Author Topic: CB400f top speeds? (Read 17814 times)

jessezm · « **on:** February 03, 2012, 08:01:21 am »

Just curious what others have found with various modifications to their 400's. I was surprised to read that the factory top speed was listed at only 95mph.

I reached 115mph on mine the other day with a little bit left to go before evolution kicked in and told me to let off... and that was flat, not on a downhill.

I've dropped about 62 lbs from the stock weight, bored to 466cc, bored carb throats, stage 1 ported heads by MReick, web cam #2, bronze valve guides, HD valve springs and hardened alloy retainers, yosh-style exhaust and velocity stacks (may go back to pods for better filtering). Other mods include dyna coils and ignition, suspension and chassis upgrades.

Still not done tuning the carbs but I think the main jets are right on at #95. Possibly still a bit lean, so I'll try 98's if I can find any.

How fast have you all gone on your 400's, and how did you do it?

phil71 · « **Reply #1 on:** February 03, 2012, 08:09:48 am »

those are some nice mods. 110+ is super respectable for a 400 (or a 466).

grcamna2 · « **Reply #2 on:** February 03, 2012, 08:36:00 am »

Hi Jess

,
I want to state right up front that I'm not and won't be a "Performance reductionist"...by NO means

.How does your plug color look to you ? I wondered if you ever ran the stock airbox on your CB400F w/ a high flow filter when it was stock;you're bike is very sensitive to airbox changes when it comes to "Street Performance"; you had all that high end work done and that will focus your powerband up the scale on rpm's a good bit..possibly narrow it more.I wonder...just for grins..if you'd consider installing you're stock airbox w/ the high flow filter installed and then run it with out the filter cover...or possibly the filter cover installed but partially lifted at varied heights...to give you a good bit more midrange...for street running; try it out w/ you're presently installed main jets...it may surprise you

. I had a rack of carbs bored out a few mm on my 78' Z1R Kawasaki w/ a Kerker back in 81'...and I seemed to have lost a lot of snap from 0- 1/4 throttle on that big engine;it would start to "catch bigger revs" w/ the Kerker installed(stock airbox w/ K&N and filter cover installed

around 6500rpm,but I lost that big fat 3-4000 rpm "walk away" power that I so enjoyed w/ stock. The way folks let you drive on the street....well...it's kind of nice to have a bit more midrange(maybe5 - 7K rpm's

for your bike;you can fine tune the performance flow of your bike w/ different intake and exhaust & jetting changes...fine tuning it to you're riding styles & preferences, and possibly degreeing the camshaft for the same...on that little bike it'll take some time to "dial-in" just what you like

...but the outcome will be Very Nice indeed

How does she feel out on the road w/ less weight and the RT mods ??

crazypj · « **Reply #3 on:** February 03, 2012, 08:51:38 am »

I've found 'big bore' 400's don't worry as much about stock airbox.
Do you have a fork brace fitted?
It will improve handling

754 · « **Reply #4 on:** February 03, 2012, 09:08:42 am »

I had better go faster than my stock 66 Ducati Mach 1 250 went...... at least it should..

jessezm · « **Reply #5 on:** February 03, 2012, 09:15:21 am »

Crazypj--I've got a great Tkat forkbrace I just installed and I love it. Definitely wouldn't be pushing the envelope so much without that and the other suspension mods I just did (Hagon shocks, Race Tech emulators and springs up front)

Bill--
I only drove this bike once in stock condition. It had been sitting in a barn some 5 or 10 years and the front brake was mostly seized, but amazingly it came right to life and I took her down the road, but just to check for funny noises and smooth shifting. It came completely apart in my driveway that night, and I sold the airbox and filter set up so I'm afraid there's no easy going back.

