Topic: CB400f top speeds?

[Kong]

Somewhere in the setup of your GPS there should be a trip meter, that is resettable, and it almost always includes the maximum speed you have traveled since the last reset.  That GPS speed will be accurate to within 0.1mph on flat ground and with a continious sky-view.  Now here is the odd thing though.  Sometimes you will see absurdly high speeds showing on a GPS that come from very short term calculations by the machine.  Its a little hard to explain all the ways it can happen but this one sort of gives the idea.  Lets say you are using the GPS to see how fast you walk on average.  So you reset the thing and take a hike up the road for a mile or so just to see how fast you walk.  As you walk you hold the GPS in your hand and now and then you glance at it and see that your walking speed is about 3 mph, sometimes a little higher, sometimes a little lower, but always around there.  So you get to your destination and hit the buttons to see what your maximum speed was during the walk and you are surprised to see that at one time you went 37 mph.  You know dam good and well you never went that fast, but there the number is.  Well, what happens is that at some time during your walk your hand, the one that was holding the GPS, swung down or swung back and forth much faster than you were walking and the machine just happened to pick the moment at the top of the swing to compare to another measurement taken at the opposite apex.  It happens all the time.  I had a boat that had a top speed just a little bit over 30 mph, but every time I looked at my trip meter I'd see that at some point it had gone between 90 and 140 mph.  Come to find out that is the speed the boat would come down off a wave when we hit a big one, but as far as the GPS is concerned there is no difference between going forward, backward, up, or down, it only measures speed in an absolute sense.

By the way, I've owned a host of stock 750s over the years and I don't recall that a single one of them would go much over 110 and even that took a cool night and a long run at it to get up to speed.

[andy750]

GPS is the way to go:

CB810K2:



That isnt the top speed but as others have said I wouldnt trust the stock  speedo to tell you the real speed. In my case the speedo is fairly accurate being out only 5 mph or so at 100 mph.  If you have an Iphone there is a speedometer app that works on GPS. 

Anyway whatever the speed enjoy you bike!
cheers
Andy

[fayettebr]

Doesn't it seem like the skinny guy always has the fastest bike.

[MCRider]

Somewhere in the setup of your GPS there should be a trip meter, that is resettable, and it almost always includes the maximum speed you have traveled since the last reset.  That GPS speed will be accurate to within 0.1mph on flat ground and with a continious sky-view.  Now here is the odd thing though.  Sometimes you will see absurdly high speeds showing on a GPS that come from very short term calculations by the machine.  Its a little hard to explain all the ways it can happen but this one sort of gives the idea.  Lets say you are using the GPS to see how fast you walk on average.  So you reset the thing and take a hike up the road for a mile or so just to see how fast you walk.  As you walk you hold the GPS in your hand and now and then you glance at it and see that your walking speed is about 3 mph, sometimes a little higher, sometimes a little lower, but always around there.  So you get to your destination and hit the buttons to see what your maximum speed was during the walk and you are surprised to see that at one time you went 37 mph.  You know dam good and well you never went that fast, but there the number is.  Well, what happens is that at some time during your walk your hand, the one that was holding the GPS, swung down or swung back and forth much faster than you were walking and the machine just happened to pick the moment at the top of the swing to compare to another measurement taken at the opposite apex.  It happens all the time.  I had a boat that had a top speed just a little bit over 30 mph, but every time I looked at my trip meter I'd see that at some point it had gone between 90 and 140 mph.  Come to find out that is the speed the boat would come down off a wave when we hit a big one, but as far as the GPS is concerned there is no difference between going forward, backward, up, or down, it only measures speed in an absolute sense.

By the way, I've owned a host of stock 750s over the years and I don't recall that a single one of them would go much over 110 and even that took a cool night and a long run at it to get up to speed.

In my google search on GPS accuracy, one of the biggest examples of discrepancy was between two boats travelling beide each other. The GPS s were 5 mph off. Maybe it was the waves and bouncing up and down?

