[Ronnie Glasgow]

Hi, Newbie here. Last year I acquired a 1990 NS125R which hadn’t run since 1999. I’ve finally got it running and MOTed.

It’s not too bad but the previous owner’s dad had messed with it and it only runs sweetly at high revs.

I asked, and got the text below from the last owner describing what was done to it. I don’t think the son ever actually rode it.

Any suggestions for re-jetting the carb based on this?…

“Here is a reply from my dad -
I cut open front pipe and cut out small pipe inside which restricts flow then welded back up. Drilled large hole in small rear silencer to open that up. Lifted carburettor needle one notch to give more fuel. Changed rear sprocket to up the gearing. Top speed increased from 70 to 100mph hope that's of some help.”

(Btw I don’t believe the 100mph!)

Thanks for any advice. Cheers

 

[Remy]

Theoretically it could achieve it on a long straight.

The opening up of the pipe seams reasonable. Some were if not mistaken delivered with a restricor on the pipe.
I would be coutious on what he did with the silencer. Youre better of starting with a fresh one maybe.

Regarding jetting best start is to have the manual of both types, and cross compare the jetting.

 

[Ronnie Glasgow]

Theoretically it could achieve it on a long straight.

The opening up of the pipe seams reasonable. Some were if not mistaken delivered with a restricor on the pipe.
I would be coutious on what he did with the silencer. Youre better of starting with a fresh one maybe.

Regarding jetting best start is to have the manual of both types, and cross compare the jetting.

Thanks Remy!