Info required on racing a 1982 CB900F

Posted: Mon Feb 06, 2006 7:23 pm

I plan to race my CB900F in Canada in the VRRA racing series. Does anyone on this site race one, or have any useful information on how to prepare this particular model of bike. Or any sites which cater to racing the CB900F?

I am particularly interested in any weaknesses in the engine I should look out for, or any do nots I should be aware of.

Any help would be appreciated.

Posted: Mon Feb 06, 2006 10:26 pm

Have you looked here:
http://www.vrra.ca/

You'd be a Period Three class: Maximum model year 1982.
There are lots of rules to read up on.

Posted: Mon Feb 06, 2006 10:40 pm

I think that Dennis the Mennace races an 82' 900 in the AHRMA.

Posted: Tue Feb 07, 2006 2:45 am

Yep, I race a 900F. For context around some of the choices I made when I built the motor I didn't have a ton of money, I do all my own work (except machine work), and I had just found this website, which saved me a lot of learning on my own.

The AHRMA rules state that I can't displace more than 1025cc, and that any Honda 'F' DOHC motor over 836cc - or is that 825cc? I forget - can only run 29mm carbs (or OEM) on my motor. If you aren't carb restricted like me, I would have opted for 35mm. Race pipe selection is tough as there isn't anything easy to come by.

The first thing I did was get a 985cc Wiseco kit; it bumps displacement and compression. My first motor has Web Cam grind #118 with .365" lift cams, and the second motor I'm building is using Megacycle .375" lift cams. Both need aftermarket valve springs; I used Web Cam's kit for the first motor and a Kibble White set for the second motor. The primary consideration for these cam choices were to be able to retain shim on top buckets, and also not install a cam that requires the motor to rev to the moon to make power, as that is how high the parts will fly when it breaks.

The first bike has a Yosh pipe with the collector centered under the motor and exits by the right foot plate. It requires removing the centerstand on a street bike. The V&H pipe is a joke for racing, you might as well go throw your bike in the dirt as it doesn't have the required clearance on the right side. I'm welding up a pipe for the second bike I'm building as I can't find anything worthy of sticky tires.

The first motor used the stock 900F 'A' chain tensioner, but the second motor uses an 1100F 'A' tensioner. There's many very good posts on this site regarding head work and valve timing - search for them and make your own call.

I've already had to replace the shift fork, 4th gear slider and 3rd gear to fix a problem jumping out of third under power. I've obtained 3rd & 4th gears from an 1100F and a 1000C as they're undercut (but weaker) but the undercut will prevent 3rd from jumping out of gear. You can also get the stock 900F tranny dogs undercut both ways (power & compression) which should fix it once and for all, but that's serious money too.

I replaced the clutch pack with an APE kit but use the stock Honda clutch springs. You should also take out the clutch's "B" thick metal plate (thick one w/ rivets) and replace it with two standard metal plates instead. Search this site for more interesting posts on that subject...

Use a dyna 2000 setup with rev limiter (save your motor!) and dyna coils. The first bike's ignition is set up in the stock location (left side of motor in oil bath), but the second bike will have the ignition where the alternator used to be. If you don't remove the alternator, you'll drag it. (I'm running total loss). The reason I'm moving it is that the ignition side is in an oil bath and I'm getting a light misting of oil that goes onto the left peg & shifter. It's coming from where the pickup wires exit the side cover and I haven't been able to make it stop. Moving the ignition to the right side will require 'engineering' to make it fit; it's not gonna just bolt right on.

My first 900F motor went into a 750F frame (Wasco) and I made aluminum plugs to replace the rubber engine mounts in the 900F cases. I wouldn't race w/ a rubber mounted engine as the damn motor would move too much and concern me. The second 900F motor is going in a 900F frame; I haven't looked at what I'll do to the frame yet, but the motor is going to be solid mounted. I replaced the stock swingarm with a Suzuki GS1100 aluminum box section swingarm also, which required machining of two collar spacers for each side of the narrower Suzuki swingarm. The second bike will have either a Suzuki arm or a ZRX1200 arm.

