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Tuning The Advance Curve/Spring Rate...
- TeK9iNe
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- What did you do!?!
If the springs are too stiff, the advance curve stays flat longer, then suddenly begins to advance closer to 3000rpm, making the bike "surgy" in the 3500 to 4500 range.
If the springs are too soft, the advance curve rises too quickly, and you get a flat throttle response very early in accelleration, at 2000 to 3000, it just feels very weird.
I have a very precise digital zenon timing light, that you can adjust to .1 degree accuracy.
Using this light, my goal is to find a spring rate that proceeds as follows:
1000rpm, 10 degrees/default advance.
2000rpm, 20 degrees advance.
3000rpm, 30 degrees advance.
4000rpm, 40 degrees Full advance.
No matter what I do, the bike seems to reach full at 4000rpm.
Any suggestions? Are there better curves to be had with different springs? Is 4000 where full should be, or earlier/later? WHAT? :laugh:
PEACE!
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- bountyhunter
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1979 KZ-750 Twin
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- otakar
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I'm trying to get as linear and smooth an advance from idle to full, that I possibly can.
If the springs are too stiff, the advance curve stays flat longer, then suddenly begins to advance closer to 3000rpm, making the bike "surgy" in the 3500 to 4500 range.
If the springs are too soft, the advance curve rises too quickly, and you get a flat throttle response very early in accelleration, at 2000 to 3000, it just feels very weird.
I have a very precise digital zenon timing light, that you can adjust to .1 degree accuracy.
Using this light, my goal is to find a spring rate that proceeds as follows:
1000rpm, 10 degrees/default advance.
2000rpm, 20 degrees advance.
3000rpm, 30 degrees advance.
4000rpm, 40 degrees Full advance.
No matter what I do, the bike seems to reach full at 4000rpm.
Any suggestions? Are there better curves to be had with different springs? Is 4000 where full should be, or earlier/later? WHAT? :laugh:
PEACE!
Full advance should be at 3300-3400rpm on a 900-1100 and at 3600 on a 550-750
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000
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- WABBMW
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- Let The Good Times Roll !
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In order to change the advance rate, I have found that you have to change one or both springs. A spring with few coils and fairly large wire diameter will hold the advance retarded until RPM is high. On the other end of the spectrum, a spring with many coils and small diameter wire will begin to advance earlier. Try a spring with smaller wire diameter on one side to see what happens. The advance should start sooner and reach full advance a little quicker. If it still does not reach full advance by about 3,400, then change the other spring. Trial and error.
Also, if you use too small a spring, the advance may begin too early - in other words at or below the idle speed. This will make the idle erratic and also may throw off your initial timing setting. Use a slightly stronger spring. Good luck.
Bill Baker
Houston, Texas
1982 KZ650 CSR
2008 Yamaha FZ1
2006 Yamaha FZ1
1977 Honda Supersport 750 four (sold)
1984 Honda Nighthawk 650 (sold)
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- 650ed
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I used to do this on cars, back before many of you guys were born.
Try a spring with smaller wire diameter on one side to see what happens.
Shouldn't both weights have the same spring rate so they pull evenly? Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- DoubleDub
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If the two arms are independent, then yes, I would think the springs would have to match.
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- loudhvx
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The later ignitions with electronic advance can get more power from the timing by allowing more total advance because the electronic advance can be made to steadily increase with RPM.
If you look at the curves for both types you will see the mechanical ones start out gradual, then suddenly jump up to full, then the advance stays there through redline.
The Electronic ones start out advancing faster, then gradually taper off to full advance as the RPMs near redline.
Because of the behavior of the mechanical advancers, they have to use less total advance otherwise you would get too much knock at middle RPMs, but then you end up with less advance than you'd want at higher RPMs.
A better mechanical advance would have a two-stage curve. One would go from around 1500 RPM to about 3500 RPM, then the next stage would go from 3500 up to 10,000. This is sort of what the electronic ones behave like.
I'm just rambling here, but the point is to get an electronic kaw ignition if you can (what model KZ probably does not matter a whole lot for street use).
Here's a mechanical curve.
1981 KZ550 D1 gpz.
Kz550 valve train warning.
Other links.
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- loudhvx
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1981 KZ550 D1 gpz.
Kz550 valve train warning.
Other links.
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- TeK9iNe
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- What did you do!?!
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I guess it will come down to trial and error...
Anyone have some magic numbers for inital timing and max advance??? How far can I advance the timing?
Thanks!
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- bountyhunter
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Correct. The reason there are two symmetric weights is so it will be balanced load when the sucker spins up to 10k RPMs.I would think they would provide a combined force against the expansion, so by changing just one you are in essence lower the spring force of the pair, just in smaller intervals.
If the two arms are independent, then yes, I would think the springs would have to match.
1979 KZ-750 Twin
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- otakar
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74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000
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- otakar
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74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000
Please Log in or Create an account to join the conversation.