Author Topic: RE: CB400f What kinda of speed to expect? (Read 3870 times)

chewbacca5000 · « **on:** June 04, 2016, 05:45:00 PM »

First time out on my 400f today about 10 miles and am still in the process of "waking her" up after a 6 year nap. Wondering what kind of speed I should expect? Bike shows 50k on the clock.

Floats are set to 22mm

Air screews are 1 1/2 turns

jonda500 · « **Reply #1 on:** June 04, 2016, 06:55:52 PM »

I would expect it to be able to hit 100mph.
Also usually there's a flat spot at around 5000rpm that you need to get the revs past.
John

MoMo · « **Reply #2 on:** June 04, 2016, 08:03:44 PM »

100 downhill with a wind behind you as it was rated 95mph

Scott S · « **Reply #3 on:** June 05, 2016, 05:57:44 AM »

You mean it won't do 85 in 2nd gear?!

dhall57 · « **Reply #4 on:** June 05, 2016, 06:06:34 AM »

I bet Chew hasn't done his 3000 mile tune-up yet. Being a 400 he might be able to hit 90 in 2nd

flatlander · « **Reply #5 on:** June 05, 2016, 07:34:40 AM »

my neighbour has a 400f. when she left once for a couple of weeks she dropped me the keys, saying: go give it a go if you like. of course i could not resist... on the highway i found myself mostly in the right hand lane (with my 550 i'm mostly on the far left...), keeping up with traffic up to around 120 - 130kph (80mph). once it was there it kept rolling but it took a while to get up to that speed, and lost responsiveness considerably as it was getting close to its limit. overtaking was a chore, had to be planned quite carefully.
it seemed pretty happy with still a bit reserve left when going at around 100kph (+/- 65mph). nice for smaller roads but on the highway i felt a bit like on a moped.
i measured these speeds on the gps, not the speedo so they should be quite realistic.
95 mph is the quoted max speed? you may be able to reach that if you don't have a stiff wind against you, but make sure you take some packed lunch coz it will take some time

strynboen · « **Reply #6 on:** June 05, 2016, 07:50:04 AM »

mine can hardly get over 100 kmh..but think i have a problem ..those carbs is making me mad..one is floting and oner is drying.

flatlander · « **Reply #7 on:** June 05, 2016, 08:07:32 AM »

it should definitely go over 100kph. it won't do it very quickly but it'll get there. my neighbour's 400 is totally stock and not too well maintained.

strynboen · « **Reply #8 on:** June 05, 2016, 08:10:46 AM »

i think i thange to rubber needels in the fuel valvets..or try to tap them carefull to seat better...its a float heigh problem

flatlander · « **Reply #9 on:** June 05, 2016, 08:20:14 AM »

good luck! hope you get it to run right. they're fun bikes, just not for longer runs on the highway.

Deltarider · « **Reply #10 on:** June 05, 2016, 08:45:40 AM »

Quote

just not for longer runs on the highway.

Wouldn't say that. A friend went all the way to (and in) Morocco on a CB400 Four.

chewbacca5000 · « **Reply #11 on:** June 05, 2016, 09:31:58 AM »

Quote from: dhall57 on June 05, 2016, 06:06:34 AM

I bet Chew hasn't done his 3000 mile tune-up yet. Being a 400 he might be able to hit 90 in 2nd

Yup I have not given it the 3,000 mile tune up yet. Adjusted the cam chain and set carbs to 22mm. Will adjust the valves and set the timing.

For some reason I was thinking it would be able to pull just as hard as my K1. I will see if I can get in a bit better tune.

Tim2005 · « **Reply #12 on:** June 05, 2016, 10:07:27 AM »

Just over 100 on the speedo if it is in top condition and set up really well, or you have a tailwind/downhill, but realistically 90-95 is what I'd expect from a decent one in normal circumstances.

nvr2old · « **Reply #13 on:** June 05, 2016, 10:11:29 AM »

My '75 400F runs like a top, and will do 95-98mph full-out. It'll cruise at 75-80, but likes 70mph best of all.

chewbacca5000 · « **Reply #14 on:** June 05, 2016, 01:13:34 PM »

I checked the timing and it had an after market plate and points. I replaced it with a TEC and both 1,4 and 2,3 are spot on for the timing.

It had a jitter before. Much better now.

Sure there will be a few more surprises like the missing o-ring on the float bowl drain srews for 1,4. Peed all over me guess that is part of the joy.

Bike sounds good.

Pipe is a little louder than what I expected. I this normal for the 400f?

chewbacca5000 · « **Reply #15 on:** June 05, 2016, 05:49:29 PM »

Got the TEC points set and it could tell right away it made a difference. Bike runs like it should. Takes some getting used to having to do all that shifting since the bike seems to only really accelerate fast when the RPMs are up there 7,000+

MoMo · « **Reply #16 on:** June 05, 2016, 05:51:36 PM »

exhaust is quiet, sure you have stock?

chewbacca5000 · « **Reply #17 on:** June 05, 2016, 06:05:57 PM »

Quote from: MoMo on June 05, 2016, 05:51:36 PM

exhaust is quiet, sure you have stock?

No exhaust is louder than I expected. I think this video explains my disappointment quite well. This is a guy I know local who is a professional mechanic and has a couple 400fs.

