Limited rpms

[dearnhardt7]

I have a 85 GS450L...just swapped motors (another 450) and I can not get rpms over 4500 at full throttle. I took carbs off a good running 450 ..so I know its not a fuel or carb problem...I am at my wits end on this...any help would be much appreciated. Thank you.

[Pyrorocketeer]

Check for vacuum leaks. Maybe cracked boots, or o-rings.

[Nessism]

Any mods on the bike? Missing airbox or not hooked up. Stock exhaust or modified? Carb jetting?

[dearnhardt7]

No mods to the bike...airbox hooked up..stock jets.

[Nessism]

Not sure what to suggest. A bad ignitor can limit rpm, a stuck mechanical advance might, carb issues can do it but you say that's not a problem, lack of fuel in the float bowls is another thing to check. Start with the basics and start crossing off things.