Topic: CB750 AHRMA Sportsman 750 Racer

[Haybus]

Alan, I was under the impression the LiPo batteries were implicated in fires, not LiFePo4??

Yeah, thinking back on why I chose the LiPo, you're probably right. I think cost was more a factor than burning the jewels!! Sorry if I misled.

Alan

[scottly]

Whew, thanks Alan. I've been doing some research on batteries lately that are capable of spinning the electric starter on my 836, and the best options look to be LiFePo4. (other than the price!! )

[turboguzzi]

gee guys, my head is spinning from all the info and chemical nomeclature here.... why not keep it simple?
dont ask me how, but i have manged to get along well for the last 10 years in my total loss ignitions with VERY dumb sealed lead acid  3 Ah batts, never had a session or race cut short because of lack of electrical power.

I plug it between sessions to a VERY old school charger without worrying if it's discharged or not.
I never have less than an hour between sessions so always end up entering the track with 13-12,7 V.
Manged to forget a few times to recharge, and still had plenty of juice.
yep, they weight 2+ pounds but are bomb proof and 15$ each....

Admittedly, the GSXR ignitions i use consume very little power, i think around 1 A.

[slikwilli420]

This has officially turned into an oil/tire question. It seems I have options ranging from cheap RC batteries, to old school lead acid, to high end LiFePO4 stuff. Generally speaking, it sounds like anything in the 3-5Ah range will work just fine for the short race/practice sessions I will be doing. Charging seems to be a thing of its own as well, ranging from plug it in and forget it, to making sure I have the right charger for my battery type.

[bwaller]

Now wait a minute, don't fool yourself, there is no easy way out of this. 

If you are well prepared and no bike issues, you will need something to occupy your time! 

Actually my situation couldn't be easier either and like Yossef says the GSX ignition runs on fumes! I was trying to shave extra weight & these batteries made perfect sense. Now that I've gained weight they're even more important!

[Old Scrambler]

Weight...........as in grams.......or stones

Slick.......I use an LI battery from Battery Tender (Deltron) on a total loss Dyna S system.  I rode the equivalent of 30 miles (15 at full throttle) on a single charge. On mile 31 I ran out of juice but the battery was not completely dead. It was slowly recharged overnight and lived for another day of running. I used that one battery on both of my bikes. I had LiPo backups but will now go back to Bonneville with 2 LI units. I use the same battery for bench-testing in the off-season and plan to carry it as a spare for my Aprilia during the next year. Besides the easy charging issues, this battery comes with 4-posts so it 'fits' any wire-harness.

The Ballistic units from Millenium Tech can be special ordered to fit your bike...........but they require a special charger..........so two units would be a must. MT does my boring and brokers my valve-train components so I may get a discount on their batteries. I just gave the MT company president a picture to hang on the wall and he seemed to be offering some help.

[slikwilli420]

At this point I am leaning toward a Shorai or Antigravity battery with the recommended charger. The Shorai had many more total reviews, but also some very negative ones, mostly about use under 30-40 degrees, which is of no concern to me.

The Antigravity is almost twice the price but after talking to the tech there (still need to call Shorai) he assured me that their 8-cell was widely used on total loss systems for track days with no issue.

Both batteries weigh just over a pound so fit the bill of weight savings which is only secondary to keeping me on the track for the full race/practice time.

[bwaller]

Check my earlier post from Shorai, she didn't like their batteries for total loss useage.

A really great feature about these Lithium jobs is they hold a charge indefinitely. Put them away charged and forget them.

[slikwilli420]

Check my earlier post from Shorai, she didn't like their batteries for total loss useage.

A really great feature about these Lithium jobs is they hold a charge indefinitely. Put them away charged and forget them.

In reading back I do remember you saying that, while the Antigravity tech rep said thats the bread and butter for some of their products.

I just got off the phone with Dynatek and they gave some semi-alarming news. The tech rep said that I should expect 6-8amps of constant draw from that ignition package, which seems much higher than what I have heard from others and remember reading. In practical applications, it sounds like racers are getting away with a 5Ah battery source for extended periods of time without any issues. This adds yet another level of complexity to my decision.

[turboguzzi]

off topic, i know, but 6-8 ampers? OMG. these ignition units cook eggs too?

[bwaller]

I remember that Dyna 2000 I used originally sucked juice like crazy.

[Haybus]

I did measure the draw on my Dyna S and Pamco, both right at 3Ah. I would imagine the coils are the main draw, special electronics (Dyna 2000 perhaps) being a secondary consideration for total amps. I have a big oil tank taking up the space where the battery was, so a small battery is nice. $15, 3Ah small lead acid battery would be awesome.

[scottly]

Matt, at this point you may want to reconsider running a total loss system; the weight increase of the charging system can be off-set somewhat by a much lighter battery, as well as a lighter tray to support it, not to mention the hassle of re-charging between rounds or worrying if the bike will run out of power. My two cents.

[voxonda]

Why not consider a magneto ignition, no charging, no battery.