If you watch this video he is doing about 90 mph and the RPMs are close to 10,000. Lots of downshifting to keep the rpms up too.

MoMo · « **Reply #18 on:** June 05, 2016, 06:24:36 PM »

If they're doing 90 they look like candidates for future road kill....Larry

chewbacca5000 · « **Reply #19 on:** June 05, 2016, 06:30:29 PM »

Quote from: MoMo on June 05, 2016, 06:24:36 PM

If they're doing 90 they look like candidates for future road kill....Larry

You could be right about that one...

Scott S · « **Reply #20 on:** June 05, 2016, 06:57:03 PM »

Quote from: chewbacca5000 on June 05, 2016, 06:05:57 PM

Quote from: MoMo on June 05, 2016, 05:51:36 PM
exhaust is quiet, sure you have stock?

No exhaust is louder than I expected. I think this video explains my disappointment quite well. This is a guy I know local who is a professional mechanic and has a couple 400fs.

If you watch this video he is doing about 90 mph and the RPMs are close to 10,000. Lots of downshifting to keep the rpms up too.

Damn.....and the 250 still walked away from him!

camelman · « **Reply #21 on:** June 05, 2016, 08:12:46 PM »

That 400f in the video seems to run as I'd expect. Against a 250 2-stroke it could lose in a drag race, but we also don't know if the 250 had a jump on the 400 and came from behind it after a longer acceleration period. The handling issues of those old 2-strokes looked pretty apparent in that video though.

My last 400f had a 466 kit and bored out carbs. It was faster than my friend's 550 with a 650 cam and would easily blast past 100mph. That 466 kit completely transforms those 400s when paired with bigger, or bored out, carbs.

flatlander · « **Reply #22 on:** June 06, 2016, 12:13:14 AM »

Quote from: Deltarider on June 05, 2016, 08:45:40 AM

Quote
just not for longer runs on the highway.
Wouldn't say that. A friend went all the way to (and in) Morocco on a CB400 Four.

sure it can be done. still, on a dutch or even german highway they would not be my ride of choice.

strynboen · « **Reply #23 on:** June 06, 2016, 02:19:56 AM »

sai"d it this vay.
..400 is a super fine looking and driving bike..
.but the 500/550 have just the power and stabillity,,for better heighvay performance(not perfekt..just better)it can easy go 160 mph..as a stock bike(good tune)
the 400 is missing a bit.against it..(.like the 550 miss a bit against the 750)
.to be the perfekt Honda sohc
.,
.the 400 just not have power..and the frame/hveels/evrything... is a bit smaller..and need rpm to delevery power
..i have both..so dont have to those one over the other..vill be a hell to let one go...

the perfekt bike vas a styling of the 400 6 gear..amd 550 frame engine and 750 cc in

flatlander · « **Reply #24 on:** June 06, 2016, 03:03:27 AM »

Quote from: strynboen on June 06, 2016, 02:19:56 AM

it can easy go 160 mph..as a stock bike(good tune)

that is pretty good for a stock bike from the 1970s!
mine must be in crappy tune as it does that number in kph

strynboen · « **Reply #25 on:** June 06, 2016, 03:50:11 AM »

Quote from: flatlander on June 06, 2016, 03:03:27 AM

Quote from: strynboen on June 06, 2016, 02:19:56 AM
it can easy go 160 mph..as a stock bike(good tune)

that is pretty good for a stock bike from the 1970s!
mine must be in crappy tune as it does that number in kph

oh damed ...i mean 160 kmh....its my cbx vho does that

chewbacca5000 · « **Reply #26 on:** June 06, 2016, 03:18:19 PM »

Took her for another spin and after 100 miles the bike seems to have woke up a bit. It does make power if you drive it like a small 6 speed keeping the revs high.

I am not as confident on th 400f in traffic as my 750, but my 750 has had everything replaced.

Tim2005 · « **Reply #27 on:** June 06, 2016, 04:08:30 PM »

Yes they do need revs- best to try to keep them above 6000 and then the fun begins.

camelman · « **Reply #28 on:** June 06, 2016, 04:17:06 PM »

Some of what you are experiencing is likely the stability of the bike even though it first seems like it's power-related. Improvements in the front end will make the low power less of a factor, and make the bike more comfortable and confidence-inspiring on the highway.

A more modern front end makes a phenomenal difference in comfort at speed. An alternate, and easier, option is to improve the existing front end. The original bearings are usually shot by now, and are fairly easily swapped. Swapping in an aluminum lower triple tree will yield HUGE handling and stability benefits over the stock lower since that stock lower flexes like mad. Swapping the upper triple won't yield much benefit. Fresh fork oil and appropriate springs makes a difference too. There's also the rear end to address, but I bet the front end is where you'll see the biggest difference.

jonda500 · « **Reply #29 on:** June 07, 2016, 05:18:06 AM »

Remember the indicated speed is typically eight percent higher than the actual speed!

John

flatlander · « **Reply #30 on:** June 07, 2016, 06:20:31 AM »

that's why i said that my speeds were measured with a gps unit. the speedo showed something more optimistic.

on my 550, the speedo shows something between 115 and 120kph when the gps says 103 or so. i remember this because that's how i get through the 100kph average speed zones

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Author Topic: RE: CB400f What kinda of speed to expect? (Read 3870 times)