Won't rev when in gear

Hi everyone,

I've just rebuilt my cb after stripping it down from a knackered road bike to rebuild it as a race bike to race in this years thunder sport 500 championship and when I fired it back up it ticked over fine, revs cleanly etc but as soon as you click it in gear and try to rev it, it sounds like it's running on one cylinder and has no power at all, would hardly even rev.

I've racked my brain as to what I have done wrong and checked over everything but can't see anything out of place or where it shouldn't be.

Please help me as I'm totally stuck to what it could be.    

Thanks
Gaz

I can only think that maybe it's an electrical issue. Perhaps a faulty neutral switch might do this....... I honestly don't know. I can't imagine it being mechanical.

Don't worry. There's some knowledgeable folk in this parish and one of 'em will chime in soon enough.

Check the side-stand switch and the clutch lever switch too. If either is borderline not-working then they could cause the ignition to be erratic when in gear, as they're part of a circuit that stops you riding away with the stand down.

I still don't see why the problem would only occur when the bike was in gear if it wasn't related to the side-stand cut-out circuit. Perhaps the circuit was disturbed when the switch was removed (if it was removed)?

Did it work before you took it all apart? (or was it so knackered you couldn't tell?)

When you engage the gears a little bit more load on the engine which might tip it over the edge, anyway, I'd still be looking for that electrical issue.

You should completely remove the side stand switch and connect the wires (or not) in the same way as when the stand is up, even if this isn't the problem - you don't want the side stand cut-out coming on at the wrong time! You might have done this already...

Do you still have a neutral light and/or switch? I wander if something is grounding itself through the neutral light and/or switch so that it works when you are in neutral but once you go into gear it has to use some dodgy other ground, which isn't going to help things..... have you checked the grounding between the frame, engine and battery on the bike? Might be worth a shot.

Hi again,
Sorry for not being clearer with what I have done and checked so far, the bike ran fine before I stripped it down so I know it's definitely something since I've rebuilt it.

My friend stripped the wiring loom to remove all the unneeded wires and I first thought that was the problem but I have since tried another standard loom with the clutch lever and side stand switch bridged out and it still did the same thing so that sort of eliminates that problem.

We've changed the spark plugs and air filter.

My friend has checked the neutral switch, generator, pulse ignition generator (or whatever it's called behind the right hand engine casing) and both coils and there all giving the correct 'ohms' readout as per the Haynes manual.

Swapped the carbs for another pair

After doing all of the above the bike is still doing the same thing which is completely baffling me.

The only thing I've not changed which I have on order is the battery as the other one I don't think was great but it ran the bike fine a few months ago and to sort off eliminate that I've connected the bike to a spare car battery and tried it and the bike fired up first turn but as soon as it was clicked into gear then it started struggling again.