Racer Resurrection

[OldSwartout]

I'd be somewhat nervous with a 2.5 Ah battery, although it should last one race.  i used to run a standard 14 Ah  battery. It would run a full weekend - 4-5 practice sessions + 2 races, but that was about it.   

[craig641]

I used, through last season, a 4ah battery.  There were too many races that I dnf'd because of a dead battery.  I realized that the few ounces I saved wasn't worth it if you don't finish.

[OldSwartout]

It seems to me that one of the Lithium-Ion automotive jump start batteries rated at 20,000 mah should work and they weigh less than a small lead acid battery.  They are less than $100 at Walmart, etc.  The issue would be vibration, I think.  They probably aren't designed for a high vibration environment. 

[al_pritchard]

This is what happens when I start over thinking things.

Taking a gamble on the battery. Two coils, rev counter, and transponder shouldn't flatten the battery in race time. Calculations vs. reality...

Standard place to mount the battery would be under the seat/tank. But I started thinking, what if I mount them on the air dam on the forks? It's a super light set up, and moving them forward would keep them away from the heat. Would need to change the material the dam is made of. I did a quick mock up with a fome core and fiberglass. Feels stiff, and can always build for USCRA, and use carbon fiber.

What do you think? Am I mad? To risky?

[hardy]

I like the idea and your thinking, but in real terms my thoughts would be from time to time race bikes do have unfortunate accidents, so perhaps a more protected location were be better?

P.S, I have really been enjoying following this thread! Keep up the good work!

Hardy.

[OldSwartout]

I'm with Hardy, it's probably more vulnerable there, although a solid hit directly in front of the forks isn't as likely as side damage from sliding.  It is more isolated from engine vibration and heat there instead of mounted directly to the frame under the seat/tank and the access might be better.   Nice setup either way.

[BRT-GTR]

             I have no experience of automotive Lithium-ion batteries but have used them extensively for model aircraft flying.    Misused they can be dangerous  ------   ask Boeing about cockpit fires!!

         They must not be overcharged - can go on fire and cannot be extinguished, contain their own oxygen supply. 
       They must not be discharged below a set voltage (forget the figure) , that kills them.

       I assume automotive Li batteries have  built in electronics to prevent over charging/discharging..

   The ones I used came with dedicated chargers that cut off at the max voltage.  The onboard electronics would also shut off or go to low rate at a set discharge voltage.

       Used sensibly and fully aware of their characteristics, they are fine and have a great perfomance/weight ratio.      Make sure the intructions are understood and don't use normal lead acid chargers, unless instructions say you can.   I've seen many expensive model aircraft burned to a pile of ash because users didn't follow the instructions.
           Hope I haven't put you off,  bikes coming on nicely,    Brian.

[bsracer]

My friend uses a Dewalt 14.4 drill battery. Not the lightest but easy to change out and will power all the tools we bring (drill and impact gun)! He typically has them charged and when he comes in he swaps new one every time. The newer batteries are much lighter. Might be tricky to adapt to still use the orig charger.

paul

[al_pritchard]

Hey Brian,

Yea, they can be a bit tricky - and flammable. But with a good charger, and charging protocols it should be safe. It's a LiFePO4 battery, slightly safer but still susceptible to fire.

So I'm going to try the airdam mount. But I also created a mounting plate for under tank, just in case.... 

About the battery selection. I think I got the calculations close??? Otherwise I'll be looking for a deferent solution. But that's part of the fun, isn't it... 

With the Dyna S ignition and a 4.6 ohm stock coil we should get something in the 2 to 3 amp draw. With one coil reaching saturation when the other fires. The trick / hope is that the coil reaches saturation just before it fires. So we don't continue to pump energy into a fully saturated coil.

Interesting idea with the Dewalt battery Paul. And makes me think I may be ok with my selection. The older 14.4v ones were only 2.4 Amp.

[al_pritchard]

Wiring harness weekend!

Not sure I completely understand how the wiring works - Dyna S, and the Coils. So if you spot something that looks off, please let me know.

Dyna S gets fed power on the RED wires (x2) to the positive post from the battery. The black and white wire from the the Dyna S, connect to the black and white wire on the coil. The blue wire on the coil connects to the positive post from the battery. In essence, two separate circuits. The Dyna S grounding through one side of the coil to the chassi. The coil grounding through the spark plug.

So it's ok to have the power side of the coil, and the power side of the Dyna S on the same pole from the battery?

The connectors are "Deans" connectors. If you ever raced RC cars, you probably encountered them.

Power comes off the battery into the "hot" side of the bus bar. The Coil, Dyna S, transponder, and tac all connect to the hot side. The ground/neutral bolts to the chassi. Then the ground side of the bus bar bolts to the chassi - safety wire will hold the bolts in place.

The tac will ground to the bus bar as well - need to tie that in yet. The white wire from the tac connects to the white wire on the coil.

[al_pritchard]

Arts and crafts night! Or as I like to call it - Fun With Cardboard.

They dont seem to be required yet - but I seem to remember seeing that they are sugested. And it's probably a good idea.

I'm a little leary about drilling into the swingarm tube. But I think I should be ok drilling into the flat axle flange. Couple of cardboard mockups to get the shape right. Then on to aluminium. Add lightness, and .... still need to dril out the flange to mount it.