You'll need to jack the bike up some for ground clearance and speed up the handling a little bit. I stayed with 18" wheels front and back, but there's many benefits (if allowed by rules) on going w/ F2 or F3 wheels (17"); there's many threads on this site telling you everything you need to know. Frame/suspension/wheel/tire setup is a big can of worms; the only thing I could do is tell you what I did but the things to remember are a) you can't go around the corner very quick when hard parts are dragging, and b) if the bike is so unstable/wobbly from being steep in front with tiny little wheels, you're not going to go very quick in the straights. With my 18" wheels I'm around a 1/2" lower in front and 2 1/2" (longer shocks, forward mounted) higher in back. I drag the pegs on both sides (sport kit) and the header collector on the right, but there isn't (at the moment) any need to try and get more cornering clearance as I've pretty much decided I don't want to go any faster than I am already going...

Tire selection is limited; I run modern race compund (medium) in vintage bias ply treaded tires and it works for me. If you run 17" wheels, that'll solve that problem but you'll have others to figure out, mostly related to ride height (which shouldn't be that hard to solve)

This is my bike last year except now the #1 is gone and replaced by my 'old' #490. I won two consecutive national championships on a Z1, and started racing the Honda some this last season. The Kaw is slower, has worse brakes, and didn't handle quite as good, but was close. This suggests that I should be able to do better on the Honda! Also, I had some problems (minor) with both bikes, and lost the championship to another guy... (but even without the problems he still would have beat me last year)

Posted: Tue Feb 07, 2006 2:54 am

here's a picture of the other side; forgot it was available. You can see the swingarm well, and the black thing on the far side of the bike where the alternator used to be is my knee.

Posted: Tue Feb 07, 2006 3:30 am

Cool stuff Dennis. The Superbike requirements are a good read; http://www.ahrma.org/rulebook/sec10.htm - I have a bike that is without title, and I've toyed with going this route.

Quote:

Any wheel size from 16 inch to 19 inch is allowed. Maximum rim width: Rear 4.5 inches, front 3 inches. Wheels may be spoked, Comstar, alloy or magnesium, period style. Straight-spoke alloy wheels painted to period specifications are allowed.

I've seen a few F's running VF1000R rears (17x3.5), but none with F2s. The F2s would meet the size requirements, but it's not clear on what 'period style' means and if they'd qualify?

Posted: Tue Feb 07, 2006 9:43 am

Hey guys,
Just a couple of points of interest. 1 Dennis, are you running you starter motor or have you blocked off the backing plate? I once had a 900 that I chased an oil leak for ages. It turned out to be the "o" ring on the starter.
2 in OZ we run similar wheel sizes on our senior class bikes as what you mention. Our rules also state the wheels must look period. ie no CBR F2 or F3. So most of the guys over here run the ZZR600 3 spoke. apparrently they go in quite easily. My CB will be running the oversized CB1000 or CBR1000.
P.S Dennis your bikes look great

Posted: Tue Feb 07, 2006 2:43 pm

Real nice bike Dennis. How do you like the works shocks? When do you exspect to have the other motor done?

Posted: Tue Feb 07, 2006 5:55 pm

I have removed the starter & starter clutch, installing a plug that doesn't leak. I've confirmed the oil leak (it isn't much) is coming from the pickup wires passing through the rubber block; 1/2 a tube of RTV slowed it down to practically nothing but it's ugly as sin.

The works shocks are great - I'd recommend them to anyone who can afford them. If you can't afford them, I'd try to figure out a way to get the money. I am impressed.

The 'period type & style' is iffy; I've seen a bike or two with F2 wheels but when I asked if I could run a front rim that didn't match the rear comstar I was told 'no'. I ended up with a period Dan Gurney Magnesium Wheel on the back, and the front is an 18" Honda wheel off either a Shadow or a DOHC 750 Nighthawk - I forget. It matches the rear pretty close, so I haven't been bugged about it.

True about the wheels, anything from 16-19". The key concern is not diameter but width. The rear rim width of 4.5 inches and a front of 3 inches I don't think gives you great tire choices, though I think SV-650s may run near that size of rim... I could be wrong.

