300-400cc Race Bike

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Delboy

Well-known member
I do some racing with AHRMA and they announced their schedule for next year and there are only 2 rounds that are even close enough to attend in 2022. It not a lot of track time and I really don’t know if its worth the time and expense of preparing 2 bikes for it.

There is a lot of local club racing though, and one of the most popular classes is Lightweight Production, so R3’s, Ninjas, etc. and you could probably find somewhere to race every weekend if you wanted to.

Is there anyone on here that has built one and wouldn’t mind if I PM’ed them some questions, or I could do it here if the information would be valuable to others.

It would also be good to know if anyone has bumped from an 80’s bike and was it better in regard to the motor, handling, speed, etc. I’m assuming yes to all.

I know I’m going to get my ass handed to me by a bunch of 16 year old’s but - C'est la vie.
 
Yes?

I built an R3 a few years ago after racing a FZR400 for a couple of decades. The R3 is better in every objective way except top end power.

Check rulebooks. In comparable states of tune the Ninja 400 is faster. They have clutch and gearbox issues but I understand that there is a fix. Rules may impose restrictions to even out Kaw vs Yam.

Jesse Norton (Nortonfab) is a great guy. Spears Racing is another resource.
 
Thanks Brian.

Someone else already mentioned NortonFab and I know Spears as I used to have a SV650.

I’m assuming it would always be cheaper buying a race prepped bike but if not what would you tackle first.

I’m assuming springs and emulators and rear shock (is the rear shocks parts bin items on these), a pipe and an ecu flash

Tires 110/140 slicks?

Brakes, braided lines and good pads?

What else. These doesn't seem to be much needed to get on the track

I’ve had a quick look at some club rules and cams and porting are legal but that’s probably around $1000 alone and may need pistons and bored throttle bodies to work at its best so for now thats off the table.

Is there anything else you would Do?

If you went head to head with your self on both bikes which one would be faster?

BTW. I went to see the MotoAmerics round at Laguna Seca and the Lightweight bikes were only 10 or 12 second a lap slower that Gagne.
 
The Ninja 400 makes more power, and the difference is not small ... unless the rulebook dictates that they have to use restrictor plates (CSBK) or rev limiters (I think MotoAmerica) or if the R3 is allowed a power-up package to even up the difference (WorldSSP300).

What follows pertains to the R3. The Ninja 400 no doubt has its own set of issues (the clutch being among them).

Suspension needs attention first (obviously). I have Ohlins NIX22 cartridges in front and an Ohlins shock but this is purely because Ohlins has the best local support around here. K-Tech is another popular one. I wouldn't bother with the springs-and-emulators route.

Footpegs need attention, the stock ones are too low. I have a Woodcraft set on mine.

Handlebars need attention, the stock ones are too high. There is an "R3 Specific" handlebar set, which I was sent by accident having actually ordered something else. I hated them ... too far apart. If you like the dirt-bike riding position then perhaps it's okay but I wanted my arms in. You can make normal Woodcraft clip-ons work, you'll just have to limit steering travel (you can get an aftermarket bolt-on steering stop to address this) and do something about clearance to the instrument cluster. I have an aftermarket Tightails front fairing and instrument panel bracket that allows the instrument panel to be mounted further in (forward). The issue is that the brake master cylinder banjo bolt wants to hit the instrument panel if you try to put the handlebars down and forward where they really should be. If rulebook allows the master cylinder to be changed, and you carefully choose an aftermarket master based upon the orientation of that banjo bolt, that might also help. Remember, it needs to be a master cylinder intended for a single-disk application.

Brakes? All I did was install Norton's braided brake line kit, and put in good-quality brake fluid. No more banjo bolt on the caliper end of the brake line - one less spot for an air bubble to get trapped. Front brake feel is really good. (My bike doesn't have ABS.) Stock caliper, stock disk, stock master cylinder (unless you change it out to stop the banjo bolt hitting the instrument cluster - then you are probably on your own for getting a brake line made up for it).

I did not opt for the lightweight 415 chain ... too scary for me. (I've had one chain-breakage incident years ago, and that was enough.) I use a 520 non-O-ring dirt bike chain and I get a couple seasons out of them.

I'm using a PowerCommander with the Dynojet quick-shifter. If it's only going to have 42 horsepower, it had better be making 42 horsepower all the time.
 
One other small thing. It is of course less expensive to buy a bike that someone else already converted to a race bike. But given my inclination to ride the same bike for many years, and also because this was replacing a bike that had already been highly tailored to my tastes over a very long time ... I wanted it done MY way, not someone else's way.
 
Thanks Brian.

This is really, really helpful, especially the bit about the cartridges. I would have probably got some gold valves from Racetech and called it a day.
 
The Spears Racing shift detent spring & arm kit seems to have solved the shifting issues on my Ninja 300. It would occasionally pop out of gear when at full throttle on the straightaways, and less frequently it would pop out of gear after downshifting in a braking zone. The detent spring kit is a relatively cheap and easy fix, but Spears and a few other shops also have undercut transmissions if the detent spring isn't sufficient.

Fast Frank Racing also has some good stuff for all of the little bikes, like captive wheel spacers and a captive rear brake caliper kit.
 
Ash said:
The Spears Racing shift detent spring & arm kit seems to have solved the shifting issues on my Ninja 300. It would occasionally pop out of gear when at full throttle on the straightaways, and less frequently it would pop out of gear after downshifting in a braking zone. The detent spring kit is a relatively cheap and easy fix, but Spears and a few other shops also have undercut transmissions if the detent spring isn't sufficient.