[BeSeeingYou]

Somewhere in the setup of your GPS there should be a trip meter, that is resettable, and it almost always includes the maximum speed you have traveled since the last reset.  That GPS speed will be accurate to within 0.1mph on flat ground and with a continious sky-view.  Now here is the odd thing though.  Sometimes you will see absurdly high speeds showing on a GPS that come from very short term calculations by the machine.  Its a little hard to explain all the ways it can happen but this one sort of gives the idea.  Lets say you are using the GPS to see how fast you walk on average.  So you reset the thing and take a hike up the road for a mile or so just to see how fast you walk.  As you walk you hold the GPS in your hand and now and then you glance at it and see that your walking speed is about 3 mph, sometimes a little higher, sometimes a little lower, but always around there.  So you get to your destination and hit the buttons to see what your maximum speed was during the walk and you are surprised to see that at one time you went 37 mph.  You know dam good and well you never went that fast, but there the number is.  Well, what happens is that at some time during your walk your hand, the one that was holding the GPS, swung down or swung back and forth much faster than you were walking and the machine just happened to pick the moment at the top of the swing to compare to another measurement taken at the opposite apex.  It happens all the time.  I had a boat that had a top speed just a little bit over 30 mph, but every time I looked at my trip meter I'd see that at some point it had gone between 90 and 140 mph.  Come to find out that is the speed the boat would come down off a wave when we hit a big one, but as far as the GPS is concerned there is no difference between going forward, backward, up, or down, it only measures speed in an absolute sense.

By the way, I've owned a host of stock 750s over the years and I don't recall that a single one of them would go much over 110 and even that took a cool night and a long run at it to get up to speed.

In my google search on GPS accuracy, one of the biggest examples of discrepancy was between two boats travelling beide each other. The GPS s were 5 mph off. Maybe it was the waves and bouncing up and down?

Don't know for sure but I would think GPS would be more accurate the faster you go.  It's measuring distance and time so the more ground covered between fixes at the higher speed would give you a more accurate speed measurement.  Makes some sense...at least to me.

[754]

 If you think weight does not affect speed, add a ton and see if it sztill has the same top speed.. I dont think it will..

[Gordon]

If you think weight does not affect speed, add a ton and see if it sztill has the same top speed.. I dont think it will..

You're well into the realm of hyperbole, there.  The rest of us are talking about real-world numbers.

[MCRider]

If you think weight does not affect speed, add a ton and see if it sztill has the same top speed.. I dont think it will..

You're well into the realm of hyperbole, there.  The rest of us are talking about real-world numbers.

Yeah a ton v a 500lb vehicle .  There will be real world friction etc, that slows it down.

I'm saying 30 to 60 lbs v a 400-500 lb vehicle. Minimal differences in friction and wind resistance. I've been googling and there's arguments both ways, with lots of math and formulas that are over my head.

My gut is still that less weight = quicker but not ultimately faster.

[crazypj]

If you think weight does not affect speed, add a ton and see if it sztill has the same top speed.. I dont think it will..

You're well into the realm of hyperbole, there.  The rest of us are talking about real-world numbers.

My gut is still that less weight = quicker but not ultimately faster.

 Yep, less weight = quicker acceleration top speed doesn't care how heavy if you have enough room to run Google Richard Noble, land speed record, supersonic car I believe weighed around 7 TONS?

 Just checked,
weighs 10 tonnes, and initial performance estimates suggest it will accelerate from standstill to 100mph (161kph) in four seconds or 0-600mph (1000kph) in 16 seconds.
 Of course, it helps if you have enough power as well (around 25,000HP  )

[grcamna2]

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.

I believe overcoming wind resistance is the biggest factor the faster you go;Jess, have you considered adapting a nice "wind cheating" fairing ?...they have plenty of them for smaller displacement cycles in Europe.The higher the speed you roll on..the more HP it takes to maintain that speed and a LOT more HP is needed to increase that speed...especially after 100 MPH !We see those special World land Speed record cycles and cars at Bonneville Salt Flats that have very nice sharp looking aerodynamically designed full fairings, full coverage body work to make them as "clean" as possible...a little like an airplane. I'm also thinking of the hull designs on certain boats..talk about resistance and drag ,that water is a lot harder to "push through" than air, I think.I think it helps(I know it does on the bicycle ) to flatten your back as much as possible and tuck into the bike for those speeds.

