Backfire out of carb?

[greg737]

To further complicate things I've discovered that my 1993 U.S. import model Bandit 400 has 7 wires leading to the CDI from the wiring harness instead of 6 wires. 

There is some speculation that the 7th wire controls a limiter that is engaged in 5th and 6th gear. Some machines apparently have a variable resistance that comes from the gear selection and controls this. My 7th wire on my '93 was just open when I got it. I've grounded it through a resistor based on various anecdotal bits of data floating around with the idea that the proper resistance will force it to be unlimited at all times.

I've never seen any definitive information on whether that is true...

I was also speculating/wondering about this 7th wire, but my guess at its purpose is different:

I searched around and found wiring diagrams for other Suzuki models that were being produced at the same time as the Bandit 400 and whenever I found a wiring diagram that showed a CDI with 7 wires coming out of it the 7th wire was just an input feed to the Tachometer.

For some reason the Bandit 400 uses a spliced-in tap-line on the #2 coil to feed the tachometer so it didn't need to have that 7th wire connected to its tachometer.  My guess is that this little difference didn't stop Suzuki from using the same 7-wire Denso CDI box on several models.  This CDI box was just a "parts bin" item, probably purchased in huge lots of several thousands at a time, so it was just economical to use it on a bunch of bikes.

[andrewsw]

To further complicate things I've discovered that my 1993 U.S. import model Bandit 400 has 7 wires leading to the CDI from the wiring harness instead of 6 wires. 

There is some speculation that the 7th wire controls a limiter that is engaged in 5th and 6th gear.

I was also speculating/wondering about this 7th wire, but my guess at its purpose is different:

I searched around and found wiring diagrams for other Suzuki models that were being produced at the same time as the Bandit 400 and whenever I found a wiring diagram that showed a CDI with 7 wires coming out of it the 7th wire was just an input feed to the Tachometer.

For some reason the Bandit 400 uses a spliced-in tap-line on the #2 coil to feed the tachometer so it didn't need to have that 7th wire connected to its tachometer.  My guess is that this little difference didn't stop Suzuki from using the same 7-wire Denso CDI box on several models.  This CDI box was just a "parts bin" item, probably purchased in huge lots of several thousands at a time, so it was just economical to use it on a bunch of bikes.

That's an interesting idea. I was never able to demonstrate any difference between leaving the wire open and grounding it. Further, there is no sensor (on *my* bike anyway) to actually inform the CDI what gear it's in. If I had a scope I could hook it up to that thing and see if it's producing a signal. Ah well. I like your idea :)

A

[CrustyOreo]

Cyl 1 had 55PSI of compression.
Cyl 2 had 30PSI.

Time for a motor.

[El Gringo]

If its been stood for a while, the rings may be gummed up, you may get away with taking the barrels off un sticking/replacing the rings and honing the barrels

[ventYl]

To further complicate things I've discovered that my 1993 U.S. import model Bandit 400 has 7 wires leading to the CDI from the wiring harness instead of 6 wires. 

There is some speculation that the 7th wire controls a limiter that is engaged in 5th and 6th gear. Some machines apparently have a variable resistance that comes from the gear selection and controls this. My 7th wire on my '93 was just open when I got it. I've grounded it through a resistor based on various anecdotal bits of data floating around with the idea that the proper resistance will force it to be unlimited at all times.

I've never seen any definitive information on whether that is true...

That may be true. AFAIK japanese regulations after 1993 forced bikes under 400cc to be limited to 170 km/h or maybe even 150km/h (in addition to have lower power output, which is why post-92 bandits have different power rating than older bandits). I've also read that german post-93 (in fact unified post-regulation change model) model had rev limiter on 10500 rpm because of reliability, but that is bullshit. But it is possible that in 6th gear rev limiter is on 10500 to limit speed to 170 km/h (or 150 km/h whichever is apropriate). Other gears limiter is higher. Older CDIs have no 7th wire, the only wire coming out of engine is neutral switch for sidestand interlock.

[Squishy]

To further complicate things I've discovered that my 1993 U.S. import model Bandit 400 has 7 wires leading to the CDI from the wiring harness instead of 6 wires. 

There is some speculation that the 7th wire controls a limiter that is engaged in 5th and 6th gear. Some machines apparently have a variable resistance that comes from the gear selection and controls this. My 7th wire on my '93 was just open when I got it. I've grounded it through a resistor based on various anecdotal bits of data floating around with the idea that the proper resistance will force it to be unlimited at all times.

I've never seen any definitive information on whether that is true...

That may be true. AFAIK japanese regulations after 1993 forced bikes under 400cc to be limited to 170 km/h or maybe even 150km/h (in addition to have lower power output, which is why post-92 bandits have different power rating than older bandits). I've also read that german post-93 (in fact unified post-regulation change model) model had rev limiter on 10500 rpm because of reliability, but that is bullshit. But it is possible that in 6th gear rev limiter is on 10500 to limit speed to 170 km/h (or 150 km/h whichever is apropriate). Other gears limiter is higher. Older CDIs have no 7th wire, the only wire coming out of engine is neutral switch for sidestand interlock.

No german gsf400's are limited to 50 bhp by not allowing the carb needle to go up fully. The cap on the carbs have a stopper.

[ventYl]

I know. but i'm not talking about german model, but about japanese model (with engine probably identical to UK, FR, IT, ESP specification of pre-1993 models). Even plain japanese "unrestricted" model is in fact restricted by Japanese manufacturer's "voluntary code" which all four big japanese manufacturers follow for years or maybe tens of years (the same code which limits every production street motorcycle not to exceed speec 300km/h). IIRC, japanese specification of B400 made pre-1992 was "restricted" this way to 59HP. Same as GSX-R 400. In 1992 (affecting 1993 models) limit was pushed down to 53 HP. Change in code in 1992 pushed limits for up-to-400cc and up-to-600cc classes down but introduced over 600cc cycles to japanese market as native article (again, IIRC). Due to this change palette of different per-country specifications of Bandits were unified into one with 53HP. Code change in 1993 introduced (again voluntary, but still followed) limitation of top speed for up-to-400cc class to 180km/h (again for all models). This limitation was not present in former "revision" of code. That's why some B400 CDIs have one more wire than other. It depends mainly on year of production and on number of motorcycles which the parts for that one particular come from.

For some reference: http://www.gaijinriders.com/showthread.php?8528-Japanese-Bike-Domestic-Restrictions&s=2f9e95e4539c9a8d4a1377f541a9d377&p=96275#post96275