after cleaning and lubricating my auto advance system on my XS2, I thought that I'd just check the timing. It is off a little bit, and I couldn't adjust it to exactly where the book says to. So, I'm thinking that, maybe my points are not set exactly where they should be. Can I adjust them using a dwell meter, like we used to do with our cars? If so, what angle number should we be looking for?
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Point dwell angle ?
- Thread starter tmikeyb
- Start date
how far out is a little bit?
Yes you can, and it's the way I always do it. I don't get a feeler gauge anywhere near the points any more. The dwell value is 93°± 5°, or 88°- 98°. Now, if this was a single points set-up, you would need to divide that in half to get the value for using the 4 cyl. scale. But since this is a dual points system, you need to divide it by 4, giving a range of 22°- 24.5° on the 4 cyl. scale. The dwell meter reading is inversely related to the gap size. That means the smaller the number, the larger the gap is. I like to set the gap as large as possible and still be in spec so I shoot for as close to 22° as I can get. Since points usually close up as they wear, I figure the gap will remain in spec longer this way.
Thanks, that's the info I was looking for. In the meantime I went back and set the points using a feeler gauge, then I set the timing using a 12 v light bulb. Then when I checked the timing with a timing light, both cylinders were slightly retarded at idle. I had the advance weights clamped down with a zip tie. The timing light showed both cylinders at about 1/8 inch past the "T" area on the stator. But I had set it to the center of the "F" area with the light bulb. I went through this proceedure twice with exactly the same result. But, the more I thought about it, I don't see where it really matters. It seems to me that being retarded a little bit shouldn't hurt starting, and since the advance system is now working smoothly, it will only be retarded at idle. The bike does seem to start easy, and run good now.
I would definitely check it with a strobe timing light both at tick over and at say 3000rpm. See where the actual ignition timing really is. I wouldn't really want to run longer term with a too far retarded ignition. A degree or two retarded is fine.
The experience of experts on this forum is they run better with the ignition retarded a degree or two from the book figure anyway.
Indeed. I wouldn't recommend retarding the ignition beyond that longer term. And I'm suggesting verifying actual ignition on the two cylinders because sometimes the old steam age mechanical advance may not be working exactly as expected. Particularly as there's effectively two separate ignition systems on a stock points equipped bike. It's not unusual to have to compromise on actual ignition timing fully advanced or retarded. Sometimes it can't be exactly right in both advance and retard conditions when it's been set statically and checked dynamically.
Yes hysteresis on the adv. mech. from slightly sticking on the way to full adv. and full retard.
Your static/dynamic example is excellent!
"Sometimes it can't be exactly right in both advance and retard conditions when it's been set statically and checked dynamically."
Most times in my experience.
fun example is a distributor set with the dist. machine. Smooth running motor up and down.
checking timing from idle to full rpm is one curve.
rechecking from full rpm to idle is another curve.
the machine lies, always
the engine is constantly speeding up and slowing down, even with the tach saying it's steady is the best way to check timing.
example is a "constant" 1000 rpm idle according to the tach. or hand held rpm counter
reality the rpm is running 1200-800 rpm every cycle
Your static/dynamic example is excellent!
"Sometimes it can't be exactly right in both advance and retard conditions when it's been set statically and checked dynamically."
Most times in my experience.
fun example is a distributor set with the dist. machine. Smooth running motor up and down.
checking timing from idle to full rpm is one curve.
rechecking from full rpm to idle is another curve.
the machine lies, always
the engine is constantly speeding up and slowing down, even with the tach saying it's steady is the best way to check timing.
example is a "constant" 1000 rpm idle according to the tach. or hand held rpm counter
reality the rpm is running 1200-800 rpm every cycle
Yes, many of us retard the idle timing a couple of degrees. Personally, I run mine set over at the right slash mark of the idle timing "range" .....
Since this "range" is 13°- 17° BTDC, that puts me around 12° or 13°. I did this to alleviate some pinging I was getting in hot weather, which it did. It insures your timing won't be over-advancing. The fact that the bike runs a bit better (at high speeds and RPMs) was just a bonus, lol. I think Yamaha speced the idle timing as a "range" to allow you to compensate for advance unit wear and cam chain stretch. The advance unit, when new, advances exactly 25°, but as it loosens up and wears, the amount grows. Eventually, setting the idle timing on the "F" mark (15° BTDC) will have it over-advancing. So, it's very important to check the timing at idle AND full advance to make sure it isn't.
And also, a dwell meter is the only way to accurately set used points. Points develop pits on the faces over time and that's where the spark jumps between. You can't measure between the pits with a feeler gauge. The gap you measure is going to be smaller than the actual gap they fire between. So, when setting used points with a feeler gauge, it's best to gap them towards the lower end of the range (around .012").
And as far as retarding the timing goes, we're actually not retarding it at all but rather we're reverting to the original timing spec these bikes had when they first came out. Yamaha changed the spec early on, supposedly to smooth out the idle and low speed running. Here's a service bulletin on the change .......
Since this "range" is 13°- 17° BTDC, that puts me around 12° or 13°. I did this to alleviate some pinging I was getting in hot weather, which it did. It insures your timing won't be over-advancing. The fact that the bike runs a bit better (at high speeds and RPMs) was just a bonus, lol. I think Yamaha speced the idle timing as a "range" to allow you to compensate for advance unit wear and cam chain stretch. The advance unit, when new, advances exactly 25°, but as it loosens up and wears, the amount grows. Eventually, setting the idle timing on the "F" mark (15° BTDC) will have it over-advancing. So, it's very important to check the timing at idle AND full advance to make sure it isn't.
And also, a dwell meter is the only way to accurately set used points. Points develop pits on the faces over time and that's where the spark jumps between. You can't measure between the pits with a feeler gauge. The gap you measure is going to be smaller than the actual gap they fire between. So, when setting used points with a feeler gauge, it's best to gap them towards the lower end of the range (around .012").
And as far as retarding the timing goes, we're actually not retarding it at all but rather we're reverting to the original timing spec these bikes had when they first came out. Yamaha changed the spec early on, supposedly to smooth out the idle and low speed running. Here's a service bulletin on the change .......
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