I'm loving those brake-cooling holes: they are BIG compared to the ones we used (and, even our 3/4" holes worked well on SuperHawks). In the wet, they made the brake ineffective for a few turns (much like the stainless discs on our SOHC4 bikes), but then they grab(bed) again.
Can I send you a transistor ignition, or is that taboo to the rules? I think I might have a Single unit still on hand. It will solidly improve the spark and let you run a points gap of .010" for much better high-RPM sparks. If so, PM me your address?
Thanks Mark,
It's definitely legal in AHRMA, and I believe in USCRA as well... if not it's easy enough to switch a few connectors.
I'll PM you.
One thing I was curious about was the performance of the points at higher RPMs. It has a single point contact mounted off the cam, but the advance has two lobes. So if I'm at 12k, then that point is opening and closing at 12k as well... which seems like that's asking a lot for a mechanical switch.
I can't remember if it was in one of your posts, or in your book, but I believe you mentioned somehow doubling up the spring on the points for the CB750 to help performance at high RPMs... would this also apply to the CB160?
Thanks,
Chris
It can, but I'm not very sure where you could get the springs? But, here's what DOES help:
On the non-moving points contact, you can vent them for more RPM. There's 2 ways you can do this:
1. take a fine-toothed jeweler's saw and cut a shallow "X" all the way across the contact face. Afterward, use some 200, then 400, then 600, then 800 (or finer) grit emery paper and wet-sand them shiny smooth again.
2. drill a small hole through the contact, dead center. then countersink the edges a bit and polish as above.
(A third thing: get a new condensor...)
In all cars prior to the "end of points" the better points came ventilated this way. In the legendary Ford 427 cu. in. SOHC engines that first appeared in 1963 for the 1964 Galaxie, the engines could (can) run well past 8500 RPM (with 4"+ pistons!) and the points could not close fast enough because air was getting trapped between the contacts. Ford did 2 things then: they ventilated the points contacts with a single hole thru the non-moving side, and added a Transistor Ignition (which I copied in 1972 as my first version), putting it into the Public Domain so any racer could use the schematic and build their own. The result: the distributor closes those points at 8500*(8/2)= 34000 RPM (if it was a CB160 this would be half, or 17000 RPM, equivalent). (By 1966 Ford made this w/o points, but all they did was add a magnetic trigger to the same circuit.)
The famous midget-car engines we helped with in IL during 1972-74 were the 750 sans tranny, with the oil pump driven off the camshaft via hand-made PTO shafts and gears. Those engines ran points with doubled-up springs, ventilated ground arms, 18 volt battery systems, OEM coils, and could reach 14,000 RPM (with lots of work!). Most of them were running 12,000 RPM consistently. We had to specially modify the spark advancers to reach the 14k versions. Since you won't have to run lights, hotwiring the Lighting Coil in the dynamo to "ON" all the time will help raise the bike's voltage, and you may even test without the Voltage Limiter to see just how high it can go? (This Transistor Ignition will run well up to 24vDC, no issues there.)
My Transistor Ignition technically has no "redline", but there are 2 things you will need to do when installing it:
1. Drill and tap a small hole into the points plate for the Ground wire. Use a points screw (2.5mm?) or similar size.
2. Run an extra ground from the the engine somewhere to the mounting bracket for the coils, i.e., an extra "ground strap". (Even a wire as small as 20 AWG is enough.)
These add-ons will ensure absolute tracking and close temperature-effect monitoring of the points, which will improve the spark at all RPM ranges.
