help asap, vboost problem i think....again

[VMAX1260]

ok. one month ago i posted a thread about my vboost which i didn't feel it to kick in. my engine is a 1300cc with carillo ,je pistons 79mm. stock carbs. t-boost installed. my mechanic had my main jet drilled so for the first 1500Km my engine untill 4000 rpm run very smoothly.the think is after the first 1500Km when i started to push the throttle i didn't feel any power. before with a 1260 i could feel a kick in the pants. now nonthing.i checked the boost butterflies which they didn't open completely. this problem is fixed. i have ordered the stock main jets and iam waiting for they arrival.
my question is... when my bike reached before my last tunning 3000k i could feel the the tboost kickin. i mean when i held my throttle not all the way and my bike reached 3k i could feel the tboost kick in . now i cant feel anything. even when i turn it to 6k. evevn when i disconnect all the vboost function. the power i feel is the same.
is possible because of the drilled main jet kit i cant feel the vboost ? ? ? ? my engine runs like it has no vboost. and in high rpm i can feel the rpm rise not very quickly. i know my butterflies open full way. but no power. please i need all the help i can get

 

[gleno]

Your engine has no V-boost.

This is either electrical or mechanical.

The thing most of us never do is check the adjustment on the v-boost cable.

It wears and gets slack (just like the throttle cables and linkages) BUT its just TOO hard to get down there and check the V-boost.

While you are in there , check the electrical contacts to the V-boost servo motor.

Would be good to have (on this forum) a 'how to' - "tune the V-boost" guide.

Anybody good at this?

 

[VMAX1260]

I know my friend. i am good in tunning the vboost. i took out my carbs and been down there. no sluck in the cable everything works perfectly. i took out the service manual and adjusted it again. it is very easy. there is one screw on the end of the slide which open the vboost butterflys. this screw is fixed on the engine, this must have a gap 0.1 - 0.3 mm when the slide is closed. now there is another bold on the slide that the vboost cable pull. in closed possition this must have 0.2 - 0.4 mm gap.and finally there is a last bolt on the the small black box. whith this bolt you adjust the cable so the butterflys are open completely. i ve done all that . and......... NO F>>#$NG boost. my nerves. i see the slide going up and down. but nothing

 

[gleno]

I know my friend. i am good in tunning the vboost. i took out my carbs and been down there. no sluck in the cable everything works perfectly. i took out the service manual and adjusted it again. it is very easy. there is one screw on the end of the slide which open the vboost butterflys. this screw is fixed on the engine, this must have a gap 0.1 - 0.3 mm when the slide is closed. now there is another bold on the slide that the vboost cable pull. in closed possition this must have 0.2 - 0.4 mm gap.and finally there is a last bolt on the the small black box. whith this bolt you adjust the cable so the butterflys are open completely. i ve done all that . and......... NO F>>#$NG boost. my nerves. i see the slide going up and down. but nothing

Ok, so the mechanics are good?

You need a signal generator to simulate the rpm input (static test)..

OR U need to rev the motor to 6k and see if the servo works. (ear splitting).

What's the go?

working at 6k or not?

How fast does the servo open the butterfly valve:ummm:

 

[VMAX1260]

everything works and in 6k the servo opens the butterflys and in 3k when i turn the T-boost switch the butterflys open. do you think is that my mechanic drilled bigger the main jets ? ? ?

 

[vmaxcruzer]

I would NOT under any circumstances run any jet that has been drilled out by any mechanic. That's one of the dumbest things Ive heard. You need to recalculate the main jets for your altitude then do a full throttle clutch-in-kill-motor run and pull the plug to see what color it is. You probably have so much fuel going through the intake that the "boost" feel is gone.

 

[VMAX1260]

i hope so man. i am waiting for the stock main jets. I ve seen in this forum that from the stock that is 152.5 many vmax owners say that they changed it to 147.5 for better performance. do you know anything about that. my engine is bored to 1300cc with K/N filter and supertrapp slip on's. do you think the factory main jet will be fine ?

 

[nd4topspd]

my carbs are untouched ontop of my 1300. Runs a little rich but not bad. put down 118hp and 83 torque with stock carbs and stock exhaust running awesome. Could have lean it up and posibly upped the hp for sure but she runs great so I havnt tweeked it yet

 

[VMAX1260]

so you suggest of buyin 2 number less from the stock... i will inform you my friend. thank you very much

 

[vmaxcruzer]

I would definitely throw away the drilled jets to keep them from getting mixed up with others. 152.5's work good with stock pipes because that's what the factory set them up as, I'm at 4200 feet and run 147.5's with a 4-2-2 pipe but if I were lower in elevation I'd have to go to a larger jet to compensate for more air.
Use this chart to figure out what main jet to start with.
Good luck.

http://www.ultralightnews.ca/rotax503/rotax2strokepdf/mainjetcorrectionchart.pdf

 

[gamorg02]

it may be naivety but i can't imagine drilling jets works all that well. i mean the tolerance of the bit has to be so perfect. no runout what so ever as you cuold drill something to a 150 and easily make it a 152.5 depending on the runout of the bit

or maybe do I just not understand how this all works?

 

[VMAX1260]

wow nice chart.... according to this chart i should use 150.975 (151) for the summer and 152.5 for winter so i will prefer the stock ones 152.5. you were very helpfull ALL .thank you guys

 

[RagingMain]

i hope so man. i am waiting for the stock main jets. I ve seen in this forum that from the stock that is 152.5 many vmax owners say that they changed it to 147.5 for better performance. do you know anything about that. my engine is bored to 1300cc with K/N filter and supertrapp slip on's. do you think the factory main jet will be fine ?

If you have stock exhaust with slip ons it really doesnt matter what you have done to the top end. Wont be able to get it out.

Try the 152s and go from there based on your elevation

 

[vmaxcruzer]

it may be naivety but i can't imagine drilling jets works all that well. i mean the tolerance of the bit has to be so perfect. no runout what so ever as you cuold drill something to a 150 and easily make it a 152.5 depending on the runout of the bit

or maybe do I just not understand how this all works?

No its not just you...Its a BAD idea. Reminds me of the old school back yard mechanics that would time a car by ear, it may be good enough to get you home but by no means is as good as a timing light. Drilling jets is a shot in the dark.

 

[gleno]

everything works and in 6k the servo opens the butterflys and in 3k when i turn the T-boost switch the butterflys open. do you think is that my mechanic drilled bigger the main jets ? ? ?

Just got back to this one. If everything is mechanically and electrically working it only leaves the the jets.

I have to agree with the other forum members, drilling out the main jets!!!! - "That's one of the dumbest things Ive heard"

Good luck with the replacements.