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Discussion Starter · #1 ·

I live in Colorado and have been having a problem with my bike loosing power and flat out dying in me. I have had the problem in the middle of the day. I will tell you that it has been hotter than hell this summer and I think that the cause may be vapor lock.

Has anyone had this problem? If so any ideas on how to fix it? Should I consider rerunning the fuel lines?

Thank you in advance.


· Premium Member
2,773 Posts
That was probably my post on the fuel pump gone bad. I have become something of an evangelist preaching my opinion that most of the carbed 900s have fuel pumps with stretched and embrittled diaphrams that still flow enough volume to run wide open, but no longer deliver enough/consistent pressure to the float bowls. The lack of consistent pressure probably causes metering inconsistencies that have led a lot of folks to blame jetting.

In my case, rebuilding the pump not only fixed the vapor lock but also several low and high speed issues that I didn't even recognize as degraded performance since the bike ran like that when I bought it.

The Mikuni pentagon style pump is also used on some Arctic Cat and maybe Polaris sled applications. I got my rebuild kit through www.mfgsupply.com .

Mark J

· Registered
3,410 Posts
Your symptoms sound much like something that happened to me last summer.

The bike would sputter and die after extended running at freeway speeds. It was NOT fun having the bike die while in the left lane on a Boston interstate!

The problem was a fuel line that was routed just a bit too tightly. When the undertank area got nice and hot (combination of weather and engine soak), the main feed line softened enough to collapse and kink. Fuel starvation ensued. Bike quit.

I'd pull over. Scratch my head (and whatever else needed scratching). Check the plugs (surprise, looked really lean!). I couldn't find anything wrong. Then I'd sit on her and fire right up.

When the line cooled, it'd stiffen enough to pop back into shape.

Solution: cut a longer piece of fuel line and route more carefully. Watch closely every time I lower the tank back in place that nothing's amiss with the line.

· Registered
209 Posts
I live in Colorado Springs, and have had the same problem twice this week, once with my buddy at the same time on his identical carbed M750.  They both died in the same way within minutes of each other. We thought it was the heat too.  This fuel line kink that CRASH suggested seems like it might be the problem.  And you're right, it's been hotter than the devil's drawers!  99 degrees at 6,000 feet above sea level?  Dizamn!
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