Fast Frank Racing also has some good stuff for all of the little bikes, like captive wheel spacers and a captive rear brake caliper kit.
Click to expand...

Nothing worse or scarier than cresting the top of T2 at Mosport and having it drop down a gear.

I have 3 race 400s and the undercutting and shiming is the only solution. If not you end up with lots of damage including bent shift forks

Some people live with the phenomenon

I did on my version for a season but the other 2 for the young boys and their pace it was too high of a risk IMHO.
 
I disagree with the need for suspension first, I ran 1.5 seasons on stock stuff, then half a season on good, then a season on stock, then back to a season on good. It was a mission, but I was able to run okay. You learn a lot if you do some time on stock suspension before you move over to the good stuff. I'd run a season before I spent the two grand on suspension if I was you.
 
Has anyone figured out what the transmission issue is?
I raced a EX and the trans was garbage. The problem was the bushes on the driven gears wore and got sloppy. Made new bushes from sintered bronze and all the trans problems went away (I also ditched that second gear lock out that Kawi seems to like).

And there are more cartridge kits available than just the $2500 Ohlins setup... and ANY cartridge setup is better/easier to work with than the metering rod setup.
IF you know what you're doing you can get 90% of a cartridge setup performance out of metering rods, emulators and oil viscosity... it just take time and effort.
And there is absolutely nothin you can do to make the stock shock work any further than corner three.
 
bitzz said:
Has anyone figured out what the transmission issue is?
Click to expand...
www.norton-motorsports.com

Kawasaki Ninja 400 / Z400 (Ninja 500 / Z500) Clutch Slipping, Poor Shifting, False Neutrals, and Dropping Gears - Explained and Fixed!

***Update 2024*** The Ninja 500 / Z500 is showing the same issues, as it’s the same components for the most part between the Ninja 400 and 500. Items that are different: clutch pull rod and bearing (updated in 2020 on the Ninja 400), and clutch springs. Our Ninja 500 Race Spec Clutch Kit has been
www.norton-motorsports.com www.norton-motorsports.com
 
Thanks guys. The information on this thread is gold. I was actually googling 400 Ninja transmission problems and came across the Norton Motorsports page. That's a very through write-up

The Ohlins cartridges are much "cheaper" than I thought. Looks like they are around $995. Its still more expensive than gold valves and springs at around $400 but I think the convenience of not having to pull the emulator out to make changes would pay for its self.
 
Reluctant to jinx myself, but I put the detent spring in my bike before I ran it in anger and it was enough to give me clean and reliable shifts for the entire season. Undercutting would be the next step up, but I don't think I need to do it at this point.
 
DoASkid said:
Reluctant to jinx myself, but I put the detent spring in my bike before I ran it in anger and it was enough to give me clean and reliable shifts for the entire season. Undercutting would be the next step up, but I don't think I need to do it at this point.
Click to expand...

Lol

That sounds familiar

I think I heard that from someone once

And I bought their 400

Which misshifted all season

Until I had it undercut
 
DoASkid said:
Reluctant to jinx myself, but I put the detent spring in my bike before I ran it in anger and it was enough to give me clean and reliable shifts for the entire season. Undercutting would be the next step up, but I don't think I need to do it at this point.
Click to expand...
I thought you were retiring and putting that bike onto the street?
 
Thanks for all the help and all useful comments posted above. Especially Brian P.

I ended up getting a used 400 Ninja but was a little concerned about the issue where they pop out of gear. I'd read about that on a number of other forums as well.

I ended up taking the motor apart to check everything, so I just went ahead and undercut the dogs on the transmission. I ended up doing it myself using a tapered end mill and dividing head in my friends mill. I didn’t want to spend $1000 at Spears. Its quite a mild undercut as the end mill had a 1 degree taper so cutting the matching dogs/slots gave me 2 degrees in total. You could see that 5th gear was already beginning to round off and there was only 8k on the motor :(

My other option was a 2 degree end mill but I was told once by Rob Egan that when you got above 4 degrees it could pop out of gear on deceleration so 2-3 degrees is optimum. I don’t know if that’s right but I'll try this for now. I also reprofiled the shift star and put a roller bearing and stiffer spring on the detent arm and upgraded the clutch springs and plates.

I ended up going for the cartridge conversion in the forks and a Nitron rear shock. Its currently using the standard front brake and caliper with better pads and a braided line with a YBR125 caliper. Its only 11mm diameter so it has a little longer travel but is much more powerful and easier to modulate. I had it out for the first time on New Years Eve. What a nice way to end the year . It was 15 degrees here and dry and I did a lot of laps.

I have to say that this thing is just so easy to ride compared to the vintage RZ or GPZ750. It actually made an embarrassingly slow old person look good…LOL. I was easily able to shave 5 seconds a lap compared to the GPZ and the 400 has half the power. Transmission was great. It didn’t pop out of gear or miss a shift once.

Still have a few things left to do. I took all the bodywork all apart again for some paint. I’ll get some pictures when its done. The big expense was the forks and shock but I had budgeted between 5-6k including the bike so I think it's going to come in around the upper end of that.

I went to the Moto America round at Laguna Seca this year and I was amazed that the 400’s were only running around 10 seconds a lap slower than Gagne. Now I know why. Well, plus the fact that a lot of those kids are just brilliant. Just shows what a light, well set up bike will do.
 
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