What I found to be true on the advice of Rick Denoon was to drop the pilot jet to a 38. That and lowering the needle a click gave me really amazing throttle response in the low to mid range. Otherwise it was pretty soggy, especially when the bike gets warm. But I had to go back to the middle position on the needle as it was too lean. Right now the feel is pretty close to hos I want it but still a little rich around town (although I get some lean popping through the exhaust as I decelerate to a stop light with the throttle closed). My plan is now to adjust the float height to lower the fuel in the bowls, and then play with the air screws to see if I can get rid of the popping. If that doesn't work I'll try shimming or even thinning the needles some...

jneuf · « **Reply #6 on:** February 03, 2012, 09:58:43 am »

I've never topped mine out. Since I don't always trust the spedometers, I took my gps with me on a little scoot down an empty road. I don't remember what the tach reading was, but I hit 87 mph in 4th gear, and it was still pulling pretty hard. With two more gears to go, I can't say what the top speed would have been, but topping 100 mph would've been no problem at all. I should also mention that I reached that 87 mph surprisingly quick. These little bikes shouldn't be underestimated!

jessezm · « **Reply #7 on:** February 03, 2012, 10:29:06 am »

Oh, and to answer your other questions, Bill--
I did a throttle chop on the highway the other day like this: installed fresh plugs on the side of the on-ramp, drove 5 minutes with mostly open throttle (dropping to 5th and dragging the rear brake so I wasn't going too fast), and cut out the engine on an uphill off-ramp and cruised to a stop. Plugs looked completely clean, if not just a slight bit discolored. But when I pull the plugs after driving around town for a while they're pretty sooty.

As for the handling, I can tell you I'm not nearly a good enough rider to take advantage of the bike's new feel. It is so light and maneuverable now, especially compared to when I get on a stock 550 or 750. It's just night and day. I had Hondaman re-work my swingarm and I installed tapered steering bearings on top of the other things I mentioned, and the bike just feels so light and responsive. I still need to fine tune the forks and shocks, and may actually need heavier springs, but so far it feels more like my '01 Guzzi V-11 Sport did than my old CB750 or xs650.

MCRider · « **Reply #8 on:** February 03, 2012, 11:23:50 am »

With all due respect, its a pet peeve of mine, there are many top speed threads, I just happen to pick yours.

If you're basing it on a 40 year old speedometer, well...

If its not a GPS or a radar gun you don't know what it is.

95 on a stocker is generous. IMO.

jessezm · « **Reply #9 on:** February 03, 2012, 11:28:37 am »

It is not the original speedo, but a new aftermarket one, but I take your point. I don't have a GPS or radar gun but I'll look for someone who does.

To be fair, I did do a search before posting for "cb400f top speed" and I did not find what I was looking for in the first several pages.

MCRider · « **Reply #10 on:** February 03, 2012, 11:48:55 am »

Quote from: jessezm on February 03, 2012, 11:28:37 am

It is not the original speedo, but a new aftermarket one, but I take your point. I don't have a GPS or radar gun but I'll look for someone who does.

To be fair, I did do a search before posting for "cb400f top speed" and I did not find what I was looking for in the first several pages.

This was the first thread on a CB400. Others have included the 500/550, but usually the CB750. As much as I love the CB750, I know how hard it is to really go fast and when I hear a stock never touched CB750 is doing 115 with "more to go" I say to myself, yeah right, show me the proof.

Maybe its true, I'm just saying.

In your case, I'd love it for your sake if it went 115. I'd be happy if i were you. That's 21% over stock, maybe more. That's expectable based on what you've done. Fun, eh?

BTW, my understanding is the weight reduction contributes little to top speed, just getting there.

jessezm · « **Reply #11 on:** February 03, 2012, 12:04:00 pm »

Yeah, I have no doubt that 60 lbs makes a significant difference. The bike weighs 330 lbs now with a little over half a tank of gas. I'm still curious, though, and I'm sure I can find a friend with a GPS I can borrow.

ttr400 · « **Reply #12 on:** February 03, 2012, 01:38:02 pm »

I remember when I bought my first 400 new in 1975. the quoted top speed was 102 mph, my buddy had just got the RD350 with a quoted top speed of 105 mph. yes he could just get me at the top. over the years I have built many 400's from std 408 to 458cc, 466cc 492cc 502cc 510cc all of them could easily do over 100 mph, the bigger bore 400's anything from 110-125 mph depending on the specs and gearing etc. tested many times along side cars, modern sport bikes etc.
Power to weight....yes lighter = faster.
That's why a modern Yamaha R1 does not shape on the track with a stock motor against other litre machines like The CBR, GSXR,ZX10,Aprilia.......it needs to go on a diet. our racing weight limits for 4 cyl 1000cc class bikes is 175kg wet, the R1 is much more than this.

