Low power - Solved

Hi all,

My GZ125 was acting a little slow lately, by slow I mean 35 - 40 MPH was maximum speed(in 4th gear; it made no sense to shift up because in fifth the bike would just slow down).
Step by step I began to troubleshoot.
1st thing I discovered was low pressure in the tires. These are the correct values -> 1,75 bar(25psi) for front wheel and 2 bar(30psi)for the back wheel. This increased the top speed with approx. 3MPH
2nd thing (i knew about this one) was chain and sprockets. A very good improvement after replacing these. I used DID428HD (High Durability) chain and JT sprockets (15 teeth for front sprocket and 45 for the back wheel). The bike felt very nice, better handling.
3rd thing - I replaced air filter, oil filter, new SAE 10W40 oil, and a Iridium NGK Spark plug. This was another improvement, bike felt better, even the gear lever seems to be moving smoother. With these changes I was now able to reach 47 MPH. There was some more performance unlocked somewhere since I knew that this bike should go 55 MPH.
4th thing I checked, was the carburetor and the fuel hoes. I replaced them and cleaned the carb and jets with compressed air. I found out that the diaphragm had a cut, a tear, and once got that solved, bike was fine. I took it off for a spin and it was just great. Back to full performance, I am now able to reach 58 MPH (if i lean on the bike ).
I saw many discussions on this topic on the internet, so this was my story, these are the steps I took in order to get my bike back into parameters.

Stay safe.

thanks for posting this, im new here and haven't rode a bike for about 10 years, good information if I find my bike looses power

The poor old GZ is never gonna be a fast bike, but getting the best out of her is mainly down to regular maintenance, well done for getting her back to her best