My second bike (as planned) should be done probably late summer / early fall. It'll be black w/ '82 orange/red stripes. The other big changes are wheels (Interceptor rear 18x3", front Sabre 18x2.5"), rearsets (tabs/mounts welded to frame, rearsets bolt on) instead of those big aluminum footplates, a weld-up pipe that'll be 4:2:1, & a black motor instead of dark gray.

I've been looking for a wheel that was three-spoke design to remind people of the dymags they ran back then; haven't thought about the ZZR wheels. I'll have to shop e-bay...

Posted: Tue Feb 07, 2006 11:51 pm

What are the EPM mag wheels on Dirty Mary worth? They are 18X4 in the rear and 18X3 in the front with rotors of unknown brand.

I am thinking of converting to f2/f3 wheels with modern radial tires.

Posted: Wed Feb 08, 2006 1:35 am

DennisTheMenace wrote:

Yep, I race a 900F. For context around some of the choices I made when I built the motor I didn't have a ton of money, I do all my own work (except machine work), and I had just found this website, which saved me a lot of learning on my own.

The AHRMA rules state that I can't displace more than 1025cc, and that any Honda 'F' DOHC motor over 836cc - or is that 825cc? I forget - can only run 29mm carbs (or OEM) on my motor. If you aren't carb restricted like me, I would have opted for 35mm. Race pipe selection is tough as there isn't anything easy to come by.

The first thing I did was get a 985cc Wiseco kit; it bumps displacement and compression. My first motor has Web Cam grind #118 with .365" lift cams, and the second motor I'm building is using Megacycle .375" lift cams. Both need aftermarket valve springs; I used Web Cam's kit for the first motor and a Kibble White set for the second motor. The primary consideration for these cam choices were to be able to retain shim on top buckets, and also not install a cam that requires the motor to rev to the moon to make power, as that is how high the parts will fly when it breaks.

The first bike has a Yosh pipe with the collector centered under the motor and exits by the right foot plate. It requires removing the centerstand on a street bike. The V&H pipe is a joke for racing, you might as well go throw your bike in the dirt as it doesn't have the required clearance on the right side. I'm welding up a pipe for the second bike I'm building as I can't find anything worthy of sticky tires.

The first motor used the stock 900F 'A' chain tensioner, but the second motor uses an 1100F 'A' tensioner. There's many very good posts on this site regarding head work and valve timing - search for them and make your own call.

I've already had to replace the shift fork, 4th gear slider and 3rd gear to fix a problem jumping out of third under power. I've obtained 3rd & 4th gears from an 1100F and a 1000C as they're undercut (but weaker) but the undercut will prevent 3rd from jumping out of gear. You can also get the stock 900F tranny dogs undercut both ways (power & compression) which should fix it once and for all, but that's serious money too.

I replaced the clutch pack with an APE kit but use the stock Honda clutch springs. You should also take out the clutch's "B" thick metal plate (thick one w/ rivets) and replace it with two standard metal plates instead. Search this site for more interesting posts on that subject...

Use a dyna 2000 setup with rev limiter (save your motor!) and dyna coils. The first bike's ignition is set up in the stock location (left side of motor in oil bath), but the second bike will have the ignition where the alternator used to be. If you don't remove the alternator, you'll drag it. (I'm running total loss). The reason I'm moving it is that the ignition side is in an oil bath and I'm getting a light misting of oil that goes onto the left peg & shifter. It's coming from where the pickup wires exit the side cover and I haven't been able to make it stop. Moving the ignition to the right side will require 'engineering' to make it fit; it's not gonna just bolt right on.

My first 900F motor went into a 750F frame (Wasco) and I made aluminum plugs to replace the rubber engine mounts in the 900F cases. I wouldn't race w/ a rubber mounted engine as the damn motor would move too much and concern me. The second 900F motor is going in a 900F frame; I haven't looked at what I'll do to the frame yet, but the motor is going to be solid mounted. I replaced the stock swingarm with a Suzuki GS1100 aluminum box section swingarm also, which required machining of two collar spacers for each side of the narrower Suzuki swingarm. The second bike will have either a Suzuki arm or a ZRX1200 arm.

