Hi,

I have a 92 sf big one jap import and i want to know if its restricted at all at the top end. Unmodified what sort of top speed should i be looking at?

at the moment i get about 100-105 and i also weigh 13.5 stone i think that could be the problem. Is there anyone who has modified with end can and filter and what extra performance you have gained?

I have seen a de restrictor on ebay for jam imports and want to know if i need it? it says' de restriction for when it hits 112 mph but im confused as i have never hit that? should i test bike further and see what happens if i do hit it on a slight downhill and see if it does cut speed then?

cheers

Originally it should be restricted to 112 mph (180km/h) Have you tried in fifth gear or in sixth? Mine is restricted (34hp) and I can just hit 112mph on the speedo.(I only weigh 11 stone) But a 53 hp version should be able to get up to 112mph.
Here is a link about the speedrestrictor=http://hondacb400.myfreeforum.org/Japan ... bout5.html
Nampus

With a standard sprocket set up, and a long enough road (!) you should see ~125mph, if you can hang on at that speed!

Has the bike been serviced recently? You won't hit max speed if the air filter is clogged, the spark plugs are old, the carbs aren't balanced or the valve clearances aren't adjusted correctly. You may also find that over the years the carbs and valves have got gummed up with old fuel - easiest way to cure this is to run a couple of tanks of Shell Optimax through it; the detergents will remove the fuel gum and you'll notice an improvement in performance straight away (you can go back to regular unleaded afterwards, but run some Optimax or similar through it every now and then to keep it clean).

Oh, and get right down on the tank with your knees and elbows tucked in!

IMHO, the best way to de-restrict the bike is to fit the kph-mph converter gear. It's an anodized blue unit containing a 5/8 gear that sits between the speedo cable and the speedo head (if your bike has one, it'll be clearly visible under the speedo housing). With one of these fitted, your speedo will read in mph, your odomoter will read in miles and the speed restrictor cuts in at 180mph, ie never! You can get them from Wemoto (and other places I think) for around £30.

The other options are:

1. Disconnect the ECU from the speedo, and solder a resistor between two of the terminals of the connector block to trick the ECU into thinking it's still connected, so the bike will run properly. There's a thread on here that details the required mod. This is the cheapest option.

2. Buy a plug-in module that basically does the same thing as option 1 above. The module costs around £30 I think.

Personally I prefer the mechanical mod, as it also converts the odo and speedo into mph.

PS You'll know when the limiter kicks in, as it cuts two of the cylinders I believe.

Top speed of a Honda "Big One" is about 145mph. Top speed of a Honda Cb400SF is about 120mph.

thanks alex that helps! checked the air filter and its fine gonna also check spark plugs etc and run some optimax through it! that anodised blue thing behind the speedo is there didnt know what it was untill now

whats the difference between a standard cb400 super four and then super four big one? it only says it on the triangle panel by seat, its def original :s

Top speed of a Honda "Big One" is about 145mph.

From an unfaired 400? You can't be serious?

no offense but thats what i thought thats the sort of speed you would get from a 600??

i thought the big one is just a variation of all SFs?

hes talking bout the cb1300 big one m8 for the faster figure :D


as opposed to cb400 "project big one"

ah yea! well my mistake i meant to right 'project big one'