Recently i have bought an SRAM X3 Rear Derailleur for my replacement of a Shimano Tourney and i have no luck getting it to shift to my 3 larger cogs on a 7 Speed Shimano Freewheel.

Things i have tried:
Tighten cable on 7th gear
Tighten cable on 1st gear

The X3 does not have a Barrel Adjuster, and my shifter cables are running slightly short ( Will buy some ).
Thanks.

Welcome to the forums!

SRAM and Shimano shifting systems are incompatible with each other. They have different cable pull ratios which means that one 'click' on the shifter pulls the cable a by different amount to move the RD by the same distance. That being said, the mechanics of the RD is also different to match the cable pull on the shifter. Their cassettes (sprocket spacing) is the same though.

It would be better to stick to matching shifters/derailleurs between SRAM or Shimano.

Thanks e_guevara, Is the a possible way to way bypass by any chance? Or do i have to buy the X3 Trigger Shifters and Brake levers, Since my shifters are with brakes ( Shimano ).

Also, Will it affect my front derailleur?, I just need the smallest and middle cog.

No way to bypass this as this is how the shifters and derailluers are designed to work. No way they will work properly with each other.

Better sell or trade-in your X3 and get an Altus or Alivio (Shimano) RD. Changing your brifters (brakes + shifters - I hate using the term BTW) is the wrong way to go about it.

Thanks e_guevara, I think i'll just stick with how it works without 6 and 7th gear. I might just get X3 Shifters and brake levers and i can't go about finding someone to buy or trade them.

That makes no sense. Replacing the shifter will cost more than buying a compatible derailleur.

Yup.

Well, The parts i bought was online and i have no stores around me that have it. Hence why i need to order more parts. Overall the SRAM X3 Runs way better than the Shimano Tourney.

Was the Tourney broken or was it just not shifting properly? If it was the latter then it may mean it was just improperly adjusted.

I could adjust/tune the Tourney to shift pretty well (I have had several Tourneys on an old MTB and a commuter). Granted it doesn't shift as nice as a Deore or XT, but it does the job.

A properly adjusted Shimano derailleur will work way better than a SRAM derailleur that cannot get to some of your gears.