FJ BOOST

[CanDman]

I would love to know how the boost works.....and how do you know if it is working well??? At what RPM is it supposed to kick in and exactly what is supposed to happen ?
Kev

[FJmonkey]

I would love to know how the boost works.....and how do you know if it is working well??? At what RPM is it supposed to kick in and exactly what is supposed to happen ?
Kev

Boost sounds like a turbo kind of thing, 6 pounds was stock on the Seca 650 turbo. Felt good when it kicked in.....Lifted the front end up and made you think about keeping the throttle wide open... Am I gonna wheelie for a while or am I gonna mess up the back side of my helmet....

[WestOzXJR]

I would love to know how the boost works.....and how do you know if it is working well??? At what RPM is it supposed to kick in and exactly what is supposed to happen ?
Kev

Are you talking about "boost" as in like they have on a V-max?

[CanDman]

I would love to know how the boost works.....and how do you know if it is working well??? At what RPM is it supposed to kick in and exactly what is supposed to happen ?
Kev

Are you talking about "boost" as in like they have on a V-max?

No..........I have a service manual for my 85 fj1100.......and in section 7-48 there is a diagram describing the boost control

[oldktmdude]

   Don't get too excited, thats the vacuum advance for your CDI that they refer to as the BOOST CONTROL HOSE.

[fj1289]

I think this is a vacuum advance setup for the early bikes.  The service manual should show the advance curves in the ignition or electrical section.  Here's a recent post Pat had about it on his 1349 engine:  http://www.fjowners.com/index.php?topic=6551.0

Wonder if yours is acting up a bit too then clears itself out?  Then you are feeling the box witch to a different curve?  Is that possible?  

Or, could you have an occaisional high-RPM miss?  How are the plugs?  Connections to the coils clean and corrosion free?  Or like Frank said, the tach is slow and you are hitting the rev limiter...

[CanDman]

I think this is a vacuum advance setup for the early bikes.  The service manual should show the advance curves in the ignition or electrical section.  Here's a recent post Pat had about it on his 1349 engine:  http://www.fjowners.com/index.php?topic=6551.0

Wonder if yours is acting up a bit too then clears itself out?  Then you are feeling the box witch to a different curve?  Is that possible?  

Or, could you have an occaisional high-RPM miss?  How are the plugs?  Connections to the coils clean and corrosion free?  Or like Frank said, the tach is slow and you are hitting the rev limiter...

Great question........mine is an 85 and I am not sure......I think the plugs went in last year and I had the wiseco piston upgrade done 3 yrs ago....I am wondering if it might be a vacuum pressure jet that needs looking at or the carbs themselves made need to be jetted since I put on new cans....althought the shop that put the cans on said it didn't need jetting.......but I will take her in and see if someting is needing adjustment.........thx
Kev 

[oldktmdude]

  If you haven't already done it, the ignition plate timing advance mod may help smooth out your top-end problem.

[CanDman]

  If you haven't already done it, the ignition plate timing advance mod may help smooth out your top-end problem.

would it be easier to disconnect the rev limiter.....?
Kev

[simi_ed]

I. Think the rev limiter is built into the ignition.

[Travis398]

I was a bit confused reading this post. Everyone is talking about a running problem, when all you are asking about is the Boost. 
But after reading back through the recent posts I see there is another thread on the same subject.

As Simi Ed just pointed out, you can disconnect the rev limiter by unplugging your ignition box. That will solve your problem.

As everyone else pointed out the Boost is just the vacuum advance for the ignition. I doubt this has anything to do with your running problem though.
But for piece of mind put a timing light on the rotor and check the timing marks, then pull the vacuum advance hose and see if the timing changes.

When the rev limiter kicks in the bike shuts off........... I have heard 10,200 is the rpm for the TCI ignition box. However 11,500rpm (indicated) is when my 1100 shuts down.
This is well after the bike stops pulling, so when it turns back on it doesn't really pull all that hard.

You can check your tach for accuracy by using an induction tach or timing light with a tach built in, this should help verify how accurate yours is. 

[CanDman]

Thank you everybody for all the great info.......looks like I have my answer.....
Kev

[FJdude]

Is that boost hose supposed to be connected to something, because mine has never been connected to anything, it's just shoved back with some wires open at the end...

[RichBaker]

It's a vacuum hose, should be connected to the tube coming out of the rubber manifold in front of the #2 carb......

[FJdude]

It's a vacuum hose, should be connected to the tube coming out of the rubber manifold in front of the #2 carb......

Ya mine is connected to the #2 carb vacuum port, but I just have it dangling not connected to anything after that...Is it supposed to be connect to something at the other end?