Help with gk73a derestrict

[Motomodmach]

Hi all. Im new here from South africa.

I have a suzuki gsxr 400 gk73a 89. Now i think it might be restricted or not, as i am confused when looking at the bikes wiring harness.

I did some research on this forum and found a post showing how to derestrict these bikes. I located the wire at the cdi (green wire with yellow tracer) but there is no resistor attached to the wire. I do feel a hesitation in 5th and 6th gear especially on the highway but, i dont really know if its restricted or not.

Also the bike does have a gk76a cdi on it as the original cdi had water damage from the PO so i dont know if that would make a big difference.

Thanks for the help in advance.

Side note: the bike revs freely to 15000rpm in neutral and also 1st,2nd and 3rd gear, thats all i could test for now. But it feels very sluggish in 5th and 6th gear. I find myself gearing down to 4th gear most of the time on the highway, if i want to change lane or just simply pass another vehicle.

Thanks again.

[moforockband]

Wow a gk73a in SA. You need something faster to out-run the wildlife :D

Didn't realise a 76 cdi would work on a 73, but guess you proved that.

Basically you need an early 73a cdi as otherwise they are all restricted. But they are easily overcome by soldering a 1.5k Ohm 1/2 watt resistor in line with the green/yellow wire to ground which is what you could probably could do to yours to get it revving in 5th and 6th again. The resistor is a mod that owners use to lose the speed restriction from the poxy gear selector switch that Suzuki put on the bike to make it Jap legal.
You may not be getting the proper ignition curve with the 76a cdi, but if it feels good, it's probably fine. Might try one on mine to see how it feels :D

[Motomodmach]

Hi mofo.

Thank you so much.

First off, im in cape town haha. We dont have any tigers or elephants roaming our streets here.

I actually had a cbr 600 f2 before this little 400 but i had to let her go due to work and financial issues.

Secondly, i have no issues with the 76 cdi, it makes the little 73 pull like a raped ape through all the gears except well, like i said, it feels a bit sluggish in 5th and 6th. A friend of mine has a gk76 we raced the other day on a quiet back road and i beat him, so he asked me if he can ride my bike as he doesnt understand why mine is faster and he admitted as well that mine, pulls a lot harder and the throttle is a lot more responsive than his, he also said if he opens it up quickly it pushes him back in the seat. I know for a fact his is in top top shape as the guy he bought it from had the engine over hauled and carbs and everything. The guy had all the receipts for everything he has done on the bike.

I have ridden his but feels a lot more sluggish than mine to be honest.

But my actual question is, what if there isnt a resistor present at the moment between the cdi and the gear selector? What would happen if someone was to pull out the resistor?

Thanks again for the reply.

Oh and im gonna do a build thread in february about my bike as im doing a restoration and some upgrades as well.

Cheers.

[moforockband]

There was never a resistor there from new. People add it to get rid of the rev limiter in 5th and 6th which is what you need to do to yours. The reason I said 1/2 watt 1500 ohm is that it has some mechanical strength over a 1/4 watt.
A good tip with 400's and to keep them fast(ish) is to keep the gas speed up through the engine. ie not putting a 2" race exhaust all the way through. My bike will do 10mph faster with the baffle in the race can for instance.
Nick.

[Motomodmach]

Ok. Thank you so much for the help.

I will make sure to put in that resistor.

Im also planning on welding the one exhaust outlet shut (the left one).

Another question if you dont mind? You have been so much help.

The 4 into 2 systems on these bikes. Does 2 manifolds go into 1 pipe, like cylinder 1 and 2 goes to the left side exhaust and 3 and 4 goes into the right hand exhaust if im correct. Is there a wall on the inside of the exhaust where the 4 outlets meet?

Thanks again.

[Motomodmach]

So i just tested the resistance on each gear and it looks like your right.

1st Gear - 1.5K ohms
Neautral - 0K ohms
2nd Gear - 1.5K ohms
3rd Gear - 1.5K ohms
4th Gear - 1.5K ohms
5th Gear - 10K ohms
6th Gear - 0K ohms

This in a way kinda terrafies me, so if im correct then these bikes makes absolutely no power in 6th gear seeing as 6th gear has the same resistance than neautral. If suzuki restricted these 400s then why even install a 6th gear on these bikes anyway?

[Variablevalves suck]

He doesn’t work like that as neutral is on a different circuit in the cdi so it’s not the same as the 6th gear reading.

[moforockband]

Forget about the gear switch, just use it as an oil seal for the crankcase. The resistance values can't be taken for gospel after 30 years anyway. Just put the 1.5k resistor inline with the green/yellow wire from the cdi to ground (not the green/yellow wire form the gear switch). Your bike will 100% deffo work then.
Although Suzuki manifolds work pretty well in good condition, I wouldn't modify yours if it was mine. They're made from mild steel, rust like crazy and weigh a ton.
A much better solution is to use the GSF400 stainless 4-1 system ( lasts forever, and is quite light), and cut off the original gsf400 can and mount a can of your choice, with a slight upbend (7 degrees) for ground clearance. There is an internal baffle in the collector which you may want to remove, but it's worthwhile keeping, as it keeps the bike at sane levels with a race can, and also keeps the gas speed up so you get good throttle response. Or you could cut it out and stick a baffle in the race can (which is what I did)
EDIT-- You will have to fit a bandit 400 sump pan and oil pickup pipe to run the bandit system as the routing is different to stock. Not a massive job.

[Motomodmach]

Thank you mofo. I think i will just throw in the resistor.

About the exhaust pipe. Yeah, here in south africa. Finding parts like that is extremely difficult or if you can find them people will charge redicilous price's for them. So here in SA people usually modify what they have and try and restore their older parts. Hence, why i would rather just restore my pipes. Take all the rust off, shoot it with heat resistant paint as well. But thanks for all the info mofo. Geez, you have been so much help i have been searching for answers to these questions about these bikes for almost a year now. Seeing as they are grey imports there aren't really any info about them.

Not going to fiddle with the pipe to much i just want one exhaust outlet thats all.

[Motomodmach]

Thanks varaible valves. I did not know that i will be install the resistor and then i will post my finding's.