I would love to find a nice 1/4 - 1/2 fairing for my little CB350 because the smaller the engine..the harder it has to work to overcome the wind resistance of my Big self + whatever luggage I'm carrying;these little bikes get thrown around a lot because of that factor..also side gusts.Jess, if you hear of any ideas on a nice bullet style fairing for your bike please let me know. I hope you're really enjoying that fully restored machine of yours down in the warm state of Ga. in the Winter  !

[jessezm]

You bet I'm enjoying it!  I had a really nice ride last evening in this bizarre 70 degree weather.    I've thought about a bikini fairing or something like the guzzi le mans has and definitely have noticed the bike's willingness to accelerate faster with my body tucked into it, but honestly, I think it would be a pretty expensive endeavor for me to get one that fits and looks right.  Given that the tank and seat are polished aluminum, I'd probably be looking at having one custom made to match, and I think I'm done dropping the big bucks on this bike for now!

[Derby cycles]

Perhaps a run Barber this October is in order? Or haul up to Franklin,TN and check out some of the best roads in the SE! Sounds like you got a quick little 400, all I can say is that I love mine! Keep it up!

Mike

[jessezm]

Definitely taking her to Barber this year!  I was disappointed I had to leave the bike at home last year, but it was all pulled apart at the time.

[grcamna2]

You bet I'm enjoying it!  I had a really nice ride last evening in this bizarre 70 degree weather.    I've thought about a bikini fairing or something like the guzzi le mans has and definitely have noticed the bike's willingness to accelerate faster with my body tucked into it, but honestly, I think it would be a pretty expensive endeavor for me to get one that fits and looks right.  Given that the tank and seat are polished aluminum, I'd probably be looking at having one custom made to match, and I think I'm done dropping the big bucks on this bike for now!

Jesse,
    What's the closest large salvage yard to you ? I mean a very large place that has indoor parts and such...any place in or around Atlanta ? I would be curious if there may be a place that has a good used 1/4 fairing for your bike that you can find & make some custom mounting brackets for. I had a little 1/4 fairing for my RD350(but always wanted a 1/2 fairing) which would let the bike cut through the wind SO much better on the Interstates.If you see anything out there please let me know...that is..if you don't want it...or if they have 2  ; Aero design is what I'm after .

[jessezm]

Well look what I just found.  VERY interesting....

http://atlanta.craigslist.org/atl/mcy/2812298999.html

[grcamna2]

That looks like a nice "race only" design 1/2 fairing ...the way it's designed...it would be difficult to cut a hole in it for the headlight w/o compromising the structural integrity and overall strength of it's body structure..very aero though  .I think there may be a few other things out there in your area...;I wouldn't mind purchasing something from the area around Atlanta;the reason i mentioned a BIG salvage yard,etc. was they may have something around & possibly still have the brackets,etc. I'll just be patient and do a long term search. Jesse, that's a great price for that fairing and it doesn't look as if it's been crashed, thanks for adding the link  .  Perhaps that man ED in the add from Kennesaw might know where else you could get a street adaptable fairing ?

[crazypj]

Looks like Aprillia 50~125 or Yamaha R? headlight would fit?
 I've seen a couple of ATV's with dual lights that could be adapted

[Psychonaut]

94.3 mph Garmin GPS. 31,000 miles, Supertrapp muffler and filter lid removed.

[400f newbie]

10,000 revs in fifth, gps 96.5 mph,speedo about 103 ,104 mph.           changed into sixth and speed dropped to 93 on gps.           able to maintain speed for about 20 seconds but not able to increase speed. decided that i had given the old girl enough punishment and headed home.conditions were no wind .bike is standard but tires are i think half inch oversize.in hindsight i chickened out on the return journey.      ray.

[RickB]

Jesse,

Great thread, I love trying to see how fast my CB400F will go!



