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V-Boost rpm shift?!

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Matt-Max

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Hi all! New V-Max owner and still kicking myself for having put it off for so long. Gone are the fire blades and the ZX12s, what a brilliant lump the old 1200 is! I'm mad keen on getting my head round how to make it tip top and will no doubt be attempting a nice resto at some point, but for now I'm hoping for a bit of help with a problem I can't quite crack.

V-Boost was going great and kicking in happily at 6k rpm, but for some weird reason it suddenly shifted to 7k! It happened on one ride, I think something may have come adrift and fallen off on the god awful bumpy roads round here as there was a noise in a bend which sounded like something small and metal pinging across the road. I put it down to clipping loose scrap, but the bike ran lumpy until 4krpm and seemed to struggle for a while. he Max then started to sound more throaty than it used to, so I started wondering if there was a link with that too, but can't spot a post that helps (or an obvious hole in the downpipes/collector etc. I'm busy scratching my head, looking at the settings page in the manual looking to see if this is an adjuster that can be wound back, but it's a bit more complex. Can anyone work out what would shift it by around 1k rpm?
 

one2dmax

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Hard to say depending on if you were running on 3 and then the 4th cylinder kicked in. They run surprisingly well on 3 by the way.
 

Matt-Max

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Thanks for this, I'll have a check on downpipe temps to see if that's the issue. It does run really well at the moment so I would probably be surprised, but it sounds like a nice and simple solution so I'll keep my fingers crossed.
 
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Parminio

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You can tell by just putting your hands in front of the exhaust at idle. You'll feel two pops per second from one side and only one from the other in the same time span.
 

Parminio

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We're all in this Vmax thing together, bud. Don't worry about it.
 

MaxMidnight

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If it is a misfire causing the problem the only cylinder you would need to investigate would be the one that supplies the signal for the V Boost to operate. This is the the grey wire (RHF cylinder up to '89) or yellow (RHR '90 on).

If it is affecting V Boost then I would have thought the tacho would also be affected as it relies on the same signal to operate. That would mean that for any given revs your indicated road speed would be some fifteen percent lower than you have been used to.
 

RempageR1

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If it is a misfire causing the problem the only cylinder you would need to investigate would be the one that supplies the signal for the V Boost to operate. This is the the grey wire (RHF cylinder up to '89) or yellow (RHR '90 on).

If it is affecting V Boost then I would have thought the tacho would also be affected as it relies on the same signal to operate. That would mean that for any given revs your indicated road speed would be some fifteen percent lower than you have been used to.
Exactly. Since you mention it moved to 7K and you probably read that from the tacho, the problem is probably somewhere in the control unit or the servo. Does the Vboost servo cycle normally when you turn on the ignition?

The noise you describe could be anything, so I suggest you start by checking if the exhaust pipes, airfilter and the intake manifolds are still properly fitted. I was once working on the Vmax of a friend of mine where the airfilter had become undone. That will also result in less power and a more throaty sound....
 

Matt-Max

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@RampageR1 thanks for those top tips - I'm going to have a poke about up top as there was something rattling before hand so could well be a drop.

@MaxMidnight I never really looked at road speeds - just the tacho so if it is reading out then I'm not sure I would notice, the only change I can imagine is that I'm shifting earlier to get out of the red end. I've never bounced it off a limiter - is there one? Cos I do think I might be going higher than normal.

PS - this forum is almost as awesome as the bike itself! Thanks all!
 

MaxMidnight

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As far as I'm aware there isn't a rev limiter.

I have a speed in gears calculator but the site won't let me upload an Excel file. Send me a PM with your e-mail if you would like it.

Assuming you have a standard rear wheel & tyre your road speed @ 4K should be as follows:

1st - 26.8
2nd - 38.3
3rd - 50.4
4th - 63.0
5th - 73.1

That is assuming your speedo is accurate but in all likelihood it will over-read a bit.
 

Fire-medic

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Hard to say depending on if you were running on 3 and then the 4th cylinder kicked in. They run surprisingly well on 3 by the way.
You can tell by just putting your hands in front of the exhaust at idle. You'll feel two pops per second from one side and only one from the other in the same time span.
I've found that apart from an infra-red heat gun, an easy and cost-free way to see which pipe is firing and which isn't, at-idle, is a spritz of water on the exhaust pipe. Do it close-to the cylinder head. A firing cylinder/pipe, the water vaporizes immediately, a non-firing cylinder, the water sits on the pipe, droplets may run-down the wall, and it lasts much-longer.

My experience is that usually, a non-firing cylinder at-idle is because of a plugged pilot jet. Rev the engine into the upper-half of the rev range (4,500+ rpm) and that cylinder begins to-fire, and the engine runs smoothly.
 

MaxMidnight

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My experience is that usually, a non-firing cylinder at-idle is because of a plugged pilot jet. Rev the engine into the upper-half of the rev range (4,500+ rpm) and that cylinder begins to-fire, and the engine runs smoothly.
Whilst you are correct regading the idle situation in this case it is the signal from the ignition control unit that needs to be investigated.
 

OEM2004RIGHT!

