Author Topic: speed restricted b4 models look at the box! (Read 11167 times)

gsxr400 racer · « **Reply #1 on:** December 09, 2006, 12:07:16 PM »

you should read this explains what to look for and how to fix your restriction!

Gavhowe
New Member

28 Posts
Posted - 04/12/2006 : 13:44:24
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Hi as some of you may know I have been building a GK73A back up to use as a track bike. I have now got it running pretty good. So loaded it up on me trailer and took it to the local air strip to give it a shack down. All well ok, but I am interested in if it is running as quick as it should be. As I have limited sports bike experience I have little to compare the performance to. I managed to get 13000rpm out of top gear, and pretty sure it is on standard gearing, does this sound ok. My road bike is a YZF600R thundercat and it is definatly slower than that.

The bike starts to pick up at about 8000rpm and kicks abit more at 10000rpm and pulls hard to 13500rpm then it starts to tail off a little though, it will rev on to 15000 though just a slight reduction in power. not sure where the limiter is in it.

Also what is the standard sprocket/ gear sizes, so I can check that it is standard.

Thanks

Gavin

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 04/12/2006 : 17:11:58
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i have 15 47/48 i use ! you have the 17 " rear or the 18" rear tire/rim do you have 3 wires to the small plug on the cdi or 2

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

youroddsox
Familiar Member

403 Posts
Posted - 04/12/2006 : 17:23:56
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my gearing is similar to jays, just slightly shorter than stock for the track. Should be able to get a few more revs. In top condition mine was pulling well to 15.5/16 krpm but mine is a 76

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Gavhowe
New Member

28 Posts
Posted - 04/12/2006 : 21:06:59
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Yes my GK73 has a 17" rear wheel, and it is not an SP model. I have just look at the sprockets and its 14/45 I think this is standard?? What gear ratio do you recommend for track use. What sort of speed was it doing at 13000rpm on standard gearing.

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 04/12/2006 : 21:16:29
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do you have 3 wires to the small plug on the cdi or 2 this is what i want to know?

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

Gavhowe
New Member

28 Posts
Posted - 04/12/2006 : 21:35:07
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It has got 3 wires. Does that make me a winner? Only joking what does this mean.

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 05/12/2006 : 00:43:39
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I have been doing some idle research on this most seem to think there bike runs fine but what you exclaimed is the same as me your bike is resricted as i beleive all the ones with the 3 wires are here is the story when i bought my bike i raced it once rod it on the street when i picked it up and man was i impressed it had a sorta hacked wiring harness on it and the guy said he maid his own to get ride of the restrictions grant you im in the US so im like ok well when i did all the work to the bike i was like this things looks to good to have the hacked up harness on it so i changed it well when i changed it i put a b4 harness on it from a newer model it started to my suprize 3 years of racing it later and my buddy telling me man your bike isnt as fast as it was well changing cams milling stuff and it seem to get to speed a bit faster but when it hit like 10000 rpm it seem to quit pulling as hard and just go flat it was hard to tell my self that my bike was restricted but with all the things that i through at my bike and money but comes to be it was i was betting my own self on the track racing a restricted bike with darrens (strips) help and a bunch of hours later of internet chatting i swapped the harness and whalaa! not restiction the harness with the 3 wires is vodoo! if a mmax cures it or a posh that is the way to go but for me i had no axcess to these things so i switched the harness. Man ill tell you what i could get off the bike and run beside it after it hit 10,000 was getting a great drive great coner speed and then boom peeps be passing me damn near pulled my hair out. but tiss all good now the b4 suffers from the same ordeal certain years.

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

Gavhowe
New Member

28 Posts
Posted - 05/12/2006 : 08:39:43
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Thanks for the reply not quite sure what you mean by:

"if a mmax cures it or a posh that is the way to go"

How can I remove the restriction, I dont mind butchering the harness up if that is what is needed. As we are talking about speed, what is the light on the instrument panel that flashes on sometime, it says speed above it?

