Gearbox problems,only 3 and 4 gear .

Hello everybody,my name is Sergio and I wrote from Spain.
I have a 1974 750 Norton Commando.

I change primary chain to a belt kit conversion,Rotor Stator,Diaphram Spring clutch discs ,carburettors and other minor things.
After buying all the parts for my Norton I'm having some troubles that maybe someone could help me to fix up.
I changed everything with afriend of mine that woks as a mechanic..
The engine starts perfectly with the new carburetors but the gear box only has two gears working!! And really can't understand it' cause we touched absolutely nothing of the gearbox, and the bike entered by it self at the garage with the 4 gears working perfectly.
We had to shift one gear to retain the engine cause we had to remove the nut that holds the stator and avoid the move of the engine...
Anyone think this thing have could cause any damage to the gearbox..??
The other thing that change is the front Isolastic and move the engine,but change it without any problem.
I think the first and second gear are missin'
I shift them and the bike doesn't run
Do you think the "Selector fork" can be bent or something???
We open the gearbox and apparently all are perfect,nothing is broke!!
I don't know but hope anyone can help me or guide me to mend this problem.
Many thanks for all!!

Greetings, and welcome! When attempting to shift, are you stopped? You've rotated the rear wheel back and forth while attempting to change gears, correct? (because the dogs may not be aligned) How does the shifter feel? Does it travel fully when attempting to engage 3rd or 4th gear? Or stop mid stroke, like it hits something?

Having the belt too tight can cause seemingly strange shifting problems.

Is this standing still, or with the engine running ?
With the engine stopped, it is quite possible for the gearbox not to want to change gear, at all. You have to rock the bike back and forward, so the rear wheel lets the gears line up, and then find the right spot for the gears to change. As above, if the belt is too tight it may not want to change gears, at all.

If the engine is running, it needs to be in neutral to be able to kickstart it....

Ola Sergio, como estas? Mi esposa es mitad Mexicana . Unless someone opened up the gearbox you should be fine. Yes to rotating the rear wheel to aid in gear selection.

Hi Sergio from Sapin.
First thanks to answer me to everybody.
To the guy with Mexican wife,un saludo desde España!!!,to her.
In this moment are eight minutes past tweelve here in Spain.
I try to explain wityh my bad english what happens today with the bike.
I put the bike up on the centre stand.
I started the bike and put the first gear and the rear weel moves,oh yea!!!
put second,third and fourth and change well up and down all the gears.
With the engine running I put the bike on the floor put first gear and the bike don't go with power, like if you try to start walk with the bike in second or third gear and the engine stops.
I don't know what happens,I turn crazy
It is as if the bike were not power.
Sorry my english is bad but tecnical english is worse.
Thanks a lot.
Regards

I forgot one thing,the belt is not tight,and when I starts the engine the belt rotate well.
Bye.

Oh ya, a clutch thread.

How does the inside of your clutch look. It's obviously slipping form either contamination or poor adjustment. You should take it apart and clean it. Take lots of pictures and study your workshop manual.

Yes it sounds like a clutch thread is evolving here. Rotor nut very tight ? Re-adjust clutch.

Hi,people.
Tomorrow I will go to rebuilt all the cluch and the rotor.
Only one question.
The rotor nut and the cluch nut is tighten with some pounds/kilos of torque????
Sorry for my english I hope everybody understand me.
Thanks.
Good night.

nortonvibrant said:

Hi,people.
Tomorrow I will go to rebuilt all the cluch and the rotor.
Only one question.
The rotor nut and the cluch nut is tighten with some pounds/kilos of torque????
Sorry for my english I hope everybody understand me.
Thanks.
Good night.

Click to expand...

It is in the manual but here is a nice reference. Take special note of the clutch torque setting of 70 ft. lbs.

http://www.oldbritts.com/n_torq.html

nortonvibrant said:

Hi,people.
Tomorrow I will go to rebuilt all the cluch and the rotor.
Only one question.
The rotor nut and the cluch nut is tighten with some pounds/kilos of torque????
Sorry for my english I hope everybody understand me.
Thanks.
Good night.

Click to expand...

BE WARNED! The torque specification for the clutch hub retaining nut is erronious in ALL service manuals, factory and aftermarket. It says "70 ft. lbs." (that will bend the circlip on the mainshaft and cause binding) and it SHOULD BE TIGHTENED TO NO MORE than 40 ft. lbs.

hobot said:

y pvisseriii » Thu May 24, 2012 1:21 pm
The circlip behind the clutch locating washer should be replaced with #15 shown here. http://www.oldbritts.com/1975_g12.html
This is a much beefier clip and does a good job. Sharp edge facing gearbox.

Click to expand...

Click to expand...

Yes, along with 40 ft lb at the clutch center nut.