Intermittent V Boost

[IdahoLocke]

I have an 86 Vmax. I have owned it for at least 4 years. Vboost worked flawlessly for the first two years. For the last couple of years it has been intermittent at 6K. I replaced the v boost controller with a newer used one off of ebay. That seemed to work at first and then it proceeded to act up after a few months. My guess is I just bought another bad controller....

The vboost cycles upon start up as expected. I am pulling my hair out trying to figure out why it is being unpredictable. Is it a tuning issue? Does the entire computer and Vboost controller need to be replaced? Just trying to get some advice on other issues I may have overlooked. On occasion I have killed the power on the bike while riding it and turned it back on. This sometimes gets the Vboost working again......Advice?

 

[MaxMidnight]

The V Boost unit is powered via a feed from th ICU (red/ white) and get a signal from the OSF (grey) coil wire. It then goes to earth.
Provided that you have continuity and good connections then the issue is likely to be in the control unit.
Suggest that you have a butchers inside and look for broken or burnt joints.

 

[Fire-medic]

Sounds to me like two independent things.

One is the VBoost controller.

One is the ignition box.

As MM suggests, opening both to examine the wires into the circuit boards from their plugs, and seeing if there are any obvious breaks, or cold-soldered joints on the boards is what I'd try. Some have had + results re-soldering the wires to the boards.

An Ignitech ignition box from Sean Morley can control both the VBoost and the ignition. [email protected]

 

[IdahoLocke]

Sounds to me like two independent things.

One is the VBoost controller.

One is the ignition box.

As MM suggests, opening both to examine the wires into the circuit boards from their plugs, and seeing if there are any obvious breaks, or cold-soldered joints on the boards is what I'd try. Some have had + results re-soldering the wires to the boards.

An Ignitech ignition box from Sean Morley can control both the VBoost and the ignition. [email protected]

Yes, getting a new Ignitech set up was my last resort. Thanks.

 

[02GF74]

What do you mean by "act up" and "being unpredictable"?

Have you recorded any data or is it purely subjective like "I'm at 6500 revs and my arms should be pulled out of my sockets".

In addition to the above, have you checked the cable and motor are set up correctly, free to move and operating correctly?

If there was a definite problem with the vboost controller, then it would be intermittent on power cycle (don't ask how I know that)

... but if it misbehaves whilst riding, that's more difficult to measure /detect.

Does at any time when you feel vboost is acting up is the rev counter erratic? (from memory the same lead from ignition coil goes to both)

To prove beyond reasonable doubt, you need to record vboost operation whilst riding.

One possible way is to use an endoscope to record movement of the motor not easy. These are cheap and connect to a mobile phone.

Another is to buy a three dollar voltmeter, the 3 digit display type and wire it across the variable resistor that the controller reads to figure out the position of the valve.

Sticking it next to the rev counter you would see voltage and revs when all is working and when acting up.

As for checking for dry joints, mine was failing intermittently during the power cycle, pressing on the case would cure it which left me to conclude something was not making contact. After resoldering a few joints, a good look with a magnifying glass identified a hairline fracture in the solder around one pin. Search forum for the photo of this.

Basically what I'm saying is don't expect it to be quick/easy to find a faulty joint , more so if it never fails during the power cycle.