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Bog down / Vacuum leak
Posted: Sun Sep 14, 2014 10:07 am
by Bob9777
I have 1990 Valcun 500 30,000 miles I have a vacuum leak some where...my vacuum gage is bouncing
Some times she will bog down as I am riding and take a few seconds on working the throttle
Until the RPM will come up again.
Any suggestions on where to start ?
Thanks
Re: Bog down / Vacuum leak
Posted: Mon Sep 15, 2014 7:47 pm
by Triangles
I'm not sure where or why you are hooking up a vacuum gauge but it will always be bouncy. The vacuum is not constant nor is it remotely consistent. It might smooth out a little at very high rpm. Sounds more like you are describing a gummed up dirty carb. Has the bike recently been sitting unused for a long period of time?
I find vacuum leaks by spraying a flammable fluid near where the leak is. When the RPM's jump up I've found my leak. Just don't be stupid about it and burn your bike to the ground.
Re: Bog down / Vacuum leak
Posted: Tue Sep 16, 2014 1:38 pm
by charnotx
I'd definitely agree with Triangles on this one. Sounds like your carbs are dirty and could use some B-12 to clean them up. Is it happen when you are shifting up? or while you are holding the throttle steady (say 40% open), is just drops?
Just had to do that same thing about week ago. After taking it apart, and getting the jets cleaned, I have no throttle response issues.