You'll need to jack the bike up some for ground clearance and speed up the handling a little bit. I stayed with 18" wheels front and back, but there's many benefits (if allowed by rules) on going w/ F2 or F3 wheels (17"); there's many threads on this site telling you everything you need to know. Frame/suspension/wheel/tire setup is a big can of worms; the only thing I could do is tell you what I did but the things to remember are a) you can't go around the corner very quick when hard parts are dragging, and b) if the bike is so unstable/wobbly from being steep in front with tiny little wheels, you're not going to go very quick in the straights. With my 18" wheels I'm around a 1/2" lower in front and 2 1/2" (longer shocks, forward mounted) higher in back. I drag the pegs on both sides (sport kit) and the header collector on the right, but there isn't (at the moment) any need to try and get more cornering clearance as I've pretty much decided I don't want to go any faster than I am already going...

Tire selection is limited; I run modern race compund (medium) in vintage bias ply treaded tires and it works for me. If you run 17" wheels, that'll solve that problem but you'll have others to figure out, mostly related to ride height (which shouldn't be that hard to solve)

This is my bike last year except now the #1 is gone and replaced by my 'old' #490. I won two consecutive national championships on a Z1, and started racing the Honda some this last season. The Kaw is slower, has worse brakes, and didn't handle quite as good, but was close. This suggests that I should be able to do better on the Honda! Also, I had some problems (minor) with both bikes, and lost the championship to another guy... (but even without the problems he still would have beat me last year)

Thanks, for your replies, and a special thanks to Dennis for taking the time to give me as much information as he did.

I figure to initially race the bike the way I have it presently. I've got the rearset kit on it, fork brace, braided lines, after market rear shocks, steering damper, four into one.

Once I find it's deficiences, I'll work on correcting them. I'm leaving the engine stock at the present time, apart from a Dynojet kit I've installed.

I was hesitant originally about racing it, even though I have had it for over 15 years. I'm somewhat used to modern sport bikes and thought that maybe I would find it hard to adapt to, seeing new bikes are so easy to ride in comparison.

But now I'm really looking forward to racing it. I've always loved this bike, and never figure to sell it. I'm not looking to win races, just have some fun.

Thanks again for the replies.

Posted: Wed Feb 08, 2006 2:03 am

stoutblock wrote:

What are the EPM mag wheels on Dirty Mary worth? They are 18X4 in the rear and 18X3 in the front with rotors of unknown brand.

I am thinking of converting to f2/f3 wheels with modern radial tires.

EMP's back in the day ran to: (note:Canadian bucks here): (see attached pictured);

Tony

Posted: Thu Feb 09, 2006 2:06 pm

Iv'e had my CB900F to 4 trackdays . Even with my fat ass on board, I've had no ground clearance problems. I run the Kerker meg that was desinged to be compatable with the centerstand, it touches on r/h turns that are bumpy, but rarely, 1/2 inch longer works shocks, 1.0 Works Fork springs, but stock wheels. the rear is a fat 140/18 and seems to work okie dokie. I use Avon Supervenoms. Pegs are cheapo Emgo billet type that mount a bit higher and are shorter than stock on stock (non-sportkit) footspeg plates.
Ill look for a pic.
Big Al
Not smart enough to post a pic, click here and you can see the CB160 racer too.
The gallery

Posted: Fri Feb 10, 2006 12:25 am

Tri750 wrote:

Iv'e had my CB900F to 4 trackdays . Even with my fat ass on board, I've had no ground clearance problems. I run the Kerker meg that was desinged to be compatable with the centerstand, it touches on r/h turns that are bumpy, but rarely, 1/2 inch longer works shocks, 1.0 Works Fork springs, but stock wheels. the rear is a fat 140/18 and seems to work okie dokie. I use Avon Supervenoms. Pegs are cheapo Emgo billet type that mount a bit higher and are shorter than stock on stock (non-sportkit) footspeg plates.
Ill look for a pic.
Big Al
Not smart enough to post a pic, click here and you can see the CB160 racer too.
The gallery