1994 gsxr750 86mph tops

[gazza49]

here is a bit of information on how to deristict the gsxr 400,as they have used m-max boxes as well to fool the cdi thinking its still in a low gear when in 5th and 6th.-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. (put the 1.5k resistor inline with the green/yellow wire from the cdi to ground )

[lowriderade]

1 hour ago, gazza49 said:

here is a bit of information on how to deristict the gsxr 400,as they have used m-max boxes as well to fool the cdi thinking its still in a low gear when in 5th and 6th.-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. (put the 1.5k resistor inline with the green/yellow wire from the cdi to ground )

I'm hoping to go over tomorrow to have a look at it and see about soldering a resistor in.

As far as know though, it doesn't have the gear selector switch. Just neutral .  No speed sensor on the drive sprocket just a cable speedometer. He's tried a few speedos and it didn't make any difference . 

But thanks for the info. 

[lowriderade]

Hi all. Not had chance to do a video.

But here's an update.

After lots of messing around. The bike now has different carbs ( with out the tps ),

A different loom and a different CDI. 

There was no fittings for a speed sensor before and still isn't.

The clocks have been changed

The bike still wouldn't pass 86mph.

The latest thing was to pinch a  gear selector switch of another engine.

 there was a difference.  It was pulling strong untill he hit a slight  bump and it dropped back down to 86. He got just over 90mph

 

So the only thing that's made any difference was adding the gear selector switch

 

[george 1100]

Theoretically, that bike should be able to do that in second gear.

Is this happening in top gear or any gear?

Maybe a fuel supply issue? Take the tank off, suck on the vaccum with a syringe and check flow.

Does it redline in first?

Does it feel like it has full power up until 90mph?

[Gixer1460]

Seems too repeatable / exact to be fuel related as load will vary due to rpm / gearing which determines fuel flow? I'd still plump for something electrical - but don't know what as all the usual suspects have been replaced - assuming they've been sourced from 'normally running bikes' to eliminate a 'like for like' problem swap?

[lowriderade]

6 hours ago, george 1100 said:

Theoretically, that bike should be able to do that in second gear.

Is this happening in top gear or any gear?

Maybe a fuel supply issue? Take the tank off, suck on the vaccum with a syringe and check flow.

Does it redline in first?

Does it feel like it has full power up until 90mph?

Fuel flow is good, I did check the breather pipe and ran it with the cap undone .  Straight up to redline in first. It was pulling hard until it hit the bump then went back to only doing 86 mph.  Doesn't matter what gear your in, it will pull strong until 86mph. 

[lowriderade]

6 hours ago, Gixer1460 said:

Seems too repeatable / exact to be fuel related as load will vary due to rpm / gearing which determines fuel flow? I'd still plump for something electrical - but don't know what as all the usual suspects have been replaced - assuming they've been sourced from 'normally running bikes' to eliminate a 'like for like' problem swap?

I totally agree.

We have tried different carbs, different clocks and ECUs . The ECU that was on it had rounded plugs with seals.

  It now has a different loom with the older looking ECU and squared plugs with no seals. That didn't make a difference until we managed to get a gear selector switch. Fitted the switch and took it for a run. Power felt the same even after 86mph. It did feel like it was going to hold back at all. Sadly the bump obviously dislodged something and it dropped back to 86mph.

So I'm thinking the gear selector is making the difference.