[bsracer]

Looks good. Might not be mandatory before brake guard levers will be. You will need to cover the chain adjuster bolts that stick out. Just use a  short piece of fuel hose.

paul 

[al_pritchard]

Yea, the adjuster bolts are already drilled for safety wire. But I think your suggestion i better. Assuming I'll be doing a fare amount of adjustment as the chain brakes in. And I work out the proper bike setup.

Thinking about brake guards as well. Found one that I think will work out of Germany, from RaceFoxx.com. I could only find a handfull that clamp around the bar. It has the added bonus of being 3D printed, so thats cool.

RaceFoxx Brake Guard - Ended up moving it out slightly on the bar to prevent interference with the lever.


Also ordered a rebuild kit for the carbs last week, from Diablo Cycles. With the thinking that the carbs are virtually identical to the Kawasaki A1 carbs. If not, I have a rebuild kit for sale. 

Only thing left to source are a pare of exhaust pipe gaskets. If anyone has some lying around, let me know.

Next week I'll pull the engin for the last time. I want to measure the total displacement, and work out the uncorrected compression ratio. Then it's wet build time.

Any one have recommendations for oil's? What does everyone use for transmission and pre-mix?

[SR-175]

Hi Al,

You probably know this already, but mentioning it anyway.

The standard SR 22 mm carbs (no chokes) ran a 250 main jet. The Kawasaki A1 carbs (with chokes) ran a 130 / 140 main jet and oil injection. These will be in the rebuild kit. As you will be running pre-mix these will need to be opened up to 250. A 0.057 inch drill bit will make close to a 250 main jet.

I just finished setting up a set of A1 carbs as I wanted to have the chokes for ease of starting.

later ... ray 

[al_pritchard]

Hi Ray,

Thanks, I'm still coming up to speed on the carbs so that was new info for me. Thanks, and don't hesitate to tell me things - odds are I will have no idea.

I'm starting to like the idea of switching to A1 carbs in the near future. The choke would be helpful, and I suspect there is some one out there rebuilding a SR that could use a factory part.

A

[bsracer]

I usually run from 200-230 main jets in my current 22mm carbs. I think I ran about the same with either the SR 22mm or the A1 22mm carbs. I run Valvoline non-detergent 30wt oil in the gearbox. That's what I've used for almost 15 years now. I started with Motul 800 for premix and I've been using Maxima Castrol 927 for the past 5-7 years. I mix it at 28:1.

You can get almost any jets from Sudco. I have from around 130-300 in mains and a bunch of the various pilot jets for the A1-SR type carbs and the newer style I run (smaller jet). I also have a selection of needles (4 series).


paul

[SR-175]

Hi Paul,

What pilot jet sizes have you played with ?

Hi Al,

As Paul says, best to have a range of main jet sizes to play with, till you find the size that suits the day / conditions you'll be riding in.

ray

[bsracer]

Hi Ray.

I was using 17.5 for some time. I've been running 22.5 for the last few years. These carbs (or Rotary valve engines) can be pretty finicky. I have a range from 17.5 to 30 in the style jet for the SR carbs. I thought I had the same for the "newer" style carbs I run but 25 is the largest. I did go up to the 25 when I last raced the bike. I wanted to go bigger to experiment, but I didn't have any 30's to try. I'll check the SR carbs I use to run to verify the jets in them.


paul

[OldSwartout]

I ran 230-250 main jets.  The airflow pattern around the carbs will have an effect.  The more protected from high speed airflow past the throats, the more fuel blowback will be drawn back in. If you use the racer carb covers, there will be a fair amount of fuel blown out, but not as bad as leaving them open.

Of course the porting, pipes, etc. make the biggest difference.  I used the basic components; idle jet, needle jet, and needle, of the standard SR 22mm carbs (which were identical to the set of A! carbs I purchased). I then found out there was a severe lean condition at part throttle, probably due to the pipes I was running. I ended up drilling the needle jet out a couple sizes with a drill bit to save pistons.

[al_pritchard]

Spent more time in the back yard last weekend than the work shop, we shall see how this weekend goes.

But I did manage to get a little further. Before doing the final build, I wanted to get an idea of the actual head volume. To work out the compression ratio, and start thinking about timing, and fuel.

So the engine is on the bench, and leveled. With the burette carefully positioned over the spark plug hole, and a little grease around the piston edge.

Using a 0.80mm base shim I get a total head volume of 8cc at TDC. This is with an o-ring gasket, the head torked to 5lb, and does not include the volume of the spark plug.

My Set Up
Base Shim: 0.80mm
Cylinder Bore: 50mm
Engine Stroke: 45mm
Exhaust Port Height from TDC: 25mm
Cylinder Volume at BDC: 90.13cc
Cylinder Volume at TDC: 8cc

Uncorrected Compression Ratio: 12.04:1
Trapped Compression Ratio: 7.14:1

To calculate Uncorrected Compression Ratio:
(radius of bore in millimeters) X (radius of bore in millimeters) X (3.14159) X (stroke in millimeters) / 1000 = cylinder volume at BDC
25mm x 25mm x 3.14159 x 45mm / 1000 = 88.36 (88.35721875)

(volume of cylinder at BDC + volume of combustion chamber at TDC) / (volume of combustion chamber at TDC)
88.35cc + 8cc / 8 = 12.04:1 UCCR

Going to try the thiner, and thicker shim this weekend. Will do a test with with no shim as well to get the numbers for all my options.