boost or bust?

[CanDman]

Hi gang......took CanD for a good run today....and found some deserted stretches where I was able to really open her up.......wow.......I don't think I have taken the tach this high before..........was reeeeeaallyyy coooooooool........but   something happened that has caught my attention and I am hoping someone knows what it is........ I hit 2nd gear at about 6500 revs....I really opened it up....and she took off.......at about 9500.....there was a flat spot(like a spit....or pop) so I shifted into third ......again rolled it up and as soon as I hit 9500....hit the same flat spot....it only lasted for a second and the power came back on with a jump.......and again I shifted........into 4th....... On another stretch I went through the same procedure...but instead of shifting this time ...I continued up to 10500......revs........it popped again....but when she came back she really jumped and I had to hold on. Now I know it was not the clutch as I upgraded the clutch with Barnett discs plates and springs last year..... .....there was zero slide to it at all....no.......this was a power issue.....so I began to wonder how the boost and vacuum hose works...........it almost felt like the vacuum hose lost its vacuum.......I am only theorizing
Kev   

[fj11.5]

rev limiter cutting in maybe

[FJmonkey]

rev limiter cutting in maybe

I don't think our FJ's have a rev limiter, Kookaloo till Kaboom.

[CanDman]

does anyone understand how and when the boost  works.....what's supposed to happen.....?
Kev

[Pat Conlon]

  Boost? As in forced induction?

[racerman_27410]

The tach on the FJ is notoriously slow.... I would bet money you were bouncing off the rev limiter.


KOokaloo!


Frank

[FJmonkey]

The tach on the FJ is notoriously slow.... I would bet money you were bouncing off the rev limiter.
KOokaloo!
Frank

I have a rev limiter, but it is my shitty second gear issue...

[CanDman]

Boost? As in forced induction?

Hey Pat....good to see you ....hope all is well.........well actually when I was taking my girl apart...I looked at my shop Manual(service) and got to the section 7-48 where it shows the boost control hose routing.....I asked a few shops and apparently there is a boost hose running into no.2 carb that is a vacuum hose and somehow does something to ignition timing and opens something up and gives the FJ a little bit more in the upper revs....I think it was a precuser to the now popular V-BOOST found in the V-MAX. I read Bob Shamas's write up on his turbo project and he does mention the boost hose and how it becomes "unusable" after he threw his turbo on his bike......so I was hoping that some of the more experienced FJ er's would know more about it....
Kev

[CanDman]

The tach on the FJ is notoriously slow.... I would bet money you were bouncing off the rev limiter.


KOokaloo!


Frank

Hi Fankie........is there a remedy for that........is it possible that it could be a vacuum pressure jet?

[CanDman]

thanks everybody for all your great comments......looks like there isn't a problem at all.....
Kev

[RichBaker]

Yamaha calls it "boost", but all it is is a vacuum advance.  V-boost is a heck of a lot different..... It lets the V-Max breathe thru 2 carbs per cylinder, over ~5k RPM, via a flap in the airbox.

[andyb]

Thought it was 6k?  The fun trick there is to change the trigger to see both coils firing, which makes it come on at half the rpm.  Or just use a switch to trigger it manually... makes the idle sound like you've got really big cams in the motor. 

[RichBaker]

Could be, I'm just going by memory from 20+ years ago....  A couple friends had 'em. 1 was an '85, the 1st & fastest of 'em all.