ZXR750 L1 horrible sound of grinding from gearbox or clutch area when bike is on sidestand or revved hard any ideas?

You need to use the clutch to downshift on most bikes as well as blipping the throttle each time. If you straight downshift from say 5th to 2nd gear without using the clutch you risk the chance of damaging the gearbox as well as over revving the engine.

Bikes are fitted with a sidestand switch and clutch switch that work together. If you try to ride off with the sidestand down (switch activated), releasing the clutch activates the clutch switch and cuts the engine out. Pull the clutch in and the engine will start on the button only to cut out again if the sidestand switch is activated and you release the clutch.
A common problem is a dirty sidestand switch that stays activated even when the sidestand is lifted up. This is because it is situated low down, generally under the bike and will get covered in all sorts of road grime, especially in wet weather.
To remedy this get someone to hold the bike upright, enabling you to get on the ground and locate the switch. This can be done by raising and lowering the stand whilst looking all along the length of it paying particular attention to where it pivots and around the spring. My bike (also a Kawasaki) has a "pin" that is pushed in when the stand is down. If it gets cloggeed with road grime it also stays pushed in when the stand is raised and then cuts the engine off when I try to ride away. A good wipe around the switch area and a good dose of WD40 remedies the problem.

If the bike sounds fine on idle and will rev freely then I would suspect the gearbox and particularly the power output shaft/drive shaft

I think removes the tyre both then check its gear box bearing noise or clutch plate bearing noise

May seem obvious but its your gear box, if you can successfully shift into first, slowly release clutch without hitting the gas your engine should slowly wind down and bog out, if it does it immediately without a winddown it could be clutch but generally any grinding when slipping into gear is a sign your gearbox needs replacing

Sounds to me like slave cylinder is out.

You don't mention the year and model...but here are some general ideas.

Most Yamahas have various safety interlocks designed into the wiring system....typically a neutral switch, a sidestand switch and a clutch switch, a tipover switch and a kill switch on the right handlebar.
The design basically is to prevent riding off with the sidestand down....so if the bike is in neutral, the neutral switch grounds to light your neutral lamp and allows for ignition and starter operation.
Is you place the unit in gear...if the sidestand switch senses the stand is still down, it kills the ignition and starter.
If the bike is in gear, starter will not operate, unless the clutch is pulled in and the clutch switch detects this happening.
Tip the bike over and the tipover switch kills the ignition and fuel pump if it has one.

So...is the igniter (black box/brain etc) getting supply voltage...if not check the ignition fuse, and the handlebar kill switch .
Is the neutral light working....if not...try starting with clutch in and sidestand up.

If you have 1/8" to 1/4" freeplay in the clutch lever the cable should not be the problem. You had best check the gearbox oil level.

Hi and welcome to FixYa,

Check, bypass (or replace) the sidestand switch. This would be especially so if the connector is not connected or if the bike laid on its left side.

Good luck and thank you for using FixYa.

I would not trust that clutch cable. Chances are it is pretty old. It could leave you stranded in traffic. Get a new, worry free, clutch cable. Also, change the gearbox oil, 10w40, and install a new oil filter. The gearbox oil could be dirty and gritty and impeding the operation of the clutch.

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