Tuning Issue

[Hodado]

1981 gs650g stock airbox,Runs great up to 7000 rpm,then falls on its face.Rebuilt carbs,new parts throughout.Original coils,replaced spark box.
I do not know if it is a rejetting problem or ignition problem.Where should I start?

[Mekanix]

Plug chop maybe.

Could be running lean on top end which isn't good at all.

Any mods at all ?

Is this new, all of a sudden?

What size main jets? 110?

Any more information would help.

[tom203]

Plug chop maybe.

Could be running lean on top end which isn't good at all.

Any mods at all ?

Is this new, all of a sudden?

What size main jets? 110?

Any more information would help.

Makes sense; also make sure air intake slots on air filter box aren't blocked with wires. rags, etc.- you need alot of air under load at 7k

[Spyder]

Does it act like you're running out of fuel?
Mine did it when I first bought it. I didn't believe it when someone told me to replace (do not attempt to repair) the petcock.
after a month of adjusting, and testing and plug chops and even 2 jet changes. I finally decided to listen to the and replaced the petcock with a new one. Instant fix...

Just some food for thought, its a 30 year old part with 30 year old rubber in it...