Spent a full day trying to fix a weird idle on my old Virago

My 1985 Yamaha Virago 700 started idling super rough last week, and I figured it was just the carbs. I spent about 8 hours over two days cleaning them, checking the jets, and even replaced the intake boots. Turns out the real problem was a tiny crack in the vacuum cap on the intake manifold I didn't even see at first. Has anyone else had a simple vacuum leak cause that much of a headache on an older bike?

3 comments

3 Comments

gonzalez.wesley24d ago

@jessereed I gotta ask, have you actually chased a vacuum leak on a bike before? Because a tiny crack on a Virago's intake cap throws everything off since it's such a small engine. Cars have more tolerance with bigger motors and vacuum systems, but bikes are way more sensitive to that stuff. A split hose the size of your pinky nail can make it buck and stall like crazy. I learned that the hard way on my old VTR250, wasted a weekend chasing carb issues too. Vacuum leaks are legit, they're not just mechanic hype.

hill.mila2mo ago

Used to think vacuum leaks were overblown until my own Shadow started running like garbage. A split hose the size of a fingernail clipping was the whole problem. Now I check those first every single time.

jessereed2mo ago

Honestly though, is a tiny leak really that big of a deal? Cars seem to run fine with small issues all the time. Tbh it feels like mechanics hype this up to charge for extra work. Maybe your Shadow just had other problems that got fixed by accident. Ngl I've seen cars with way worse vacuum lines that still started and drove okay. Just seems like an easy thing to blame when the real cause is harder to find.