Kevin

Tews19 · « **Reply #13 on:** February 03, 2012, 01:51:30 pm »

Local builder here in Milwaukee discusses his top speed with his 400F
Cafe Racer TV's, Cafe A La Cart w/ Tim Schneider Cafe - 1976 CB400F Race/Street

jessezm · « **Reply #14 on:** February 03, 2012, 01:56:09 pm »

cool, thanks for posting!

MCRider · « **Reply #15 on:** February 03, 2012, 02:12:57 pm »

Quote from: ttr400 on February 03, 2012, 01:38:02 pm

I remember when I bought my first 400 new in 1975. the quoted top speed was 102 mph, my buddy had just got the RD350 with a quoted top speed of 105 mph. yes he could just get me at the top. over the years I have built many 400's from std 408 to 458cc, 466cc 492cc 502cc 510cc all of them could easily do over 100 mph, the bigger bore 400's anything from 110-125 mph depending on the specs and gearing etc. tested many times along side cars, modern sport bikes etc.
Power to weight....yes lighter = faster.
That's why a modern Yamaha R1 does not shape on the track with a stock motor against other litre machines like The CBR, GSXR,ZX10,Aprilia.......it needs to go on a diet. our racing weight limits for 4 cyl 1000cc class bikes is 175kg wet, the R1 is much more than this.

Kevin

Hi Kevin"
I googled the 400 and found spec sheets that say 102 as well as the 95 mentioned by jessezm, top speed. I don't doubt that built bikes can achieve those higher speeds. My peeve is mostly for claims of stock bikes doing more than even the factory claims they can, usually the 750, doing more than 120 with more to go.

I'm sure the weight reduction = quicker. But faster? And so, gets to top speed quicker. But does it really affect top speed? A google on the subject in inconclusive. There are many in both camps. The extra weight will cause small load on the drive train, but other than that, top speed will be the same given enough distance to reach it. On a road race course with a 1/4 to 3/8 mile straightaway, the lighter bike will get to top speed quicker and carry it further down the straight, making it appear it is faster than the heavier bike which gets to top speed only in time to back off for the first turn. But in reality the top speed attained was equal.

Maybe.

In any event I take it all with a grain of salt, unless its a GPS number. Even radar guns are suspect though much better than they were.

Gordon · « **Reply #16 on:** February 03, 2012, 02:28:36 pm »

Quote from: MCRider on February 03, 2012, 02:12:57 pm

Quote from: ttr400 on February 03, 2012, 01:38:02 pm
I remember when I bought my first 400 new in 1975. the quoted top speed was 102 mph, my buddy had just got the RD350 with a quoted top speed of 105 mph. yes he could just get me at the top. over the years I have built many 400's from std 408 to 458cc, 466cc 492cc 502cc 510cc all of them could easily do over 100 mph, the bigger bore 400's anything from 110-125 mph depending on the specs and gearing etc. tested many times along side cars, modern sport bikes etc.
Power to weight....yes lighter = faster.
That's why a modern Yamaha R1 does not shape on the track with a stock motor against other litre machines like The CBR, GSXR,ZX10,Aprilia.......it needs to go on a diet. our racing weight limits for 4 cyl 1000cc class bikes is 175kg wet, the R1 is much more than this.

Kevin
Hi Kevin"
I googled the 400 and found spec sheets that say 102 as well as the 95 mentioned by jessezm, top speed. I don't doubt that built bikes can achieve those higher speeds. My peeve is mostly for claims of stock bikes doing more than even the factory claims they can, usually the 750, doing more than 120 with more to go.

I'm sure the weight reduction = quicker. But faster? And so, gets to top speed quicker. But does it really affect top speed? A google on the subject in inconclusive. There are many in both camps. The extra weight will cause small load on the drive train, but other than that, top speed will be the same given enough distance to reach it. On a road race course with a 1/4 to 3/8 mile straightaway, the lighter bike will get to top speed quicker and carry it further down the straight, making it appear it is faster than the heavier bike which gets to top speed only in time to back off for the first turn. But in reality the top speed attained was equal.

Maybe.

In any event I take it all with a grain of salt, unless its a GPS number. Even radar guns are suspect though much better than they were.

I was going to say the same thing, but then got to your post.

