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Motorcycle Repair/Fuel Starvation

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Question
Hi I have a Virago VX750 1992. It runs lovely until it grts to 4500-5000 RPM then its just as though it is running out of petrol. If I operate the choke it then runs OK iT SEEMS TO DO IT IN ALL GEARS. hAVE STRIPPED AND CLEANED CARBS BUT MADE NO DIFFERENCE hELP pLEASE

Answer
Peter, I am not very familiar with Yamaha products specifically, but a quick look at some online microfiches shows that the petcock/fuel valve has screens up inside the fuel tank, which may be plugged up from rust/debris or just aging components.

The things that slow fuel flow are the petcock filters and perhaps if the gas cap or venting system for the fuel tank is causing a partial vacuum at higher fuel demand situations.

If your petcock looks like this:

http://www.ebay.com/itm/like/360501250613?lpid=82&chn=ps

There is also a vacuum diaphragm line on the back side. If the diaphragm fails, you get an air leak and loss of fuel delivery.

Bill Silver

Motorcycle Repair

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Bill Silver

Expertise

Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.

Experience

I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

Organizations
VJMC (Vintage Japanese Motorcycle Club) of North America

Publications
VJMC newsletter, as editor for two years and as contributing editor currently.

Education/Credentials
3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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