[slikwilli420]

Matt, at this point you may want to reconsider running a total loss system; the weight increase of the charging system can be off-set somewhat by a much lighter battery, as well as a lighter tray to support it, not to mention the hassle of re-charging between rounds or worrying if the bike will run out of power. My two cents.

The weight penalty of all that stuff and the wider cover are what I'm trying to avoid. Narrowing down what this system really draws is key. Almost no one is running the charging system on these,I just need to figure out how much juice they are running. I can recharge the battery in 15 minutes so that's not really a concern. I am leaning toward a 7.5Ah battery which should give me plenty for half hour sessions.

[slikwilli420]

Why not consider a magneto ignition, no charging, no battery.

All of that exposed on the side to get damaged is my worry. I was looking at the cycle x our electrix world system but worried about damaged on the event of a crash.

[Kickstart]

I've been away from the forums for a while and completely missed this thread!
I'm very excited about having another CB750 on the track!... Welcome to the club SlikWilli!

How are you making out with the the current build? Still think you can get it on the track by June?  I plan on doing either Road America or Gingerman this year, and maybe hit Mid-Ohio if we can swing it... and then NJ (home track) and Barber.  Did we meet down at Barber?  I remember someone asking about a 750 build.

Regarding the battery... if you're going with the LiFePO... get the largest one you're comfortable with.  I'm running total loss on my 750 - 3-Ohm coils (but with a 1-ohm power resistor in line) and HM ignition with points, so less current draw than you'll have with your set-up. I'm using a Shorai LFX14A4-BS12 (I think - I need to double check) and I charge it with the Shorai battery charger after every session on the track... and it takes a while to come back to full charge.  I'd be comfortable doing one back to back race... but I wouldn't push it more than that.  I definitely would not be comfortable with a 5Ah in a LiFe.

Regarding the stock engine.  I raced my first year and a half with a totally stock 1975 CB750F engine (with approximately 20k miles on it)... rode her hard with no major problems except for poping out of gear after a while (but that was probably due to me dropping the bike on the shifter side).  Bolt that baby in and get some track time!

- Chris

[slikwilli420]

I've been away from the forums for a while and completely missed this thread!
I'm very excited about having another CB750 on the track!... Welcome to the club SlikWilli!

How are you making out with the the current build? Still think you can get it on the track by June?  I plan on doing either Road America or Gingerman this year, and maybe hit Mid-Ohio if we can swing it... and then NJ (home track) and Barber.  Did we meet down at Barber?  I remember someone asking about a 750 build.

Regarding the battery... if you're going with the LiFePO... get the largest one you're comfortable with.  I'm running total loss on my 750 - 3-Ohm coils (but with a 1-ohm power resistor in line) and HM ignition with points, so less current draw than you'll have with your set-up. I'm using a Shorai LFX14A4-BS12 (I think - I need to double check) and I charge it with the Shorai battery charger after every session on the track... and it takes a while to come back to full charge.  I'd be comfortable doing one back to back race... but I wouldn't push it more than that.  I definitely would not be comfortable with a 5Ah in a LiFe.

Regarding the stock engine.  I raced my first year and a half with a totally stock 1975 CB750F engine (with approximately 20k miles on it)... rode her hard with no major problems except for poping out of gear after a while (but that was probably due to me dropping the bike on the shifter side).  Bolt that baby in and get some track time!

- Chris

Chris, good to hear from you. I picked the brain of every guy at Barber with a 750 this last year, walking around with my uncle, Jeff Hargis. He is the one that got me into Sportsman class to begin with so I have him to thank. I met a number of 750 guys down there so if you remember that, it was me.

The build is coming along well and I have a plan in my head for every aspect I want to address on this bike. The engine is a low mileage '76 model that I have simply dropped the starter/charging system from and will be hitting the track with that this year. Funds won't allow me to get my hi-po engine done AND race, so that one will wait until 2018, but I am confident that my braking/suspension will be dialed in to make the most of the bike this year. Race Tech goodies are being built now, and the 4-bolt Grimeca and cast iron rotor should provide the absolute max braking power allowed within class rules.

How has the Shorai responded to constant drain/recharge cycles? I have heard they are not much for that treatment, especially compared to something like an Antigravity, though the price for a 14Ah battery is better than a 7.5Ah made by Antigravity. I suppose I could try one and see how it works out.

I will be ready for Gingerman this year and am already signed up for the race school that Friday before we race Sat/Sun. Clock's ticking!!

[Kickstart]

I do remember you and Jeff!.... I remember he complimented me on writing down my oil change date on the oil tank cap.

Hey, as I recall, my #1 suggestion to you was to keep it stock and keep it simple.  Ha!... well, so much for trying to keep my competition at bay

It's really hard to resist not going full-in on go-fast mods... we're doing the same thing with my CB160 racer right now - building a CL175 sloper race engine with all the mods - but we're in a similar spot and probably won't have it ready for this season.

BTW, every year I tell my wife I won't be spending endless hours in the garage "next year", but I'm coming to the realization there is always something to rebuild or improve for next year.

