Question about 1999 Honda V-Twin Magna

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Magna engine surges

Just bought a 1999 honda magna with 4000 miles on it. previous owner said he had carbs cleaned. bike starts fine and idles fine. it surges at all speeds up to about 55 mph. after that it runs great. does it need the carbs to be cleaned again or shim the needles or both. or is it something else? love the bike but need to get it running like it should.

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  • leoandmarymu Mar 02, 2009

    the plugs look like they are new. the air cleaner is new and is stock and the exhaust pipes are stock. It does not have a jet kit installed as far as I know.

  • leoandmarymu Apr 06, 2009

    I found out through the magna owners group that these bikes surge at lower rpms due to a lean fuel mixture (emissions req). I ordered a shim kit from Dave Dodge Racing Products, installed it and the bike runs great now. Thanks for the help.

  • joe May 11, 2010

    with the petcock off, remove the main fuel line to the carbs and place that end in a coffee can. turn on petcock and observe the flow of gas into the can. is it a strong flow or does it look weak?

    if weak, then change out the fuel filter and repeat. if still weak, then drain gas out of tank and look inside to see if particles are clogging the point where gas flows out of it.

    if strong, then carb float may not be adjusted properly. the brass tang may be adjusted ok for a low demand of fuel, but when throttle increases, its not letting enough fuel past the jet needle into the carb bowl. all this is assuming you don't have a spec of dirt in the carb obstructing the main jet.

    try the above and report back.

  • joe May 11, 2010

    how do the spark plugs look? black (running rich) or white like they are new (running lean)?

    does the bike have an after market air cleaner or exhaust pipes?

    does it have a jet kit installed?

    how does the flow of fuel look to the carbs? is it strong or weak? if weak, clogged fuel filter?

    if all stock and and plugs look good, then gotta be fuel related which might mean taking the carbs off and looking for an obstruction on a jet or checking to make sure the float is working properly (ie, allowing fuel to enter the carb).


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The carbs may need to be cleaned. Try running seafoam in the tank first and see if that clears some of it up. The slow jets may be plugged up inside the carbs. If the snorkel had been removed from the airbox, it could cause siminlar problems as well. have you changed the spark plugs yet? be sure to check out the Honda Magna forums for more info:

Posted on Sep 08, 2009

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