Mystery rough-running problem - please help

First topic message reminder :

Hoping for some help from the Brains Trust to get my Bandit running right.
 
It’s a long story, but the important points are:

• It’s a 1997 Bandit 1200 with some modifications.
  
• These problems only show up when the engine is HOT.
  
• It won’t rev above 6k RPM, at which point it fits and farts like it’s hitting a dodgy rev limiter or something.
  
• At lower speeds it runs rough, as if it were only on two cylinders, and this symptom clears somewhat when the throttle is opened wider.
  
• One of the modifications is an Acewell digital dash, on which the gear indicator behaves weirdly, giving a reading that I’m in 8^th gear.
  

 
The mechanic at the moment is looking into the possibility that there’s something going wrong with the relationship between the Throttle Position Indicator, the Gear Position Indicator, the CPU and thus the timing.
 
Is there anything I can tell him that is a known trouble spot on these older Bandits?
 
I’ve already spent an eye-watering amount of $ chasing this problem, from a Dyno run (where the bloody thing behaved perfectly), a new (S/H) air box and K&N filter, new coils (they were arcing across to the engine) and leads & plug caps & Iridium plugs.
 
While it’s nice to know that the bike has some new bits, none of them improved the problem.
 
Any help would be appreciated.

I've put this up on the FB page too, and i'll probably be able to check that more frequently, because this forum is really hard to read on the phone.


Matt

G'day Normanby,

How much mileage has the bike got?

Do the plugs come out clean after a proper warm up and run or do they  foul/carbon-up?

Are the valve clearances/adjustment  properly with-in spec?

Have you checked if the the air vent / hole in your tank is clear & not blocked causing the tank to pressurise after a while ( try opening the fuel cap after it is playing up to check ) .....................Just a funny thought I had , it happened to me on a previous bike I had  .

Not a bad idea mate. A friend of mine had an XT Yamaha that a wasp had made a home in the breather. He always had problems within a couple of kms from home

There should be quiet a few rotor bungs getting around, as people do replace them for 5* advancers

I wish you could have done some of this check list yourself, to find out what`s with wrong your bike.

Every minute its been dealt with by the business, its costing you a lot of money, as its a process of elimination.
Also, you then know things have definitely been checked.

I hate giving my bike or car to anyone, as I don`t trust anyone.

I hear ya, now that i've fallen down this rabbit hole i feel the same way.
I live in a 3rd floor apartment and have no garage, and i don't have very many tools yet either. Even so, i wish i'd tackled it myself, perhaps in a friend's garage. It's just that i thought it might be a simple fix, and i'll let a 'professional' tackle it because it ought to be faster that me with my meagre facilities.
Lesson learnt...

I'll start another thread in the Buy, Swap & Sell section just for this part.

Have you talked to the previous owner to see if he had a similar problem before & what it was ? Might be worth a shot .

(Edit):

Previous owner got back to me and has supplied me with an un-damaged signal generator rotor, bless his cotton socks.

It'll be installed tomorrow, i'll post here with the test ride results after that.