stuck Vboost

Yesterday on my way home,my bike was acting very funny,hard time staying at idle,excessive low end power,then when i cam to a stop light the bike just shut off,all of my light were functioning correctly,but i had no vboost servo noise,and when i hit the start button,nothing would happen,i had a good friend come pick me and my bike up,went to his home,took a voltage meter and traced the "wont start issue" found the problem(the harness that goes from the start button to the place that cable hooks to had alot of corrosion) so we cleaned it,bike starts up fine,but the vboost is stuck open,the servo isnt cycling like it should,turn the key off and on,no noise,no fuel pump clicks,nothing,the question is,what could cause this to be stuck open,while the power i have off the line is nice,its not right.
all my fuses were replaced
:ummm:

Could be the controller. Especially on an older bike. They go bad and this can happen. You'll want to check to see if the servo is getting power and trace it back to make sure it's not a bad connection, but this isn't overly rare. It is ODD to see it stuck open though. Usually it's stuck closed. Also make sure everything is working freely.

Chris

OR. get an exhaust, and get a morley kit. then tune for vboost always on! vrooom vroom!


i know, an expensive fix.

make sure its getting voltage.

gamorg02 said:

OR. get an exhaust, and get a morley kit. then tune for vboost always on! vrooom vroom!


i know, an expensive fix.

make sure its getting voltage.

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lol,oh trust me,i RLY like the fact its stuck open,but u rly gotta be carefull on the throttle,cuz its all there,and then some,but like my bud said,if its stuck,then it could mean something more serious is going on,and i dont wanna start frying things

You may have some gremlins hidden in there based on the fact you have already found corrosion in other places.

Regardless, you can check to see if the bike is feeding power into the controller and if it is, you can check to see if power is coming out of the controller and feeding to the servo.

Take the left scoop off. The vboost controller is a small black box on the upper right. Rectangular and kin of thin. There are two connectors on it. The round one is the output to the servo. The other one is the input to the controller.

Disconnect the connector that goes to the bikes harness (not the round one) and check for voltage on the side of the connector that goes to the bike, not controller. Key and engine switch must be on. Didn't see what year your bike was but on the newer models there were three wires if I remember right. Don't test the yellow one, test the other two. You should get 12 volts DC.

If this checks out you most likely have an issue with the controller. You can check for power coming out of the controller on the round connector. Connect the one you previously unplugged. Disconnect the round one. I can't remember what color wires to test for sure but I think they were both black one with a red stripe, one with yellow, maybe. Its in the Clymer manual. Test the controller side of the connector for voltage. Voltage will only be on these two wires with the key on and for a second or so after you turn on the ignition switch. Basically just long enough to cycle the vboost when you turn the bike on. Your timing will have to be right to test this side.

If you are getting voltage on the input side from the main harness but not the output side on the round connector coming from the controller then that is most likely your problem.

If this is the case try to put some pressure on the controller box with your finger or wiggle the wiring. If the vboost cycles then you know for sure you have found the issue. Some have had luck with removing the cover from the controller, scraping off the coatings, and re-soldering the input wires that lead to the connector that goes to the bike harness.

If all else fails you can buy a used controller from pinwall on ebay, a new aftermarket one from micromachines or something like that, or buy a momentary switch and wire it up to replace the controller. Thats what I did and it only cost a few dollars if you have some wire and soldering skills. See this thread......
http://www.vmaxforum.net/showthread.php?t=13143

Forgot to add that you can test you servo motor very easily just to eliminate it as part of the equation. When the left scoop is off, disconnect the round connector from the vboost controller. Get yourself two pieces of to feed 12 VDC to the servo. Check the manual to make sure which two to use. When you feed it one way, the servo should open the butterflies. When you reverse polarity of the feed the servo will close the butterflies. This test is done on the same two wires in the connector, just reverse the polarity.

so what is the problem? Many would love to have that issue LOL
Scooter

Sorry,I forgot to put my bikes year,its a 1988
and thx alot for the feedback.

steven61467 said:

lol,oh trust me,i RLY like the fact its stuck open,but u rly gotta be carefull on the throttle,cuz its all there,and then some,but like my bud said,if its stuck,then it could mean something more serious is going on,and i dont wanna start frying things

Click to expand...

i completely agree. glad u saw the humor in my post tho!

Looks like you found the controller. Its the one on the right.

steven61467 said:

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not sure which of these i should be looking at

The one on the right. Says yamaha on it. Has some faint white lettering on it too. Got a manual? If not, you should download one or buy one

ok,yeh,i took that box off,opened it up,and u could eat off of it it looks so clean,i did wiggle all of the wires in that area,including the box,still no cycle,so im assuming if it is the box,something on the board let go