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Manifold Rubbers with & without restrictors

Old 07-31-2005, 02:08 PM
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Manifold Rubbers with & without restrictors

What is it ???????
VTR1000 Manifold Rubbers with & without restrictors :
http://www.dynobike.com/vtr1000_tips.htm

Do you think I will have to rejet the bike in case I have it and decide to remove it ?

Is it the way honda restricted my 2001 french model ?
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Old 07-31-2005, 02:34 PM
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Absolutely not.
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Old 08-01-2005, 12:28 AM
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Re: Manifold Rubbers with & without restrictors


absolutely not ... what ?
The fact I have to rejet it or the way Honda restricts the bike to 106 Hp ?
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Old 08-01-2005, 01:31 AM
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Re: Manifold Rubbers with & without restrictors

One theory here for the manifold intake :

I also read something in a tech column about Superhawks stalling under heavy braking or low idling. The deal is that since the carb throats are pretty big, under certain conditions, there isn't enough velocity to pull enough mixture from the carbs into the engine, and the bike stalls out. Honda fixed this in '99 by putting 5mm restrictor rings in the intake manifolds -- Peter has a '98, but apparently the '99 manifolds will fit the '98 bike, so I'm going to swap them in and see how it runs.
http://www.bluepoof.com/motorcycles/1202/121302.html
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Old 08-01-2005, 06:44 AM
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Re: Manifold Rubbers with & without restrictors

You don't have to rejet. I'm not calling you a liar. (That would make me quite the ***, don't you think? :wink: )
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Old 08-01-2005, 08:03 AM
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Re: Manifold Rubbers with & without restrictors

Thanks ;-)
Then, do you think I will benefit supressing these restrictors without rejetting or would it be just another chance to get into problems ?
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Old 08-01-2005, 08:10 AM
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Re: Manifold Rubbers with & without restrictors

Originally Posted by roadrun_fr";p=&quot View Post
What is it ???????
VTR1000 Manifold Rubbers with & without restrictors :
http://www.dynobike.com/vtr1000_tips.htm

Do you think I will have to rejet the bike in case I have it and decide to remove it ?

Is it the way honda restricted my 2001 french model ?
The reason why the european models after 2001 have 3 HP less is because the PAIR system and the EVAP system was installed.

The intake restrictor is a restriction that germans VTR have or had. They are restricted at 100 Hp (engine Hp)
I thought rejetting was not needed. I'm not sure!
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Old 08-01-2005, 08:47 AM
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Re: Manifold Rubbers with & without restrictors

I thought Pair system is working only on decceleration ...
And Evap is for California type only ...
Sounds like the restrictors exist on Australian models too ...

Do I miss something ?
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Old 08-01-2005, 09:00 AM
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Re: Manifold Rubbers with & without restrictors

Originally Posted by roadrun_fr";p=&quot View Post
Thanks ;-)
Then, do you think I will benefit supressing these restrictors without rejetting or would it be just another chance to get into problems ?
I'd pull them out and see. Chances are you won't need to do anything else but enjoy the benefits.

If you do create any sort of lean condition, you'd just jet to the USA specs. A lean condition presents itself as a hesitation then recovery when you roll on the throttle. There are three circuits where it might exist: just off idle (idle jets,) in the midrange (needle circuit,) and WFO (on the mains.) A rich condition, btw feels like a burble (sort of like clearing your throat.)

When you open the throttle, these circuits correspond to roughly under 2500 rpm, 2500-5500, and higher but thats not the most accurate way to understand them.
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Old 08-01-2005, 09:14 AM
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Re: Manifold Rubbers with & without restrictors

Thanks ;-)
I think I have to check if I'm really restricted for my model and think about removing these restrictors if it is confirmed ;-)
Any US or other countries models has been detected with these restrictors ?

Originally Posted by jschmidt";p=&quot View Post
When you open the throttle, these circuits correspond to roughly under 2500 rpm, 2500-5500, and higher but thats not the most accurate way to understand them.
Don't you think circuits are simply related to "throttle open" ?
I mean :
zero throttle : most used : idle jet (engine at idle or decellerate)
1/3 to 2/3 open : most used : needle (light acceleration or cruise at mid speeds)
2/3 to full open : most used : main jet (full acceleration until limiter cuts ;-) )

The tests you're speaking about is at neutral or riding the bike ?
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Old 08-01-2005, 01:41 PM
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Yes, that's a better explanation. The bike needs to be ridden to reveal the condition or run on a gas dyno if you can.
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Old 08-02-2005, 08:04 AM
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Re: Manifold Rubbers with & without restrictors

Originally Posted by roadrun_fr";p=&quot View Post
I thought Pair system is working only on decceleration ...
And Evap is for California type only ...
Sounds like the restrictors exist on Australian models too ...

Do I miss something ?
OK I could be wrong,

but where does the newer moddels loose the 3 HP? Nothing else is changed, I thought.
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Old 08-03-2005, 08:23 AM
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Re: Manifold Rubbers with & without restrictors

have seen :
What you are proberly experiencing is a design fault with Firestorms which due to the size of the inlet manifolds being very big, there isnt enough air velocity passing through the carb with throttle shut. Therefore not pulling enough fuel through, making the engine run lean causing misfire/backfire!
Honda in there wisdom for later models to cure this issue, reduced the diameter of the manifold internally by circa 5mm.
So, suppressing these restrictors would drive me to more carb backfires that I already have ?
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Old 08-03-2005, 08:32 AM
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We may be confusing the stalling problem with a lean condition. I hope I can explain this well enough.

All fuel is pulled by the air in a carburator. The jets are actually flow restrictors affecting the mixture of air and fuel. But it is the venturi effect of the passing air that pulls the gas into the mix. If there is no air velocity, there is no gas. If there is too little air velocity, there will be a corresponding decline in gas.

(A little gravity fed gas will dribble for a second in the absence of air. A tiny amount)

The only way to have a lean condition is if the jet (restrictor) is too small to allow enough fuel for the amount of air volume in the mix. Too little air will not cause leaness. But it will cause stalling.
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Old 08-03-2005, 08:51 AM
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Re: Manifold Rubbers with & without restrictors

So the previous theory for restrictors fixes a problem of stalling at idle, not deccelerating nor blipping throttle ?

Do you believe in this theory ?
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Old 08-03-2005, 10:29 AM
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In 2000 the SH got a necked down intake boot in an effort to increase minimum air velocity.

Does it work? I don't know but it doesn't seem to have eliminated complaints about the stalling problem. However it does make more sense than twisting the vent tubes in a different direction.

I don't actually think the problem is fixable.
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Old 08-07-2005, 04:50 AM
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Re: Manifold Rubbers with & without restrictors

after removing air filter, I checked the manifold rubbers thru the trompets with a spot light, I didn't notice restricting metal pieces.
There are stamped MBB-G. (my VTR is a 2001 european model)
No restriction in there I think.
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Old 08-07-2005, 02:09 PM
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No but it was worth a try I suppose. I've reduced mine greatly by upping the idle to 1300.
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