Gavhowe
New Member

28 Posts
Posted - 05/12/2006 : 23:09:16
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gsxr400 racer you are correct my GK73a is restricted in both 5th and 6th. This may not be the case on all GK73a.I have looked at 3 neutral sensors that I have in my garage and they are all the restricted model. 1st to 4th resistance measures 1.5Kohm 5th is 9.12kohm and 6th is O ohm. neutral also measures 0 ohms.

Now the fix!! I carefully scrapped the sealant any from the circuit board on the sensor. Run cut the resistor closest to the green/yellow wire out. then created a link from the 4th pin to the 5th then to the 6th. This way all pins now have a resistance of 1.5 Kohms. Then back filled the sensor with resin to seal it up.

Have not road tested it yet but it has got to work as it does on the bench.

Gavin

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 05/12/2006 : 23:17:44
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That sounds about right your a flippen genious!!! the mmax i think would plug in some were and be doing the same thing wish you would have taken pictures Heres a little not i fixed mine by changing the whole harness i had freshened up my motor before the 442 kit went in was supposed to race forgot i cut the wires at the neutral switch didnt have spark for like 2-3 months me and stripes figured it out! I have a video of me warming the bike up for the first time after i finally fixed the electrical problem
cheers and congrates.

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

youroddsox
Familiar Member

403 Posts
Posted - 05/12/2006 : 23:45:28
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Definitely the nice and tidy way of doing it. For some odd reason mine doesn't seem to be restricted even with the de-restrictor out. Probably down to the fact i have had to resoldermy cdi so many times!

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www.soxracing.s5.com Taking on the world with a GSX-R400 gk76a!!!

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 06/12/2006 : 02:30:16
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Ok so you say well power runs on a dyno would be done in 4 th gear not restricted in forth gear gonna make the power that it would anyways when you notice it is 5 th when coming out of a corner good in 4th then shift to 5th just feels like you hit a wall same with 6th me i tried to over ride it and just balmed it on my riding ability its hard to notice if you ride it all the time. cause you get used to it! any time your cdi is hooked to your transmission that is bad news!

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

Gavhowe
New Member

28 Posts
Posted - 06/12/2006 : 12:40:30
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Here is the picture of the modded neutral switch, the epoxy is clear I used so you can just see though it. Resistor 1 creates the 1.5 Kohm for gears 1st to 4th, leave this alone. Resistor 2 highlighted by the red line needs cutting out, I just used some snips. Then you need to create the link wires highlighted by the yellow lines. The one that goes from 4th to 5th needs a slight bend so it does not contact the small pin between them.

your switch should now give a reading of 1.5 Kohm on all pins other than the neutral pin. I then resolder the wires to make sure they had a good/ strong connection and then filled it with glue.

The CDI will now not be able to tell when you are in 5th and 6th. Now until I road test it I can not say if there is a limiter (some say there is some say there is not) or if this switch drives the "SPEED" light on the instrument panel. but either way the CDI will not be able to tell. I personnelly think it is a limiter, as I can not see how to pass Japanese regulations on the GK71, they had to fit limiter and of the GK76 they had to fit a limiter. But on the gk73 they were aloud to get away with a light on instrument panel. Who is going to take any notice of the light anyway. Do all other Japanese 400 have limiters.

img]http://www.imagestation.com/picture/sraid220/p52a5b5f98545a5f7b596d2b7e1919e6b/ebbca8d0.jpg[/img

stripes1976
Senior Member

United Kingdom
2520 Posts
Posted - 06/12/2006 : 20:46:16
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there is another way without touching the neutral switch! But i haven't been about much to reply!

