Timing and powerbamd

Nice. Do you downshift to pass with that setup? I don't think my bike would have the power to handle an 18/40 combo. I've got a 16/41 as it is and I'm thinking about going back to a 40 rear sprocket but worried it may harm my 2 up riding. The 50 mpg I'm getting now is pretty respectful (should be higher once I'm done with carb and ignition fixes)and I'd definitely have to downshift to pass to go back to a 40. But, like I said before, I have a much smaller engine.

Downshift? That's an understatement! On the highway at 70mph I downshift to 2nd, and punch it. The engine gos to about 6.6k and the front end gos up. The bike becomes a rocket at that point. You can be at about 130 in the bat of an eyelash if you aren't careful. with my engine configuration things really start to happen at about 6k.

otakar wrote:

And, since when dose "retarding" your ignition give you more power at top end????[/quote]


Since the start of time!

Advancing the timing gives you more bottom end/mid range.

Retarding the timing gives you more mid range/top end, increasing your MPH.

MPH is the weak point of these motors.

kzz1p wrote:

Advancing the timing gives you more bottom end/mid range.
Retarding the timing gives you more mid range/top end, increasing your MPH.

In that case, couldn't the spring rates on the advancer be modified so the timing advance takes place at a slower rate? If this could be done, the advance could be set a little higher at low RPM (giving best bottom end/mid range) and would still not advance so far or as fast as the RPMs increased (giving more mid range/top end).

kzz1p wrote:

otakar wrote:

And, since when dose "retarding" your ignition give you more power at top end????

Since the start of time!

Advancing the timing gives you more bottom end/mid range.

Retarding the timing gives you more mid range/top end, increasing your MPH.

MPH is the weak point of these motors.[/quote]

:ohmy: ????????? That's the first time I have ever heard that? I was always taught that low rpm requires low advance and hi RPM requires large advance. Than, I wonder why the timing advancer on the engine is not made to work the other way around from the way it is? I've learned something new here after 34 years of working on these bikes. Thanks for that info.

650ed wrote:

kzz1p wrote:

Advancing the timing gives you more bottom end/mid range.
Retarding the timing gives you more mid range/top end, increasing your MPH.

In that case, couldn't the spring rates on the advancer be modified so the timing advance takes place at a slower rate? If this could be done, the advance could be set a little higher at low RPM (giving best bottom end/mid range) and would still not advance so far or as fast as the RPMs increased (giving more mid range/top end).

Actually the advancer should be reversed, so it retards the timing as the RPM gos up. ????????????

en.wikipedia.org/wiki/Ignition_timing

Otto;
You didn't get to Dyno that motor did you? Those are sure some tall gears. A Dyno sheet would make some interesting reading if you have one to post.
Timing curve, Initial advance-Total advance, , curve goes up, only a vacuum system would incorporate a Retard, at Idle, for emissions. But sometimes Total advance is to much, so backing it off, and shorting the curve, so the Initial setting is unchanged works best.

Not yet I didn't. I did not have the spare cash this year because of my unemployment. However I will have the cash next season since I just found a job, and at virtually the same money as I was making before but there are bonuses. Next spring I will put it on the dyno.

I'll bet Motor Head knows that professional drag racers retard the timing at top end to increase mph through the traps.

Strange things happen sometimes, read a story (think it was in Camerons book) that talked about legendary Harley factory tuner O'Brian (sp?) being amazed at a Harley motor he was helping a friend tune, max power was at something near 11 degrees advance total.

With computer controlled Ignitions, you can dial till your Motors content, both Dyno and/ or track.
Mechanical systems still like a good tuning. The Hot Headed Air Cooled KZ motor seems like a good candidate for somewhere around 32-35 degrees total. But 40 sounds a bit much, so I can see where nads.com was coming from on the thread.
A lot of the racers in the past used to get rid of the advance weights or springs and weld the distributor plate. Then tune just for total advance, as these don't stop and go like a street machine.

Otto;
Yea I read about the Job, it sure will be nice to go back to work!
The last one I had sucked, so I dragged up. I hate it when they gouge customers. Back to flipping Cars and Bikes for a bit of cash, all on the up & up, legal and all.

otakar wrote:

kzz1p wrote:

otakar wrote:

And, since when dose "retarding" your ignition give you more power at top end????

Since the start of time!

Advancing the timing gives you more bottom end/mid range.

Retarding the timing gives you more mid range/top end, increasing your MPH.

MPH is the weak point of these motors.

:ohmy: ????????? That's the first time I have ever heard that? I was always taught that low rpm requires low advance and hi RPM requires large advance. Than, I wonder why the timing advancer on the engine is not made to work the other way around from the way it is? I've learned something new here after 34 years of working on these bikes. Thanks for that info.[/quote]

I am not talking about the advancer........