Hi there,

I've been back riding my NC21 having taken the engine out to replace the sump (another story) and to change the plugs and freshen hard to get to bits when the engine is in.

However upon riding the bike, it accelerates fine from around 0-40mph (in the lower gears) but then the bike hesitates in the higher gears (but will eventually rev up fine). It's more noticable when putting a load on the bike i.e. when going up hills or accelerating from slower speeds in higher gears and is also present when cruising in top gear on the motorway.

Have gapped the plugs (and double checked that the correct ones were put in!), the bike is running with fresh fuel and I've cleaned and inspected the connectors to the ECU.

I have been looking for someone with a similar problem online but I can't find someone with the exact problem. From reading the other solutions the vaccuum line or alternator seem to be suspect.

Any suggestions?

Cheers
Geraint

Just to update the post - After putting a new voltage rectifier on the bike and ultrasonically cleaning out the carbs and jets, the bike was still the same. Eventually the problem was that I had connected a pipe to what I thought was the carb overflow pipe. This was the small black plastic pipe above the fuel delivery connector. This turned out to be the Carb. vent pipe and therefore the long pipe which I had connected was interfering with the carbs because at high speed as it needs to vent to a quiet area not below the rear wheel with loads of turbulence. I replaced this with a short pipe 100mm long which drops behind the cards and bingo the bike ran perfectly.
Geraint