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WELL it is my turn to maybe help somebody. From my experience and reading everything above you may have two problems but I am trying to tie them together from one occurrence. I will share what I learned from BARRY from DYNATEK who is right now the only teck. guy they have working. Now this applies to 93 to 07. The OME rev limit from the ignition control unit is 9500RPM. It gets a lot of its information from the vacuum pressure sensor that gets its information from the vacuum hose coming off the left front intake manifold or the #2 cyl. You can start by testing this sensor because it plugs straight into the ignition unit witch I was told by BARRY was what took the rpms and send that to the v-boost unit. You can start checking the electronics end with a voltage meter where the connector from the I C U plugs into the map sensor. THE BLACK/YELLOW WIRE IS THE SENSOR GROUND,USE IT AS THE GROUND FOR YOUR METER, RED/BLACK WIRE SHOULD BE 12 + VOLTS WITH KEY ON,BLACK/RED SENSOR SIGNAL APPROX. 2.1V ATM. If this test is bad you may have jarred loose one of only 2 screws holding the icu. IF one was already gone a loose connection with the wiring harness . I hope you got that and I did not sound like a fool but i am only trying to help you, not be a know it all. How i got my info. is by putting a dynatek digital ignition in my 2004 v-max. I love it. I can plug my laptop into my bike by popping the air cover/fake tank off and pluging into a usb to change the ignition curve. YOU can set your rev limit , and if you wanted to, you could set when the servo on the v-boost start to open if you want to get that deep in the free software you download . If I can help you any more or any way let me know. These guys on here are supper smart from what help they have given me. (MANY THANKS) by the way. Any thing I have shared today will not hurt your bike or you so good luck and be safe. PS if I gave misleading info. please correct me so I will not pass on bad or wrong info. thanks.
 
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MaxMidnight

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Perhaps I have missed something here but does Mr Matt-Max have a Dynatec unit on his bike?

I also don't see how the vacuum pressure sensor would influence a rev limiter as its job is to provides the signal to help determine ignition advance...I would have thought that the control of the spark timing would be down to the ICU?

Sorry to be pedantic but your test procedure will only check that the unit is passing a voltage at ambient air pressure. You would need to apply a vacuum to ensure the voltage varies as pressure alters.
 

Fire-medic

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Perhaps I have missed something here but does Mr Matt-Max have a Dynatec unit on his bike?

I also don't see how the vacuum pressure sensor would influence a rev limiter as its job is to provides the signal to help determine ignition advance...I would have thought that the control of the spark timing would be down to the ICU?

Sorry to be pedantic but your test procedure will only check that the unit is passing a voltage at ambient air pressure. You would need to apply a vacuum to ensure the voltage varies as pressure alters.
A job for MityVac!

A question, The OME rev limit from the ignition control unit is 9500RPM. What does OME stand-for? Is that a mis-spelling of O.E.M.? That one, I know. Since he's been speaking of a Dynatek ignition box, I'm guessing that's what he means, except now, I'm still confused. The Gen. 1 doesn't have a rev-limiter. If he's writing about the setting for a Gen. 1 ignition unit from Dynatek, and that the factory rev-limiter for a Dynatek is set-at 9500 rpm, OK, I understand that. Is that it?

Sean Morley has mentioned that the VMax doesn't like over-revving. I believe that at some point, the redline was reduced from 9500 to 9000 rpm in the interests of allowing the engine to have a longer life, as-long as it was observed. My '92 has the 9500 rpm redline. I don't know the exact post where Sean mentioned this, but as I recall, he said the lower end will eventually develop issues from too-many trips past the redline. That's a good reason for an aftermarket ignition box. On my '92, I have a DYNA old-style ignition box w/the 'dip-switches.'
 
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OEM2004RIGHT!

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A job for MityVac!

A question, The OME rev limit from the ignition control unit is 9500RPM. What does OME stand-for? Is that a mis-spelling of O.E.M.? That one, I know. Since he's been speaking of a Dynatek ignition box, I'm guessing that's what he means, except now, I'm still confused. The Gen. 1 doesn't have a rev-limiter. If he's writing about the setting for a Gen. 1 ignition unit from Dynatek, and that the factory rev-limiter for a Dynatek is set-at 9500 rpm, OK, I understand that. Is that it?

Sean Morley has mentioned that the VMax doesn't like over-revving. I believe that at some point, the redline was reduced from 9500 to 9000 rpm in the interests of allowing the engine to have a longer life, as-long as it was observed. My '92 has the 9500 rpm redline. I don't know the exact post where Sean mentioned this, but as I recall, he said the lower end will eventually develop issues from too-many trips past the redline. That's a good reason for an aftermarket ignition box. On my '92, I have a DYNA old-style ignition box w/the 'dip-switches.'
Yea it was a typographical error on my part. You see (I) don't see very well and make mistakes typing but it is the dyslexia that really makes comments of this nature common. It is my Schizoaffective disorder that makes me uncertain of the nature of your QUESTION. I will no longer try to help people but only ask for it.
 

Fire-medic

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Hey, don't sweat it, you have to comprehend things correctly, or your interpretation of the wrong signal is tainted itself, leading to wasted time trying to decide a situation's resolution, based upon that faulty info input. GIGO.
 

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