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www.gsxr400.com

Gavhowe
New Member

28 Posts
Posted - 06/12/2006 : 22:03:10
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I knew there would be an easier way, are you going to let us in on the secret?? What is your opinion on the limiter of GK73A, myth or fiction. do all the GK73 have 3 wires on the small plug.

youroddsox
Familiar Member

403 Posts
Posted - 06/12/2006 : 23:48:25
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Jay, mine hits 16k in 5th and 6th without the de-restrictor so it definitely ain't got a restriction on it. Probably buggered that part of the chip!

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www.soxracing.s5.com Taking on the world with a GSX-R400 gk76a!!!

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 07/12/2006 : 02:33:44
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they do go that high but they seem to not build anymore power even shows on a dyno but i cant find my old charts

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

Gavhowe
New Member

28 Posts
Posted - 07/12/2006 : 12:24:20
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Have all GK73A got the 3 wires to the plug, as this would explain why some people dont think there is a limiter and others do.

youroddsox
Familiar Member

403 Posts
Posted - 07/12/2006 : 18:19:55
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I only rev it that high on one track and that is in 6th gear flat. Only usually developes decent power to about the redline. Do you reckon an ECU that only goes to 15k would be enough or with a better ignition map can higher power figures behond this be acheived?

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www.soxracing.s5.com Taking on the world with a GSX-R400 gk76a!!!

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 09/12/2006 : 01:09:03
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quote:
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Originally posted by Gavhowe

Have all GK73A got the 3 wires to the plug, as this would explain why some people dont think there is a limiter and others do.

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Some earlyier bandits dont i think earlyier gk73 didnt later did and stripes would have to answer if the others were limited!

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

gsxr400 racer
Senior Member

USA
1218 Posts
Posted - 09/12/2006 : 01:10:07
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better ignition map can higher power figures behond this be acheived" this one works for me

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Supplier of the cheapest 442cc big bore piston kit for gsxr400 73,76, bandit 400, and other suzuki's.

Bartjan · « **Reply #2 on:** December 09, 2006, 03:19:57 PM »

my B4 doesnt rev beyond 13k in any of the gears. it tops in 6th gear at 12k rev at a calibrated 172km/h (or about 200+km/h on the standard speedo-meter)

would this mean my B4 is restricted? its the USA-model of 1990

ps. my neutral light doesnt work anymore (since a few months) but the B4 still works flawless (it just wont start when in neutral and the side-stand is out)

Farre · « **Reply #3 on:** December 09, 2006, 03:38:53 PM »

Strange.. what about revving it up in neutral, can you reach higher than 13k?
Did you check if you have the 3 pin connector on your CDI? there are 2 connectors on your CDI, look at the smallest one.

Bartjan · « **Reply #4 on:** December 09, 2006, 04:30:59 PM »

i never tried revying up to 13k in neutral, but i doubt my B4 would go beyond it anyway

it only has 2 wires as you can see here

does this mean my B4 is restricted?

Herr Tod · « **Reply #5 on:** December 09, 2006, 05:12:42 PM »

Mine revs to 14500 in any gear except 6th, then hits the limiter. In 6th gear I've got it to about 14200 which is almost 215 km/h.

gsxr400 racer · « **Reply #6 on:** December 09, 2006, 06:20:37 PM »

maybe someone with the 2 wire version could test the resistance of there nuey=tral indicator and some more with three wires could too!

matt_400bandit · « **Reply #7 on:** December 09, 2006, 07:19:04 PM »

Ok i up for that i have a 3 wire version what do have to do! i own a multi meter, so give us an idea on what to do and i'll post results

gsxr400 racer · « **Reply #8 on:** December 09, 2006, 11:38:55 PM »

it was a few post up so i copied it for you!

"Here is the picture of the modded neutral switch, the epoxy is clear I used so you can just see though it. Resistor 1 creates the 1.5 Kohm for gears 1st to 4th, leave this alone. Resistor 2 highlighted by the red line needs cutting out, I just used some snips. Then you need to create the link wires highlighted by the yellow lines. The one that goes from 4th to 5th needs a slight bend so it does not contact the small pin between them.

your switch should now give a reading of 1.5 Kohm on all pins other than the neutral pin. I then resolder the wires to make sure they had a good/ strong connection and then filled it with glue.

