Hi Guys I have a CBR400rr 1989 NC29 and have just fitted another engine (it is a used one) and when driving the bike in 2nd gear it lurches violently in 2nd gear. In 1st,3,4,5,6 gears their is no problem. It is not jumping out of gear it is as if the ignition is being turned off for a fraction of a second. I have put the origional engine ignition pickup, clutch and altenator back on, checked the carbs and inlet rubbers. The lurching only starts about 5000-6000rpm but goes on right up to 12000rpm. I have drained the oil and checked for any metal from possible damaged gears but nothing. Anyone got any ideas

Ian

Yes I'll tell you exactly what it is as its a known issue.

It's a worn selector dog in the gearbox.

And yes you will have to split the casings to fix it.

What happened with this in the end? Mine did something very similar and having now split the casings I've found 2nd gear to be missing a tooth. It only lurched under hard throttle after 3/4k revs. And only under load as I couldn't replicate this on a paddock stand.

2nd gear is a known problem gear on these bikes. And good luck finding a new one or one in good shape.

I do a lot - a lot of NC29 gearboxes .... and have both new OE Honda Selector forks and good used 2nd gears in stock.

Take a look:
https://www.facebook.com/media/set/?set ... 2c75bb2a3b

Cheers