Weight reduction has very little if anything to do with top speed, unless you're talking about the difference between a 300 lb guy vs a 120 lb guy riding the bike, but then it's not the weight that's making the difference, it's the increased drag caused by the much larger rider.

phil71 · « **Reply #17 on:** February 03, 2012, 11:52:27 pm »

Ok... To add fuel to the fuel.... I have a well tuned k1 that I've had at 115 (oem speedo ,sprockets& stock tire size) i was limited only by my balls and the road quality. Didn't seem very close to the end of its rope, but I could be wrong.

ivanhoew · « **Reply #18 on:** February 04, 2012, 12:04:42 am »

pre turbo , in the 1978/79 area ,running a straight through dunstall silencer,no filter box lid,and dropped bars ,regularly read 108 mph indicated on the speedo . rd tests for the stock bike in magazines were 102 mph .

it was definately faster than my friends bikes ,a kz400/4 kawasaki with full laser exhaust ,and a ported rd250 yamaha.

regards
robert

Gordon · « **Reply #19 on:** February 04, 2012, 05:48:39 am »

Quote from: phil71 on February 03, 2012, 11:52:27 pm

Ok... To add fuel to the fuel.... I have a well tuned k1 that I've had at 115 (oem speedo ,sprockets& stock tire size) i was limited only by my balls and the road quality. Didn't seem very close to the end of its rope, but I could be wrong.

Near the top end it's not uncommon for the stock speedometers to be generous by as much as 10 mph, sometimes more.

crazypj · « **Reply #20 on:** February 04, 2012, 07:43:42 am »

I posted on a different forum about this as well, Yamaha were well known to have 'race tuned speedo' usually showing around 20~30mph fast at top end, no other way of explaining 115mph RD200's and 125mph RD250's

bwaller · « **Reply #21 on:** February 04, 2012, 07:58:38 am »

Hey we've all done it...gone out on a quiet stretch of road to see how "it'll do." It's certainly not likely anyone would convince their local sherriff to come out and clock us on his radar. Who knows how accurate a gps unit would be either. SO be happy, it's obvious your bike is now faster than stock.

Making a few pulls on a dyno with a sniffer to finish tune anyones non-stock engine is a good thing and gives you a RWHP number to compare to what others have done. Then if you want to see a computed top speed figure you can go to gearingcommander.com and plug in all your values and it'll show you.

Just sayin.

jessezm · « **Reply #22 on:** February 04, 2012, 08:52:57 am »

Quote from: bwaller on February 04, 2012, 07:58:38 am

Hey we've all done it...gone out on a quiet stretch of road to see how "it'll do." It's certainly not likely anyone would convince their local sherriff to come out and clock us on his radar. Who knows how accurate a gps unit would be either. SO be happy, it's obvious your bike is now faster than stock.

Making a few pulls on a dyno with a sniffer to finish tune anyones non-stock engine is a good thing and gives you a RWHP number to compare to what others have done. Then if you want to see a computed top speed figure you can go to gearingcommander.com and plug in all your values and it'll show you.

Just sayin.

I'm looking for a local shop I can go to for some dyno runs, actually.

MCRider · « **Reply #23 on:** February 04, 2012, 09:12:00 am »

bwaller: Now I'm really bummed. Not thinking the GPS could be inaccurate, I did a google on it. While the GPS MAY be the most accurate, and can be the most accurate, from one to another there can be differences. Now we don't know which is right. The theory of the GPS would be correct, but the quality control and other factors render it unknowable.

So everyone go back to claiming whatever makes you feel good, and I'll quietly skulk off into the corner.

Gordon · « **Reply #24 on:** February 04, 2012, 10:35:05 am »

Quote from: MCRider on February 04, 2012, 09:12:00 am

bwaller: Now I'm really bummed. Not thinking the GPS could be inaccurate, I did a google on it. While the GPS MAY be the most accurate, and can be the most accurate, from one to another there can be differences. Now we don't know which is right. The theory of the GPS would be correct, but the quality control and other factors render it unknowable.

So everyone go back to claiming whatever makes you feel good, and I'll quietly skulk off into the corner.

Compare what your GPS says to a newer car's speedometer. Or better yet, test it by traveling one mile at what it says is 60mph, and see if it takes you exactly 60 seconds.

News:

Author Topic: CB400f top speeds? (Read 17814 times)