The CDI will now not be able to tell when you are in 5th and 6th. Now until I road test it I can not say if there is a limiter (some say there is some say there is not) or if this switch drives the "SPEED" light on the instrument panel. but either way the CDI will not be able to tell. I personnelly think it is a limiter, as I can not see how to pass Japanese regulations on the GK71, they had to fit limiter and of the GK76 they had to fit a limiter. But on the gk73 they were aloud to get away with a light on instrument panel. Who is going to take any notice of the light anyway. Do all other Japanese 400 have limiters.

img]http://www.imagestation.com/picture/sraid220/p52a5b5f98545a5f7b596d2b7e1919e6b/ebbca8d0.jpg[/img

"

Bartjan · « **Reply #9 on:** December 10, 2006, 12:53:14 PM »

today i tested how high my B4 would rev....
and i found out it is idd able to rev to 15k, however the power doesnt gain anymore above 12,5k which is why i use to switch gears at that number. and i havent got above 13k in 2 years

but in 5th and 6th it wouldn't go that far (also there were strong winds which didnt help)

so i guess it's restriced, like posted above.
and i also guess it doesnt gain more power above 12,5k because the carbs are a bit lean. and high rpm's like a rich mixture because that burns faster.

could someone explain in a easy to understand way how to de-restrict it?

Farre · « **Reply #10 on:** December 10, 2006, 05:32:04 PM »

i don't think yours is restricted actually, i'm guessing you should sync the carbs firstly.. see if this helps a bit.
If it doesn't then it should be the carb mixture, much fussing about

the 2 wire version is supposed to be the unrestricted, i have this one and i can reach in higher rpm's but just like you say there ain't much power above 12k.
That said, of course in each higher gear you have less torque but a higher top speed, so it's kind of to be expected that you can't reach as high in rpm's as in the lower gears... unless you tweaked your bike like some here

Herr Tod · « **Reply #11 on:** December 10, 2006, 06:19:28 PM »

If you shift at 13500 you will always be at 10000 RPM or more in the next gear. When shifting from 5th gear to 6th gear you will be at 12500

Bartjan · « **Reply #12 on:** December 10, 2006, 07:49:13 PM »

Quote from: "Farre"

i don't think yours is restricted actually, i'm guessing you should sync the carbs firstly.. see if this helps a bit.
If it doesn't then it should be the carb mixture, much fussing about

it was synced about 2000 km's ago

didnt make much difference then, because it was synched about 5000 km before that

and synching should only help at the lower rpm range.

gsxr400 racer · « **Reply #13 on:** December 10, 2006, 10:06:27 PM »

This isnt because of the carbs this is due to the extra wire conected to the cdi and the neutral switch changing the amps or ohms that run threw it! Any time your cdi is conected to your gear indicator this is a bad thing meaning that something about your bike may get better once the restriction is taken off! there is no reason thet the bike pulls hard all the way through the rev range up to 15 or 155 in 1st threw4th then 5th and 6th the bike falls on it face bettre yet find a buddy with a 2 wire one and ride that!

gsxr400 racer · « **Reply #14 on:** December 10, 2006, 10:08:44 PM »

Quote from: "Farre"

i don't think yours is restricted actually, i'm guessing you should sync the carbs firstly.. see if this helps a bit.
If it doesn't then it should be the carb mixture, much fussing about

the 2 wire version is supposed to be the unrestricted, i have this one and i can reach in higher rpm's but just like you say there ain't much power above 12k.
That said, of course in each higher gear you have less torque but a higher top speed, so it's kind of to be expected that you can't reach as high in rpm's as in the lower gears... unless you tweaked your bike like some here

dude if you rode a 3 wire compared to yours you would be like what the hell just happen and start smaking the side of your bike like a horse saying come on geteup!