Cuts off at high rpms

[chronoman]

My GS450 developed a problem at 8K the motor feels like it shuts of then at 7K it starts back until it hits 8k and it does it again, it also backfires through the exhaust.

I recently purchsed the bike its an 87 gs450, that sat fo 5 years.
I've rebuilt the carbs, removed the inline fuel filter,new fuel line, checked and clean the tank filter and petcock, new plugs, oil change, new battery,tires, chain so on.also the bike had pods(it ran terible) found used airbox on E-bay.installed airbox and filter.
The problem seemed to start right after I added some seafoam to the fuel.
I've put around 600 miles so far.the bike has 29k
Should I rebuilt the carbs again, maybe the seamfoam cleaned the tank and now carbs are gunked up, or can the problem be with the ignition? no points, electronic.
The bike pulls strong off the line and it will cruise a 5 to 6K with no problem, average fuel economy 48 to 55 mph I guess I could live with it no hitting 8K, But that's no fun.
Any ideas?

[Kcwiro]

If I had to guess... I'd check first for any intake leaks. I have had simular troubles and the poping your describing from what I understand is your fuel leaning out.... could have this backwards but I would look for that before taking carbs apart.

Start simple and work your way up

Since you said you had pods... did you do anything with the jetting / re-adjsut after adding the stock box back?

[tkent02]

What do your spark plugs look like ???

Perhaps they got fouled by something that was dislodged by the seafoam.
At least a look at the plugs may tell you where to go from here.

[chronoman]

The jets are stock, airbox and filter are tight no leaks that I know.
Spark plugs look good grayish looking.
I'm going to replace the intake rubbers I purchased them a while back.
As far as checking the plugs I could try shutting the bike off and going in neutral as soon as it cuts off and check plugs then, off course pulling over to the side of the road before checking plugs

[Kcwiro]

you can try teh wd-40 trick to see if the idle gets messed with when you spray...that should give you a clue if that is happening