One thing I forgot to mention with the Shoria is their charger is maddening to use.  The thing just beeps and turns off when done charging (no, indicator lights saying it's done... just turns off)... we've had problems where it didn't actually charge (charger was unplugged) and we thought we had a charged battery but didn't.  I'm invested now (both my CB160 and CB750 race bikes have Shoria batteries), so it's not worth changing over to another brand right now. 

Also, my experience on the 750 may not be typical as we probably damaged our battery.  When we first used it (fully charged), we were at a track day and I went out for three or four 20 minute sessions during the day... without charging in between... As we thought based on the Ah rating we could go the whole day without any issues.  The voltage dropped abruptly all of a sudden... really low (like 9 volts) and it took until the next day to "restore" (we left it plugged into the charger - even thought it didn't appear to do anything) until it finally came back up to proper voltage.  So ever since then it's been a little finicky about charging.

We have a smaller Shoria on the CB160 (using a single 3 ohm coil and points - no power resistor) and haven't had any trouble... but now we charge after every session just out of caution.

All that said, it sounds like you've done more research than me... so keep me posted on what you pick battery wise.

Whatever you use, it's a good idea to bring a charged backup... or use a holder that can accept a lead acid just in case.  Better to race with 10 extra pounds than miss the race completely.

The work you've done so far looks very impressive!  Glad to hear you're signed up for the race school... from what I've heard from others who've recently taken it, it's a good class. 

Hopefully I'll see you there or at Road America.

Don't hesitate to reach out with any questions.

- Chris

[slikwilli420]

Chris, thanks for the perspective on your battery ordeal. Talking to the guy at Antigravity and Dynatek, a 5Ah battery matched to a system that draws 6-8amps according to Dynatek will still get me over 30 minutes of track time and the 7.5Ah will just be added insurance. Its pricier than the Shorai but Antigravity claims people use their batteries in total-loss systems often and as long as you don't hit the amp hour wall and kill the battery, you will be good. He also said with their charger, I should be able to get the battery back to 13.5v in about 15 min, and 30 min for their battery tender version.

Its been easy to get in too deep and I need to keep reminding myself that it doesn't all need to be done this year. I guarantee it will come down to the wire but come hell or high water, I will at least be ready for race school, even if something doesn't shake out and I can't race. Then at least I can get back on my feet and go to Road America the next weekend.

Let me know if you are going to make it to Gingerman this year. I will be camped out with Jeff and a few other Sportsman 750 guys.

[turboguzzi]

keep forgetting that you are not even racing yet! so unless you are a rossi type talent just waiting to be discovered, not even the + 4-5 pounds of a sealed battery are what going  to stand between you and decent lap times....
last thing you need when setting up your carbs, suspension or working on your riding is worrying if all the stars are aligned before you charge your mega-high-tech-super battery.
slap on a simple high capacity batt and move on to other problems. got to the point in your riding where that extra batt weight is standing between you and podiums? ok, invest in the high tech stuff.





 

[slikwilli420]

You can't get caught up in the minutiae of my ability as a rider. Regardless of my skill I should (and do) want to build the best I can with resources available. Yes a cheaper heavier battery will work just fine but this isn't about what works just fine, but about what works better than it did yesterday. Reducing weight is as much about speed and power as it is about handling. Each thing is not a big deal but the sum of reducing weight and adding reliability can amount to a substantial performance gain through better braking, acceleration and handling. Regardless of my skill level I intend to be my best self any time I am on the track. I should expect no less of my equipment.

[Kickstart]

Half the fun with vintage racing is wrenching on the bike... so I hear you... have fun with it and build the bike you want to build.

I will add one word of caution though... at least half our our upgrade/performance mods introduced unexpected complications and reliability issues until we got them ironed out.  For instance, I've missed three races between my CB160 and CB750 due to rear set shift linkage issues.  If at all possible, try to get your bike ready ahead of time and see if you can squeeze in a track day before the class... or at the very least strap on a temporary brake light (and borrowed license plate) and drive the bike around a bunch to work out any kinks (I've done this before, and fortunately didn't get pulled over).  This way you can focus on the race class and not thinking about "did I tighten that bolt?" while you're on the track.

I'll definitely keep you posted on our plans for the midwest races.

- Chris





 

[754]

Saving 5 lbs on a battery isnt worth it to be the lightest guy in the DNF line.
I ran total loss lead acid on the ice and at the drags, you can get very long use with points.
I know points is a bit of a dirty word here, but I bet not a lot on here used the Maxi-Dwell...I had good results with it.
 A small square battery like a 12N-5.5A 3B... Would probably be good with points, and you can pack spares.
And it weighs 1.7 k plus .48 L of acid.
Remember what they said about keep it simple..

[scottly]

To put things into perspective, weight-wise, the stock charging system with the field, stator, and late rotor weighs 9.65 lbs. 1/2 pound can be shaved off the rotor with no loss in charging. With a shaved 4 pound rotor, my complete system including a 4 cell A123, the regulator, the rectifier, and the battery tray weighed about 10.5 pounds. A stock battery tray alone is over two pounds. Have a read through this thread:
http://forums.sohc4.net/index.php/topic,88214.25.html