Open v boost.

[run990]

I am trying to derestrict my japanese import vmax ,I have replaced the slides and bored thru the v boost block off pipes .I had to put the needles on the bottom clip and have the pilot screws 4.5 to 5 turns out to get an acceptable idle .
I bought some UK spec idle jets that were exactly the same as the ones fitted . The bike goes well if you keep it above 2000rpm below that you need to feather the throttle and it is very jerky.
I derestricted a 90bhp UK bike in the past swapped the slides and bored the vboost blocks and it ran great with a better idle and low end than the japanese one I have now .
Any ideas before I block the vboost blocks up again and just run without thanks

 

[Radioguylogs]

IDEAS:

Check to see if US jet sizes are different than what you are using?

Consider if the pilot circuit might need cleaning?

-Mike

 

[run990]

The pilot circuit is clean and the pilot jets are the same as a full power machine.
I was wondering if the ignition module had a different advance curve for the japanese market as it has a speed limiter built into it which others do not .
I am going to try it with the vacuum switch disconnected as it is worse at periods of high vacuum.

 

[Fire-medic]

Info for you and reference material.



VMX12- Service-Manual.pdf (vmoa.net)

 

[MaxMidnight]

You also need to make sure the basics are right. Now that you have opened up the V Boost connecting tubes is how to balance the carbs?

These are the ignition units I'm aware of but there may be others.



Not sure if that helps.

 

[run990]

View attachment 82549

Looking at the settings I would say califonia settings were closest for the jap vmax ,I may try setting it up with an 1100rpm idle speed rather the lumpy 950 rpm mine has at the moment.

 

[run990]

Finally sorted it ,disconnected the ignition vac switch and blanked the manifold off now perfect idle and perfect transition to on and off the throttle .What I think was the problem was too much advance at idle and with open v boost uneven pulses giving the weird Jerky uneven overun