or straight down (depending which cylinder is on it's compression stroke).

View attachment 325119

It's also possible the cam chain is badly stretched and should have been replaced during that rebuild but wasn't. Running out of timing plate adjustment is the classic sign of a worn out chain.
Click to expand...
My thoughts too. But....... a stretched camchain would retard the ignition? And I found the opposite, which is why over the weekend I started thinking about the cam timing being one tooth incorrect.

I have checked a few minutes ago and I think it's spot on. I can't see a reason for running out of points plate adjustment in the way I have. But I plan to carry on now I've checked the points cam keyway position. Hopefully won't be long now and I'll be posting that the bike runs beautifully, or won't start. One or the other :laugh:

Pictures below.

1000001808.jpg


1000001807.jpg
 
If you're looking at the keyway in the points cam, that's not the one you check. You need to look at the pin hole in the cam on the advance side. It may require you to remove the advance unit, but maybe not if you're lucky. There is a retaining pin pressed into the advance plate just above the slot that fits on the locating pin and it shows through on the outside of the plate .....

Pin Retension Peg.jpg


Pin Retension Peg-Front.jpg


Like I said, if you're lucky, the notched ring won't be covering it and you'll be able to see it. It's located by the notch in the flat side of the plate to the left of or before the direction arrow .....

Advance Pin Front.jpg
 
5twins said:
If you're looking at the keyway in the points cam, that's not the one you check. You need to look at the pin hole in the cam on the advance side. It may require you to remove the advance unit, but maybe not if you're lucky. There is a retaining pin pressed into the advance plate just above the slot that fits on the locating pin and it shows through on the outside of the plate .....

View attachment 325148

View attachment 325149

Like I said, if you're lucky, the notched ring won't be covering it and you'll be able to see it. It's located by the notch in the flat side of the plate to the left of or before the direction arrow .....

View attachment 325150
Click to expand...
Ah...... my apologies for not understanding. I will try again. Thanks for taking the interest in this. It's appreciated.
 
Points gap/dwell time affects this am I not correct?
will he really know before doing a timing/dwell check while running?
Another thought is the cam lobe may be deformed/galled?

My chain was stretched and the cam was correct on the chain (as correct as it could be with stretched chain) and the points disk was fully CW (opposite as OP)
 
Melnic said:
Points gap/dwell time affects this am I not correct?
will he really know before doing a timing/dwell check while running?
Another thought is the cam lobe may be deformed/galled?

My chain was stretched and the cam was correct on the chain (as correct as it could be with stretched chain) and the points disk was fully CW (opposite as OP)
Click to expand...
Thank you for that. Your experience is what I would expect to see with a stretched camchain.

I have just been reading the Yamaha shop manual. I believe I can verify camshaft timing by just removing one inlet valve cover.

Basically, the manual states the inlet valve lifts off it's seat at 36 degrees btdc. The fully advanced timing mark on the stator is at 38 degrees btdc. By putting a dial gauge on the top of an inlet valve I will be able to check camshaft timing. The manual says 1 tooth incorrectly timed is 10 degrees which should be obvious against the fully advanced timing mark. I will give it a try.
 
Its been a long time said:
I have checked a few minutes ago and I think it's spot on. I can't see a reason for running out of points plate adjustment in the way I have. But I plan to carry on now I've checked the points cam keyway position. Hopefully won't be long now and I'll be posting that the bike runs beautifully, or won't start. One or the other :laugh:

Pictures below.

View attachment 325125
Click to expand...

The rotor hash mark in your pic isn't pointing to anything.
Just so we're all on the same page, here's the timing marks.


Timing marks.png
 
Jim said:
The rotor hash mark in your pic isn't pointing to anything.
Just so we're all on the same page, here's the timing marks.


View attachment 325152
Click to expand...
Thanks. I thought the "T" was TDC, now I understand the line to the right of T is TDC.

What I see reading the manual is the inlet valve should open at 36 degrees btdc or around 9/10 of the distance from the TDC mark to the fully advanced mark. The manual says a timing error of one tooth is 10 degrees so a timing error should be pretty obvious. I am going to try it as it's simple to try providing I can find my DTI.
 
For completeness, this is a screenshot of the page in the Yamaha manual for checking inlet valve opening point with a DTI. Inlet valve opens at 36 degrees btdc. Fully advanced timing mark is at 38 degrees btdc. One tooth error in camshaft timing is 10 degrees. So it should be pretty obvious if camshaft timing is correct or not. I need to convince myself one way or the other about this. Following this procedure I think is about as quick and easy as it gets. (Now, where did I put that DTI?).

1000001810.jpg
 
5twins said:
Well, you could go through all that if you like I guess, but I think it's just much easier to look at the locating pin hole in the advance unit end of the cam, lol.
Click to expand...
Just three nuts to check inlet valve timing. I guess it's moot which is the easiest. Anyhow, thanks yet again for helping me out.
 

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