just had another thought ,may be something is sticking in the carbs and its just flooding which would possibly make it worse with the hrc tap, take the airbox off and spray some carb cleaner down there, i think its just a case of try one thing at a time , youll get there

Thanks all for your help. Very appreciated and the offer of lending kit etc.

I will get it all checked first to see if it is the reg etc. What should I be looking for regarding regulator and battery checks? I really don't think it is that though. But we will see.

Thanks again all.

Andy

http://vfr400-nc30.blogspot.co.uk/2011/ ... ow-to.html
this may help, there is a couple of threads on this forum about checking the reg and battery but i dont know how to link them, also the haynes manual shows how to,

leef82 wrote:http://vfr400-nc30.blogspot.co.uk/2011/ ... ow-to.html
this may help, there is a couple of threads on this forum about checking the reg and battery but i dont know how to link them, also the haynes manual shows how to,

Thanks bud.

I am now sure after reading that, that it is not my problem. My battery is fine and holds it's charge and is charging no problem. Something else is causing my problem. It is a mystery alright. My bike seems fine up until 8000 rpm. Does the limp mode strike any bells with this? Could it be going into limp mode?

I reckon CDI's either work or they don't - not a lot in between.

Is your bike's speedo all standard and reads in KMs? If not, does it have some kinf of convertor? Or does it have a resistor modification/plug in box to prevent the 180kmh restriction?

How sure are you that the fuelling is OK? When did this happen and or has it always happened?

The bike was running fine a couple of weeks ago. Then laid up for a couple of weeks. I really think it is electrical. Sometimes whilst it is running (idling) rough as though on 2 cylinders or running low on fuel it might suddenly kick in and idle clean and rev clean. But only occasionally. Like I said, on the road it's fine up til about 8000 rpm and then it goes bad but with intermittant splurges of power coming in almost like a loose connection. I have checked all cables etc.

And yes, it has a speedo modification and now reads in mph etc. But I also have a de-restrictor box fitted in line with the CDI. I have tried the bike with and without that. But my problems dont come from any speed, mine come from the revs. Is there a limp mode on these bikes? If there is, what does it do and what does it feel like? Anyone?

There is no "limp mode". If the road speed exceeds 180kph (113mph), the speed detector unit located in the speedo causes the ignition to stop for the rear cylinders. This road speed limit occurs at approximately 5000 rpm in sixth gear. If the oem speedo is removed or the speed sensor is faulty the ignition defaults to the speed limited mode after engine start up. A de-restrictor box is just the "resistor modification" that simulates the speedo speed detector to keep the ignition control unit happy and also ignore the 180kph limit.

You said the problem is heat sensitive. Does this mean that when the engine is cold it runs smooth and revs ok but once hot the fault appears?

Yes, just startee it up and it warmed up nice. Blipped the throttle past 7000 rpm or thereabouts and imediately it has gone and bogged down/run on two etc. I am bamfuzled. If the speed detector is faulty would that cause this problem even though I have a black box fitted?

Just so I understand, when the engine is cold you can rev it without any problem and it rides ok too. Then once the engine is hot, the problem appears. How long between running ok and heating up before the problem, one minute, 5 minutes, what reading on the temperature gauge?