The speedo and mileage has stopped working since i got the front tyre changed,anything i can do at home to fix it easily without taking it to the garage,thank you

You'll need to take it to a transmission specialist. They might be able to correct the ratio by fitting either a different rim size, a different tyre size or both. One full rotation of a tyre gets shorter as the profile, (sidewall height), gets smaller. So the correct 'low profile' tyre could fix the problem for not too much money.

Year make and model? replace the speed sensor on the transmission.

try to remove the air filter, if it does still stall, try to adjust the air-fuel screw on your carb or better yet, overhaul your carb.

it;s most likely the cable but it could also be the drive gear or the speedo its self. remove cable from speedo and start the bike if cable turns its the speedo then just work your way back

I would take it back to the shop that changed the fuel filter and have them find and fix what they have done. They are responsible for anything that they have messed up while in their care.

unfortunatey you may not be able to fix this, speedos generally run from a sensor or cable at the front axle, and rely on the rotating wheel, and are not generally able to be calibrated.
An instrument tech amy be able to do something if your model?? has an electronic speedo, but the reading can change with different tyre sizes, and even slightly as the tyre wears

Ken Budd's answer is incorrect: There is only a potential engine problem when the oil light comes on permanently.

The speedo/mileometer on thge Majesty normally sends pulses to a counter that switches on the oil-change warning light at 3,000 km. If the speedo/mileometer ceases to function the oil-change warning light blinks steadily simply to let you know the pulses aren't getting sent to the counter.
The most likely problem is a broken speedo cable; a new one costs £5.72 from AJSutton and you can easily fit it yourself: Take off the windscreen then reach through the gap above the headlamp to unscrew the outer cable beneath the speedo.

I've got the same problem as you right at the moment with my 1996 Majesty but in my case its the gear unit on the front axle (to which the speedo cable connects) that has stopped working: I'm currently on the look out for a new gear unit. Does anybody have one ?

is it still connected to the front wheel is the cable broken

Hi ..... Welcome to the 'custom' world ! As you've discovered changing one thing leads to another. The chain angle has changed due to the shock length. You could try going to a breakers and buy another chain guide rubber ? More involved solutions could be to off set gear box sprocket, intermediate chain tensioner pully, go back to stansard shocks (which is main problem) and widen rear mudhuard/fender (which as you can weld isn't a big issue) or make up a 'tunnel' out of a round or square section of nylon and allow the chain to run through it. Let us know how you get on.