So my setup:

New OEM pistons (+.25 when I did the rebuild), rings, valves, big end bearings, NOS cam shaft, rockers, new HD springs, HD cam chain, TTR400 horseshoe tensioner, stock clutch with HD springs. I have a Dyna ignition and coils with new leads and stock spark plugs.

Completely stock airbox, rebuilt carbs and OEM jetting (except #38 idle jet). I have the stock 4-1 header but I have a $50 straight through Norton Commando Peashooter replica muffler.

Tires are Dunlop K70 knock-offs from Mitas (eastern europe's leading manufacturer of agricultural tires!) and suspension is 'performance' Redwing springs on the back (ie, not performance at all and very cheap), stock springs in the stock tubes at the front but with 20mm preload spacers in the top. No fork brace. Sprockets are new OEM in stock sizes.

My gauges are the 60mm mini gauges from CRC2 imports.

I have put less than 1000 miles on this bike and have new oil and 98 octane BP petrol in it. The tank is from a CB350F, the seat a fibreglass base I made myself that has to be heavier than the original! To offset the amount of resin and aluminum I used in the seat, I have no rear fender.

Anyway, I've only been brave enough to get her up to just over 100MPH After that I get scared and worry I'm going to blow something up and let off. But if I had enough courage and road, I think it would reach 10,000RPM before it went much over 100MPH.

On that note, when trying to achieve top speed in 6th gear, do I have to worry about hitting that 10,000RPM redline? Or will the bike simple not go any faster and that's how I know to stop going for it?

Rick.

[grcamna2]

Rick,
   I've looked at your project build and that is a very Nice :)completed project restoration build on your "custom" O.E. Honda CB400F...brought back from the Dead for sure ! How does your Commando muffler work out for you? does it give any low end power? & how is the bark  ?

[jessezm]

Awesome, Rick.  Love the glamor shot, too!  With the HD springs I'd think you could push the revs past 10,000.  Shoot, I've taken mine to 11,500 with no (apparent) ill effects.  With the ported heads and bored carbs and cam, she really loves to rev...

[MCRider]

As 400F implies, I wonder if 6th is an overdrive. In which case you'll get the highest speed in 5th gear.

96+ in 5th, which would be a respectable top speed for a 350/400F, and the bikes reaction to 6th, would so indicate.

[RickB]

Thanks guys. Ok, so I won't blow it up if I go to 10,000RPM, that's good to know.

Is the 6th gear on a CB400F an overdrive? I haven't heard that before but would love to know. Top speed in 5th would be handy to know.

As for the peashooter exhaust. I am having trouble with my low end power. The bike is sluggish off the line for sure. As Jesse is aware, I intend to change the float height a few mm (from 21mm to 22mm/23mm) in an effort to get off the mark quicker. Are you suggesting that the peashooter exhaust may be the reason why I've been sluggish from take off? Not meaning to hijack this thread so feel free to post in my project build thread.

As for the noise, it is fantastic! When I'm accelerating it sounds similar to a Ferrari I think. Much more sports car than motorcycle. Then when I let off the throttle it gives off this addictive gurgling sound. Not sure if that's healthy or not, but it sure does sound mean!

Rick.

[grcamna2]

Thanks guys. Ok, so I won't blow it up if I go to 10,000RPM, that's good to know.

Is the 6th gear on a CB400F an overdrive? I haven't heard that before but would love to know. Top speed in 5th would be handy to know.

As for the peashooter exhaust. I am having trouble with my low end power. The bike is sluggish off the line for sure. As Jesse is aware, I intend to change the float height a few mm (from 21mm to 22mm/23mm) in an effort to get off the mark quicker. Are you suggesting that the peashooter exhaust may be the reason why I've been sluggish from take off? Not meaning to hijack this thread so feel free to post in my project build thread.

As for the noise, it is fantastic! When I'm accelerating it sounds similar to a Ferrari I think. Much more sports car than motorcycle. Then when I let off the throttle it gives off this addictive gurgling sound. Not sure if that's healthy or not, but it sure does sound mean!

Rick.

If you can find a stock O.E. Honda muffler for your CB400F you'll gain all the low end power your engine can deliver, especially off the line ...but you may miss that "bark" a little .