Open v boost

[FIRELS1]

I have a 95 vmax all stock except for the v boost being open all the time. I have the mixture screws out 4.5 turns and can't seem to get the idle rich enough. It has a stuble off idle until about 5000. I am guessing I need to fatten up the idle circuit. How do I do this? Thanks for your help

 

[gamorg02]

bigger pilot jet would help i think. if you have a stock max it may just be easier to put the vboost back to stock or get tboost (opens at 3krpms).

 

[[email protected]]

I'm running open boost as well. When trying to optimize fuel mileage and playing around with my carbs I raised the clip on the needle one postion to lean out the midrange a bit. The bike ran like crap from 2500 rpm up to about 4.5K. When I was running down the road, it would buck and jerk and stumble as soon as I opened the throttle until I got to around 4500 rpm. I dropped the clip on the needle back where it was and it was totally fine.

 

[FIRELS1]

How much bigger pilot jet? Are u refering to pilot jet 1 or 2? Where can I get them?

 

[Damon]

I've used 40.0 Mikuni pilot jets (stock are 37.5)

http://www.carbparts.com/

N151.067 Non-Bleed
Used in many original
equipment carburetors
OEM for new
Triumph, Ducati
30 thru 55
Increments of 2.5

 

[gamorg02]

pilot jet, not the pilot air jet. its in the jet block. i'd say u might have a tough time dialing it in running a stock setup.

 

[MaxMidnight]

I would be surprised (but happy to be corrected) that you will be able to get a satisfactory idle and low revs running.

With V Boost open from idle one issue that you will be fighting against will be low air velocity through the venturi's at low revs.

The higher the air speed through the venturi the better the fuel will atomize thus better running and more power.

If you think about how Yameringha have specified the carb size, they have used items on with a small venturi.
On a conventional motor this would give good low down power ('cos the small venturi = high air speed even at low revs = good fuel atomization = more power) but as they would not be able to flow sufficient air at higher revs you would loose power as the motor is starved of air.
V Boost allows each cylinder to draw through two venturi's thus allowing it to continue to produce power much higher in the rev range.

 

[FIRELS1]

If I go smaller on the pilot air jet 1, will it not be the same as going bigger on the pilot jet?

 

[[email protected]]

Try a small shim on the needle before you buy any jets. It only takes 15 minutes to do and only costs a couple dollars.

 

[Vmaxattacks]

Been there, done that. IMHO re-connect the V-boost. You'll be chasing your arse till doomsday trying to get it to run right. :bang head:

 

[FIRELS1]

Shimmed needles .020 and it is almost gone depending on the outside temp. Thanks for all your help!!!