5th gear problem

[realnutter]

Afternoon all!

I got given a 650 engine, which I was going to give a full service to - camchains, clutch, the full works.... and then stick in my 600 chassis....

So today I cleaned it up externally, stripped off the clutch cover, and got stuck in.....

I followed the Haynes book of lies, and put a spanner on the uj on the gearbox output shaft, and put it in gear to lock up the clutch so I could undo the centre nut....

The book says select 5th gear...so I went up thru the box as far as 4 1/2, where I found another neutral.... and it just will not select 5th!!!!!!!

I've even put a socket on the end of the selector drum, and turned it directly.... it goes up and down from 1 to 4 with no problem and minimal effort..but just will not go into 5th!!!!

I'm suspecting a bent selector fork or something similar...

Any thoughts???

[groovylee]

not got much experience on bike gear boxes i'm afraid mate. but, if the internals are the same as a bros 400, then i might be able to provide replacement parts when i strip the bros engine i have?

no idea if that would work though......

[McF]

Very strange if you have lost 5th, could it be first that is missing? - much more common to have a problem with either first or second but the selector should usually click into gear.

Worth just checking what the problem is, so I would start with neutral and confirm it's in neutral by rotating drive shaft - it should move freely
You can also confirm by checking for continuity across the neutral switch, when in gear you should get no continuity and in neutral, you should get full continuity between the terminal on the switch and the crankcase.

After establishing neutral, confirm each gear individually. Turn the crankshaft using the bolt head on left hand side (worth taking a spark plug out of each cylinder) and confirm the output shaft is rotating for each gear change.

as a complete long shot, cross your fingers and hope that the reason it hasn't been selecting a gear is just because the selectors, shafts etc aren't quite lined up while the engine is not running

If you have a bent selector something pretty damaging has happened to the engine. If a selector is worn, I would still expect you to be able to put the box into each gear

[realnutter]

With the.clutch side cover off, I can see the end of the selector drum, and the detent disc.... It's completely fine from 1st, through neutral, and up to fourth... if I try to go beyond 4th, I can see the detent wheel get to the peak of the last "hill" but then the drum won't go any further.... It's disengaged 4th by this point, and something is stopping 5th engaging.... no amount of shaft rotation will let it engage, so its not just the dogs clashing.....

The engine has been sat in a damp lockup for ages, with little oil in, so maybe some rust has broken out and stopped something sliding on its shaft.....

Whatever, I'm not ready for a full engine rebuild, so I'll put all the new bits in my 600 engine, and enjoy the lower road tax......

If anyone wants the 650......